Polarizing plate and optical display device

Abstract

Provided is a polarizing plate comprising a polarizer and a retardation layer laminated on the lower surface of the polarizer, the retardation layer comprising a negative C layer, a negative A layer, and a positive A layer laminated in this order from the lower surface of the polarizer, and the thickness direction retardation of the negative C layer at a wavelength of 550 nm is 20 nm to 60 nm, and an optical display device including the polarizing plate.

Description

[Technical Field]

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

[0002] Organic light emitting diode display devices can suffer from problems such as reduced visibility and contrast due to reflection of external light. Polarizing plates are used to solve these problems. Polarizing plates can reduce the reflectance of reflected external light and exhibit anti-reflection properties. Polarizing plates are fundamentally required to significantly improve screen quality by improving the black visibility from the front.

[0003] The polarizing plate includes a polarizer and an anti-reflection layer laminated on the lower surface of the polarizer. The anti-reflection layer may be a single-layer retardation layer or a double-layer retardation layer. A single-layer retardation layer primarily provides reverse wavelength dispersion characteristics. Most double-layer retardation layers achieve reverse wavelength dispersion characteristics by laminating two retardation layers, each with a positive wavelength dispersion retardation characteristic. A double-layer retardation layer may be relatively thicker than a single-layer retardation layer. However, a double-layer retardation layer is less expensive than a single-layer retardation layer with reverse wavelength dispersion characteristics. By laminating an existing retardation layer with a positive wavelength dispersion characteristic, price competitiveness can be ensured and productivity can be improved.

[0004] The retardation layer can be manufactured by stretching an unstretched film formed from a composition containing a polymer resin, or by coating a liquid crystal to a predetermined thickness on an alignment film and drying and / or curing the coating. A retardation layer formed from two liquid crystal layers is relatively thinner than a retardation layer formed from two stretched films. However, when exposed to high temperature and humidity, iodine leaching from the polarizer can diffuse into the panel, causing corrosion of the electrodes and reducing the durability of the panel. While methods for fundamentally preventing iodine leaching from the polarizer can be applied, there are limitations to this.

[0005] The background art of the present invention is disclosed in Korean Patent Application Publication No. 10-2013-0103595 and the like. Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present invention is to provide a polarizing plate that exhibits extremely low reflectance at the side and excellent black visual impression.

[0007] Another object of the present invention is to provide a polarizing plate that minimizes contamination of a liquid crystal layer and / or panel due to iodine eluted from the polarizer after the polarizing plate is left at high temperature and humidity for a long period of time.

[0008] It is still another object of the present invention to provide a polarizing plate whose thickness can be reduced. [Means for solving the problem]

[0009] One aspect of the present invention is a polarizing plate.

[0010] 1. The polarizing plate comprises a polarizer and a retardation layer laminated on the lower surface of the polarizer. The retardation layer comprises a negative C layer, a negative A layer, and a positive A layer laminated in this order from the lower surface of the polarizer. The negative C layer has a thickness direction retardation of 20 nm to 60 nm at a wavelength of 550 nm.

[0011] In 2.1, the negative C layer may have an in-plane retardation of 0 nm to 10 nm at the front surface at a wavelength of 550 nm.

[0012] In 3.1-2, the negative C layer may have a ratio represented by the following formula 1 of 0.0005 nm / nm to 0.003 nm / nm. (Equation 1) A / B

[0013] In Equation 1, A is the thickness direction retardation (unit: nm) of the negative C layer at a wavelength of 550 nm, B is the thickness of the negative C layer (unit: nm).

[0014] In 4.1-3, the negative C layer has a moisture permeability of 400 g / m 2 · days or less is also acceptable.

[0015] In 5.1-4, the negative C layer may be a film or coating layer containing a polymer with positive intrinsic birefringence.

[0016] In 6.1-5, the negative C layer may be a triacetyl cellulose (TAC)-based, cyclic olefin polymer (COP)-based, or cyclic olefin copolymer (COC)-based film or coating layer.

[0017] In 7.1-6, the thickness ratio of the laminate of the negative C layer, negative A layer, and positive A layer to the retardation layer may be 95% or more.

[0018] In 8.1-7, the laminate of the negative A layer and the positive A layer may have reverse wavelength dispersion.

[0019] In 9.1-8, the laminate of the negative A layer and the positive A layer may have a linear retardation of 120 nm to 180 nm at a wavelength of 550 nm.

[0020] In 10.1-9, the positive A layer may have a lower in-plane retardation at the front at a wavelength of 550 nm than the negative A layer.

[0021] In 11.10, the positive A layer may have a front in-plane retardation of 100 nm to 140 nm at a wavelength of 550 nm, and the negative A layer may have a front in-plane retardation of 200 nm to 280 nm at a wavelength of 550 nm.

[0022] In 12.1-11, the angle between the slow axis of the positive A layer and the slow axis of the negative A layer may be 55° to 65°.

[0023] In 13.1-12, the slow axis of the positive A layer may form an angle of 70° to 85° with respect to the light transmission axis of the polarizer, and the slow axis of the negative A layer may form an angle of 10° to 25° with respect to the light transmission axis of the polarizer.

[0024] In 14.1-13, the positive A layer and the negative A layer may each be a liquid crystal layer.

[0025] In 15.14, the positive A layer may be a nematic liquid crystal layer and the negative A layer may be a discotic liquid crystal layer.

[0026] In 16.1-15, the polarizing plate may further include a second protective layer laminated on the upper surface of the polarizer.

[0027] One aspect of the present invention is an optical display device.

[0028] An optical display device includes the polarizing plate of the present invention. [Effects of the Invention]

[0029] The present invention can provide a polarizing plate that exhibits extremely low reflectance at the side surfaces and excellent black visual impression.

[0030] The present invention can provide a polarizing plate that minimizes contamination of a liquid crystal layer and / or panel due to iodine eluted from a polarizer after the polarizing plate is left at high temperature and humidity for a long period of time.

[0031] The present invention can provide a polarizing plate whose thickness can be reduced. [Brief explanation of the drawings]

[0032] [Figure 1] FIG. 1 is a cross-sectional view of a polarizing plate according to an embodiment of the present invention. [Figure 2] FIG. 10 is a cross-sectional view of a polarizing plate according to another embodiment of the present invention. [Figure 3]1 is a graph showing the maximum reflectance (Y-axis, unit: %) at a side surface 60° relative to the Rth (X-axis, unit: nm) of a negative C layer. DETAILED DESCRIPTION OF THE INVENTION

[0033] The present invention will now be described in detail by way of example with reference to the accompanying drawings, in order to enable those skilled in the art to easily carry out and practice the invention. As the invention may be embodied in various different forms, it is not limited to the embodiments set forth herein.

[0034] The terms used herein are merely used to describe exemplary embodiments and are not intended to limit the present invention. The singular expressions include the plural expressions unless the context clearly indicates otherwise.

[0035] In the drawings, parts that are not relevant to the description are omitted in order to clearly explain the present invention, and the same names are used for the same or similar components throughout the specification. The length and size of each component in the drawings are for the purpose of explaining the present invention, and the present invention is not limited to the length and size of each component shown in the drawings.

[0036] In this specification, "upper" and "lower" are defined based on the drawings, and "upper" may be changed to "lower" and "lower" may be changed to "upper" depending on the viewing point.

[0037] In this specification, the "front in-plane retardation (Re)" is expressed by the following formula A, the "thickness direction retardation (Rth)" is expressed by the following formula B, and the "degree of biaxiality (NZ)" is expressed by the following formula C. (Formula A) Re=(nx-ny)×d (Formula B) Rth=((nx+ny) / 2-nz)×d (Formula C) NZ=(nx-nz) / (nx-ny)

[0038] In Formulas A to C, nx, ny, and nz are the refractive indices of the retardation layer in the slow axis direction, fast axis direction, and thickness direction at the measurement wavelength, respectively, and d is the thickness of the retardation layer (unit: nm).

[0039] Unless otherwise specified in this specification, nx, ny, and nz respectively represent the refractive index in the slow axis direction, fast axis direction, and thickness direction at a wavelength of 550 nm.

[0040] In this specification, the in-plane axis with the highest refractive index is defined as the "slow axis," and the in-plane axis with the lowest refractive index is defined as the "fast axis." The "slow axis" and the "fast axis" may be substantially perpendicular to each other, but the present invention is not limited thereto.

[0041] In this specification, "reflectance" refers to the reflectance excluding the outermost primary reflectance, and is a value calculated assuming that the reflectance of an OLED bare panel (an OLED panel without a polarizing plate laminated thereon) is 100%.

[0042] In this specification, the "water vapor transmission rate (WVTR)" may be measured by a conventional method known to those skilled in the art. For example, the water vapor transmission rate means a value measured at a temperature of 23°C and a relative humidity of 99% to 100%. Although not particularly limited, the water vapor transmission rate may be measured using a water vapor transmission rate measurement device (PERMATRAN-W, MODEL 700). A sample for measuring the water vapor transmission rate, for example, a negative C layer, may be cut into a horizontal x vertical dimension (10 cm x 10 cm) and then measured.

[0043] The present invention provides a polarizing plate that is adhered to a panel equipped with organic light-emitting elements, inorganic light-emitting elements, or organic / inorganic light-emitting elements and exhibits extremely low side reflectance and excellent black visual impression.The present invention is characterized by providing an anti-reflection polarizing plate that achieves a maximum reflectance of less than 2.5% at a side viewing angle of 60°, for example.

[0044] The present invention provides a polarizing plate that minimizes the problem of iodine eluting from a polarizer and contaminating a liquid crystal layer and / or panel after long-term storage at high temperature and humidity. The retardation layer includes a liquid crystal layer, which has a smaller thickness than a film. When the retardation layer between the polarizer and the panel includes a liquid crystal layer, iodine may elute from the polarizer and contaminate the liquid crystal layer and panel when the polarizing plate is stored at high temperature and humidity for a long period of time. When iodine contaminates the liquid crystal layer and panel, image quality deteriorates because iodine has a colored hue (e.g., purple).

[0045] The present invention has improved the durability of polarizing plates by solving the above-mentioned problems. "Iodine elution" can be evaluated by leaving a polarizing plate in a high-temperature and high-humidity chamber (temperature 60°C, relative humidity 90%) for 250 hours, and then observing the edge of the polarizing plate under a microscope to determine the degree of iodine elution based on color change, etc.

[0046] The present invention provides a polarizing plate having a small retardation layer thickness, which allows the thickness of the polarizing plate to be reduced. In one embodiment, the thickness of the retardation layer in the polarizing plate may be 20 μm to 100 μm, for example, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 60 μm, 65 μm, 70 μm, 75 μm, 80 μm, 85 μm, 90 μm, 95 μm, or 100 μm, preferably 20 μm to 90 μm, and more preferably 20 μm to 85 μm. By satisfying the above range, the polarizing plate can be made thinner.

[0047] The polarizing plate of the present invention comprises a polarizer and a retardation layer laminated on the lower surface of the polarizer, the retardation layer comprising a negative C layer, a negative A layer, and a positive A layer laminated in this order from the lower surface of the polarizer, and the negative C layer has a thickness direction retardation of 20 nm to 60 nm at a wavelength of 550 nm.

[0048] In one embodiment, the retardation layer may be a stack of three retardation layers: a negative C layer, a negative A layer, and a positive A layer.

[0049] In the present invention, a negative A layer and a positive A layer are sequentially laminated on the lower surface of the polarizer as a retardation layer, and a negative C layer is further laminated between the polarizer and the negative A layer. By adjusting the thickness direction retardation of the negative C layer at a wavelength of 550 nm to within the specific range of 20 nm to 60 nm of the present invention, a maximum reflectance of less than 2.5% on the side can be easily achieved.

[0050] In the polarizing plate of the present invention, if the negative C layer is placed between the positive A layer and the negative A layer, or placed on the underside of the positive A layer, it may be difficult to achieve a maximum reflectance of less than 2.5% on the side surface.

[0051] In the polarizing plate of the present invention, if the thickness direction retardation of the negative C layer at a wavelength of 550 nm is less than 20 nm, it may be difficult to achieve a maximum reflectance of less than 2.5% at the side surfaces, and the thickness of the negative C layer may become excessively small, which may cause problems with iodine contamination of the polarizing plate and / or panel when the polarizing plate is left at high temperature and high humidity for a long period of time.In the polarizing plate of the present invention, if the thickness direction retardation of the negative C layer at a wavelength of 550 nm is more than 60 nm, it may be difficult to achieve a maximum reflectance of less than 2.5% at the side surfaces, and it may be impossible to reduce the thickness of the polarizing plate.

[0052] In one embodiment, the thickness direction retardation of the negative C layer at a wavelength of 550 nm may be 20 nm, 21 nm, 22 nm, 23 nm, 24 nm, 25 nm, 26 nm, 27 nm, 28 nm, 29 nm, 30 nm, 31 nm, 32 nm, 33 nm, 34 nm, 35 nm, 36 nm, 37 nm, 38 nm, 39 nm, 40 nm, 41 nm, 42 nm, 43 nm, 44 nm, 45 nm, 46 nm, 47 nm, 48 nm, 49 nm, 50 nm, 51 nm, 52 nm, 53 nm, 54 nm, 55 nm, 56 nm, 57 nm, 58 nm, 59 nm, or 60 nm, and preferably, the thickness direction retardation at a wavelength of 550 nm may be 30 nm to 40 nm.

[0053] Each component of the polarizing plate of the present invention will be described in detail below.

[0054] Polarizer A polarizer converts incident natural light or polarized light into linearly polarized light in a specific direction and may be manufactured from a polymer film containing a polyvinyl alcohol-based resin as a main component. Specifically, a polarizer may be manufactured by dyeing a polymer film with iodine or a different color dye and stretching the dye in the MD (machine direction). In one embodiment, the polarizer may be manufactured by swelling, dyeing, and stretching a polyvinyl alcohol-based film, and may further be subjected to complementary color and / or crosslinking.

[0055] The polarizer has a light contraction axis and a light transmission axis in the in-plane direction, and the light absorption axis may correspond to the MD of the polarizer, and the light transmission axis may correspond to the TD (transverse direction) of the polarizer.

[0056] The total light transmittance of the polarizer may be 40% or more, for example, 40% to 46%, and the polarization degree may be 95% or more, for example, 95% to 99.999%. By satisfying these ranges, anti-reflection performance can be improved when combined with a retardation layer. The "light transmittance" and "polarization degree" are values ​​measured at wavelengths of 380 nm to 780 nm, and reflect the luminosity in that wavelength range.

[0057] The thickness of the polarizer may be 2 μm to 30 μm, specifically 4 μm to 25 μm, and by satisfying this range, the polarizer can be used as a polarizing plate.

[0058] The polarizer may be laminated directly to the negative C layer without using an adhesive or bonding layer for the negative C layer described below, or may be laminated directly to the negative C layer via an adhesive or bonding layer.

[0059] Positive A layer and negative A layer The laminate of the positive A layer and the negative A layer can promote the achievement of a maximum reflectance of less than 2.5% on the side surface. However, the laminate of the positive A layer and the negative A layer alone cannot reach a maximum reflectance of less than 2.5% on the side surface.

[0060] The laminate of the positive A layer and the negative A layer is laminated on the lower surface of the polarizer. The polarizing plate can include a negative A layer and a positive A layer laminated sequentially from the polarizer, and in this case, the effects of the present invention can be easily realized.

[0061] The laminate may have reverse wavelength dispersion. Thereby, the polarizing plate can easily reach a maximum reflectance of less than 2.5% on the side surface. "Reverse wavelength dispersion" means that the laminate satisfies Re(450) < Re(550) and Re(550) < Re(650). At this time, Re(450), Re(550), and Re(650) are the linear retardations of the laminate at wavelengths of 450 nm, 550 nm, and 650 nm.

[0062] In one embodiment, Re(450) / Re(550) may be less than 1, for example, 0.8 or more and less than 1. Re(650) / Re(550) may exceed 1, for example, exceed 1 and be 1.2 or less. By satisfying this range, the polarizing plate can easily realize reverse wavelength dispersion.

[0063] For example, the retardation of the laminate of the positive A layer and the negative A layer at a wavelength of 450 nm may be 110 nm to 170 nm, preferably 120 nm to 160 nm, the retardation at a wavelength of 550 nm may be 120 nm to 180 nm, preferably 130 nm to 170 nm, and the retardation at a wavelength of 650 nm may be 130 nm to 190 nm, preferably 140 nm to 180 nm. By satisfying the above range, the polarizing plate can easily realize reverse wavelength dispersion.

[0064] Specifically, in this specification, the retardation of the "retardation laminate" is expressed as a linear retardation calculated by the Mueller matrix of the retardation layer. In this specification, the Mueller matrix of the retardation layer is expressed by the following formula D, and can be easily measured using an Axoscan, which is an example of a retardation measuring device.

[0065]

number

[0066] In this specification, "linear retardation (R L ) is expressed by the following mathematical formula E, which is well known to those skilled in the art and can be easily measured using an Axoscan, which is an example of a phase difference measuring device.

[0067]

number

[0068] In formula E, m 23 , m 32 , m 31 , m 13 , m 11 , m 22 , and m 33 is the value obtained from the formula D.

[0069] The measurement wavelength in Equation D and Equation E may be 450 nm, 550 nm, or 650 nm.

[0070] The positive A layer is a retardation layer that satisfies the refractive index relationship nx>ny≒nz. The positive A layer may have a lower in-plane retardation at the front at a wavelength of 550 nm than the negative A layer. This makes it possible to easily achieve the effects of the present invention.

[0071] In one embodiment, the positive A layer may have a front in-plane retardation of 100 nm to 140 nm at a wavelength of 550 nm. By satisfying this range, the negative A layer and the negative C layer can easily achieve a maximum side reflectance of less than 2.5%.

[0072] For example, the in-plane retardation of the front surface of the positive A layer at a wavelength of 550 nm may be 100 nm, 101 nm, 102 nm, 103 nm, 104 nm, 105 nm, 106 nm, 107 nm, 108 nm, 109 nm, 110 nm, 111 nm, 112 nm, 113 nm, 114 nm, 115 nm, 116 nm, 117 nm, 118 nm, 119 nm, 120 nm, 121 nm, 122 nm, 123 nm, 124 nm, 125 nm, 126 nm, 127 nm, 128 nm, 129 nm, 130 nm, 131 nm, 132 nm, 133 nm, 134 nm, 135 nm, 136 nm, 137 nm, 138 nm, 139 nm, or 140 nm. Preferably, the positive A layer may have a front in-plane retardation of 110 nm to 130 nm at a wavelength of 550 nm.

[0073] The positive A layer may exhibit positive wavelength dispersion. As used herein, "positive wavelength dispersion" means that the in-plane retardation decreases with increasing wavelength. In one embodiment, the Re(450) / Re(550) of the positive A layer may be greater than 1, e.g., 1.01 to 1.5, and the Re(650) / Re(550) may be less than 1, e.g., 0.8 to 0.99.

[0074] The thickness direction retardation of the positive A layer at a wavelength of 550 nm may be 50 nm to 70 nm, for example, 50 nm, 51 nm, 52 nm, 53 nm, 54 nm, 55 nm, 56 nm, 57 nm, 58 nm, 59 nm, 60 nm, 61 nm, 62 nm, 63 nm, 64 nm, 65 nm, 66 nm, 67 nm, 68 nm, 69 nm, or 70 nm, specifically 55 nm to 65 nm. By satisfying this range, the effects of the present invention can be easily achieved.

[0075] The degree of biaxiality of the positive A layer at a wavelength of 550 nm may be 0.9 to 1.1, for example, 0.9, 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98, 0.99, 1, 1.01, 1.02, 1.03, 1.04, 1.05, 1.06, 1.07, 1.08, 1.09, or 1.1, specifically 0.95 to 1.05. By satisfying the above range, the effects of the present invention can be easily achieved.

[0076] The positive A layer has a slow axis and a slow axis in the in-plane direction, and the slow axis of the positive A layer can form an angle of 70° to 85°, for example, 70°, 71°, 72°, 73°, 74°, 75°, 76°, 77°, 78°, 79°, 80°, 81°, 82°, 83°, 84°, or 85°, preferably 75° to 80°, with respect to the light transmission axis of the polarizer. By satisfying the above range, the effects of the present invention can be easily achieved.

[0077] The thickness of the positive A layer may be 1.0 μm to 3.0 μm, specifically 1.0 μm to 2.0 μm. By satisfying this range, the polarizing plate can be made thin.

[0078] The positive A layer may be a non-liquid crystal layer, but is preferably a liquid crystal layer, which can provide the effect of making the polarizer thinner. In one embodiment, the positive A layer may be a nematic liquid crystal layer.

[0079] The nematic liquid crystal layer may be formed of a composition exhibiting nematic liquid crystal properties, and the composition may include a polymerizable compound.

[0080] The polymerizable compound may have one or more polymerizable crosslinking groups. For example, the polymerizable crosslinking group may be an acrylate group, a methacrylate group, a vinyl group, a vinyloxy group, an epoxy group, an oxetane group, a thiol group, a maleimide group, or a derivative thereof. Specifically, the polymerizable crosslinking group may include one or more of the following chemical formulas R-1 to R-15:

[0081] [ka]

[0082] The composition may further comprise a liquid crystal compound, which does not have a polymerizable crosslinking group but can provide liquid crystallinity when the composition is cured.

[0083] The composition may further contain additives that are typically contained in forming a liquid crystal layer, such as a photoinitiator, a surface modifier, an antioxidant, etc. The composition may contain a solvent to facilitate the formation of a liquid crystal layer having a uniform surface.

[0084] The negative A layer is a retardation layer that satisfies the refractive index relationship nz≈nx>ny.

[0085] The negative A layer may have a positive wavelength dispersion. As used herein, "positive wavelength dispersion" means that the in-plane retardation decreases as the wavelength increases. In one embodiment, the negative A layer has a Re(450) / Re(550) ratio greater than 1, for example, 1.01 to 1.5, and a Re(650) / Re(550) ratio less than 1, for example, 0.8 to 0.99.

[0086] In one embodiment, the negative A layer may have a front in-plane retardation of 200 nm to 280 nm at a wavelength of 550 nm. By satisfying this range, both the positive A layer and the negative C layer can easily achieve a reflectance of less than 2.5% at the side. In one embodiment, the in-plane retardation of the front surface of the negative A layer is 200 nm, 201 nm, 202 nm, 203 nm, 204 nm, 205 nm, 206 nm, 207 nm, 208 nm, 209 nm, 210 nm, 211 nm, 212 nm, 213 nm, 214 nm, 215 nm, 216 nm, 217 nm, 218 nm, 219 nm, 220 nm, 221 nm, 222 nm, 223 nm, 224 nm, 225 nm, 226 nm, 227 nm, 228 nm, 229 nm, 230 nm, 231 nm, 232 nm, 233 nm, 234 nm, 235 nm, 236 nm, 237 nm, 238 nm, 239 nm, 240 nm, 241 nm, 242 nm, 243 nm, 244 nm, 245 nm, 246 nm, 247 nm, 248 nm, 249 nm, 250 nm, 251 nm, 252 nm, 253 nm, 254 nm, 255 nm, 256 nm, 257 nm, 258 nm, 259 nm, 260 nm, 261 nm, 262 nm, 263 nm, 264 nm, 265 nm, 266 nm, 267 nm, 268 nm, 269 nm, 270 nm, 271 nm, 272 nm, 273 nm, 274 nm, 275 nm, 276 nm, 277 nm, 278 nm, 279 nm, 280 nm, 281 nm nm, 239nm, 240nm, 241nm, 242nm, 243nm, 244nm, 245nm, 246nm, 247nm, 248nm, 2 49nm, 250nm, 251nm, 252nm, 253nm, 254nm, 255nm, 256nm, 257nm, 258nm, 259nm, 260nm, 261nm, 262nm, 263nm, 264nm, 265nm, 266nm, 267nm, 268nm, 269nm, 270nm , 271nm, 272nm, 273nm, 274nm, 275nm, 276nm, 277nm, 278nm, 279nm, 280nm. Preferably, the negative A layer may have an in-plane retardation of 220 nm to 280 nm at the front surface at a wavelength of 550 nm.

[0087] The thickness direction retardation of the negative A layer at a wavelength of 550 nm is −140 nm to −100 nm, for example, −140 nm, −139 nm, −138 nm, −137 nm, −136 nm, −135 nm, −134 nm, −133 nm, −132 nm, −131 nm, −130 nm, −129 nm, −128 nm, −127 nm, −126 nm, −125 nm, −124 nm, −123 nm, −122 nm , -121 nm, -120 nm, -119 nm, -118 nm, -117 nm, -116 nm, -115 nm, -114 nm, -113 nm, -112 nm, -111 nm, -110 nm, -109 nm, -108 nm, -107 nm, -106 nm, -105 nm, -104 nm, -103 nm, -102 nm, -101 nm, -100 nm, specifically -130 nm to -110 nm. By satisfying the above range, the effects of the present invention can be easily realized.

[0088] The degree of biaxiality of the negative A layer at a wavelength of 550 nm may be -0.1 to 0.1, for example, -0.1, -0.09, -0.08, -0.07, -0.06, -0.05, -0.04, -0.03, -0.02, -0.01, 0, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, or 0.1, specifically, -0.05 to 0.05. By satisfying the above range, the effects of the present invention can be easily achieved.

[0089] The negative A layer has a slow axis and a fast axis in the in-plane direction, and the slow axis of the negative A layer can form an angle of 10° to 25°, for example, 10°, 11°, 12°, 13°, 14°, 15°, 16°, 17°, 18°, 19°, 20°, 21°, 22°, 23°, 24°, or 25°, and preferably 15° to 20°, with respect to the light transmission axis of the polarizer. By satisfying the above range, the effects of the present invention can be easily achieved.

[0090] The angle formed by the slow axis of the positive A layer and the slow axis of the negative A layer may be 55° to 65°, for example, 55°, 56°, 57°, 58°, 59°, 60°, 61°, 62°, 63°, 64°, or 65°, and preferably 57° to 63°. By satisfying the above range, the effects of the present invention can be easily achieved.

[0091] The thickness of the negative A layer may be 1.0 μm to 5.0 μm, specifically 2.0 μm to 4.0 μm. By satisfying this range, it is possible to make the polarizing plate thinner.

[0092] The negative A layer may be a non-liquid crystal layer, but is preferably a liquid crystal layer, which can provide a thin polarizing plate. In one embodiment, the negative A layer may be a discotic liquid crystal layer.

[0093] The discotic liquid crystal layer may be formed from a composition that exhibits discotic liquid crystal properties, and the composition may include a polymerizable compound.

[0094] The polymerizable compound may have one or more polymerizable crosslinking groups. For example, the polymerizable crosslinking group may be an acrylate group, a methacrylate group, a vinyl group, a vinyloxy group, an epoxy group, an oxetane group, a thiol group, a maleimide group, or a derivative thereof. Specifically, the polymerizable crosslinking group may include one or more of the following chemical formulas R-1 to R-15:

[0095] [ka]

[0096] The composition may further contain a liquid crystal compound, which does not have a polymerizable crosslinking group but can exhibit liquid crystallinity when the composition is cured.

[0097] The composition may further contain additives that are commonly included in the formation of a liquid crystal layer, such as a photoinitiator, a surface modifier, an antioxidant, etc. The composition may contain a solvent to facilitate the formation of a liquid crystal layer having a uniform surface.

[0098] The thickness of the laminate of the positive A layer and the negative A layer, including the interlayer adhesive or adhesive, may be 2.0 μm to 13.0 μm, preferably 4.0 μm to 11.0 μm. By satisfying this range, the polarizing plate can be made thinner.

[0099] The laminate of the positive A layer and the negative A layer may be formed by bonding the positive A layer and the negative A layer together with an adhesive layer, etc. Alternatively, the laminate of the positive A layer and the negative A layer may be formed by applying a composition for the positive A layer to one surface of the negative A layer and drying and / or curing it, in which case the positive A layer may be formed by coating directly onto the negative A layer without using an adhesive layer or a pressure-sensitive adhesive layer.

[0100] The laminate of the positive A layer and the negative A layer may further include one or more first protective layers. The first protective layer may be included in the laminate and provide additional functions to the laminate and / or the polarizer. For example, the first protective layer may enhance the durability and mechanical strength of the laminate by supplementing the thickness of the laminate. Alternatively, if one or more of the positive A layer and the negative A layer is a liquid crystal layer, the first protective layer may be a substrate film for forming the liquid crystal layer.

[0101] The first protective layer is an optically transparent film, and may be a film made of one or more resins selected from the group consisting of cellulose-based resins including triacetyl cellulose (TAC) and the like, polyester-based resins including polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate and the like, cyclic olefin polymer (COP)-based resins, cyclic olefin 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.

[0102] In one specific example, the in-plane retardation of the first protective layer at the front surface at a wavelength of 550 nm may be 10 nm or less, for example, 0 nm to 5 nm. By satisfying this range, it is possible to avoid affecting the reflectance reduction effect on the side surfaces of the laminate.

[0103] A polarizing plate having only the above-mentioned laminate of negative A layer and positive A layer as a retardation layer may have difficulty achieving a reflectance of less than 2.5% at the side. In particular, when the negative A layer and positive A layer are each liquid crystal layers, iodine may leach out of the polarizer and contaminate the liquid crystal layer and panel after the polarizing plate is left at high temperature and high humidity for a long period of time. The negative C layer having a thickness direction retardation at a wavelength of 550 nm described below can be laminated between the laminate of negative A layer and positive A layer and the polarizer, thereby easily achieving a reflectance of less than 2.5% at the side. This prevents the phenomenon of iodine leach out of the polarizer and contaminating the liquid crystal layer and panel after the polarizing plate is left at high temperature and high humidity for a long period of time.

[0104] Negative C layer The thickness direction retardation of the negative C layer at a wavelength of 550 nm is 20 nm to 60 nm. By satisfying this range, the negative C layer can be stacked between the polarizer and the negative A layer and achieve a side reflectance of less than 2.5%. Preferably, the thickness direction retardation of the negative C layer may be 30 nm to 40 nm.

[0105] In particular, when the thickness direction retardation of the negative C layer at a wavelength of 550 nm is 20 nm to 60 nm, in the laminate of the above-mentioned positive A layer and negative A layer, the linear retardation (R L ) is between 120 nm and 180 nm, preferably between 130 nm and 170 nm, a maximum reflectance of less than 2.5% at the side surface can be easily achieved.

[0106] FIG. 3 is a graph showing the maximum reflectance at 60° side (Y-axis, unit: %) versus Rth (X-axis, unit: nm) of the negative C layer.

[0107] 3, it can be seen that when the thickness direction retardation of the negative C layer at a wavelength of 550 nm is 20 nm to 60 nm, the maximum reflectance at the side surface can be less than 2.5%. On the other hand, when the thickness direction retardation of the negative C layer at a wavelength of 550 nm is less than 20 nm or more than 60 nm, the maximum reflectance at the side surface cannot be less than 2.5%. In particular, when the thickness direction retardation of the negative C layer at a wavelength of 550 nm is 20 nm, the maximum reflectance at the side surface is significantly reduced compared to when it is 10 nm. Furthermore, when the thickness direction retardation of the negative C layer at a wavelength of 550 nm is 60 nm, the maximum reflectance at the side surface is significantly reduced compared to when it is 70 nm.

[0108] The in-plane retardation of the negative C layer at the front surface at a wavelength of 550 nm may be 0 nm to 10 nm, for example, 0 nm, 1 nm, 2 nm, 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, or 10 nm, and preferably 0 nm to 5 nm. By satisfying the above range, the effects of the present invention can be easily achieved.

[0109] The negative C layer is a retardation layer that satisfies the refractive index relationship nx≈ny>nz.

[0110] In one embodiment, the ratio of the negative C layer in the following formula 1 may be 0.0005 nm / nm to 0.003 nm / nm. By satisfying this range, the effect of reducing the reflectance at the side surface to less than 2.5% can be easily achieved. For example, the ratio in the following formula 1 may be 0.0005 nm / nm, 0.0006 nm / nm, 0.0007 nm / nm, 0.0008 nm / nm, 0.0009 nm / nm, 0.001 nm / nm, 0.0011 nm / nm, 0.0012 nm / nm, 0.0013 nm / nm, 0.0014 nm / nm, 0.0015 nm / nm, 0.0016 nm / nm, 0.0017 nm / nm, 0.0019 nm / nm, 0.0020 nm / nm, 0.0021 nm / nm, 0.0022 nm / nm, 0.0023 nm / nm, 0.0024 nm / nm, 0.0025 nm / nm, 0.0026 nm / nm, 0.0027 nm / nm, 0.0028 nm / nm, 0.0029 nm / nm, 0.0030 nm / nm, 0.0031 nm / nm, 0.0032 nm / nm, 0.0033 nm / nm, 0.0034 nm / nm, 0.0035 nm / nm, 0.0036 nm / nm, 0.0037 nm / nm, 0.0038 nm / nm, 0.0039 ... nm / nm, 0.0018 nm / nm, 0.0019 nm / nm, 0.002 nm / nm, 0.0021 nm / nm, 0.0022 nm / nm, 0.0023 nm / nm, 0.0024 nm / nm, 0.0025 nm / nm, 0.0026 nm / nm, 0.0027 nm / nm, 0.0028 nm / nm, 0.0029 nm / nm, or 0.003 nm / nm. Preferably, the ratio in the following formula 1 is 0.001 nm / nm to 0.003 nm / nm, and more preferably 0.0015 nm / nm to 0.003 nm / nm. By satisfying the above range, a maximum reflectance of less than 2.5% at the side surfaces can be easily achieved, and excellent effects such as prevention of iodine elution can be obtained even when the polarizing plate is left at high temperature and humidity for a long period of time.

[0111] (Equation 1) A / B

[0112] In Equation 1, A is the thickness direction retardation (unit: nm) of the negative C layer at a wavelength of 550 nm, B is the thickness of the negative C layer (unit: nm).

[0113] In one embodiment, the moisture permeability of the negative C layer is 400 g / m 2 -day or less, e.g., 0g / m 2 ·day, 10g / m2 ·day, 20g / m 2 ·day, 30g / m 2 ·day, 40g / m 2 ·day, 50g / m 2 ·day, 60g / m 2 ·day, 70g / m 2 ·day, 80g / m 2 ·day, 90g / m 2 ·day, 100g / m 2 ·day, 150g / m 2 ·day, 200g / m 2 ·day, 250g / m 2 ·day, 300g / m 2 ·day, 350g / m 2 ·day, 400g / m 2 day, e.g., 0 g / m 2 ·day~400g / m 2 ·day, 0g / m 2 ·day~300g / m 2 By satisfying the above range, it is possible to prevent the phenomenon that iodine elutes from the polarizer and contaminates the liquid crystal layer and panel when the polarizing plate is left at high temperature and high humidity for a long period of time.

[0114] The thickness of the negative C layer may be 10 μm to 80 μm, for example, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 60 μm, 65 μm, 70 μm, 75 μm, or 80 μm, preferably 20 μm to 80 μm, and more preferably 20 μm to 40 μm. By satisfying the above range, the negative C layer can be used in a polarizing plate.

[0115] The material of the negative C layer is not limited as long as it satisfies the thickness direction retardation at a wavelength of 550 nm, the ratio of Equation 1, and the moisture permeability. In one embodiment, the negative C layer may be a non-liquid crystal layer.

[0116] Preferably, the negative C layer may be a film or coating layer containing a polymer with positive intrinsic birefringence, which means that the refractive index in the stretched direction (MD) increases.

[0117] In one embodiment, the negative C layer may be a cellulose-based resin including triacetyl cellulose (TAC), a cyclic olefin polymer (COP)-based resin, a norbornene-based resin including cyclic olefin copolymer (COC)-based resin, or the like.

[0118] The negative C layer may be formed directly on the polarizer without using an adhesive or sticking layer, or may be adhered to the polarizer by an adhesive or sticking layer.

[0119] The negative C layer can be formed by a solution casting method using a composition containing a polymer with positive intrinsic birefringence. The solution casting method involves dissolving a polymer with positive intrinsic birefringence and an additive in a solvent and casting the resulting solution onto a substrate. The negative C layer can be obtained after removing the solvent. This allows the thickness direction retardation at a wavelength of 550 nm and the ratio of Equation 1 of the present invention to be easily achieved.

[0120] Alternatively, the negative C layer can easily achieve the thickness direction retardation at a wavelength of 550 nm and the ratio of Formula 1 of the present invention by changing the degree of polymerization or substitution of a cellulose resin such as cellulose ester.

[0121] The thickness of the laminate of the negative C layer, negative A layer, and positive A layer may be 95% or more of the thickness of the retardation layer laminated on the lower surface of the polarizer, for example, 95%, 96%, 97%, 98%, 99%, 100%, 98% to 100%, for example, 100%. By satisfying the above range, the processability of the polarizing plate can be improved. Preferably, only the laminate of the negative C layer, negative A layer, and positive A layer may be laminated on the lower surface of the polarizer.

[0122] The laminate of the negative C layer, negative A layer, and positive A layer may be 80% or more, for example, 80%, 85%, 90%, 95%, 100%, or 80% to 100%, of the sum of the thicknesses of the retardation layer and the first protective layer laminated on the lower surface of the polarizer. By satisfying this range, the processability of the polarizing plate can be improved. Preferably, only the laminate of the negative C layer, negative A layer, and positive A layer may be laminated on the lower surface of the polarizer.

[0123] The polarizing plate may further include a second protective layer, which will be described below, on the upper surface of the polarizer. One or more second protective layers may be laminated on the upper surface of the polarizer.

[0124] 2nd protective layer The second protective layer protects the polarizer from the external environment and increases the mechanical strength of the polarizing plate, and may be one or more of a protective film and a protective coating layer.

[0125] In one embodiment, the second protective layer is an optically transparent film, and may be a film made of one or more resins selected from the group consisting of cellulose-based resins including triacetyl cellulose (TAC) and the like, polyester-based resins including polyethylene terephthalate (PET), polybutylene terephthalate, polyethylene naphthalate (PEN), polybutylene naphthalate and the like, cyclic olefin polymer (COP)-based resins, cyclic olefin 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.

[0126] A functional coating layer may be further formed on at least one surface of the second protective layer, such as an anti-reflection layer, a low-reflection layer, a hard coating layer, an anti-fingerprint layer, an anti-glare layer, or a primer layer.

[0127] The thickness of the second protective layer may be 5 μm to 70 μm, specifically 15 μm to 45 μm dw, and by satisfying this range, the second protective layer can be used in a polarizing plate.

[0128] 1 and 2 are cross-sectional views of a polarizing plate according to the present invention.

[0129] 1, the polarizing plate may include a polarizer 30, a negative C layer 10, a negative A layer 20, and a positive A layer 40 that are sequentially stacked on the lower surface of the polarizer 30. Referring to FIG. 2, the polarizing plate may include a polarizer 30, a negative C layer 10, a negative A layer 20, and a positive A layer 40 that are sequentially stacked on the lower surface of the polarizer 30, and a second protective layer 50 that is stacked on the upper surface of the polarizer 30.

[0130] The optical display device of the present invention includes a polarizer according to an embodiment of the present invention. The optical display device may include an organic light emitting diode (OLED) display device and a liquid crystal display device.

[0131] In one embodiment, an organic light emitting device display device may include an organic light emitting device panel including a flexible substrate, and a polarizer of the present invention laminated on the organic light emitting device panel.

[0132] In another embodiment, the organic light emitting device display device may include an organic light emitting device panel including a non-flexible substrate, and the polarizer of the present invention laminated on the organic light emitting device panel. [Example]

[0133] The structure and operation of the present invention will be described in more detail below through preferred embodiments of the present invention, which are presented as preferred examples of the present invention and should not be construed as limiting the present invention in any way.

[0134] Example 1 A polyvinyl alcohol film (PS#60, manufactured by Kuraray Co., Ltd., Japan, thickness before stretching: 60 μm) was stretched 6 times along the MD axis of the film in an iodine solution at 55°C to produce a polarizer with a single light transmittance of 45%.

[0135] A positive A layer (QLAA218, manufactured by FUJI), a negative A layer (QLAB218, manufactured by FUJI), and a negative C layer (manufactured by SDI) were prepared.

[0136] A negative C layer, a negative A layer, and a positive A layer were adhered in that order to the bottom surface of the prepared polarizer using an adhesive, and a TAC film (KC4UX, manufactured by KONICA) was adhered to the top surface of the polarizer, thereby producing a polarizing plate laminated in the following order: TAC film - polarizer - negative C layer - negative A layer - positive A layer.

[0137] The positive layer A was a nematic liquid crystal layer with positive wavelength dispersion. Furthermore, at a wavelength of 550 nm, the positive layer A had a front in-plane retardation of 120 nm, a thickness retardation of 60 nm, a biaxiality of 1, and a slow axis at an angle of 77.5° to the light transmission axis of the polarizer.

[0138] The negative layer A was a discotic liquid crystal layer with positive wavelength dispersion. Furthermore, the negative layer A had a front in-plane retardation of 240 nm, a thickness retardation of -120 nm, a degree of biaxiality of 0, and a slow axis angle of 17.5° with respect to the light transmission axis of the polarizer at a wavelength of 550 nm.

[0139] The laminate of the positive A layer and the negative A layer has reverse wavelength dispersion and an in-plane retardation R L was 151.5 nm.

[0140] The negative C layer was a non-liquid crystal layer made of a cyclic olefin copolymer (COC) film. The negative C layer had a front in-plane retardation of 0 nm at a wavelength of 550 nm, a thickness retardation of 40 nm, and a moisture permeability of 35 g / m 2 / day, the ratio of Equation 1 was 0.002 nm / nm.

[0141] Examples 2 to 4 A polarizing plate was prepared in the same manner as in Example 1, except that a cyclic olefin copolymer (COC) film was used as the negative C layer, and the negative C layer having the specifications shown in Table 1 below was used by adjusting the drying temperature and / or air volume and / or thickness during the preparation of the COC film.

[0142] Examples 5 and 6 A polarizing plate was prepared in the same manner as in Example 1, except that a triacetyl cellulose (TAC) film, which is a non-liquid crystal layer, was used as the negative C layer, and the negative C layer had the specifications shown in Table 1 below, which were obtained by adjusting the drying temperature and / or air volume during the preparation of the TAC film and / or adjusting the thickness.

[0143] Comparative Example 1 A polarizing plate was prepared in which the TAC film, polarizer, negative A layer and positive A layer were laminated in this order without laminating the negative C layer.

[0144] Comparative Example 2, Comparative Example 4 to Comparative Example 7 A polarizing plate was prepared in the same manner as in Example 1, except that a cyclic olefin copolymer (COC) film was used as the negative C layer, and the negative C layer having the specifications shown in Table 2 below was used by adjusting the drying temperature and / or air volume during the preparation of the COC film and / or adjusting the thickness.

[0145] Comparative Example 3 A polarizing plate was manufactured in the same manner as in Example 1, except that the TAC film, polarizer, negative C layer, positive A layer and negative A layer were laminated in this order.

[0146] The Re, Rth and NZ of each retardation layer were measured at a wavelength of 550 nm using an AXOSCAN.

[0147] The polarizing plates of the examples and comparative examples were evaluated for the following physical properties, and the results are shown in Tables 1 and 2 below.

[0148] (1) Prevention of iodine elution The polarizing plates prepared in the examples and comparative examples were left in a high-temperature, high-humidity chamber (temperature 60°C, relative humidity 90%) for 250 hours, and then the edges of the polarizing plates were observed under a microscope to compare and evaluate the degree of iodine dissolution. When viewed with the naked eye, the polarizing plate was rated as "poor" if it completely turned purple due to iodine dissolution, "good" if it slightly turned purple, and "excellent" if it showed no discoloration at all.

[0149] (2) Maximum reflectance at the side (incident angle 60°) For the polarizing plates prepared in the examples and comparative examples, the maximum reflectance in the direction where the reflectance of external light incident inside was greatest when measured in all directions except for primary reflection was calculated using the simulation program Techwiz 1D (manufactured by Sanai Systems, Republic of Korea).

[0150] [Table 1]

[0151] [Table 2]

[0152] As shown in Table 1, the polarizing plate of the present invention exhibited significantly low reflectance at the side, a maximum reflectance of less than 2.5%, and excellent black luminance, and minimized contamination of the liquid crystal layer and / or panel by iodine eluted from the polarizer when the polarizing plate was left at high temperature and humidity for a long period of time.

[0153] On the other hand, as shown in Table 2, when the polarizing plates of the comparative examples were left at high temperature and humidity for a long period of time, contamination of the liquid crystal layer and / or panel occurred due to iodine eluted from the polarizer, and / or extremely low reflectance on the side surfaces and a maximum reflectance of less than 2.5% were not achieved.

[0154] Simple variations or modifications of the present invention can be easily implemented by those skilled in the art, and all such variations or modifications can be considered to be included within the scope of the present invention.

Claims

1. a polarizer and a retardation layer laminated on a lower surface of the polarizer, the retardation layer includes a negative C layer, a negative A layer, and a positive A layer, which are laminated in this order from the lower surface of the polarizer, The negative C layer has a thickness direction retardation of 20 nm to 60 nm at a wavelength of 550 nm.

2. 2. The polarizing plate according to claim 1, wherein the negative C layer has a front in-plane retardation of 0 nm to 10 nm at a wavelength of 550 nm.

3. The ratio of the negative C layer represented by the following formula 1 is 0.0005 nm / nm to 0.003 nm / nm, (Equation 1) A / B In the above formula 1, A is the thickness direction retardation (unit: nm) of the negative C layer at a wavelength of 550 nm, 2. The polarizer according to claim 1, wherein B is the thickness of the negative C layer (unit: nm).

4. The moisture permeability of the negative C layer is 400 g / m ２ 2. The polarizing plate according to claim 1, wherein the average reflection coefficient is 0.05-0.5 days or less.

5. 2. The polarizing plate according to claim 1, wherein the negative C layer is a film or coating layer containing a polymer having positive intrinsic birefringence.

6. 2. The polarizing plate according to claim 1, wherein the negative C layer is made of a triacetyl cellulose (TAC)-based resin, a cyclic olefin polymer (COP)-based resin, or a cyclic olefin copolymer (COC)-based resin.

7. 2. The polarizing plate according to claim 1, wherein the thickness of the laminate of the negative C layer, the negative A layer, and the positive A layer is 95% or more of the thickness of the retardation layer.

8. The polarizing plate according to claim 1 , wherein the laminate of the negative A layer and the positive A layer has reverse wavelength dispersion.

9. 2. The polarizing plate according to claim 1, wherein the linear retardation of the laminate of the negative A layer and the positive A layer at a wavelength of 550 nm is 120 nm to 180 nm.

10. 2. The polarizing plate according to claim 1, wherein the positive A layer has a lower in-plane retardation in the front direction at a wavelength of 550 nm than the negative A layer.

11. 11. The polarizing plate according to claim 10, wherein the positive A layer has a front in-plane retardation of 100 nm to 140 nm at a wavelength of 550 nm, and the negative A layer has a front in-plane retardation of 200 nm to 280 nm at a wavelength of 550 nm.

12. 2. The polarizing plate according to claim 1, wherein the angle between the slow axis of the positive A layer and the slow axis of the negative A layer is 55[deg.] to 65[deg.].

13. 2. The polarizing plate according to claim 1, wherein the slow axis of the positive A layer is at an angle of 70° to 85° to the light transmission axis of the polarizer, and the slow axis of the negative A layer is at an angle of 10° to 25° to the light transmission axis of the polarizer.

14. 2. The polarizing plate according to claim 1, wherein the positive A layer and the negative A layer are liquid crystal layers.

15. 15. The polarizer of claim 14, wherein the positive A layer is a nematic liquid crystal layer and the negative A layer is a discotic liquid crystal layer.

16. The polarizing plate of claim 1 , further comprising a second protective layer laminated on the upper surface of the polarizer.

17. An optical display device comprising the polarizing plate of any one of claims 1 to 16.

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