Polarizing plate and stereoscopic image display device

Abstract

Disclosed are a polarizing plate and a stereoscopic image display device including the same. The polarizing plate includes: a polarizer; and a stack of a first negative wavelength dispersion retardation layer and a positive C retardation layer on at least one surface of the polarizer, and the stack has a biaxial degree of 0.1 to 0.5 at a wavelength of 450 nm, a biaxial degree of 0.2 to 0.6 at a wavelength of 550 nm, and a biaxial degree of 0.3 to 0.7 at a wavelength of 650 nm.

Description

[0001] Cross - reference to related applications

[0002] This application claims the priority and benefits of Korean Patent Application No. 10 - 2024 - 0002827, filed with the Korean Intellectual Property Office on January 8, 2024, the entire disclosure of which is incorporated herein by reference. Technical Field

[0003] Aspects of embodiments of the present invention relate to a polarizing plate and a stereoscopic image display device. Background Art

[0004] Recently, display devices that can display stereoscopic images instead of simply displaying images on a flat screen have received attention.

[0005] Conventional stereoscopic image display devices use pancake lenses. However, the resolution of the stereoscopic images provided by such devices is limited. Here, the resolution refers to the contrast ratio, that is, the luminance difference between the bright region and the dark region on the screen of the display device. It is desirable that such a stereoscopic image display device provides a wide lateral field of view.

[0006] The background art of the present invention is disclosed in Korean Patent Early Publication No. 10 - 2013 - 0103595 and similar disclosures. Summary of the Invention

[0007] According to one or more aspects of embodiments of the present invention, there is provided a polarizing plate for a stereoscopic image display device and a stereoscopic image display device including the polarizing plate, the polarizing plate capable of generating the same level of light output for each wavelength so that a user can perceive the same level of light output for each wavelength, capable of eliminating light leakage at the edge of the screen within the viewer's field of view, and capable of providing high resolution and a wide field of view.

[0008] According to one or more embodiments of the present invention, a polarizing plate includes: a polarizer; and a retardation layer stack composed of a first negative - wavelength - dispersion retardation layer and a positive C - retardation layer, laminated on at least one surface of the polarizer, wherein the retardation layer stack has a biaxiality of 0.1 to 0.5 at a wavelength of 450 nm, a biaxiality of 0.2 to 0.6 at a wavelength of 550 nm, and a biaxiality of 0.3 to 0.7 at a wavelength of 650 nm.

[0009] According to one or more embodiments of the present invention, a stereoscopic image display device includes: a display unit including a light - emitting device; a first polarizing plate; and a pancake lens assembly, wherein the first polarizing plate includes a polarizing plate according to an embodiment of the present invention.

[0010] Embodiments of the present invention provide a polarizing plate for a stereoscopic image display device and a stereoscopic image display device including the polarizing plate. The polarizing plate can generate the same level of light output for each wavelength so that a user can perceive the same level of light output for each wavelength, can eliminate light leakage at the edge of a screen within the viewing field of a viewer, and can provide high resolution and a wide viewing field. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 is a view showing the relationship between the optical axes of polarizing plates according to an embodiment.

[0012] Figure 2 is a cross-sectional view of a polarizing plate according to an embodiment.

[0013] Figure 3 is a cross-sectional view of a polarizing plate according to another embodiment.

[0014] Figure 4 is a cross-sectional view of a polarizing plate according to another embodiment.

[0015] Figure 5 is a schematic view of a stereoscopic image display device according to an embodiment.

[0016] Figure 6 is a view showing the axial relationship between a first polarizing plate and a retardation film of a pancake lens assembly according to an embodiment.

[0017] Figure 7 is a schematic view of a stereoscopic image display device according to another embodiment.

[0018] Figure 8 is a view showing the axial relationship between a first polarizing plate, a retardation film of a pancake lens assembly, and a third polarizing plate of the pancake lens assembly according to another embodiment.

[0019] Figure 9 is a cross-sectional view of a second polarizing plate according to an embodiment.

[0020] Figure 10 is a schematic view of a stereoscopic image display device according to another embodiment.

[0021] Figure 11 is a view showing the axial relationship between a first polarizing plate, a second polarizing plate, and a retardation film of a pancake lens assembly according to an embodiment.

[0022] REFERENCE NUMERAL DESCRIPTION

[0023] 1: User's eyes

[0024] 100: Display unit

[0025] 200: First polarizing plate

[0026] 210: First polarizer / polarizer

[0027] 211, 341, 411: Optical absorption axis

[0028] 220: First negative wavelength dispersion retardation layer / negative wavelength dispersion retardation layer

[0029] 221, 241, 321, 421, 441: Slow axis

[0030] 230: Positive C retardation layer

[0031] 240: Second negative wavelength dispersion retardation layer / negative wavelength dispersion retardation layer

[0032] 250, 450: Protective layer

[0033] 300, 300': Pancake lens assembly

[0034] 310: First lens

[0035] 320: Retardation film

[0036] 330: Reflective polarizer

[0037] 340: Third polarizer

[0038] 400: Second polarizing plate

[0039] 410: Second polarizer

[0040] 420: First retardation layer

[0041] 430: Positive C layer / positive C retardation layer

[0042] 440: Second retardation layer Detailed implementation manners

[0043] Some exemplary embodiments of the present invention will be described in more detail with reference to the accompanying drawings to facilitate the practice by those of ordinary skill in the art to which the present invention pertains. It should be understood that the present invention can be implemented in different ways and is not limited to the following embodiments. In the drawings, parts irrelevant to this description may be omitted for clarity. Throughout the specification, the same components will be denoted by the same reference numerals. The lengths, sizes, and similar properties of the components in the drawings are for illustrative purposes of the present invention, but the present invention is not limited thereto.

[0044] The terms used herein are for the purpose of describing some exemplary embodiments and are not intended to limit the present invention. Unless the context clearly indicates otherwise, the singular forms "a (and an)" and "the" used herein are also intended to include the plural forms.

[0045] In this text, spatial relative terms such as "upper" and "lower" are defined with reference to the accompanying drawings. Therefore, it should be understood that the term "upper surface" can be used interchangeably with the term "lower surface", and when an element such as a layer or a film is said to be placed "on" another element, the element can be placed directly on the other element, or there may be an intermediate element. On the other hand, when an element is said to be placed "directly" "on" another element, there is no intermediate element therebetween.

[0046] In this text, the "in-plane retardation Re", the "out-of-plane retardation Rth", and the "degree of biaxiality NZ" are represented by the following Equation A, Equation B, and Equation C respectively:

[0047] Re = (nx – ny) × d, ----(A);

[0048] Rth = ((nx + ny) / 2 - nz) × d, ----(B);

[0049] NZ = (nx - nz) / (nx - ny), ----(C),

[0050] where nx, ny, and nz are the refractive indices measured in the slow axis direction, fast axis direction, and thickness direction of the corresponding optical element at the measurement wavelength, respectively, and d is the thickness of the corresponding optical element (unit: nanometer (nm)).

[0051] In this text, the "slow axis" refers to the axis along which the refractive index of the optical element reaches the maximum level in the in-plane light direction, and the "fast axis" refers to the axis along which the refractive index of the optical element reaches the minimum level in the in-plane light direction.

[0052] In Equations A to C, the "optical element" can be a retardation layer, a protective layer, or a retardation layer stack. In Equations A to C, the "measurement wavelength" can be 450 nm, 550 nm, or 650 nm.

[0053] In this text, the "short-wavelength dispersion" refers to Re(450) / Re(550), and the "long-wavelength dispersion" refers to Re(650) / Re(550), where Re(450), Re(550), and Re(650) are the in-plane retardations (Re) of the retardation layer at wavelengths of about 450 nm, 550 nm, and 650 nm, respectively.

[0054] In this text, the "negative wavelength dispersion" means that the short-wavelength dispersion < 1 and the long-wavelength dispersion > 1.

[0055] In this document, a "positive C retardation layer" means that the corresponding layer has a refractive index relationship of nz > nx ≒ ny.

[0056] In this document, "crossed transmittance (Tc)" is the average value of the values measured on polarized light passing through polarizers arranged perpendicular to each other at wavelengths from 380 nm to 780 nm.

[0057] The expression "X to Y" used in this document to represent a specific numerical range means "greater than or equal to X and less than or equal to Y (X ≤ and ≤ Y)".

[0058] Disclosed in this document is a polarizer for a stereoscopic image display device, which can generate the same level of light output for each wavelength so that a user can perceive the same level of light output for each wavelength, can eliminate light leakage at the screen edge in the viewer's field of view, and can provide high resolution. Specifically, when used as a polarizer of a stereoscopic image display device including a pancake lens assembly, the polarizer according to the present invention can improve contrast and resolution, and can eliminate light leakage occurring at the screen edge in the viewer's field of view.

[0059] In addition, when used in a stereoscopic image display device, the polarizer of the present invention can provide a wide field of view (FOV). Using a negative wavelength dispersion retardation film to provide a wide field of view can cause light leakage and ghost images to occur at the sides of the screen due to a decrease in ellipticity at the sides of the screen. The polarizer of the present invention can avoid these problems, thereby broadening the field of view where no light leakage and ghost images appear.

[0060] According to one aspect of one or more embodiments of the present invention, a polarizer includes: a polarizer; and a retardation layer stack composed of a first negative wavelength dispersion retardation layer and a positive C retardation layer, laminated on at least one surface of the polarizer, wherein the retardation layer stack has a biaxiality of 0.1 to 0.5 at a wavelength of 450 nm, a biaxiality of 0.2 to 0.6 at a wavelength of 550 nm, and a biaxiality of 0.3 to 0.7 at a wavelength of 650 nm.

[0061] In one or more embodiments, the retardation layer stack may have different biaxialities at a wavelength of 450 nm, at a wavelength of 550 nm, and at a wavelength of 650 nm, respectively.

[0062] A stack composed of a first negative wavelength dispersion retardation layer and a positive C retardation layer

[0063] If the biaxiality of the retardation layer stack at a wavelength of 450 nm is less than 0.1 or exceeds 0.5, a blue ghost image may be perceived due to the leakage of short-wavelength light at the edge of the screen within the viewer's field of view. For example, the retardation layer stack may have a biaxiality of 0.1 to 0.4 or 0.2 to 0.4 at a wavelength of 450 nm. Within this range, the retardation layer stack can more effectively provide the desired effects of the present invention.

[0064] If the biaxiality of the retardation layer stack at a wavelength of 550 nm is less than 0.2 or exceeds 0.6, a green ghost image may be perceived due to the leakage of medium-wavelength light at the edge of the screen within the viewer's field of view. For example, the retardation layer stack may have a biaxiality of 0.2 to 0.5 or 0.3 to 0.5 at a wavelength of 550 nm. Within this range, the retardation layer stack can more effectively provide the desired effects of the present invention.

[0065] If the biaxiality of the retardation layer stack at a wavelength of 650 nm is less than 0.3 or exceeds 0.7, a red ghost image may be perceived due to the leakage of long-wavelength light at the edge of the screen within the viewer's field of view. For example, the retardation layer stack may have a biaxiality of 0.3 to 0.6 or 0.3 to 0.5 at a wavelength of 650 nm. Within this range, the retardation layer stack can more effectively provide the desired effects of the present invention.

[0066] According to an embodiment, by adjusting the in-plane retardation and out-of-plane retardation of the retardation layer stack, the biaxiality of the retardation layer stack at wavelengths of 450 nm, 550 nm, and 650 nm can be adjusted to the above ranges. The in-plane retardation and out-of-plane retardation of the retardation layer stack can be adjusted by adjusting the in-plane retardation and / or out-of-plane retardation of the first negative wavelength dispersion retarder and / or the positive C retarder layer of the retardation layer stack.

[0067] The retardation layer stack has negative wavelength dispersion, and in an embodiment, may have an in-plane retardation of 112 nm to 132 nm (e.g., 117 nm to 127 nm) at a wavelength of 450 nm, an in-plane retardation of 130 nm to 150 nm (e.g., 136 nm to 146 nm) at a wavelength of 550 nm, and an in-plane retardation of 133 nm to 153 nm (e.g., 138 nm to 148 nm) at a wavelength of 650 nm. Within these ranges, the retardation layer stack can have a biaxiality within the above ranges.

[0068] In an embodiment, the retardation layer stack may have an out-of-plane retardation of -70 nm to -10 nm (e.g., -60 nm to -30 nm) at a wavelength of 450 nm, an out-of-plane retardation of -55 nm to 5 nm (e.g., -45 nm to -10 nm) at a wavelength of 550 nm, and an out-of-plane retardation of -40 nm to 15 nm (e.g., -25 nm to 5 nm) at a wavelength of 650 nm. Within these ranges, the retardation layer stack may have a biaxiality within the above ranges.

[0069] According to another embodiment, by adjusting the in-plane retardation and / or out-of-plane retardation and / or biaxiality of the first negative wavelength dispersion retardation layer and / or the positive C layer of the retardation layer stack, the biaxiality of the retardation layer stack at a wavelength of 450 nm, at a wavelength of 550 nm, and at a wavelength of 650 nm can be adjusted to the above ranges.

[0070] In an embodiment, the first negative wavelength dispersion retardation layer may have an in-plane retardation of 115 nm to 125 nm (e.g., 119 nm to 123 nm) at a wavelength of 450 nm, an in-plane retardation of 135 nm to 145 nm (e.g., 139 nm to 143 nm) at a wavelength of 550 nm, and an in-plane retardation of 140 nm to 150 nm (e.g., 142 nm to 146 nm) at a wavelength of 650 nm. Within these ranges, the retardation layer stack may have a biaxiality within the above ranges.

[0071] In an embodiment, the first negative wavelength dispersion retardation layer may have an out-of-plane retardation of 40 nm to 60 nm (e.g., 50 nm to 60 nm) at a wavelength of 450 nm, an out-of-plane retardation of 50 nm to 70 nm (e.g., 55 nm to 70 nm) at a wavelength of 550 nm, and an out-of-plane retardation of 60 nm to 75 nm (e.g., 65 nm to 75 nm) at a wavelength of 650 nm. Within these ranges, the retardation layer stack may have a biaxiality within the above ranges.

[0072] In an embodiment, the first negative wavelength dispersion retardation layer may have a biaxiality of 0.82 to 1.02 (e.g., 0.91 to 1.00) at a wavelength of 450 nm, a biaxiality of 0.84 to 1.02 (e.g., 0.88 to 1.00) at a wavelength of 550 nm, and a biaxiality of 0.90 to 1.04 (e.g., 0.95 to 1.03) at a wavelength of 650 nm. Within these ranges, the retardation layer stack may have a biaxiality within the above ranges.

[0073] In an embodiment, the positive C retardation layer may have an in-plane retardation of -3 nm to 7 nm (e.g., -2 nm to 4 nm) at a wavelength of 450 nm, an in-plane retardation of -5 nm to 5 nm (e.g., -3 nm to 3 nm) at a wavelength of 550 nm, and an in-plane retardation of -7 nm to 3 nm (e.g., -4 nm to 2 nm) at a wavelength of 650 nm. Within these ranges, the retardation layer stack may have a biaxiality within the above ranges.

[0074] The positive C retardation layer has a negative out-of-plane retardation at a wavelength of 450 nm, a wavelength of 550 nm, and a wavelength of 650 nm, and in an embodiment, may have an out-of-plane retardation of -120 nm to -70 nm (e.g., -110 nm to -70 nm) at a wavelength of 450 nm, an out-of-plane retardation of -105 nm to -65 nm (e.g., -100 nm to -70 nm) at a wavelength of 550 nm, and an out-of-plane retardation of -100 nm to -60 nm (e.g., -95 nm to -65 nm or -95 nm to -70 nm) at a wavelength of 650 nm. Within these ranges, the retardation layer stack may have a biaxiality within the above ranges.

[0075] In an embodiment, the positive C retardation layer may have positive wavelength dispersion, and the positive C retardation layer can thus effectively provide the desired effects of the present invention. Herein, "positive wavelength dispersion" means that the positive C retardation layer satisfies the following Equation 1:

[0076] |R th (450)| > |R th (550)| > |R th (650)|, ----(1),

[0077] where R th (450), R th (550), and R th (650) are the out-of-plane retardations of the positive C retardation layer measured at a wavelength of 450 nm, a wavelength of 550 nm, and a wavelength of 650 nm, respectively.

[0078] For example, the ratio of |R th (450)| to |R th (550)| (|R th (450)| / |R th (550)|) may be in the range of 1.01 to 1.14 (e.g., 1.01 to 1.09), and the ratio of |R th (650)| to |R th (550)| (|R th (650)| / |R th(550)|) can range from 0.92 to 0.99 (for example, from 0.94 to 0.99). Within these ranges, the positive C delay layer can effectively provide the desired effects of the present invention.

[0079] In an embodiment, the first negative wavelength dispersion delay layer can have a short wavelength dispersion of 0.81 to 0.88 and a long wavelength dispersion of 1.01 to 1.10. Within these ranges, when used in a stereoscopic image display device, the polarizing plate can effectively eliminate or reduce light leakage and provide high resolution. For example, the first negative wavelength dispersion delay layer can have a short wavelength dispersion of 0.81 to 0.86 or 0.81 to 0.84 and a long wavelength dispersion of 1.01 to 1.07 or 1.01 to 1.04.

[0080] In an embodiment, the first negative wavelength dispersion delay layer can have a thickness of 1 μm to 40 μm (for example, 1.5 μm to 35 μm). Within this range, the first negative wavelength dispersion delay layer can be used in a polarizing plate.

[0081] According to an embodiment, the first negative wavelength dispersion delay layer can include a liquid crystal layer or a non-liquid crystal layer. The liquid crystal layer and the non-liquid crystal layer can be formed of any suitable material capable of meeting the wavelength dispersion and delay requirements of the first negative wavelength dispersion delay layer.

[0082] In some embodiments, the first negative wavelength dispersion delay layer can be a liquid crystal layer or a non-liquid crystal layer.

[0083] In an embodiment, the first negative wavelength dispersion delay layer can include a liquid crystal layer. For example, the liquid crystal layer can contain a cured product of a liquid crystal composition, and the liquid crystal composition includes at least one of a nematic liquid crystal, a smectic liquid crystal, a discotic liquid crystal, or a cholesteric liquid crystal. In an embodiment, the first negative wavelength dispersion delay layer can further include an alignment film to facilitate the alignment of the liquid crystal in the liquid crystal layer. Here, the liquid crystal layer and the alignment film can be easily manufactured by typical methods known to those skilled in the art.

[0084] The first negative wavelength dispersion delay layer can further include an optical film.

[0085] The optical film can facilitate the formation of the first negative wavelength dispersion delay layer without affecting the delay characteristics of the first negative wavelength dispersion delay layer. In an embodiment, the optical film can have an in-plane delay of 10 nm or less (for example, 0 nm to 5 nm) at a wavelength of 550 nm. Within this range, the optical film can have no effect on the delay characteristics of the first negative wavelength dispersion delay layer.

[0086] In an embodiment, the optical film may be a film comprising an optically transparent resin. For example, the resin may include at least one of the following: cellulose resins (e.g., triacetyl cellulose), polyester resins (e.g., polyethylene terephthalate (PET), polybutylene terephthalate, polyethylene naphthalate, and polybutylene naphthalate), cyclic olefin copolymer (COC) resins, cyclic olefin polymer (COP) resins, polycarbonate resins, polyethersulfone resins, polysulfone resins, polyamide resins, polyimide resins, polyolefin resins, polyarylate resins, polyvinyl alcohol resins, polyvinyl chloride resins, polyvinylidene chloride resins, or acrylic resins.

[0087] In another embodiment, the first negative wavelength dispersion retardation layer may include a non-liquid crystal layer.

[0088] For example, the non-liquid crystal layer may be a film obtained by uniaxially stretching the unstretched film in the machine direction (MD) or transverse direction (TD) of the unstretched film or by biaxially stretching the unstretched film in the MD and TD of the unstretched film. For example, the non-liquid crystal layer may be a coating.

[0089] In an embodiment, the unstretched film may include the optically transparent resin as described above.

[0090] For example, the non-liquid crystal layer may be a coating obtained by coating a composition comprising at least one of a cellulose-based compound or a polystyrene-based compound as a main component and then drying and / or curing the composition.

[0091] In an embodiment, the first negative wavelength dispersion retardation layer may further include an optical film.

[0092] The optical film may facilitate the formation of the coating without affecting the retardation characteristics of the first negative wavelength dispersion retardation layer. The optical film may be substantially the same as the above-described optical film and will not be described further herein.

[0093] The positive C retardation layer may be formed of any suitable material capable of meeting the wavelength dispersion and retardation requirements of the positive C retardation layer. The positive C retardation layer may include a liquid crystal layer or a non-liquid crystal layer. The liquid crystal layer and the non-liquid crystal layer may be the same as the above-described liquid crystal layer and non-liquid crystal layer.

[0094] According to an embodiment, in a polarizing plate, a first negative wavelength dispersion retardation layer may be disposed between a polarizer and a positive C retardation layer. With such a structure, the polarizing plate can provide a wide viewing angle as described above while improving the resolution.

[0095] According to an embodiment, the first negative wavelength dispersion retardation layer may be directly formed on the positive C retardation layer.

[0096] According to another embodiment, an adhesive layer, a bonding layer, or an adhesive bonding layer may also be formed between the first negative wavelength dispersion retardation layer and the positive C retardation layer.

[0097] In an embodiment, the polarizing plate may further include a second negative wavelength dispersion retardation layer.

[0098] Second negative wavelength dispersion retardation layer

[0099] When used in a stereoscopic image display device, the second negative wavelength dispersion retardation layer can ensure that the polarizing plate effectively eliminates light leakage and improves the resolution.

[0100] In an embodiment, the second negative wavelength dispersion retardation layer may have a short wavelength dispersion of 0.81 to 0.88 (e.g., 0.81 to 0.86 or 0.81 to 0.84). In an embodiment, the second negative wavelength dispersion retardation layer may have a long wavelength dispersion of 1.01 to 1.10 (e.g., 1.01 to 1.08 or 1.01 to 1.04). Within these ranges, the second negative wavelength dispersion retardation layer, together with the first negative wavelength dispersion retardation layer having the aforementioned wavelength dispersion characteristics, can help eliminate or reduce light leakage and improve the resolution.

[0101] In an embodiment, the short wavelength dispersion of the second negative wavelength dispersion retardation layer may have a value substantially the same as that of the first negative wavelength dispersion retardation layer, and the long wavelength dispersion of the second negative wavelength dispersion retardation layer may have a value substantially the same as that of the first negative wavelength dispersion retardation layer. Therefore, the second negative wavelength dispersion retardation layer can facilitate achieving the desired effects of the present invention. In particular, if the second negative wavelength dispersion retardation layer is disposed on both surfaces of the polarizer and the positive C retardation layer having the aforementioned wavelength dispersion characteristics is disposed on one surface of the polarizer, the polarizing plate can effectively provide the desired effects of the present invention.

[0102] In an embodiment, the second negative wavelength dispersion retardation layer may have an in-plane retardation of 115 nm to 125 nm (e.g., 119 nm to 123 nm) at a wavelength of 450 nm, an in-plane retardation of 135 nm to 145 nm (e.g., 139 nm to 143 nm) at a wavelength of 550 nm, and an in-plane retardation of 140 nm to 150 nm (e.g., 142 nm to 146 nm) at a wavelength of 650 nm. Within these ranges, the second negative wavelength dispersion retardation layer may have a short wavelength dispersion and a long wavelength dispersion falling within the above ranges.

[0103] In an embodiment, the second negative wavelength dispersion retardation layer may have an out-of-plane retardation of 50 nm to 80 nm (e.g., 55 nm to 75 nm) at a wavelength of 550 nm. Within this range, the second negative wavelength dispersion retardation layer may have an in-plane retardation within the above range while enabling the thickness of the polarizing plate to be reduced.

[0104] In an embodiment, the second negative wavelength dispersion retardation layer may have a biaxiality of 0.7 to 1.1 (e.g., 0.8 to 1.0) at a wavelength of 550 nm. Within this range, the second negative wavelength dispersion retardation layer may have an in-plane retardation within the above range while enabling the thickness of the polarizing plate to be reduced.

[0105] In an embodiment, the second negative wavelength dispersion retardation layer may have a thickness of 1 μm to 40 μm (e.g., 1.5 μm to 35 μm). Within this range, the second negative wavelength dispersion retardation layer can be used in a polarizing plate.

[0106] The second negative wavelength dispersion retardation layer can be formed of any suitable material that can meet the wavelength dispersion and retardation requirements of the second negative wavelength dispersion retardation layer. The second negative wavelength dispersion retardation layer may include a liquid crystal layer or a non-liquid crystal layer. The liquid crystal layer and the non-liquid crystal layer may be substantially the same as the above-mentioned liquid crystal layer and non-liquid crystal layer. The second negative wavelength dispersion retardation layer may also include the optical film as described above. The second negative wavelength dispersion retardation layer can be a liquid crystal layer or a non-liquid crystal layer.

[0107] According to an embodiment, the polarizing plate may have a structure in which a first negative wavelength dispersion retardation layer is disposed on one surface of the polarizer and a second negative wavelength dispersion retardation layer is disposed on the other surface of the polarizer. With this structure, the polarizing plate can eliminate or reduce light leakage and improve resolution.

[0108] In the polarizing plate, an axial relationship (e.g., a predetermined axial relationship) may exist between the polarizer, the first negative wavelength dispersion retardation layer, and the second negative wavelength dispersion retardation layer. According to an embodiment, the slow axis of the first negative wavelength dispersion retardation layer may be perpendicular to the slow axis of the second negative wavelength dispersion retardation layer. Therefore, the polarizing plate can effectively provide the desired effect of the present invention.

[0109] For example, the slow axis of the first negative wavelength dispersion retardation layer may be inclined at an angle of approximately 45° with respect to the light absorption axis of the polarizer, and the slow axis of the second negative wavelength dispersion retardation layer may be inclined at an angle of approximately 135° with respect to the light absorption axis of the polarizer.

[0110] In an embodiment, the slow axis of the first negative wavelength dispersion retardation layer may be inclined at an angle of approximately 135° with respect to the light absorption axis of the polarizer, and the slow axis of the second negative wavelength dispersion retardation layer may be inclined at an angle of approximately 45° with respect to the light absorption axis of the polarizer.

[0111] Polarizer

[0112] The polarizer linearly polarizes the circularly polarized light from the first negative wavelength dispersion retardation layer or the second negative wavelength dispersion retardation layer, and enables the linearly polarized light to exit the polarizer.

[0113] In an embodiment, the polarizer may have a cross-axis transmittance of 0.2% or less than 0.2% (e.g., 0% to 0.2%). Within this range, the polarizer can contribute to minimizing or reducing ghost images by enhancing the antireflection performance of the display device, in which the angular relationship between the slow axes is set as described above.

[0114] In an embodiment, the polarizer may have a polarization degree of 99% or greater than 99% (e.g., 99.99% to 100%) and a single light transmittance (Ts) of 42% or greater than 42% (e.g., 42% to 45%). Within these ranges of the polarization degree and the single light transmittance, the polarizer can have a significantly low reflectance when used in a polarizing plate. Here, the "single light transmittance" refers to the single light transmittance (Ts) measured in the visible spectrum (e.g., at wavelengths from 400 nm to 700 nm), and can be measured by typical methods known to those skilled in the art. Additionally, the "polarization degree" can be measured by typical methods known to those skilled in the art. In an embodiment, the polarizer may have a polarization degree of 99% to 99.9999% and a single light transmittance of 42% to 50%.

[0115] The light absorption axis of the polarizer may correspond to the stretching direction of the polyvinyl alcohol film when manufacturing the polarizer from the polyvinyl alcohol film, e.g., the machine direction (MD) of the polarizer. The polarizer may include a polyvinyl alcohol-based polarizer obtained by uniaxially stretching the polyvinyl alcohol film. In an embodiment, the polarizer can be manufactured by subjecting the polyvinyl alcohol film to a dyeing process, a stretching process, a crosslinking process, and a color correction process. By appropriately changing the conditions of the above dyeing process, stretching process, crosslinking process, and color correction process, a polarizer having a polarization degree and a light transmittance within the above ranges can be obtained.

[0116] In an embodiment, the polarizer may have a thickness of 5 μm to 40 μm. Within this range, the polarizer can be used in a polarizing plate.

[0117] The polarizing plate may further include a resin layer formed on at least one surface of the polarizer.

[0118] Resin layer

[0119] In an embodiment, the resin layer may be directly formed on at least one surface of the polarizer. Herein, the expression "directly formed" means that no other adhesive layer, bonding layer, and / or curable coating is formed between the polarizer and the resin layer. The resin layer can improve the effectiveness of the polarizing plate in eliminating or reducing ghost images by covering the fine surface irregularities of the polarizer. The resin layer may be a cured product of a composition including at least one of a thermosettable resin or an ultraviolet (UV) curable resin. Each of the thermosettable resin and the UV curable resin may be selected from typical thermosettable resins or UV curable resins known to those skilled in the art. For example, the resin layer may be a cured product of a composition including a (meth)acrylic resin. In an embodiment, the resin layer may be a hard coat, but is not limited thereto.

[0120] The polarizing plate may further include a stack formed of the resin layer and an optical film on at least one surface of the polarizer.

[0121] The stack formed of the resin layer and the optical film

[0122] The optical film can increase the mechanical strength of the polarizer, and the resin layer can improve the effectiveness of the polarizing plate in eliminating ghost images by covering the fine surface irregularities of the optical film.

[0123] The resin layer and the optical film may be substantially the same as the above-mentioned resin layer and optical film.

[0124] In an embodiment, the optical film and the resin layer may be sequentially stacked on the polarizer.

[0125] The polarizing plate may further include a protective layer.

[0126] Protective layer

[0127] The protective layer may be formed on one or both surfaces of the polarizer.

[0128] The protective layer can protect the polarizer and can improve the reliability and mechanical strength of the polarizing plate. If the desired mechanical properties of the polarizing plate can be ensured without the protective layer, the protective layer may be omitted.

[0129] The protective layer may include at least one of an optically transparent protective film or an optically transparent protective coating.

[0130] The protective film may include a film formed of at least one of the following: cellulose ester resin (e.g., triacetylcellulose (TAC)), cyclic polyolefin resin (e.g., amorphous cyclic olefin (COP)), polycarbonate resin, polyester resin (e.g., polyethylene terephthalate (PET)), polyethersulfone resin, polysulfone resin, polyamide resin, polyimide resin, acyclic polyolefin resin, poly(meth)acrylate resin (e.g., poly(methyl methacrylate)), polyvinyl alcohol resin, polyvinyl chloride resin, or polyvinylidene chloride resin, but not limited thereto.

[0131] The protective coating may be formed of a photoactinic radiation-curable resin composition containing a photoactinic radiation-curable compound and a polymerization initiator. The photoactinic radiation-curable compound may include at least one of a cationically polymerizable and curable compound, a free-radically polymerizable and curable compound, a urethane resin, or a silicone resin.

[0132] The protective layer may be a zero-delay layer or may have an in-plane delay within a specific range (e.g., a predetermined range). For example, the protective layer may have an in-plane delay of less than 5,000 nm, greater than or equal to 5,000 nm, 120 nm to 160 nm, or 5 nm to 0 nm at a wavelength of 550 nm. Within this range, the protective layer can protect the polarizing plate without changing the desired effect of the retardation layer stack.

[0133] In an embodiment, the protective layer may have a thickness of 10 μm or less than 10 μm, 5 μm to 300 μm, 5 μm or less than 5 μm, or 5 μm to 200 μm. Within this range, the protective layer can be used in a polarizing plate.

[0134] The polarizing plate may further include a functional coating formed on one or both sides of the protective layer.

[0135] The functional coating can provide additional functions to the protective layer or the polarizing plate. The functional coating may include at least one of a hard coat, an anti-fingerprint layer, an anti-reflection layer, an anti-glare layer, a low reflectance layer, or an ultra-low reflectance layer, but not limited thereto.

[0136] In an embodiment, the functional coating may be a low reflectance layer, an anti-reflection layer, or an anti-glare layer. The low reflectance layer, the anti-reflection layer, or the anti-glare layer can help minimize or reduce ghost images by reflecting unwanted light from the outside or by absorbing light reflected at the interface. The polarizing plate may include at least one of a low reflectance layer, an anti-reflection layer, or an anti-glare layer.

[0137] For example, each of the low reflectivity layer and the antireflection layer may have a minimum reflectivity of 3% or less than 3% (e.g., 0% to 2%). Within this range, the low reflectivity layer and the antireflection layer may help to minimize or reduce ghost images.

[0138] For example, the antiglare layer may have an external haze of 0% to 50% and an internal haze of 0% to 10%. Within these ranges, the antiglare layer may help to minimize or reduce ghost images. As used herein, "internal haze" is a value measured in the same manner as the overall haze of a polarizer after spraying alcohol (e.g., ethanol) on a glass plate with an overall haze of less than 1%, and then attaching the glass plate to the antiglare layer to flatten the surface irregularities of the antiglare layer. As used herein, the "overall haze" of the antiglare layer is a value measured using a typical haze meter (e.g., haze meter NHD-2000). As used herein, the "external haze" of the antiglare layer may be the difference between the overall haze of the antiglare layer and the internal haze of the antiglare layer. As used herein, unless otherwise stated, "haze" is measured in the visible spectrum (e.g., at wavelengths from 380 nm to 780 nm) and refers to the average value.

[0139] The low reflectivity layer, the antireflection layer, and the antiglare layer may be manufactured by typical methods known to those skilled in the art.

[0140] Figure 1 is a diagram showing the relationship between the optical axes of polarizers according to an embodiment.

[0141] Referring to Figure 1 , the polarizer may include: a first negative wavelength dispersion retardation layer 220 and a positive C retardation layer 230, sequentially stacked on one surface of the polarizing sheet 210; and a second negative wavelength dispersion retardation layer 240 and (in the embodiment) a protective layer 250, as further shown in Figure 2 , sequentially stacked on the other surface of the polarizing sheet.

[0142] The slow axis 221 of the first negative wavelength dispersion retardation layer 220 may be substantially perpendicular to the slow axis 241 of the second negative wavelength dispersion retardation layer 240, and may be inclined at an angle of substantially 45° or 135° with respect to the light absorption axis 211 of the polarizing sheet 210.

[0143] Structure of the polarizer

[0144] A retardation layer stack may be formed on at least one surface of the polarizing sheet.

[0145] According to an embodiment, the retardation layer stack may be formed only on one surface of the polarizer. Here, the second negative wavelength dispersion retardation layer may be formed on the other surface of the polarizer.

[0146] According to another embodiment, the retardation layer stack may be formed on both surfaces or opposite surfaces of the polarizer.

[0147] Figures 2 to 4 Shows a polarizing plate according to some embodiments.

[0148] Referring to Figure 2 , the polarizing plate may include: a polarizer 210; a first negative wavelength dispersion retardation layer 220 and a positive C retardation layer 230, sequentially stacked on one surface of the polarizer 210; and a second negative wavelength dispersion retardation layer 240 and a protective layer 250, sequentially stacked on the other surface of the polarizer 210. Although not shown in Figure 2 , the polarizing plate may further include the functional coating as described above on the other surface of the protective layer. Although not shown in Figure 2 , the polarizing plate may further include the resin layer, optical film or stack composed of the resin layer and optical film as described above between the polarizer 210 and the second negative wavelength dispersion retardation layer 240.

[0149] Referring to Figure 3 , the polarizing plate may include: a polarizer 210; a second negative wavelength dispersion retardation layer 240, stacked on one surface of the polarizer 210; and a first negative wavelength dispersion retardation layer 220, a positive C retardation layer 230 and a protective layer 250, sequentially stacked on the other surface of the polarizer 210. Although not shown in Figure 3 , the polarizing plate may further include the functional coating as described above on the other surface of the protective layer. Although not shown in Figure 3 , the polarizing plate may further include the resin layer, optical film or stack composed of the resin layer and optical film as described above on one or both surfaces of the polarizer 210.

[0150] Referring to Figure 4 , the polarizing plate may include: a polarizer 210; a first negative wavelength dispersion retardation layer 220 and a positive C retardation layer 230, sequentially stacked on one surface of the polarizer 210; and a first negative wavelength dispersion retardation layer 220, a positive C retardation layer 230 and a protective layer 250, sequentially stacked on the other surface of the polarizer 210. Although not shown in Figure 4 , the polarizing plate may further include the functional coating as described above on the other surface of the protective layer. Although not shown in Figure 4 , the polarizing plate may further include the resin layer, optical film or stack composed of the resin layer and optical film as described above on one or both surfaces of the polarizer 210.

[0151] Although inFigures 2 to 4 Although not shown in the drawings, in the embodiments, the polarizing plate may further include an adhesive layer or a bonding layer to facilitate the stacking of the polarizer, the first negative wavelength dispersion retardation layer, the positive C retardation layer, the protective layer, and the second negative wavelength dispersion retardation layer.

[0152] In an embodiment, the polarizing plate may have a light transmittance of 3% or less than 3% (e.g., 0% to 3%) at a wavelength of 380 nm. Within this range, the polarizing plate can prevent or substantially prevent the light-emitting device of the display unit described below from being damaged by external UV light. Methods for achieving the light transmittance within the above range are well known to those skilled in the art. For example, a light absorber capable of absorbing light with a wavelength of 380 nm may be considered to be incorporated into one of the components of the polarizing plate.

[0153] Stereoscopic image display device

[0154] According to another aspect of the present invention, a stereoscopic image display device includes: a display unit having a light-emitting device; a first polarizing plate and a lenticular lens assembly, wherein the first polarizing plate includes the above-described polarizing plate.

[0155] First polarizing plate

[0156] The first polarizing plate may be substantially the same as the above-described polarizing plate. Therefore, the first polarizing plate will not be described in detail herein.

[0157] The first polarizing plate may be disposed between the display unit and the lenticular lens assembly.

[0158] The first polarizing plate may include a negative wavelength dispersion retardation layer disposed on a side of the first polarizing plate facing the display unit and a negative wavelength dispersion retardation layer disposed on a side of the first polarizing plate facing the lenticular lens assembly.

[0159] According to an embodiment, the negative wavelength dispersion retardation layer disposed on the side of the first polarizing plate facing the display unit may be the above-described first negative wavelength dispersion retardation layer, and the negative wavelength dispersion retardation layer disposed on the side of the first polarizing plate facing the lenticular lens assembly may be the above-described second negative wavelength dispersion retardation layer.

[0160] According to another embodiment, the negative wavelength dispersion retardation layer disposed on the side of the first polarizing plate facing the display unit may be the above-described second negative wavelength dispersion retardation layer, and the negative wavelength dispersion retardation layer disposed on the side of the first polarizing plate facing the lenticular lens assembly may be the above-described first negative wavelength dispersion retardation layer.

[0161] According to another embodiment, the negative wavelength dispersion retardation layer disposed on the side of the first polarizing plate facing the display unit may be the above-described first negative wavelength dispersion retardation layer, and the negative wavelength dispersion retardation layer disposed on the side of the first polarizing plate facing the pancake lens assembly may be the above-described first negative wavelength dispersion retardation layer.

[0162] In an embodiment, the slow axis of the negative wavelength dispersion retardation layer disposed on the side of the first polarizing plate facing the pancake lens assembly is substantially perpendicular to the slow axis of the retardation film of the pancake lens assembly described below. Herein, "substantially perpendicular" means that the angle is within the range of 90° ± 5°, and in the embodiment, it means an angle of 90°. With such a structure, the first polarizing plate can eliminate or reduce ghost images while preventing or substantially preventing light leakage due to internal scattering.

[0163] The slow axis of the negative wavelength dispersion retardation layer disposed on the side of the first polarizing plate facing the display unit may be substantially perpendicular to the slow axis of the negative wavelength dispersion retardation layer disposed on the side of the first polarizing plate facing the pancake lens assembly. Herein, "substantially perpendicular" means that the angle is within the range of 90° ± 5°, and in the embodiment, it means an angle of 90°. By satisfying the following limiting conditions, this structure can help reduce light loss and generate the same level of light output for each wavelength: the circular polarization degree experienced by the light from the display unit when passing through the negative wavelength dispersion retardation layer disposed on the side of the first polarizing plate facing the display unit is substantially the same as the circular polarization degree experienced by the light when sequentially passing through the polarizer and the negative wavelength dispersion retardation layer disposed on the side of the first polarizing plate facing the pancake lens assembly.

[0164] If the display unit has a long side in the longitudinal direction and a short side in the transverse direction, the light absorption axis of the first polarizer may be oriented in a direction substantially the same as the transverse direction of the display unit. The light absorption axis of the first polarizer corresponds to the machine direction of the first polarizer.

[0165] Figure 6 Shows the axial relationship between the first polarizing plate and the retardation film of the pancake lens assembly according to an embodiment.

[0166] Refer to Figure 6 In the first polarizing plate, the light absorption axis 211 of the first polarizer 210 may be inclined at an angle of approximately 45° with respect to the slow axis 221 of the negative wavelength dispersion retardation layer 220 disposed on the side of the first polarizing plate facing the display unit, and the slow axis 221 of the negative wavelength dispersion retardation layer 220 disposed on the side of the first polarizing plate facing the display unit may be substantially parallel to the slow axis 321 of the retardation film 320 of the pancake lens assembly.

[0167] Pancake lens assembly

[0168] The pancake lens assembly can generate a stereoscopic image by changing the optical path of light that is emitted from a display unit including a light-emitting device, enters a first polarizing plate, and has exited the first polarizing plate.

[0169] The pancake lens assembly may include a first lens, a retardation film, and a reflective polarizer that are sequentially arranged with respect to the first polarizing plate.

[0170] The first lens can display a stereoscopic image by transmitting light from the first polarizing plate through it to the retardation film or by reflecting circularly polarized light from the retardation film, while providing enhanced light-emitting efficacy.

[0171] One of the two surfaces of the first lens may be curved to facilitate the realization of the above functions. For example, the first lens may be a spherical concave lens, a spherical convex lens, a plano lens, a rotationally symmetric aspherical lens, or a free-form lens.

[0172] The first lens may be formed of glass or plastic and may be manufactured by methods known in the art for typical pancake lenses.

[0173] The retardation film has a slow axis in the in-plane light direction, wherein the slow axis of the retardation film may be perpendicular or approximately perpendicular to the slow axis of a negative wavelength dispersion retardation layer provided on the side of the first polarizing plate facing the pancake lens assembly. If the slow axis of the retardation film is not substantially perpendicular to the slow axis of the negative wavelength dispersion retardation layer provided on the side of the first polarizing plate facing the pancake lens assembly, then even if the light entering the pancake lens assembly is magnified along the normal optical path in the pancake lens assembly, the pancake lens assembly may not be able to generate a magnified image through its optical system because the light entering the pancake lens assembly cannot return to its original polarization state.

[0174] Refer to Figure 6 , the slow axis 241 of the negative wavelength dispersion retardation layer 240 provided on the side of the first polarizing plate facing the pancake lens assembly may be substantially perpendicular to the slow axis 321 of the retardation film 320 of the pancake lens assembly.

[0175] In an embodiment, the retardation film may have an in-plane retardation of 130 nm to 150 nm (e.g., 135 nm to 145 nm) at a wavelength of 550 nm. Within this range, the retardation film can generate circularly polarized light.

[0176] The retardation film may be formed of a liquid crystal layer or a non-liquid crystal layer as described above. In an embodiment, the liquid crystal layer and the non-liquid crystal layer are substantially the same as the above-described liquid crystal layer and non-liquid crystal layer, and will not be described in detail again.

[0177] The reflective polarizer can reflect a part of the circularly polarized light from the retardation film back to the retardation film, while allowing the other part of the circularly polarized light to pass through the reflective polarizer for transmission.

[0178] In an embodiment, the reflective polarizer may have a structure in which two different layers with different refractive indices are stacked alternately on top of each other. For example, the reflective polarizer may be a film in which two different layers with different refractive indices are stacked in the order of a higher refractive index layer / a lower refractive index layer or a lower refractive index layer / a higher refractive index layer.

[0179] Display unit

[0180] The display unit may include a typical display unit including a light-emitting device. The light-emitting device may include at least one of an organic light-emitting device, an inorganic light-emitting device, or an organic / inorganic hybrid light-emitting device.

[0181] Figure 5 is a schematic diagram of a stereoscopic image display device according to an embodiment.

[0182] Referring to Figure 5 , the stereoscopic image display device includes: a display unit 100; a first polarizing plate 200 including a positive C retardation layer 230, a first negative wavelength dispersion retardation layer 220, a first polarizer 210, and a second negative wavelength dispersion retardation layer 240; and a pancake lens assembly 300 including a first lens 310, a retardation film 320, and a reflective polarizer 330. The light that exits the stereoscopic image display device through the pancake lens assembly 300 can be perceived by the user's eye 1.

[0183] Referring to Figure 5 , the circularly polarized light from the second negative wavelength dispersion retardation layer 240 passes through the first lens 310 and the retardation film 320, is reflected back from the reflective polarizer 330 to the retardation film 320 for circular polarization through the retardation film 320, is reflected back from the first lens 310 to the retardation film 320 to pass through the retardation film 320, and is linearly polarized by the reflective polarizer 330 before leaving the pancake lens assembly 300.

[0184] In an embodiment, the pancake lens assembly may further include a third polarizer disposed on the side of the reflective polarizer facing away from the retardation film, that is, at the outermost side of the stereoscopic image display device.

[0185] The third polarizer can help minimize or reduce ghost images by absorbing linearly polarized light traveling in a direction different from the direction of the linearly polarized light from the reflective polarizer (that is, linearly polarized light substantially perpendicular to the linearly polarized light from the reflective polarizer).

[0186] The third polarizer may have an optical absorption axis in its in-plane optical direction, where the optical absorption axis may be substantially perpendicular to the optical absorption axis of the first polarizer of the first polarizing plate. Herein, "substantially perpendicular" may include an angle of 90° or an angle within the range of 90° ± 5°.

[0187] In an embodiment, the optical absorption axis of the third polarizer may be substantially the same as the machine direction of the third polarizer.

[0188] In an embodiment, the third polarizer may be manufactured by the same or substantially the same method as the method described above for the first polarizer.

[0189] Figure 7 is a schematic view of a stereoscopic image display device according to another embodiment.

[0190] Referring to Figure 7 , the stereoscopic image display device according to the present embodiment may include a pancake lens assembly 300' including a first lens 310, a retardation film 320, a reflective polarizer 330, and a third polarizer 340, instead of Figure 5 the pancake lens assembly 300 shown. The third polarizer 340 may minimize or reduce ghost images by transmitting a part of the linearly polarized light from the reflective polarizer 330 through it while absorbing the linearly polarized light substantially perpendicular thereto.

[0191] Figure 8 shows the axial relationship between the first polarizing plate, the retardation film of the pancake lens assembly, and the third polarizer of the pancake lens assembly according to an embodiment.

[0192] Referring to Figure 8 , in the first polarizing plate, the optical absorption axis 211 of the first polarizer 210 may be inclined at an angle of approximately 45° with respect to the slow axis 221 of the first negative wavelength dispersion retardation layer 220 provided on the side of the first polarizing plate facing the display unit; the slow axis 221 of the first negative wavelength dispersion retardation layer 220 provided on the side of the first polarizing plate facing the display unit is parallel or substantially parallel to the slow axis 321 of the retardation film 320 of the pancake lens assembly 300; and the optical absorption axis 211 of the first polarizer 210 may be perpendicular or substantially perpendicular to the optical absorption axis 341 of the third polarizer 340.

[0193] Now, a stereoscopic image display device according to another embodiment will be described.

[0194] The stereoscopic image display device may further include a second polarizing plate located between the first polarizing plate and the pancake lens assembly.

[0195] The second polarizing plate can improve the luminous efficacy by transmitting the circularly polarized light from the first polarizing plate therethrough or by circularly polarizing the non-circularly polarized light from the first polarizing plate before it exits the second polarizing plate.

[0196] The second polarizing plate may include: a second polarizer; a first retardation layer bonded to the surface of the second polarizer facing the display unit; and a second retardation layer bonded to the surface of the second polarizer facing the pancake lens assembly.

[0197] According to an embodiment, each of the first retardation layer and the second retardation layer may have negative wavelength dispersion.

[0198] In an embodiment, each of the first retardation layer and the second retardation layer has a short-wavelength dispersion of 0.81 to 0.88 and a long-wavelength dispersion of 1.01 to 1.04. Within these ranges, the first retardation layer and the second retardation layer can enhance the brightness of the stereoscopic image display device by increasing the internal transmittance.

[0199] In an embodiment, the first retardation layer may have an in-plane retardation of 115 nm to 125 nm (e.g., 119 nm to 123 nm) at a wavelength of 450 nm. In an embodiment, the first retardation layer may have an in-plane retardation of 135 nm to 145 nm (e.g., 139 nm to 143 nm) at a wavelength of 550 nm. In an embodiment, the first retardation layer may have an in-plane retardation of 140 nm to 150 nm (e.g., 142 nm to 146 nm) at a wavelength of 650 nm. Within these ranges, the first retardation layer can have a short-wavelength dispersion and a long-wavelength dispersion within the above ranges.

[0200] In an embodiment, the second retardation layer may have an in-plane retardation of 115 nm to 125 nm (e.g., 119 nm to 123 nm) at a wavelength of 450 nm. In an embodiment, the second retardation layer may have an in-plane retardation of 135 nm to 145 nm (e.g., 139 nm to 143 nm) at a wavelength of 550 nm. In an embodiment, the second retardation layer may have an in-plane retardation of 140 nm to 150 nm (e.g., 142 nm to 146 nm) at a wavelength of 650 nm. Within these ranges, the second retardation layer can have a short-wavelength dispersion and a long-wavelength dispersion within the above ranges.

[0201] In an embodiment, the short-wavelength dispersion of the first retardation layer may be substantially equal to the short-wavelength dispersion of the second retardation layer, and the long-wavelength dispersion of the first retardation layer may be substantially equal to the long-wavelength dispersion of the second retardation layer. Thus, it is possible to prevent the user from perceiving different levels of light output for different wavelengths due to different degrees of circular polarization of different wavelengths, and thus an uneven image cannot be provided. Herein, "substantially equal" includes an error range of -0.001 to +0.001 in addition to being exactly equal.

[0202] Each of the first retardation layer and the second retardation layer has a slow axis in the in-plane light direction, wherein the slow axis of the first retardation layer is substantially perpendicular to the slow axis of the second retardation layer.

[0203] The slow axis of the first retardation layer may be inclined at an angle of approximately 45° with respect to a reference. The slow axis of the second retardation layer may be inclined at an angle of approximately 135° with respect to the reference. Within these ranges, each of the first retardation layer and the second retardation layer can enhance the circular polarization degree of light of each wavelength from the display unit. Herein, the "reference" refers to the light absorption axis of the first polarizer of the first polarizing plate. The light absorption axis of the first polarizer corresponds to the machine direction of the first polarizing plate. Assuming that the display unit has a long side in the longitudinal direction and a short side in the transverse direction, the light absorption axis of the first polarizing plate can be oriented in a direction substantially the same as the transverse direction of the display unit.

[0204] In an embodiment, the first retardation layer may have an out-of-plane retardation of 50 nm to 80 nm (e.g., 55 nm to 75 nm) at a wavelength of 550 nm. Within this range, the first retardation layer can have an in-plane retardation within the above range while allowing the thickness of the second polarizing plate to be reduced.

[0205] In an embodiment, the first retardation layer may have a biaxiality of 0.7 to 1.1 (e.g., 0.8 to 1.0) at a wavelength of 550 nm. Within this range, the first retardation layer can have an in-plane retardation within the above range while allowing the thickness of the first polarizing plate to be reduced.

[0206] In an embodiment, the second retardation layer may have an out-of-plane retardation of 50 nm to 80 nm (e.g., 55 nm to 75 nm) at a wavelength of 550 nm. Within this range, the second retardation layer can have an in-plane retardation within the above range while allowing the thickness of the second polarizing plate to be reduced.

[0207] In an embodiment, the second retardation layer may have a biaxiality of 0.7 to 1.1 (e.g., 0.8 to 1.0) at a wavelength of 550 nm. Within this range, the second retardation layer can have an in-plane retardation within the above range while allowing the thickness of the second polarizing plate to be reduced.

[0208] In an embodiment, each of the first retardation layer and the second retardation layer may have a thickness of 1 μm to 40 μm (e.g., 1.5 μm to 35 μm). Within this range, each of the first retardation layer and the second retardation layer can be used in the first polarizing plate.

[0209] Each of the first retardation layer and the second retardation layer can be formed of any suitable material capable of meeting the above wavelength dispersion and retardation requirements. Each of the first retardation layer and the second retardation layer can be a liquid crystal layer or a non-liquid crystal layer.

[0210] In an embodiment, the liquid crystal layer and the non-liquid crystal layer may be the same as the liquid crystal layer and the non-liquid crystal layer described above with respect to the first polarizing plate, and will not be described herein again. It should be understood that each of the first retardation layer and the second retardation layer may further include an optical film as described above.

[0211] In an embodiment, each of the first retardation layer and the second retardation layer may further include an optical film. The optical film may facilitate the formation of the coating as described above without affecting the retardation characteristics of the first retardation layer and the second retardation layer. The optical film may be substantially the same as the above-described optical film and will not be described herein again.

[0212] The second polarizer may linearly polarize the circularly polarized light from the first retardation layer to direct the linearly polarized light to the second retardation layer.

[0213] The second polarizer may have an optical absorption axis in the in-plane light direction thereof, wherein the optical absorption axis may be substantially parallel to the optical absorption axis of the first polarizer of the first polarizing plate. Herein, "substantially parallel" means an angle of 0° or an angle in the range of 0° ± 5°.

[0214] In an embodiment, the second polarizer may have a cross-axis transmittance of 0.2% or less than 0.2% (e.g., 0.01% or less than 0.01%, e.g., 0% to 0.2% or 0% to 0.01%). Within this range, the second polarizer may contribute to minimizing or reducing ghost images by enhancing the antireflection performance of the display device, in which the angular relationship between the slow axes is set as described above.

[0215] In an embodiment, the second polarizer may have a degree of polarization of 99% or greater than 99% (e.g., 99.99% to 100%) and a single light transmittance (Ts) of 42% or greater than 42% (e.g., 42% to 45%). Within these ranges of the degree of polarization and the single light transmittance, the second polarizer may have a significantly low reflectance when stacked on the retardation layer stack.

[0216] The optical absorption axis of the second polarizer may be the stretching direction of the polyvinyl alcohol film when manufacturing the second polarizer from the polyvinyl alcohol film, e.g., the machine direction (MD) of the second polarizer. The second polarizer may include a polyvinyl alcohol-based polarizer obtained by uniaxially stretching the polyvinyl alcohol film. In an embodiment, the second polarizer may be manufactured by subjecting the polyvinyl alcohol film to a dyeing process, a stretching process, a crosslinking process, and a color correction process. A polarizer having a degree of polarization and a light transmittance within the ranges stated above may be obtained by appropriately changing the conditions of the above dyeing process, stretching process, crosslinking process, and color correction process.

[0217] In an embodiment, the second polarizing sheet may have a thickness of 5 μm to 40 μm. Within this range, the second polarizing sheet can be used in the second polarizing plate.

[0218] The second polarizing plate may further include a resin layer formed on a surface of the second polarizing sheet facing the pancake lens assembly.

[0219] In an embodiment, the resin layer may be directly formed on the surface of the second polarizing sheet facing the pancake lens assembly and bonded to the surface. Herein, the expression "directly formed" means that no other adhesive layer, bonding layer, and / or curable coating is formed between the second polarizing sheet and the resin layer. The resin layer can improve the effectiveness of the second polarizing plate in eliminating or reducing ghost images by covering the fine surface irregularities of the second polarizing sheet. The resin layer may be a cured product of a composition including at least one of a thermally curable resin or a UV curable resin. Each of the thermally curable resin and the UV curable resin may be selected from typical thermally curable resins or UV curable resins known to those skilled in the art. For example, the resin layer may be a cured product of a composition including a (meth)acrylic resin.

[0220] In another embodiment, a stack formed of a resin layer and an optical film may be formed on the surface of the second polarizing sheet facing the pancake lens assembly. The optical film can increase the mechanical strength of the second polarizing sheet, and the resin layer can improve the effectiveness of the second polarizing plate in eliminating or reducing ghost images by covering the fine surface irregularities of the optical film. The resin layer and the optical film may be substantially the same as the above-mentioned resin layer and optical film.

[0221] In an embodiment, the resin layer may be a hard coat, but is not limited thereto.

[0222] The second polarizing plate may further include a protective layer, a functional coating, or a protective layer formed with a functional coating on its outermost side facing the pancake lens assembly. In an embodiment, the protective layer, the functional coating, or the protective layer formed with a functional coating is substantially the same as the above, and will not be described herein again.

[0223] The second polarizing plate may further include a positive C layer. In an embodiment, the positive C layer is substantially the same as the above-mentioned positive C layer, and will not be described herein again.

[0224] Figure 9 is a cross-sectional view of a second polarizing plate according to an embodiment.

[0225] Refer to Figure 9, the second polarizing plate may include: a second polarizer 410; a first retardation layer 420 and a positive C retardation layer 430, sequentially bonded to the surface of the second polarizer 410 facing the display unit (not shown in the figure); and a second retardation layer 440 and a protective layer 450, sequentially bonded to the surface of the second polarizer 410 facing the pancake lens assembly (not shown in the figure), wherein the protective layer 450 has a functional coating formed thereon.

[0226] Although not shown in Figure 9 , a bonding layer or an adhesive layer (e.g., a pressure-sensitive adhesive (PSA) layer) may be provided to bond the first retardation layer, the second retardation layer, and the protective layer to the second polarizer.

[0227] Figure 11 Shows the axial relationship between the first polarizing plate, the retardation film of the pancake lens assembly, and the second polarizing plate according to another embodiment.

[0228] Referring to Figure 11 , in the second polarizing plate, the optical absorption axis 411 of the second polarizer 410 may be inclined at an angle of approximately 45° with respect to the slow axis 421 of the first retardation layer 420, and the slow axis 421 of the first retardation layer 420 may be perpendicular or substantially perpendicular to the slow axis 441 of the second retardation layer 440.

[0229] In an embodiment, the second polarizing plate may have a light transmittance of 3% or less (e.g., 0% to 3%) at a wavelength of 380 nm. Within this range, the second polarizing plate can prevent or substantially prevent damage to the light-emitting device of the display unit caused by UV light entering from the outside. The method of achieving a light transmittance within the above range is well known to those skilled in the art. For example, a light absorber capable of absorbing light with a wavelength of 380 nm may be considered to be incorporated into one of the components of the first polarizing plate.

[0230] Figure 10 Is a schematic diagram of a stereoscopic image display device according to another embodiment.

[0231] Referring to Figure 10 , compared with the Figure 5 stereoscopic image display device shown, the stereoscopic image display device according to this embodiment may further include a second polarizing plate 400 disposed between the pancake lens assembly 300 and the first polarizing plate 200, wherein the second polarizing plate 400 includes a second polarizer 410, a first retardation layer 420, a positive C layer 430, and a second retardation layer 440.

[0232] Although not shown in Figure 10 , the stereoscopic image display device may further include a second lens disposed between the second polarizing plate 400 and the first polarizing plate 200.

[0233] The second lens can generate an enlarged image by magnifying the circularly polarized light from the first polarizing plate.

[0234] One of the two surfaces of the second lens may be curved to facilitate the realization of the above function. For example, the second lens may be a spherical concave lens, a spherical convex lens, a plano lens, a rotationally symmetric aspherical lens, or a free-form lens.

[0235] The second lens can be formed of glass or plastic. The second lens can be manufactured by methods known in the art for typical pancake lenses.

[0236] Next, the present invention will be described in more detail with reference to some examples. However, these examples are provided for illustrative purposes only and should not be construed as limiting the present invention in any way.

[0237] Example 1

[0238] A first polarizer (single light transmittance: 44%, orthogonal transmittance: 0.2%, thickness: 10 μm) was manufactured by dyeing a polyvinyl alcohol film (thickness: 60 μm, Kuraray Co., Ltd.) in an aqueous solution of iodine at 55°C and then uniaxially stretching the dyed film in the MD direction to six times the initial length of the film.

[0239] After laminating a triacetyl cellulose film to one surface of the first polarizer, a composition containing an acrylic resin was coated on one surface of the triacetyl cellulose film and then cured, thereby manufacturing a stack in which the triacetyl cellulose film and the resin layer were sequentially formed on one surface of the first polarizer.

[0240] A stack composed of a positive C retardation layer and a first negative wavelength dispersion retardation layer was laminated to one surface of the manufactured stack. Table 1 shows the biaxiality of the stack composed of the positive C retardation layer and the first negative wavelength dispersion retardation layer at wavelengths of 450 nm, 550 nm, and 650 nm.

[0241] A second negative wavelength dispersion retardation layer was laminated to the other surface of the manufactured stack, thereby manufacturing a first polarizing plate in which a positive C retardation layer (liquid crystal layer), a first negative wavelength dispersion retardation layer (liquid crystal layer), a first polarizer, a triacetyl cellulose film, a resin layer, and a second negative wavelength dispersion retardation layer (liquid crystal layer) were sequentially stacked on top of each other. Each of the first negative wavelength dispersion retardation layer and the second negative wavelength dispersion retardation layer has negative wavelength dispersion. The short wavelength dispersion and long wavelength dispersion of each of the first negative wavelength dispersion retardation layer and the second negative wavelength dispersion retardation layer are shown in Table 1.

[0242] As Figure 5 shown, the manufactured first polarizing plate, a display unit including an organic light emitting diode (OLED) device, and a pancake lens assembly are combined to manufacture a module for a stereoscopic image display device.

[0243] Here, the slow axis of the second negative wavelength dispersion retardation layer of the first polarizing plate is perpendicular to the slow axis of the retardation film of the pancake lens assembly.

[0244] In the first polarizing plate, the light absorption axis of the first polarizer is inclined at an angle of 45° with respect to the slow axis of the first negative wavelength dispersion retardation layer, and the slow axis of the first negative wavelength dispersion retardation layer is perpendicular to the slow axis of the second negative wavelength dispersion retardation layer.

[0245] Examples 2 to 5

[0246] A module for a stereoscopic image display device was manufactured in the same manner as in Example 1, except that the biaxiality of the stack composed of the positive C retardation layer and the first negative wavelength dispersion retardation layer was changed as listed in Table 1.

[0247] Example 6

[0248] A second polarizer (light transmittance: 44%, orthogonal transmittance: 0.2%, thickness: 10 μm) was manufactured by dyeing a polyvinyl alcohol film (thickness: 60 μm, Kuraray Co., Ltd.) in an aqueous solution of iodine at 55°C and then uniaxially stretching the dyed film six times the initial length of the film in the MD direction.

[0249] After laminating a triacetyl cellulose film to one surface of the second polarizer, a composition containing an acrylic resin was coated on one surface of the triacetyl cellulose film and then cured to manufacture a stack composed of the second polarizer, the triacetyl cellulose film, and a resin layer.

[0250] A stack composed of a positive C retardation layer and a first retardation layer was laminated to one surface of the manufactured stack.

[0251] A second retardation layer was laminated to the other surface of the manufactured stack to manufacture a second polarizing plate, in which a positive C retardation layer (liquid crystal layer), a first retardation layer (liquid crystal layer), a second polarizer, a triacetyl cellulose film, a resin layer, and a second retardation layer (liquid crystal layer) are stacked on top of each other in this order. Each of the first retardation layer and the second retardation layer has negative wavelength dispersion. The short wavelength dispersion and long wavelength dispersion of each of the first retardation layer and the second retardation layer are shown in Table 1.

[0252] In addition to further disposing the manufactured second polarizing plate between the first polarizing plate and the pancake lens assembly such that the module for the stereoscopic image display device has the structure as shown in Figure 10 , the module for the stereoscopic image display device was manufactured in the same manner as in Example 1.

[0253] Example 7

[0254] In addition to changing the short-wavelength dispersion and long-wavelength dispersion of each of the first retardation layer and the second retardation layer of the second polarizing plate as listed in Table 1, the module for the stereoscopic image display device was manufactured in the same manner as in Example 6.

[0255] Comparative Examples 1 to 6

[0256] In addition to changing the biaxiality of the stack composed of the positive C retardation layer and the first negative wavelength dispersion retardation layer as listed in Table 2, the module for the stereoscopic image display device was manufactured in the same manner as in Example 1.

[0257] * Resolution (modulation transfer function (MTF)) (unit: %): The resolution was evaluated by measuring the contrast (i.e., the luminance difference between the bright area and the dark area on the screen) using an imaging photometer (ProMetric, Radiant Imaging Co.).

[0258] MTF = {(maximum contrast - minimum contrast) / (maximum contrast + minimum contrast)} x 100

[0259] * Light leakage: Diagonal light leakage was observed with the naked eye in a dark room. When no light leakage was observed with the naked eye, the corresponding module was rated as "undetectable", and when light leakage was observed with the naked eye, the corresponding module was rated as "weak", "medium", or "strong" based on the observed light leakage intensity.

[0260] * Color uniformity: The front color (u'1, v'1 (Commission Internationale de L'Eclairage (CIE) 1976 user coordinate system (UCS) color coordinate system)) of the screen was measured using an imaging photometer (ProMetric, Radiant Imaging Co.), and the side color (u'2, v'2) of the screen was measured at an azimuth angle of 45° and an incident angle of 60°. Based on the measured u' values and v' values, △u'v' was calculated according to the following equation. A higher △u'v' value indicates a narrower field of view due to lower color uniformity of the screen when viewed from the front and the side.

[0261]

[0262] Table 1

[0263]

[0264] Table 2

[0265]

[0266] As can be seen from Table 1, the polarizers of Examples 1 to 7 can produce the same level of light output for each wavelength so that a user can perceive the same level of light output for each wavelength, can eliminate light leakage at the screen edge in the viewer's field of view, and can provide high resolution and a wide field of view.

[0267] In contrast, as can be seen from Table 2, compared with the polarizers of Examples 1 to 7, the polarizers of Comparative Examples 1 to 6 exhibit poorer properties in terms of resolution, light leakage, and color uniformity.

[0268] Although some exemplary embodiments have been described herein, it should be understood that those skilled in the art can make various refinements, changes, alterations, and equivalent embodiments without departing from the spirit and scope of the present invention.

Claims

1. A polarizing plate, comprising: A polarizer; And A stack composed of a first negative wavelength dispersion retardation layer and a positive C retardation layer, located on at least one surface of the polarizer, Wherein the stack has a biaxiality of 0.1 to 0.5 at a wavelength of 450 nm, a biaxiality of 0.2 to 0.6 at a wavelength of 550 nm, and a biaxiality of 0.3 to 0.7 at a wavelength of 650 nm.

2. The polarizing plate according to claim 1, wherein the first negative wavelength dispersion retardation layer is located between the polarizer and the positive C retardation layer.

3. The polarizing plate according to claim 1, wherein the stack has an in-plane retardation of 130 nm to 150 nm and an out-of-plane retardation of -55 nm to 5 nm at a wavelength of 550 nm.

4. The polarizing plate according to claim 1, wherein the first negative wavelength dispersion retardation layer has an in-plane retardation of 135 nm to 145 nm and an out-of-plane retardation of 50 nm to 70 nm at a wavelength of 550 nm.

5. The polarizing plate according to claim 1, wherein the positive C retardation layer has positive wavelength dispersion.

6. The polarizing plate according to claim 1, wherein the polarizer has a cross-polarization transmittance of 0.2% or less than 0.2%.

7. The polarizing plate according to claim 1, further comprising a resin layer located on at least one surface of the polarizer.

8. The polarizing plate according to claim 1, further comprising a stack composed of a resin layer and an optical film located on at least one surface of the polarizer.

9. The polarizing plate according to claim 1, further comprising a second negative wavelength dispersion retardation layer.

10. The polarizing plate according to claim 9, wherein the first negative wavelength dispersion retardation layer is located on the surface of the polarizer, and the second negative wavelength dispersion retardation layer is located on the other surface of the polarizer.

11. The polarizing plate according to claim 9, wherein the second negative wavelength dispersion retardation layer has the same short-wavelength dispersion and the same long-wavelength dispersion as the first negative wavelength dispersion retardation layer.

12. The polarizing plate according to claim 9, wherein the slow axis of the first negative wavelength dispersion retardation layer is perpendicular to the slow axis of the second negative wavelength dispersion retardation layer.

13. The polarizing plate according to claim 1, further comprising a protective layer located on at least one surface of the polarizer.

14. A stereoscopic image display device, comprising: A display unit including a light-emitting device; A first polarizing plate; And A pancake lens assembly, Wherein the first polarizing plate includes the polarizing plate according to claim 1.

15. The stereoscopic image display device according to claim 14, wherein the first polarizing plate is located between the display unit and the pancake lens assembly.

16. The stereoscopic image display device according to claim 14, wherein the slow axis of the negative wavelength dispersion retardation layer located on the side of the first polarizing plate facing the pancake lens assembly is perpendicular to the slow axis of the retardation film of the pancake lens assembly.

17. The stereoscopic image display device according to claim 15 further includes a second polarizing plate located between the first polarizing plate and the pancake lens assembly.

18. The stereoscopic image display device according to claim 17, wherein the second polarizing plate includes: A second polarizing sheet, a first retardation layer, and a positive C retardation layer are sequentially bonded to a surface of the second polarizing sheet facing the display unit; and a second retardation layer is bonded to a side of the second polarizing sheet facing the pancake lens assembly.

19. The stereoscopic image display device according to claim 18, wherein each of the first retardation layer and the second retardation layer has negative wavelength dispersion.

20. The stereoscopic image display device according to claim 14, wherein the pancake lens assembly includes a third polarizing plate.

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