Polarizing plate and optical display device

Abstract

A polarizing plate and an optical display device including the same are provided. The polarizing plate includes: a polarizer; and a phase difference layer laminated on the lower surface of the polarizer, in which the maximum value of the ratio represented by Formula 1 in the phase difference layer is 1.1 to 1.8, and the minimum value is 0.3 to 0.7. [Formula 1] Ratio B / A (A is a surface phase difference (unit: nm) of the phase difference layer at a wavelength of 550 nm, and B is a tilt phase difference (unit: nm) measured at a wavelength of 550 nm after the phase difference layer is rotated by + 60 degrees or-60 degrees with the fast axis of the phase difference layer as an axis of rotation).

Description

Technical Field

[0001] The present invention relates to a polarizing plate and an optical display device including the polarizing plate. Background Art

[0002] An organic light emitting diode display may be provided with a polarizing plate. The polarizing plate may achieve an antireflection function by reducing the reflectance of external light. It is desirable to improve the screen quality by improving the black visibility of the front side of the polarizing plate.

[0003] The polarizing plate may include a polarizer and a retardation layer. Generally, the retardation layer may be a two-sheet type retardation layer including a half wave plate (HWP) layer and a quarter wave plate (QWP) layer. It is desirable to use a single-sheet type retardation layer instead of the two-sheet type retardation layer in this technology to achieve a significant reduction in reflectance at the front and lateral sides while improving processability.

[0004] The background art of the present invention is disclosed in Korean Patent Laid-Open Publication No. 10-2013-0103595, etc. Summary of the Invention

[0005] [Technical Problem]

[0006] An object of the present invention is to provide a polarizing plate that provides a significant reduction in reflectance at the front and lateral sides, and ensures screen uniformity between the front and the lateral sides by significantly reducing the reflectance difference between the front and the lateral sides of the polarizing plate.

[0007] Another object of the present invention is to provide a polarizing plate that includes a single-sheet type liquid crystal retardation layer while ensuring the above effects.

[0008] Still another object of the present invention is to provide a polarizing plate that includes a single sheet O-plate type liquid crystal retardation layer while ensuring the above effects.

[0009] Another object of the present invention is to provide a polarizing plate that can achieve thickness reduction, manufacturing process simplification, and economic feasibility.

[0010] [Technical Solution]

[0011] One embodiment of the present invention relates to a polarizing plate.

[0012] 1. The polarizing plate includes: a polarizer; and a retardation layer stacked on the lower surface of the polarizer, wherein the retardation layer has a maximum ratio of 1.1 to 1.8 and a minimum ratio of 0.3 to 0.7 calculated according to Equation 1:

[0013] [Equation 1]

[0014] Ratio = B / A,

[0015] (where A is the front retardation (unit: nanometer) of the retardation layer at a wavelength of 550 nanometers; and

[0016] B is the oblique retardation (unit: nanometer) of the retardation layer, and the oblique retardation is measured at a wavelength of 550 nanometers when the retardation layer is rotated by an angle of +60° or -60° with the fast axis of the retardation layer as the rotation axis.)

[0017] 2. In 1, in Equation 1, the retardation layer may have an A value of 110 nanometers to 170 nanometers.

[0018] 3. In 1-2, in Equation 1, the retardation layer may have a maximum B value of 120 nanometers to 310 nanometers and a minimum B value of 20 nanometers to 120 nanometers.

[0019] 4. In 1-3, the retardation layer may have a difference of 45 nanometers or more than 45 nanometers between the maximum oblique retardation and the minimum oblique retardation, and the maximum oblique retardation and the minimum oblique retardation are measured at a wavelength of 550 nanometers when the retardation layer is rotated by an angle of +60° or -60° with the fast axis of the retardation layer as the rotation axis.

[0020] 5. In 1-4, the retardation layer may have an oblique retardation of 130 nanometers to 240 nanometers, and the oblique retardation is measured at a wavelength of 550 nanometers when the retardation layer is rotated by an angle of +60° or -60° with the slow axis of the retardation layer as the rotation axis.

[0021] 6. In 1-5, the retardation layer may have negative wavelength dispersion.

[0022] 7. Among 1 - 6, the retardation layer may have an asymmetric relative value in a graph where the X-axis represents the rotation angle (°) of a retardation meter and the Y-axis represents the relative value (skew retardation / forward retardation) of the skew retardation (nanometers) to the forward retardation (nanometers), and the skew retardation is measured with the fast axis of the retardation layer set as the rotation axis.

[0023] 8. Among 1 - 7, the retardation layer may have a symmetric relative value in a graph where the X-axis represents the rotation angle (°) of a retardation meter and the Y-axis represents the relative value (skew retardation / forward retardation) of the skew retardation (nanometers) to the forward retardation (nanometers), and the skew retardation is measured with the slow axis of the retardation layer set as the rotation axis.

[0024] 9. Among 1 - 8, assuming the light transmission axis of the polarizer is set to 0°, the slow axis of the retardation layer may be inclined at an angle of 40° to 50° relative to the light transmission axis of the polarizer.

[0025] 10. Among 1 - 9, the retardation layer may include an O-plate type liquid crystal retardation layer.

[0026] 11. In 10, assuming one surface in the thickness direction of the O-plate type liquid crystal retardation layer is the top surface and the other surface opposite to the top surface is the bottom surface, the liquid crystal tilt angle on the top surface of the O-plate type liquid crystal retardation layer may be greater than the liquid crystal tilt angle on the bottom surface.

[0027] 12. In 11, the O-plate type liquid crystal retardation layer may have a liquid crystal tilt angle of 30° to 90° on the top surface and a liquid crystal tilt angle of 0° to 10° on the bottom surface.

[0028] 13. In 11 - 12, the top surface may be closer to the polarizer than the bottom surface.

[0029] 14. In 11 - 13, the range of the absolute difference between the liquid crystal tilt angle on the top surface and the liquid crystal tilt angle on the bottom surface may be between 30° and 90°.

[0030] 15. In 10 - 14, the O-plate type liquid crystal retardation layer may be a nematic liquid crystal layer.

[0031] 16. In 10 - 15, the retardation layer may only include the O-plate type liquid crystal retardation layer.

[0032] 17. In 10 - 16, the polarizing plate may further include a first protective layer on the lower surface of the polarizer.

[0033] 18. In 17, the first protective layer may have a positive retardation of 10 nm or less than 10 nm at a wavelength of 550 nm.

[0034] 19. In 1 - 18, the polarizing plate may further include at least one of a second protective layer and a third protective layer, the second protective layer being located on the upper surface of the polarizer, and the third protective layer being located on the lower surface of the polarizer.

[0035] Another embodiment of the present invention relates to an optical display device.

[0036] The optical display device includes a polarizing plate according to the present invention.

[0037] [Advantageous Effects]

[0038] The present invention provides a polarizing plate that ensures screen uniformity between the front and side surfaces by significantly reducing the reflectance at the front and side surfaces to reduce the reflectance difference between the front and side surfaces.

[0039] The present invention provides a polarizing plate that includes a single - layer liquid crystal retardation layer while ensuring the above effects.

[0040] The present invention provides a polarizing plate that includes a single - layer O - plate type liquid crystal retardation layer while ensuring the above effects.

[0041] The present invention provides a polarizing plate that can achieve thickness reduction, manufacturing process simplification, and economic feasibility. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 is an exploded view of a retardation layer and a polarizer according to an embodiment of the present invention.

[0043] Figure 2 is a conceptual diagram of the liquid crystal tilt angle.

[0044] Figure 3 is a graph showing the change in the retardation value according to the rotation angle of the retardation layer with the fast axis or slow axis of the retardation layer as the rotation axis. In the graph, the X - axis represents the rotation angle (°) of the retardometer, and the Y - axis represents the relative value (skew retardation / positive retardation) of the skew retardation (nm) to the positive retardation (nm). In the graph, the solid line represents the relative value of the retardation layer rotated with the fast axis as the rotation axis, and the dashed line represents the relative value of the retardation layer rotated with the slow axis as the rotation axis.

[0045] Figures 4 to 9 is a cross - sectional view of a polarizing plate according to an embodiment of the present invention. DETAILED DESCRIPTION

[0046] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily implement the present invention. It should be understood that the present invention can be implemented in different ways and is not limited to the following embodiments.

[0047] The terms used herein are for the purpose of describing exemplary embodiments and are not intended to limit the scope of the present invention. As used herein, unless the context clearly indicates otherwise, the singular forms "a / an" and "the" are intended to include the plural forms as well.

[0048] In the drawings, for clarity, parts irrelevant to this description will be omitted. Throughout the specification, the same components will be denoted by the same reference numerals. Although the lengths, thicknesses, or widths of various components may be exaggerated in the drawings for the purpose of describing the present invention, the present invention is not limited thereto.

[0049] As used herein, spatial relative terms such as "upper" and "lower" are defined with reference to the drawings. Therefore, it should be understood that the "upper surface" can be used interchangeably with the "lower surface", and vice versa.

[0050] As used herein, the "front in-plane retardation (Re)", "degree of biaxiality (NZ)", and "out-of-plane retardation (Rth)" of an optical device are represented by Equation A, Equation B, and Equation C, respectively:

[0051] [Equation A]

[0052] Re = (nx - ny) × d

[0053] [Equation B]

[0054] NZ = (nx - nz) / (nx - ny)

[0055] [Equation C]

[0056] Rth = ((nx + ny) / 2 - nz) × d

[0057] (where nx, ny, and nz are the refractive indices of the optical device in the slow axis direction, fast axis direction, and thickness direction of the optical device at the measurement wavelength, respectively, and d represents the thickness of the optical device (unit: nanometer)).

[0058] The optical device may be a retardation layer, a protective layer, or a laminate formed of a retardation layer and a protective layer. Unless otherwise specified, retardation, birefringence, and out-of-plane retardation refer to values measured by transmitting light through the optical device in the direction normal to the in-plane direction of the optical device.

[0059] The axis having the highest refractive index in the in-plane direction used herein is defined as the "slow axis", and the axis having the lowest refractive index in the in-plane direction is defined as the "fast axis". In one embodiment, the slow axis and the fast axis may be substantially orthogonal to each other, but are not limited thereto.

[0060] "X to Y" used herein to represent a specific numerical range means "greater than or equal to X and less than or equal to Y (X ≤ and ≤ Y)".

[0061] The polarizing plate according to the present invention includes a polarizer and a retardation layer stacked on the lower surface of the polarizer. When the polarizing plate is applied to an optical display device, the retardation layer is disposed between the polarizer and the panel of the optical display device. That is, the retardation layer may be disposed on the light incident surface of the polarizer in the light emitting direction of a light emitting diode such as an organic light emitting diode (OLED). The optical display device may be a light emitting diode display including an OLED or the like.

[0062] The retardation layer may have a maximum ratio of 1.1 to 1.8 and a minimum ratio of 0.3 to 0.7 calculated according to Equation 1:

[0063] [Equation 1]

[0064] Ratio = B / A,

[0065] (where A is the forward retardation (unit: nanometer) of the retardation layer at a wavelength of 550 nanometers; and

[0066] B is the skew retardation (unit: nanometer) of the retardation layer, and the skew retardation is measured at a wavelength of 550 nanometers when the retardation layer is rotated by an angle of +60° or -60° about the fast axis of the retardation layer.)

[0067] When the polarizing plate is applied to an optical display device, the ratio of Equation 1 is designed to determine conditions for significantly improving the reflectance reduction effect at the front and side surfaces of the retardation layer. Therefore, the polarizing plate can be used as an antireflection polarizing plate in light emitting device displays such as organic light emitting diode displays, inorganic light emitting device displays, and organic-inorganic light emitting diode displays.

[0068] As described below, when the retardation layer is a monolithic (single-layer) O-plate type liquid crystal retardation layer, based on the ratio of Equation 1, it can be determined whether the retardation layer can provide a significant reflectance reduction effect at the front and side surfaces of the polarizer. Additionally, when the retardation layer exhibits negative wavelength dispersion, the ratio of Equation 1 is designed to determine the conditions for reducing the reflectance of the retardation layer at the front and side surfaces of the polarizer while minimizing the reflectance difference between the front and side surfaces.

[0069] The in-plane retardation of the retardation layer in the forward direction is a single value. In contrast, the retardation layer has a maximum tilt retardation and a minimum tilt retardation, which are measured when the retardation layer is rotated by an angle of +60° or -60° with the fast axis of the retardation layer as the rotation axis. The ratio of Equation 1 is obtained based on the in-plane retardation value in the forward direction of the retardation layer and the tilt retardation value of the retardation layer.

[0070] When the maximum ratio of Equation 1 is in the range of 1.1 to 1.8 and the minimum ratio of Equation 1 is in the range of 0.3 to 0.7, the polarizer can ensure a significant reduction in reflectance at the front and side surfaces of the polarizer, while providing better screen uniformity between the front and side surfaces of the display device by reducing the reflectance difference between the front and side surfaces of the polarizer. For example, the maximum ratio can be 1.1, 1.15, 1.2, 1.25, 1.3, 1.35, 1.4, 1.45, 1.5, 1.55, 1.6, 1.65, 1.7, 1.75, 1.8, 1.2 to 1.75, 1.2 to 1.7, or 1.3 to 1.6. For example, the minimum value can be 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.3 to 0.65, 0.35 to 0.65, or 0.4 to 0.6.

[0071] As calculated according to Equation 1, in the manufacture of the retardation layer (especially the O-plate type liquid crystal retardation layer), by adjusting the solvent evaporation rate (e.g., air volume) and / or drying temperature and / or the irradiation amount of ultraviolet (UV) light during the photocuring of the coating formed from the composition for the O-plate type liquid crystal retardation layer, a maximum ratio of 1.1 to 1.8 and a minimum ratio of 0.3 to 0.7 can be achieved. This will be elaborated in detail below.

[0072] Hereinafter, each component of the polarizer according to the present invention will be elaborated in detail.

[0073] Polarizer

[0074] A polarizer is used to convert natural light or polarized light into linearly polarized light by linearly polarizing in a specific direction. The polarizer can be made from a polymer film mainly composed of a polyvinyl alcohol-based resin. For example, the polarizer can be made by dyeing the polymer film with iodine or a dichroic dye and then stretching the dyed film in its machine direction (MD), or can be made by dehydrating the polymer film using an acid catalyst or the like to form a polyene bond. In one embodiment, the polarizer can be made by swelling, dyeing, stretching, and optionally color correction and / or crosslinking of a polyvinyl alcohol-based film.

[0075] The polarizer has an optical absorption axis and an optical transmission axis in its in-plane direction, where the optical absorption axis corresponds to the machine direction (MD) of the polarizer, and the optical transmission axis can correspond to the transverse direction (TD) of the polarizer.

[0076] The polarizer can have a single light transmittance of 40% or more than 40% (e.g., 40% to 47%) and a degree of polarization of 95% or more than 95% (e.g., 95% to 99.9999%). Within this range, the polarizer can be combined with a retardation layer to improve the antireflection efficiency. Here, the "light transmittance" and "degree of polarization" can be measured at wavelengths from 380 nm to 780 nm by methods known to those skilled in the art and can correspond to the visibility within the corresponding wavelength range.

[0077] The polarizer can have a thickness of 2 μm to 30 μm, specifically 4 μm to 25 μm. Within this range, the polarizer can be applied to a polarizing plate.

[0078] The polarizer can be directly stacked on the retardation layer or the protective layer without an adhesive layer or a bonding layer, or can be stacked on the retardation layer or the protective layer through an adhesive layer or a bonding layer.

[0079] Retardation layer

[0080] The retardation layer may have a maximum ratio of Equation 1 in the range of 1.1 to 1.8 and a minimum ratio of Equation 1 in the range of 0.3 to 0.7. Within this range, the polarizer can ensure a significant reduction in reflectance at the front and side surfaces of the polarizer, while providing good screen uniformity by reducing the reflectance difference between the front and side surfaces. In one embodiment, the retardation layer may have a maximum ratio of 1.2 to 1.75, 1.2 to 1.7, or 1.3 to 1.6 and a minimum ratio of 0.3 to 0.65, 0.35 to 0.65, or 0.4 to 0.6.

[0081] In one embodiment, the retardation layer may have a ratio of Equation 1 in the range of 0.3 to 1.8 (e.g., 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1.0, 1.05, 1.1, 1.15, 1.2, 1.25, 1.3, 1.35, 1.4, 1.45, 1.5, 1.55, 1.6, 1.65, 1.7, 1.75, or 1.8).

[0082] In the ratio of Equation 1, A and B will be elaborated in detail. A and B are measured at a wavelength of 550 nm using a retardometer (e.g., AxoScan). Those skilled in the art generally use AxoScan to measure retardation.

[0083] A represents the forward in-plane retardation value of the retardation layer measured when light is incident on the polarizer in the normal direction of the in-plane direction of the retardation layer with the retardation layer mounted on the retardometer.

[0084] B can be obtained from the retardation of the retardation layer when the retardation layer is mounted on the retardometer and rotated by an angle of +60° or -60° with the fast axis of the retardation layer as the rotation axis. +60° is defined as the clockwise direction with respect to the rotation axis, and -60° is defined as the counterclockwise direction with respect to the rotation axis, and vice versa.

[0085] In one embodiment, the retardation layer may have an A value of 110 nm to 170 nm (e.g., 110, 115, 120, 125, 130, 135, 140, 145, 150, 155, 160, 165, 170 nm), 120 nm to 160 nm, or 130 nm to 150 nm in Equation 1. Within this range, the retardation layer can easily reach the above range of the maximum ratio and minimum ratio of Equation 1 and can be easily formed.

[0086] In one embodiment, the delay layer may have a maximum B value of 120 nanometers to 310 nanometers (e.g., 120, 130, 140, 150, 160, 170, 180, 190, 200, 210, 220, 230, 240, 250, 260, 270, 280, 290, 300, 310 nanometers), 130 nanometers to 290 nanometers, or 140 nanometers to 270 nanometers in Equation 1, and may have a minimum B value of 30 nanometers to 120 nanometers (e.g., 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 105, 110, 115, 120 nanometers), 35 nanometers to 110 nanometers, or 40 nanometers to 100 nanometers in Equation 1. Within this range, the delay layer can easily reach the above ranges of the maximum ratio and the minimum ratio of Equation 1 and can be easily formed.

[0087] In one embodiment, there may be a difference of 45 nanometers or greater than 45 nanometers between the maximum skew delay and the minimum skew delay of the delay layer, such as 45 nanometers to 250 nanometers (45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 105, 110, 115, 120, 125, 130, 135, 140, 145, 150, 155, 160, 165, 170, 175, 180, 185, 190, 195, 200, 205, 210, 215, 220, 225, 230, 235, 240, 245, 250 nanometers), and the maximum skew delay and the minimum skew delay are measured at a wavelength of 550 nanometers when the delay layer rotates at an angle of +60° or -60° with the fast axis of the delay layer as the rotation axis. Within this range, the effects of the present invention can be easily achieved.

[0088] The delay layer may have a skew delay of 130 nanometers to 240 nanometers (e.g., 130, 135, 140, 145, 150, 155, 160, 165, 170, 175, 180, 185, 190, 195, 200, 205, 210, 215, 220, 225, 230, 235, 240 nanometers), 140 nanometers to 220 nanometers, or 150 nanometers to 200 nanometers, and the skew delay is measured at a wavelength of 550 nanometers when the delay layer rotates at an angle of +60° or -60° with the slow axis of the delay layer as the rotation axis. Within this range, the effects of the present invention can be easily achieved.

[0089] The retardation layer may have negative wavelength dispersion. In this way, the polarizer can easily provide the effect of reducing the reflectance at the front and side surfaces of the polarizer. Here, the "negative wavelength dispersion" of the retardation layer means that the retardation layer satisfies the relationships: Re(450) < Re(550) and Re(550) < Re(650). Re(450), Re(550), and Re(650) respectively represent the in-plane retardation values of the retardation layer at wavelengths of 450 nm, 550 nm, and 650 nm.

[0090] In one embodiment, the retardation layer may have a Re(450) / Re(550) value less than 1, such as from 0.82 to less than 1 (0.82, 0.83, 0.84, 0.85, 0.86, 0.87, 0.88, 0.89, 0.9, 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98, or 0.99). In one embodiment, the retardation layer may have a Re(650) / Re(550) value greater than 1, such as from greater than 1 to 1.18 (1.01, 1.02, 1.03, 1.04, 1.05, 1.06, 1.07, 1.08, 1.09, 1.10, 1.11, 1.12, 1.13, 1.14, 1.15, 1.16, 1.17, 1.18). Within this range, the retardation layer can easily achieve wavelength dispersion.

[0091] In one embodiment, the retardation layer may have an in-plane retardation of 90 nm to 170 nm (e.g., 100 nm to 160 nm) at a wavelength of 450 nm, and an in-plane retardation of 110 nm to 200 nm (e.g., 120 nm to 190 nm) at a wavelength of 650 nm.

[0092] In one embodiment, the retardation layer may be a single-layer retardation layer. Here, the "single-layer retardation layer" means that the retardation layer is composed of a single layer having the same composition, rather than a laminate formed by two or more retardation layers having different in-plane retardation values (which is formed by lamination or direct stacking). In this way, even with a single-layer retardation layer stacked on the lower surface of the polarizer (e.g., between the lower surface of the polarizer and the optical display panel) and satisfying Equation 1, the polarizer according to the present invention also provides good effects in reducing the reflectance at the front and side surfaces of the polarizer and reducing the difference in reflectance between the front and side surfaces of the polarizer, thereby achieving a reduction in the thickness of the polarizer, simplification of the manufacturing process, and economic feasibility.

[0093] In one embodiment, the retardation layer may have a thickness of 1 μm to 10 μm (e.g., 2 μm to 8 μm). Within this range, the polarizer can have a reduced thickness.

[0094] The retardation layer may be an O-plate type liquid crystal layer. The polarizing plate according to the present invention includes an O-plate type liquid crystal layer as the retardation layer, wherein the maximum ratio and the minimum ratio of Equation 1 of the O-plate type liquid crystal layer are adjusted to provide the effects of reducing the reflectance at the front and side surfaces and reducing the reflectance difference between the front and side surfaces.

[0095] Here, the O-plate type means that the liquid crystal compound is aligned in the thickness direction of the retardation layer such that the liquid crystal tilt angle of the liquid crystal compound is formed in the skew direction, and assuming that one surface of the retardation layer in the thickness direction is the top surface and the other surface of the retardation layer opposite to the top surface is the bottom surface, the liquid crystal tilt angle gradually increases or gradually decreases from the top surface to the bottom surface. Here, the skew direction means a direction that is not substantially parallel to the top surface or the bottom surface of the retardation layer and / or a direction that is not substantially perpendicular to the top surface or the bottom surface of the retardation layer.

[0096] Figure 1 is a cross-sectional view of an O-plate type retardation layer, which shows that the retardation layer (10) has a liquid crystal tilt angle (θ P 、θ B ) that gradually decreases from the top surface (11) to the bottom surface (12).

[0097] In one embodiment, the liquid crystal tilt angle of the retardation layer on the top surface may be greater than the liquid crystal tilt angle on the bottom surface, and may have a liquid crystal tilt angle of 30° to 90° (for example, 30°, 35°, 40°, 45°, 50°, 55°, 60°, 65°, 70°, 75°, 80°, 85°, 90°) or 40° to less than 90° on its top surface and may have a liquid crystal tilt angle of 0° to 10° (for example, 0°, 1°, 2°, 3°, 4°, 5°, 6°, 7°, 8°, 9°, 10°), 0° to 5° or greater than 0° to 5° on its bottom surface.

[0098] In another embodiment, the liquid crystal tilt angle of the retardation layer on the top surface may be less than the liquid crystal tilt angle on the bottom surface, and may have a liquid crystal tilt angle of 0° to 10° (for example, 0°, 1°, 2°, 3°, 4°, 5°, 6°, 7°, 8°, 9°, 10°), 0° to 5° or greater than 0° to 5° on its top surface and may have a liquid crystal tilt angle of 30° to 90° (for example, 30°, 35°, 40°, 45°, 50°, 55°, 60°, 65°, 70°, 75°, 80°, 85°, 90°) or 40° to less than 90° on its bottom surface.

[0099] In one embodiment, as Figure 1As shown, the top surface of the retardation layer may be closer to the polarizer (30) than the bottom surface of the retardation layer. In the retardation layer, the tilt angle of the liquid crystal on the top surface may be greater than the tilt angle of the liquid crystal on the bottom surface. In this way, the effects of the present invention can be achieved more easily.

[0100] In one embodiment, the range of the absolute difference between the tilt angle of the liquid crystal on the top surface and the tilt angle of the liquid crystal on the bottom surface may be between 30° and 90° (e.g., 30°, 35°, 40°, 45°, 50°, 55°, 60°, 65°, 70°, 75°, 80°, 85°, 90°) or 40° to 80°. Within this range, the effects of the present invention can be achieved more easily.

[0101] As used herein, the "tilt angle of the liquid crystal" may have a meaning substantially the same as that defined by those skilled in the art. For example, the tilt angle of the liquid crystal may be measured inside the retardation layer and refers to the tilt alignment angle of the liquid crystal in the thickness direction of the retardation layer, and the tilt alignment angle gradually changes from the top surface of the retardation layer to the bottom surface of the retardation layer. When the tilt alignment angle is parallel to the top surface or the bottom surface of the retardation layer, the tilt angle of the liquid crystal is defined as 0°.

[0102] The tilt angle of the liquid crystal may be represented by a positive (+) or negative (-) value, depending on whether the tilt angle of the liquid crystal corresponds to the direction of the maximum refractive index of the liquid crystal compound relative to one surface of the layer adjacent to the retardation layer. Here, for convenience, the tilt angle of the liquid crystal will be described as a positive (+) value. As an alternative, the tilt angle of the liquid crystal may be a negative (-) value. For example, when the tilt angle of the liquid crystal is 60°, it means -60°.

[0103] Referring to Figure 2 , the tilt angle of the liquid crystal is defined as the angle of the direction of the maximum refractive index of the liquid crystal compound relative to one surface of the retardation layer. As in θ1, when the angle of the direction of the maximum refractive index of the liquid crystal compound relative to the one surface of the layer adjacent to the retardation layer corresponds to the counterclockwise direction, the angle is defined as a positive (+) value. As in θ2, when the angle of the direction of the maximum refractive index of the liquid crystal compound relative to the one surface of the layer adjacent to the retardation layer corresponds to the clockwise direction, the angle is defined as a negative (-) value.

[0104] The tilt angle of the liquid crystal can be measured by typical methods known to those skilled in the art. For example, the tilt angle of the liquid crystal can be measured by a liquid crystal tilt angle meter such as Exensor or Kobra.

[0105] In one embodiment, the retardation layer may have an asymmetric skew retardation, which is measured when the retardation layer is mounted on a retardometer and rotated by an angle of +60° or -60° about the fast axis of the retardation layer. Such a structure can help achieve the effects of the present invention. This structure will be described with reference to Figure 3 as follows.

[0106] Figure 3 is a graph showing the trend of the ratio of the skew retardation to the forward retardation of the retardation layer of a polarizing plate according to an embodiment of the present invention, where the skew retardation and the forward retardation are measured when the retardation layer is rotated by an angle of ±60°.

[0107] In Figure 3 , the X-axis represents the rotation angle (°) of the retardometer, and the Y-axis represents the relative value (skew retardation / forward retardation) of the skew retardation (nanometers) to the forward retardation (nanometers). In Figure 3 , the solid line represents the relative value of the retardation layer rotated about the fast axis of the retardation layer, and the dashed line represents the relative value of the retardation layer rotated about the slow axis of the retardation layer. Figure 3 is obtained from the measurement results of the retardation layer in the following examples.

[0108] Referring to Figure 3 , in the graph where the X-axis represents the rotation angle (°) of the retardometer and the Y-axis represents the relative value (skew retardation / forward retardation) of the skew retardation (nanometers) to the forward retardation (nanometers), it can be seen that when measuring the relative value while rotating the retardation layer about the fast axis of the retardation layer, the retardation layer has an asymmetric relative value, and when measuring the relative value while rotating the retardation layer about the slow axis of the retardation layer, the retardation layer has a symmetric relative value.

[0109] Figure 3 shows the relative value at a wavelength of 550 nm, but is not limited thereto.

[0110] In one embodiment, the retardation layer may be a liquid crystal layer or a non-liquid crystal layer. For example, the retardation layer may be a liquid crystal layer to provide an O-plate type liquid crystal retardation layer.

[0111] In one embodiment, the retardation layer may be formed of a composition containing a liquid crystal compound. For example, the retardation layer may be formed of a composition capable of achieving a nematic liquid crystal. When the retardation layer is rotated by +60° or -60° about the fast axis of the retardation layer, the nematic liquid crystal causes the skew retardation of the retardation layer to be as Figure 3The asymmetry shown in [Figure] enables the ratio of Equation 1 within the desired range of the present invention to be easily achieved. Here, even for a composition capable of achieving a nematic liquid crystal, a retardation layer satisfying the ratio of Equation 1 according to the present invention can be achieved by adjusting the solvent evaporation rate (e.g., air volume), and / or drying temperature, and / or the irradiation amount of UV light during the photocuring of the coating formed from the composition.

[0112] In one embodiment, the composition capable of achieving a nematic liquid crystal may include a polymerizable compound.

[0113] The polymerizable compound may have at least one polymerizable crosslinking group. For example, the polymerizable crosslinking group may include an acrylate group, a methacrylate group, a vinyl group, a vinyloxy group, an epoxy group, an oxetanyl group, a thiol group, a maleimide group, or a derivative thereof. Specifically, the polymerizable crosslinking group may include at least one selected from Formulas R-1 to R-15:

[0114]

[0115] The composition may further contain a liquid crystal compound. Although the liquid crystal compound does not have a polymerizable crosslinking group, the liquid crystal compound also promotes the formation of the retardation layer.

[0116] The composition may further contain typical additives for achieving a liquid crystal layer, such as a photoinitiator, a surface modifier, an antioxidant, and similar additives. The composition may contain a solvent to facilitate the formation of a liquid crystal layer having a uniform surface.

[0117] When the optical transmission axis of the polarizer is set to 0°, the slow axis of the retardation layer (e.g., the slow axis of the O-plate type liquid crystal retardation layer) is inclined at an angle of 40° to 50° (e.g., 40°, 41°, 42°, 43°, 44°, 45°, 46°, 47°, 48°, 49°, 50°) or 43° to 47° with respect to the optical transmission axis of the polarizer. Within this range, the effects of the present invention can be more easily achieved.

[0118] A retardation layer (e.g., an O-plate type liquid crystal retardation layer) can be formed from a composition containing a composition including the above liquid crystal compound. According to the present invention, in order to satisfy the minimum ratio of 1.1 to 1.8 and the minimum ratio of 0.3 to 0.7 calculated according to Equation 1, the irradiation amount of UV light, the drying temperature, the air volume, etc. are adjusted in the formation of the retardation layer. Here, it can be seen that the solvent evaporation rate may significantly affect the liquid crystal tilt angle on the top surface. It can be seen that the solvent evaporation rate and the liquid crystal tilt angle generally increase as the drying temperature and the air volume increase. The liquid crystal tilt angle on the bottom surface is related to the anchoring energy and can be adjusted according to the photo-alignment or rubbing conditions. Generally, the liquid crystal tilt angle on the bottom surface increases as the anchoring energy increases.

[0119] In one embodiment, the retardation layer can be composed only of an O-plate type liquid crystal retardation layer. This means that only an O-plate type liquid crystal retardation layer having a positive in-plane retardation greater than 0 nm (e.g., greater than 10 nm) at a wavelength of 550 nm exists on the lower surface of the polarizer. Here, the O-plate type liquid crystal retardation layer can be directly stacked on the lower surface of the polarizer, or can be stacked on the lower surface of the polarizer through an adhesive layer or a bonding layer.

[0120] In another embodiment, the polarizing plate may further include a first protective layer on the lower surface of the polarizer.

[0121] In one embodiment, the polarizing plate may include a first protective layer and an O-plate type liquid crystal retardation layer sequentially stacked on the lower surface of the polarizer.

[0122] In another embodiment, the polarizing plate may include an O-plate type liquid crystal retardation layer and a first protective layer sequentially stacked on the lower surface of the polarizer.

[0123] The first protective layer can provide additional functions for the retardation layer and / or the polarizing plate. For example, the first protective layer can improve the durability and mechanical strength of the retardation layer by supplementing the thickness of the thin O-plate type liquid crystal retardation layer. As an alternative, the first protective layer can be a base film for the O-plate type liquid crystal retardation layer. Additionally, the first protective layer can prevent the retardation layer and / or the panel from being contaminated by iodine that may elute from the polarizer after the polarizing plate is placed in high temperature / high humidity conditions for a long time.

[0124] The first protective layer is an optically transparent film and can be a film formed of at least one resin selected from, for example, cellulose-based ester resins including triacetylcellulose (TAC), polyester-based resins including polyethylene terephthalate (PET), polyethylene naphthalate, polybutylene naphthalate, etc., cyclic polyolefin-based resins, polycarbonate-based resins, polyethersulfone-based resins, polysulfone-based resins, polyamide-based resins, polyimide-based resins, polyolefin-based resins, polyacrylate-based resins, polyvinyl alcohol-based resins, polyvinyl chloride-based resins, and polyvinylidene chloride-based resins.

[0125] In one embodiment, the first protective layer may have a positive in-plane retardation of 10 nanometers or less than 10 nanometers (e.g., 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 nanometers) or 0 nanometers to 5 nanometers at a wavelength of 550 nanometers. Within this range, the first protective layer can ensure its inherent effect without affecting the effect of the O-plate type liquid crystal retardation layer for reducing the reflectance on the front and side surfaces of the polarizing plate.

[0126] The first protective layer may have a thickness of 5 micrometers to 100 micrometers (e.g., 15 micrometers to 45 micrometers). Within this range, the first protective layer can be used in a polarizing plate.

[0127] For example, a retardation layer can be formed by coating a composition containing a liquid crystal compound on the first protective layer and then drying and curing the composition. Here, the composition can be coated on the surface of the first protective layer where the alignment of the liquid crystal compound is achieved to form an alignment layer. The alignment layer can be formed by typical methods known to those skilled in the art. For example, the alignment layer can be an acrylic-based alignment layer. The laminate formed of the O-plate type liquid crystal layer and the first protective layer can be coupled to a polarizer.

[0128] In another embodiment, a retardation layer can be formed by coating a composition containing a liquid crystal compound on a base film and then drying and curing the composition. Here, the composition can be coated on the surface of the base film where the alignment of the liquid crystal compound is achieved to form an alignment layer. The alignment layer can be formed by typical methods known to those skilled in the art. For example, the alignment layer can be an acrylic-based alignment layer. The laminate formed of the O-plate type liquid crystal layer and the base film can be coupled to a polarizer.

[0129] An adhesive layer or a bonding layer can be stacked on the lower surface of the retardation layer so that the polarizing plate can be adhesively bonded to the panel through the adhesive layer or the bonding layer.

[0130] The polarizing plate may further include a second protective layer located on the upper surface of the polarizer. The second protective layer can be stacked on the upper surface of the polarizer singly or in multiple layers.

[0131] Second protective layer

[0132] The second protective layer is used to protect the polarizer from the external environment while improving the mechanical strength of the polarizing plate. The second protective layer may include a protective film and / or a protective coating.

[0133] The second protective layer may be an optically transparent film formed of at least one selected from, for example, cellulose-based resins including triacetyl cellulose (TAC), polyester-based resins including polyethylene terephthalate (PET), polybutylene terephthalate, polyethylene naphthalate (PEN), polybutylene naphthalate, etc., cycloolefin polymer (COP)-based resins, cycloolefin copolymer (COC)-based resins, polycarbonate-based resins, polyethersulfone-based resins, polysulfone-based resins, polyamide-based resins, polyimide-based resins, polyolefin-based resins, polyarylate-based resins, polyvinyl alcohol-based resins, polyvinyl chloride-based resins, and polyvinylidene chloride-based resins.

[0134] The second protective layer may have a positive retardation of 0 nm or greater than 0 nm (e.g., 0 nm to 10,000 nm) at a wavelength of 550 nm. Within this range, the effects of the present invention can be more easily achieved.

[0135] The polarizing plate may further include a functional coating on at least one surface of the second protective layer. For example, the functional coating may include an antireflection layer, a low reflectivity layer, a hard coating layer, an anti-fingerprint layer, an anti-glare layer, a primer layer, etc.

[0136] The second protective layer may have a thickness of 5 μm to 100 μm (specifically 15 μm to 90 μm). Within this range, the second protective layer can be used in the polarizing plate.

[0137] The polarizing plate may further include a third protective layer on the lower surface of the polarizer. The third protective layer may be stacked on the lower surface of the polarizer singly or in multiple layers. In one embodiment, the third protective layer may be sandwiched between the polarizer and the retardation layer, or may be provided on the lower surface of the retardation layer.

[0138] Third protective layer

[0139] The third protective layer may be an optically transparent film formed of at least one selected from, for example, cellulose-based resins including triacetyl cellulose (TAC), polyester-based resins including polyethylene terephthalate (PET), polybutylene terephthalate, polyethylene naphthalate (PEN), polybutylene naphthalate, etc., cyclic polyolefin-based resins, polycarbonate-based resins, polyethersulfone-based resins, polysulfone-based resins, polyamide-based resins, polyimide-based resins, polyolefin-based resins, polyarylate-based resins, polyvinyl alcohol-based resins, polyvinyl chloride-based resins, and polyvinylidene chloride-based resins.

[0140] In one embodiment, the third protective layer may have a positive retardation of 10 nm or more than 10 nm (e.g., 0 nm to 5 nm) at a wavelength of 550 nm. Within this range, the third protective layer can ensure its inherent effects without affecting the effects of the O-plate type liquid crystal retardation layer for reducing the reflectance on the front and side surfaces of the polarizing plate.

[0141] The third protective layer may have a thickness of 5 μm to 100 μm (specifically 15 μm to 45 μm). Within this range, the third protective layer can be used in the polarizing plate.

[0142] The material, retardation, and / or thickness of the third protective layer may be the same as or different from those of the first protective layer.

[0143] Figures 4 to 9 is a cross-sectional view of a polarizing plate according to an embodiment of the present invention.

[0144] The polarizing plate may include a polarizer (30), an O-plate type liquid crystal retardation layer (10) stacked on the lower surface of the polarizer (30), and a second protective layer (20) stacked on the upper surface of the polarizer (30).

[0145] As another alternative, the polarizing plate may include: a polarizer (30); a first protective layer (40) and an O-plate type liquid crystal retardation layer (10) stacked on the lower surface of the polarizer (30) in the stated order; and a second protective layer (20) stacked on the upper surface of the polarizer (30).

[0146] As another alternative, the polarizing plate may include: a polarizer (30); an O-plate type liquid crystal retardation layer (10) and a first protective layer (40) stacked on the lower surface of the polarizer (30) in the stated order; and a second protective layer (20) stacked on the upper surface of the polarizer (30).

[0147] As another alternative, the polarizing plate may include: a polarizer (30); a third protective layer (50) and an O-plate type liquid crystal retardation layer (10) stacked on the lower surface of the polarizer (30) in the stated order; and a second protective layer (20) stacked on the upper surface of the polarizer (30).

[0148] Alternatively, the polarizing plate may include: a polarizer (30); a third protective layer (50), an O-plate type liquid crystal retardation layer (10), and a first protective layer (40), which are stacked on the lower surface of the polarizer (30) in the stated order; and a second protective layer (20), which is stacked on the upper surface of the polarizer (30).

[0149] Alternatively, the polarizing plate may include: a polarizer (30); a third protective layer (50), a first protective layer (40), and an O-plate type liquid crystal retardation layer (10), which are stacked on the lower surface of the polarizer (30) in the stated order; and a second protective layer (20), which is stacked on the upper surface of the polarizer (30).

[0150] Although not shown in Figures 4 to 9 , it is assumed that one surface of the O-plate type liquid crystal retardation layer in its thickness direction is the top surface, and the other surface opposite to the top surface is the bottom surface, and the liquid crystal tilt angle of the O-plate type liquid crystal retardation layer on the top surface is greater than that on the bottom surface. The top surface of the O-plate type liquid crystal retardation layer is placed closer to the polarizer than its bottom surface, or the bottom surface of the O-plate type liquid crystal retardation layer is placed closer to the polarizer than its top surface.

[0151] Although not shown in Figures 4 to 9 , the optical display panel may be stacked on the lower surface of the polarizing plate through an adhesive layer or a bonding layer to form an optical display device.

[0152] The optical display device according to the present invention includes a polarizing plate according to an embodiment of the present invention. The optical display device may include a light-emitting diode display, such as an organic light-emitting diode (OLED) display and a liquid crystal display.

[0153] In one embodiment, the organic light-emitting diode display may include an organic light-emitting diode panel including a flexible substrate and a polarizing plate according to the present invention stacked on the organic light-emitting diode panel. In another embodiment, the organic light-emitting diode display may include an organic light-emitting diode panel including a non-flexible substrate and a polarizing plate according to the present invention stacked on the organic light-emitting diode panel.

[0154] Ways to Implement the Present Invention

[0155] Next, the present invention will be described in more detail with reference to some examples. However, it should be noted that the provided examples are for illustrative purposes only and should not be construed as limiting the present invention in any way.

[0156] Example 1

[0157] A polarizer with a light transmittance of 45% was prepared by stretching a polyvinyl alcohol-based membrane (TS#20, thickness: 20 μm, Nippon Kuraray Co., Ltd.) to 6 times its original thickness in an aqueous iodine solution at 55°C.

[0158] An acrylic alignment film (HSPA-239, Nissan Chemical Co., Ltd.) was formed on the base film. An O-plate type retardation layer was formed by coating a composition for a nematic liquid crystal layer (RMM-2126, Merck) on the acrylic alignment layer to a predetermined thickness and then curing the composition at a predetermined temperature and air volume. The O-plate type retardation layer was removed from the base film. The O-plate type retardation layer was bonded to the lower surface of the prepared polarizer through a bonding layer, and a TAC film (KC2UAW, KONICA, positive retardation @550 nm: 3 nm) was bonded to the upper surface of the polarizer through a bonding layer, thereby preparing a polarizing plate formed by a TAC film - bonding layer - polarizer - bonding layer - O-plate type liquid crystal retardation layer.

[0159] The O-plate type retardation layer has negative wavelength dispersion. The top surface of the O-plate type retardation layer is placed closer to the polarizer than the bottom surface, and the slow axis of the O-plate type retardation layer is inclined at an angle of 45° with respect to the optical transmission axis of the polarizer. Details of the polarizing plate and the O-plate type liquid crystal retardation layer are shown in Table 1.

[0160] Examples 2 to 4

[0161] A polarizing plate was prepared in the same manner as in Example 1, except that the temperature and air volume for curing the composition were changed when forming the O-plate type liquid crystal retardation layer.

[0162] Comparative Examples 1 to 4

[0163] A polarizing plate was prepared in the same manner as in Example 1, except that the temperature and air volume for curing the composition were changed when forming the O-plate type liquid crystal retardation layer.

[0164] The retardation value of each of the retardation layer and the protective layer was measured at a wavelength of 550 nm using a retardometer (Exson).

[0165] The following properties of the polarizing plates of the examples and comparative examples were evaluated, and the evaluation results are shown in Table 1.

[0166] (1) In-plane retardation and skew retardation 1 of the O-plate type liquid crystal retardation layer 1 (unit: nanometers, @550 nanometers): For each of the retardation layers prepared in the examples and comparative examples, the in-plane retardation in the forward direction of the retardation layer was measured using Exson by transmitting light through the retardation layer in the normal direction of the in-plane direction of the retardation layer. The skew retardation 1 of each of the retardation layers prepared in the examples and comparative examples was measured using Exson by transmitting light through the retardation layer while rotating the retardation layer by ±60° around the fast axis of the retardation layer.

[0167] (2) Skew retardation 2 of the O-plate type liquid crystal retardation layer (unit: nanometers, @550 nanometers): The skew retardation 2 of each of the retardation layers prepared in the examples and comparative examples was measured using Exson by transmitting light through the retardation layer while rotating the retardation layer by ±60° around the slow axis of the retardation layer.

[0168] (3) Reflectance at the front and side surfaces: For each of the polarizing plates prepared in the examples and comparative examples, the reflectance in the direction providing the maximum reflectance was calculated by measuring the reflectance with respect to external light in all directions except the primary reflection using a simulation program (Techwiz 1D, Sanai System Co., Ltd., Korea).

[0169] [Table 1]

[0170]

[0171] * Reflectance difference: Lateral reflectance – Forward reflectance

[0172] As shown in Table 1, even with a single-layer type retardation layer, the polarizing plate according to the present invention ensures screen uniformity by providing excellent effects in reducing the reflectance at the front and side surfaces of the polarizing plate and reducing the reflectance difference between the front and side surfaces of the polarizing plate.

[0173] In contrast, the polarizing plates of the comparative examples that do not satisfy the maximum ratio and minimum ratio of Equation 1 according to the present invention cannot provide the effects of the present invention.

[0174] For each of the retardation layers used in the examples, while changing the rotation axis of the retardometer, the in-plane retardation in the forward direction and the skew retardation were measured at a wavelength of 550 nanometers using Exson. Here, the fast axis or slow axis of the retardation layer was set as the rotation axis. The relative value (ratio) of the skew retardation to the forward retardation was calculated, and the calculation results are shown in Table 2 and Table 3 and Figure 3 in.

[0175] [Table 2]

[0176]

[0177] [Table 3]

[0178]

[0179] [Table 4]

[0180]

[0181] [Table 5]

[0182]

[0183] As Figure 3 shown, it can be seen that the retardation layer included in the polarizing plate of the present invention has an asymmetric relative value according to the rotation angle with the fast axis as the rotation axis and a symmetric relative value according to the rotation angle with the slow axis as the rotation axis.

[0184] It should be understood that various modifications, changes, alterations and equivalent embodiments can be made by those skilled in the art without departing from the spirit and scope of the present invention.

Claims

1. A polarizing plate, comprising: A polarizer; And A retardation layer stacked on the lower surface of the polarizer, Wherein the retardation layer has a maximum ratio of 1.1 to 1.8 and a minimum ratio of 0.3 to 0.7 calculated according to the following Equation 1: [Equation 1] Ratio = B / A, (where A is the forward retardation (unit: nanometer) of the retardation layer at a wavelength of 550 nanometers; and B is the skew retardation (unit: nanometer) of the retardation layer, and the skew retardation is measured at a wavelength of 550 nanometers when the retardation layer is rotated by an angle of +60° or -60° with the fast axis of the retardation layer as the rotation axis).

2. The polarizing plate according to claim 1, wherein the retardation layer has an A value of 110 nanometers to 170 nanometers in Equation 1.

3. The polarizing plate according to claim 1, wherein the retardation layer has a maximum B value of 120 nanometers to 310 nanometers and a minimum B value of 20 nanometers to 120 nanometers in Equation 1.

4. The polarizing plate according to claim 1, wherein the difference between the maximum skew retardation and the minimum skew retardation of the retardation layer is 45 nanometers or greater than 45 nanometers, and the maximum skew retardation and the minimum skew retardation are measured at a wavelength of 550 nanometers when the retardation layer is rotated by an angle of +60° or -60° with the fast axis of the retardation layer as the rotation axis.

5. The polarizing plate according to claim 1, wherein the retardation layer has a skew retardation of 130 nanometers to 240 nanometers, and the skew retardation is measured at a wavelength of 550 nanometers when the retardation layer is rotated by an angle of +60° or -60° with the slow axis of the retardation layer as the rotation axis.

6. The polarizing plate according to claim 1, wherein the retardation layer has negative wavelength dispersion.

7. The polarizing plate according to claim 1, wherein the retardation layer has an asymmetric relative value in a graph, in which the X-axis represents the rotation angle (°) of a retardometer, and the Y-axis represents the relative value (skew retardation / forward retardation) of the skew retardation (nanometer) to the forward retardation (nanometer), and the skew retardation is measured with the fast axis of the retardation layer set as the rotation axis.

8. The polarizing plate according to claim 1, wherein the retardation layer has a symmetric relative value in a graph, in which the X-axis represents the rotation angle (°) of a retardometer, and the Y-axis represents the relative value (skew retardation / forward retardation) of the skew retardation (nanometer) to the forward retardation (nanometer), and the skew retardation is measured with the slow axis of the retardation layer set as the rotation axis.

9. The polarizing plate according to claim 1, wherein assuming that the optical transmission axis of the polarizer is set to 0°, the slow axis of the retardation layer is inclined at an angle of 40° to 50° with respect to the optical transmission axis of the polarizer.

10. The polarizing plate according to claim 1, wherein the retardation layer includes an O-plate type liquid crystal retardation layer.

11. The polarizing plate according to claim 10, wherein, Assume that one surface of the O-plate type liquid crystal retardation layer in the thickness direction of the O-plate type liquid crystal retardation layer is the top surface and the other surface of the O-plate type liquid crystal retardation layer opposite to the top surface is the bottom surface. Then, the liquid crystal tilt angle of the O-plate type liquid crystal retardation layer on the top surface is greater than the liquid crystal tilt angle on the bottom surface.

12. The polarizing plate according to claim 11, wherein the O-plate type liquid crystal retardation layer has a liquid crystal tilt angle of 30° to 90° on the top surface and a liquid crystal tilt angle of 0° to 10° on the bottom surface.

13. The polarizing plate according to claim 11, wherein the top surface is closer to the polarizer than the bottom surface.

14. The polarizing plate according to claim 11, wherein the absolute difference range between the liquid crystal tilt angle on the top surface and the liquid crystal tilt angle on the bottom surface is between 30° and 90°.

15. The polarizing plate according to claim 10, wherein the O-plate type liquid crystal retardation layer is a nematic liquid crystal layer.

16. The polarizing plate according to claim 10, wherein the retardation layer only includes the O-plate type liquid crystal retardation layer.

17. The polarizing plate according to claim 10, wherein the retardation layer includes the O-plate type liquid crystal retardation layer and a first protective layer.

18. The polarizing plate according to claim 17, wherein the first protective layer has a positive retardation of 10 nanometers or less than 10 nanometers at a wavelength of 550 nanometers.

19. The polarizing plate according to claim 1, further comprising: At least one of a second protective layer and a third protective layer, the second protective layer is on the upper surface of the polarizer, and the third protective layer is on the lower surface of the polarizer.

20. An optical display device, comprising the polarizing plate according to any one of claims 1 to 19.

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