Polarizing plate and optical display device

Abstract

Provided are a polarizing plate comprising a polarizer and a retardation layer laminated on one surface of the polarizer, wherein the retardation layer has an in-plane retardation of 0 nm to 10 nm and a thickness direction retardation of −30 nm to −3 nm at a wavelength of 550 nm, and the polarizing plate has a light transmittance ratio of greater than 0.445 and less than 0.470 as defined by mathematical formula 1, and a light transmittance ratio of greater than 0.710 and less than 0.730 as defined by mathematical formula 2, 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] One example of an LCD device is one that has a liquid crystal layer in which liquid crystals are aligned in a horizontal alignment mode, such as an IPS (in-plane switching) mode or FFS (fringe field switching) mode LCD device. A horizontal alignment mode LCD device aligns liquid crystals horizontally, and when two electrodes are driven on one substrate, the liquid crystals rotate in a plane to transmit or block light, improving the viewing angle.

[0003] However, in a horizontal alignment mode LCD device, if there is a pretilt in the liquid crystal alignment, there is a high possibility that anisotropy in the hue or visual sensation between the left and right sides occurs. As a result, the visual sensation becomes non-uniform between the left and right sides, resulting in a bluish region that appears blue and a yellowish region that appears yellow, resulting in a difference in visual sensation or color sensation between the left and right sides.

[0004] Currently, technological development is underway to realize large screens, high resolution, and slim designs, and there is a demand for the development of polarizing plates that can eliminate the difference in visual perception between the left and right sides. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-251659 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, when applied to an optical display panel, reduces the difference in visual perception or color perception between the left and right sides, thereby improving the visual perception or color perception between the left and right sides.

[0007] Another object of the present invention is to provide a polarizing plate that has the effect of improving color uniformity when applied to a panel for an optical display device.

[0008] It is still another object of the present invention to provide a polarizing plate that provides the above-mentioned effects even when a single retardation layer is provided on the lower surface of the polarizer. [Means for solving the problem]

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

[0010] 1. A polarizing plate includes a polarizer and a retardation layer laminated on one surface of the polarizer, wherein the retardation layer has an in-plane retardation of 0 nm to 10 nm and a thickness direction retardation of −30 nm to −3 nm at a wavelength of 550 nm, and the polarizing plate has a light transmittance ratio of more than 0.445 and less than 0.470 as expressed by the following formula 1, and a light transmittance ratio of more than 0.710 and less than 0.730 as expressed by the following formula 2:

[0011] [Formula 1] Light transmittance ratio = TS390 / TS550

[0012] [Formula 2] Light transmittance ratio = TS400 / TS550 (In the above formulas 1 and 2, TS550 is the light transmittance (unit: %) of the polarizer at a wavelength of 550 nm. TS390 is the light transmittance of the polarizer at a wavelength of 390 nm (unit: %). TS400 is the light transmittance (unit: %) of the polarizing plate at a wavelength of 400 nm.

[0013] In 2.1, the polarizing plate may have a light transmittance of 10% to 20% at a wavelength of 390 nm, and a light transmittance of 25% to 35% at a wavelength of 400 nm.

[0014] In 3.1 to 3.2, the polarizing plate may have a light transmittance ratio of more than 0.795 and less than 0.805 as expressed by the following formula 3, and a light transmittance ratio of more than 0.835 and less than 0.850 as expressed by the following formula 4: [Formula 3] Light transmittance ratio = TS410 / TS550 [Formula 4] Light transmittance ratio = TS420 / TS550 (In the above formulas 3 and 4, TS550 is the light transmittance (unit: %) of the polarizer at a wavelength of 550 nm. TS410 is the light transmittance (unit: %) of the polarizer at a wavelength of 410 nm. TS420 is the light transmittance (unit: %) of the polarizing plate at a wavelength of 420 nm.

[0015] In 4.1 to 3, the polarizing plate may have a light transmittance of 33% to 35% at a wavelength of 410 nm, and the polarizing plate may have a light transmittance of 36% to 38% at a wavelength of 420 nm.

[0016] In 5.1 to 4, the retardation layer can be a negative C layer or a positive C layer.

[0017] In 6.1 to 6.5, the retardation layer may have higher light transmittance than the polarizer at wavelengths of 390 nm, 400 nm, 410 nm, 420 nm, and 550 nm.

[0018] In 7.1 to 6, the retardation layer may have a light transmittance of 45% to 62% at a wavelength of 390 nm, 70% to 90% at a wavelength of 400 nm, 75% to 95% at a wavelength of 410 nm, and 75% to 95% at a wavelength of 420 nm.

[0019] In 8.1 to 7, the retardation layer may include a film or coating layer containing a polymer having a positive intrinsic birefringence.

[0020] In 9.1 to 8, the retardation layer can be a triacetyl cellulose (TAC)-based, cyclic olefin polymer (COP)-based, or cyclic olefin copolymer (COC)-based layer.

[0021] In 10.1 to 9, the retardation layer may have a thickness ratio of 90% or more of the total retardation layers (total thickness of layers) laminated on the lower surface of the polarizer.

[0022] In 11.1 to 10, the slow axis of the retardation layer can be −5° to 5° when the light absorption axis of the polarizer is 0°.

[0023] In 12.1 to 11, a second protective layer may be further included which is laminated on another surface of the polarizer.

[0024] In 13.12, the second protective layer may have an in-plane retardation of 3,000 nm or more at a wavelength of 550 nm.

[0025] Another aspect of the present invention is an optical display device.

[0026] The optical display device includes the optical laminate of the present invention. [Effects of the Invention]

[0027] The present invention can provide a polarizing plate that, when applied to a panel for an optical display device, reduces the difference in visual perception or color perception between the left and right sides, thereby improving the visual perception or color perception between the left and right sides.

[0028] The present invention can provide a polarizing plate that can improve color uniformity when applied to an optical display panel.

[0029] The present invention can provide a polarizing plate that provides the above-mentioned effects even when a single retardation layer is provided on the lower surface of the polarizer. [Brief explanation of the drawings]

[0030] [Figure 1] 1 shows the results of the light transmittance of the polarizing plate at each wavelength for one example of the present invention (shown by a solid line) and a comparative example of the present invention (shown by a dotted line or a dashed-dotted line). In Fig. 1, the X axis represents wavelength (unit: nm), and the Y axis represents the ratio of the light transmittance at each wavelength on the X axis to the light transmittance at a wavelength of 550 nm. [Figure 2] FIG. 1 is a cross-sectional view of a polarizing plate according to an embodiment of the present invention. [Figure 3] 1 shows the evaluation results of Example 1. [Figure 4] 1 shows the evaluation results of Comparative Example 1. [Figure 5] The graph shows the color coordinate results for Example 2 and Comparative Example 1 at an azimuth angle of 60°, a left image of 135°, and a right image of 45°. [Figure 6] The graph shows the color coordinate results for Example 2 and Comparative Example 1 at an azimuth angle of 45°, with the left image at 135° and the right image at 45°. DETAILED DESCRIPTION OF THE INVENTION

[0031] The present invention may, however, be embodied in various different forms and should not be construed as limited to the embodiments set forth herein.

[0032] 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 a different meaning.

[0033] In order to clearly explain the present invention in the drawings, parts that are not relevant to the explanation are omitted, and the same or similar components are designated by the same reference numerals 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.

[0034] In this specification, "upper" and "lower" are defined based on the drawings, and "upper" may be changed to "lower" and "lower" to "upper" depending on the viewpoint, and what is described as "on" or "on" may include not only directly on but also the case where another structure is interposed between them. On the other hand, what is described as "directly on," "directly on," "directly formed on," or "formed in direct contact with" means that there is no other structure interposed between them.

[0035] In this specification, the "in-plane retardation (Re)", "thickness direction retardation (Rth)", and "degree of biaxiality (NZ)" are represented by the following mathematical formulas A, B, and C:

[0036] [Formula A] Re=(nx-ny)xd

[0037] [Formula B] Rth=((nx+ny) / 2-nz)xd

[0038] [Formula C] NZ=(nx-nz) / (nx-ny)

[0039] (In the above numbers A, B, and C, nx, ny, and nz are the refractive index in the slow axis direction, the fast axis direction, and the thickness direction of the optical element, respectively, at the measurement wavelength, and d is the thickness (unit: nm) of the optical element.) In the present invention, the in-plane retardation, thickness direction retardation, and degree of biaxiality are values ​​measured by transmitting light in the normal direction to the in-plane direction of the optical element.

[0040] In this specification, when describing angles, "+" indicates a clockwise angle relative to the reference (0°), and "-" indicates a counterclockwise angle relative to the reference (0°).

[0041] In this specification, when describing a numerical range, "X to Y" means X or more and Y or less.

[0042] The inventors of the present invention have provided a polarizer that reduces the difference in visual perception or color between the left and right sides when applied to an optical display panel, particularly a liquid crystal panel with a horizontal alignment mode of liquid crystal. The horizontal alignment mode of liquid crystal can be an in-plane switching (IPS) mode or a fringe field switching (FFS) mode.

[0043] The polarizing plate of the present invention includes a polarizer; and a retardation layer laminated on one surface of the polarizer, wherein (i) the retardation layer has an in-plane retardation of 0 nm to 10 nm and a thickness direction retardation of −30 nm to −3 nm at a wavelength of 550 nm, (ii) the polarizing plate has a light transmittance ratio of more than 0.445 and less than 0.460 as determined by the following mathematical formula 1, and (iii) the polarizing plate has a light transmittance ratio of more than 0.710 and less than 0.730 as determined by the following mathematical formula 2: [Formula 1] Light transmittance ratio = TS390 / TS550 [Formula 2] Light transmittance ratio = TS400 / TS550 (In the above formulas 1 and 2, TS550 is the light transmittance (unit: %) of the polarizer at a wavelength of 550 nm. TS390 is the light transmittance of the polarizer at a wavelength of 390 nm (unit: %). TS400 is the light transmittance (unit: %) of the polarizing plate at a wavelength of 400 nm.

[0044] In this specification, the "light transmittance" of a polarizing plate is not the crossed transmittance but the single transmittance, and is a value measured at specific wavelengths of 390 nm, 400 nm, 410 nm, 420 nm, and 550 nm by placing the polarizing plate in a light transmittance measuring device, for example, a V-7100, and transmitting light from the retardation layer side to the polarizer side in the normal direction to the in-plane direction of the polarizing plate.

[0045] By simultaneously satisfying the above (i), (ii), and (iii), a polarizing plate can provide the effect of improving the left-right visual perception or color perception by reducing the difference in visual perception or color perception between the left and right sides when applied to a horizontal alignment mode liquid crystal panel, and the effect of improving color uniformity when applied to an optical display panel. If any of the above (i), (ii), and (iii) is not satisfied, the effect of the present invention may not be achieved or may be significantly lower than that of the polarizing plate of the present invention. In the present invention, a retardation layer that satisfies the above (i) is laminated on one side of the polarizer, and the above (ii) and (iii) were devised to achieve the effect of improving the left-right visual perception or color perception and the effect of improving color uniformity by reducing the difference in visual perception or color perception between the left and right sides.

[0046] The above (ii) and (iii) are requirements for simultaneously improving the visual perception or color perception between the left and right sides and improving color uniformity in a polarizing plate having a retardation layer on one side of a polarizer, the retardation layer having an in-plane retardation of 0 nm to 10 nm and a thickness retardation of −30 to −3 nm at a wavelength of 550 nm. The above (ii) and (iii) are calculated by calculating the ratios of the light transmittance at wavelengths of 390 nm and 400 nm to the light transmittance at wavelengths of 550 nm of the polarizing plate, respectively. The wavelengths of 390 nm and 400 nm are wavelengths associated with blue light in the entire light spectrum, and the higher the light transmittance at wavelengths of 390 nm and 400 nm, the lower the degree of blue light absorption. However, the present inventors have confirmed that simply increasing the light transmittance at wavelengths of 390 nm and 400 nm only slightly improves the difference in the visual perception or color perception between the left and right sides. In response to this, the present inventors have derived the above (ii) and (iii) by considering the light transmittance at wavelengths of 390 nm and 400 nm, and the light transmittance at a wavelength of 550 nm together, and have confirmed that when the above (ii) and (iii) reach the specific ranges of the present invention, the visual perception or color perception of the left and right sides is significantly improved.

[0047] FIG. 1 shows the ratio of light transmittance at a specific wavelength to the light transmittance at a wavelength of 550 nm for a polarizing plate according to an embodiment of the present invention and a polarizing plate according to a comparative embodiment of the present invention that is not included in the present invention.

[0048] Referring to Figure 1, the polarizer of an embodiment of the present invention exhibited a difference in the ratio of light transmittance at a specific wavelength to light transmittance at a wavelength of 550 nm compared to the polarizers of the comparative examples. That is, the polarizer of an embodiment of the present invention exhibited a significantly higher or slightly higher ratio of light transmittance at a specific wavelength to light transmittance at a wavelength of 550 nm compared to the polarizers of the comparative examples. Nevertheless, the polarizer of an embodiment of the present invention exhibited a significant effect in terms of the difference in visual perception or color perception between the left and right sides compared to the polarizers of the comparative examples. This will be explained in the following examples and comparative examples.

[0049] In one specific example, the polarizing plate may have a light transmittance ratio of 0.450 to 0.460 as expressed in Formula 1, and may have a light transmittance ratio of 0.711 to 0.729 as expressed in Formula 2. Within these ranges, it is easy to control the effects of the present invention and to manufacture the polarizing plate of the present invention.

[0050] In one embodiment, the polarizing plate may have a light transmittance of 42.5% to 43.5%, preferably 42.7% to 43.3% at a wavelength of 550 nm. Within this range, the effects of the present invention may be easily realized.

[0051] In one embodiment, the polarizing plate may have a light transmittance of 10% to 20%, preferably 19% to 20%, at a wavelength of 390 nm. Within this range, the effects of the present invention may be easily realized.

[0052] In one embodiment, the polarizing plate may have a light transmittance of 25% to 35%, preferably 30% to 32%, more preferably 30.5% to 32%, or 30.5% to 31% at a wavelength of 400 nm. Within this range, the effects of the present invention may be easily realized.

[0053] The ratio of the above formula 1 and the ratio of the above formula 2 can be realized by adjusting the polarizer and / or the retardation layer in the polarizing plate, which will be described in detail below.

[0054] The polarizing plate may have a light transmittance ratio of more than 0.795 and less than 0.805 as expressed in the following mathematical formula 3, and a light transmittance ratio of more than 0.835 and less than 0.850 as expressed in the following mathematical formula 4. Within these ranges, the difference in visual perception or color perception between the left and right sides is reduced, thereby further improving the effect of improving the visual perception or color perception between the left and right sides, and when applied to a panel for an optical display device, the effect of improving color uniformity can be further improved.

[0055] [Formula 3] Light transmittance ratio = TS410 / TS550 [Formula 4] Light transmittance ratio = TS420 / TS550 (In the above formulas 3 and 4, TS550 is the light transmittance (unit: %) of the polarizer at a wavelength of 550 nm. TS410 is the light transmittance (unit: %) of the polarizer at a wavelength of 410 nm. TS420 is the light transmittance (unit: %) of the polarizing plate at a wavelength of 420 nm.

[0056] The ratios of Formula 3 and Formula 4 are requirements for achieving significant effects of improving left-right visual perception or color perception and color uniformity in a polarizing plate having a retardation layer on one side of a polarizer, the retardation layer having an in-plane retardation of 0 nm to 10 nm and a thickness direction retardation of -30 nm to -3 nm at a wavelength of 550 nm. The ratios of Formula 3 and Formula 4 are calculated by calculating the ratios of the light transmittance at wavelengths of 410 nm and 420 nm to the light transmittance at wavelengths of 550 nm of the polarizing plate, respectively. The wavelengths of 410 nm and 420 nm are wavelengths associated with blue light in the entire light spectrum, and the higher the light transmittance at wavelengths of 410 nm and 420 nm, the lower the degree of blue light absorption. The inventors have derived the ratio of the above formula 3 and the ratio of the above formula 4 by considering the light transmittance in the wavelength bands of 410 nm and 420 nm and the light transmittance at a wavelength of 550 nm together, and have confirmed that when the ratio of the above formula 3 and the ratio of the above formula 4 fall within the specific range of the present invention, the visual perception or color perception of the left and right eyes is significantly improved.

[0057] In one specific example, the polarizing plate may have a light transmittance ratio of 0.798 or more but less than 0.805 as expressed in Formula 3, and may have a light transmittance ratio of 0.836 to 0.849 as expressed in Formula 4. Within these ranges, it may be easy to control the effects of the present invention and to manufacture the polarizing plate of the present invention.

[0058] In one embodiment, the polarizing plate may have a light transmittance of 33% to 35%, preferably 34% to 35%, or 34.3% to 34.8% at a wavelength of 410 nm. Within this range, the effects of the present invention may be easily realized.

[0059] In one embodiment, the polarizing plate may have a light transmittance of 36% to 38%, preferably 36% to 37% or 36.3% to 37.2% at a wavelength of 420 nm. Within this range, the effects of the present invention may be easily realized.

[0060] The ratio of Equation 3 and the ratio of Equation 4 can be realized by adjusting the polarizer and / or the retardation layer in the polarizing plate, which will be described in detail below.

[0061] The components of the polarizing plate of the present invention will be described in detail below.

[0062] retardation layer The retardation layer may be laminated on one side of the polarizer to help reduce the difference in visual perception or color perception between the left and right sides of the present invention. In one embodiment, the retardation layer may be laminated on the light incident surface of the polarizer for internal light, thereby making it easier to realize the effects of the present invention. The "internal light" refers to light emitted from a backlight unit, passed through a liquid crystal panel, and then incident on the polarizer.

[0063] The retardation layer has an in-plane retardation of 0 nm to 10 nm and a thickness direction retardation of −30 nm to −3 nm at a wavelength of 550 nm. The in-plane retardation and thickness direction retardation ranges can help reduce the difference in visual perception or color perception between the left and right sides. For example, the retardation layer has an in-plane retardation of 0 nm, 1 nm, 2 nm, 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, or 10 nm at a wavelength of 550 nm, and a thickness direction retardation of -30 nm, -29 nm, -28 nm, -27 nm, -26 nm, -25 nm, -24 nm, -23 nm, -22 nm, -21 nm, -20 nm, -19 nm, -18 nm, -17 nm, -16 nm, -15 nm, -14 nm, -13 nm, -12 nm, -11 nm, -10 nm, -9 nm, -8 nm, -7 nm, -6 nm, -5 nm, -4 nm, or -3 nm at a wavelength of 550 nm.

[0064] In one specific example, the retardation layer can have an in-plane retardation of 0 nm to 5 nm and a thickness direction retardation of −20 nm to −3 nm.

[0065] The retardation layer may have a degree of biaxiality at a wavelength of 550 nm of 1.40 to 1.60, for example, 1.45 to 1.50. Within this range, the retardation layer may be easily manufactured and may help reduce the difference in visual perception or color perception between the left and right.

[0066] In one embodiment, the retardation layer may be a negative C layer having a refractive index relationship of the following Equation 5: [Formula 5] nx≒ny>nz (In the above formula 5, nx, ny, and nz are the refractive indices of the retardation layer in the slow axis direction, fast axis direction, and thickness direction at a wavelength of 550 nm).

[0067] In one embodiment, the retardation layer may have higher light transmittance at wavelengths of 390 nm, 400 nm, 410 nm, 420 nm, and 550 nm than the polarizer at the same wavelengths, thereby enabling the polarizing plate of the present invention to reduce color unevenness between the left and right sides.

[0068] For example, the retardation layer may have a light transmittance of 45% to 62%, preferably 48% to 60%, at a wavelength of 390 nm. For example, the retardation layer may have a light transmittance of 70% to 90%, preferably 72% to 85%, at a wavelength of 400 nm. For example, the retardation layer may have a light transmittance of 75% to 95%, preferably 80% to 90%, at a wavelength of 410 nm. For example, the retardation layer may have a light transmittance of 75% to 95%, preferably 80% to 92%, at a wavelength of 420 nm. For example, the retardation layer may have a light transmittance of 80% to 95%, preferably 83% to 92%, at a wavelength of 550 nm.

[0069] In another embodiment, the retardation layer can be a positive C layer.

[0070] The retardation layer may have a slow axis, which is an axis with a high refractive index, and a fast axis, which is an axis with a low refractive index, in the in-plane direction. The slow axis of the retardation layer may be at an angle of -5° to 5°, preferably -3° to 3°, relative to the light absorption axis of the polarizer being 0°. Within this range, the effects of the present invention may be easily realized.

[0071] The retardation layer may be made of any material as long as it can achieve the in-plane retardation and thickness retardation described above by stretching, coating, and / or drying. For example, the retardation layer may be a liquid crystal layer or a non-liquid crystal layer. For example, the retardation layer may be a stretched film or a hardened coating layer. The liquid crystal layer essentially requires the formation of an alignment film for aligning the liquid crystal, and the generation of foreign matter during the formation of the liquid crystal layer may be a problem.

[0072] In one embodiment, the retardation layer can 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.

[0073] In one specific example, the retardation layer may be a cellulose-based material including triacetyl cellulose (TAC), a cyclic olefin polymer (COP), a norbornene-based material including cyclic olefin copolymer (COC), etc. In one specific example, the retardation layer may be a film made of one or more resins including polyester-based materials including polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate (PEN), polybutylene naphthalate, etc., polycarbonate-based materials, polyethersulfone-based materials, polysulfone-based materials, polyamide-based materials, polyimide-based materials, polyolefin-based materials, polyarylate-based materials, polyvinyl alcohol-based materials, polyvinyl chloride-based materials, and polyvinylidene chloride-based materials.

[0074] In another embodiment, the retardation layer may contain at least one of a polystyrene-based polymer and a cellulose-based polymer. In one embodiment, the retardation layer may be formed of a composition containing at least one of a halogen-containing polystyrene-based polymer and a halogen-containing cellulose-based polymer. The halogen may be fluorine.

[0075] The halogen-containing polystyrene polymer may include repeating units of Formula 1:

[0076] [ka] [Chemical formula 1]

[0077] (In the above Chemical Formula 1, JPEG2025540530000003.jpg416 is the linkage site, R 1 ,R 2 ,R 3 are each independently a hydrogen atom, an alkyl group, a substituted alkyl group, or a halogen; R are each independently an alkyl, substituted alkyl, halogen, hydroxy, carboxy, nitro, alkoxy, amino, sulfonate, phosphate, acyl, acyloxy, phenyl, alkoxycarbonyl, or cyano group; R 1 ,R 2 ,R 3 and / or at least one R is a halogen and n is an integer from 0 to 5).

[0078] In one embodiment, halogen means fluorine (F), Cl, Br or I, preferably F.

[0079] The halogen-containing polystyrene polymer can be formed by polymerizing a mixture containing at least one of 1-(2,2-difluoroethenyl)-2-fluorobenzene and 1',2',2'-trifluorostyrene, for example. The mixture can further contain styrene.

[0080] The cellulose-based polymer may contain at least units in which at least some of the hydrogen atoms (H) of the hydroxyl groups (C2 hydroxyl, C3 hydroxyl, or C6 hydroxyl) of the sugar monomers constituting cellulose are substituted with acyl groups or ether groups. In other words, the cellulose-based polymer may contain one or more of a cellulose ester polymer and a cellulose ether polymer.

[0081] For example, the cellulose-based polymer may include a cellulose ester-based polymer containing at least a unit in which at least some of the hydrogen atoms (H) of the hydroxyl groups of the sugar monomers constituting cellulose [hydroxyl group at C2, hydroxyl group at C3, or hydroxyl group at C6] are substituted with acyl groups, as represented by the following formula 2: In this case, the acyl groups may be substituted or unsubstituted.

[0082] [ka] [Chemical formula 2] (In the above formula 2, n is an integer of 1 or more)

[0083] Substituents for the cellulose ester or acyl groups can each include one or more of halogen, nitro, alkyl (e.g., alkyl groups having 1 to 20 carbon atoms), alkenyl (e.g., alkenyl groups having 2 to 20 carbon atoms), cycloalkyl (e.g., cycloalkyl groups having 3 to 10 carbon atoms), aryl (e.g., aryl groups having 6 to 20 carbon atoms), heteroaryl (e.g., aryl groups having 3 to 10 carbon atoms), alkoxy (e.g., alkoxy groups having 1 to 20 carbon atoms), acyl, and halogen-containing functional groups. The substituents may be the same or different.

[0084] As known to those skilled in the art, the "acyl" can be RC(=O)-* (* is a linking symbol, and R is an alkyl group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, or an arylalkyl group having 7 to 20 carbon atoms). The "acyl" is bonded to the cellulose ring through an ester bond (via an oxygen atom) in cellulose.

[0085] The "alkyl", "alkenyl", "cycloalkyl", "aryl", "heteroaryl", "alkoxy", and "acyl" are each, for convenience, non-halogen-based. The composition for the second retardation layer may contain the cellulose ester alone or a mixture of the cellulose esters.

[0086] The "halogen" means fluorine (F), Cl, Br or I, and preferably F.

[0087] The "halogen-containing functional group" may be an organic functional group containing one or more halogens, and may include an aromatic, aliphatic, or alicyclic functional group. For example, the halogen-containing functional group may be a halogen-substituted alkyl group having 1 to 20 carbon atoms, a halogen-substituted alkenyl group having 2 to 20 carbon atoms, a halogen-substituted alkynyl group having 2 to 20 carbon atoms, a halogen-substituted cycloalkyl group having 3 to 10 carbon atoms, a halogen-substituted alkoxy group having 1 to 20 carbon atoms, a halogen-substituted acyl group, a halogen-substituted aryl group having 6 to 20 carbon atoms, or a halogen-substituted arylalkyl group having 7 to 20 carbon atoms, but is not limited thereto.

[0088] The "halogen-substituted acyl group" can be R'-C(=O)-* (* is a linking symbol, and R' is a halogen-substituted C1-C20 alkyl group, a halogen-substituted C3-C20 cycloalkyl group, a halogen-substituted C6-C20 aryl group, or a halogen-substituted C7-C20 arylalkyl group). The "halogen-substituted acyl group" is bonded to the cellulose ring through an ester bond (via an oxygen atom) in cellulose.

[0089] Cellulose ester polymers can be prepared by conventional methods known to those skilled in the art, or can be purchased and used as commercially available products.For example, cellulose ester polymers having acyl as a substituent can be prepared by reacting trifluoroacetic acid or trifluoroacetic anhydride with the sugar monomer or sugar monomer polymer that constitutes cellulose of the above formula 2, or by reacting trifluoroacetic acid or trifluoroacetic anhydride and then further reacting with an acylating agent (for example, carboxylic acid anhydride or carboxylic acid), or by reacting trifluoroacetic acid or trifluoroacetic anhydride and an acylating agent together, followed by polymerization.

[0090] The retardation layer can have a thickness of 20 μm to 80 μm, preferably 30 μm to 50 μm. A thickness in this range can be used in a polarizing plate.

[0091] The retardation layer may have a thickness ratio of 90% or more, for example, 99% to 100%, of the total thickness of the retardation layer laminated on the lower surface of the polarizer. Within this range, the effects of the present invention can be realized, and the effect of making the polarizing plate thinner can also be realized.

[0092] The retardation layer may further have one or more first protective layers laminated on one surface or another surface.

[0093] The first protective layer can increase the mechanical strength of the polarizing plate or provide an additional function to the retardation layer.

[0094] In one specific example, the first protective layer can be a positive A layer satisfying nx>ny≒nz or a negative A layer satisfying nx≒nz>ny. The first protective layer can be a liquid crystal layer or a non-liquid crystal layer. Here, nx, ny, and nz are the refractive indices of the first protective layer in the slow axis direction, fast axis direction, and thickness direction at a wavelength of 550 nm.

[0095] In one embodiment, the retardation layer may be disposed closer to the polarizer than the first protective layer, which may facilitate realization of the effects of the present invention.

[0096] The retardation layer can be attached to the polarizer or the first protective layer via an adhesive layer or pressure-sensitive adhesive layer. The adhesive layer or pressure-sensitive adhesive layer can be formed of a photocurable or thermosetting adhesive or pressure-sensitive adhesive. The adhesive layer or pressure-sensitive adhesive layer can have a thickness of 1 μm to 30 μm, for example, 2 μm to 10 μm, or 2 μm to 3 μm. A thickness within this range can be used in a polarizing plate.

[0097] Polarizer The polarizer includes a light-absorbing polarizer that has the function of separating incident light into two orthogonal polarized components, transmitting one polarized component, and absorbing the other polarized component.

[0098] In one embodiment, the axis with a higher refractive index in the in-plane direction of the polarizer may be the polarizer's light absorption axis, and the axis with a lower refractive index may be the polarizer's light transmission axis. In one embodiment, the polarizer's light absorption axis may be the polarizer's machine direction (MD), and the polarizer's light transmission axis may be the polarizer's transverse direction (TD).

[0099] The polarization degree of the polarizer can be 95% or more, specifically 95% to 100%, and more specifically 98% to 100%. Within this range, the effects of the present invention can be easily achieved.

[0100] The polarizer may include a uniaxially stretched polarizer containing a dichroic dye. Specifically, the polarizer containing a dichroic dye may include a polarizer manufactured by uniaxially stretching a polarizer substrate film in the MD direction and dyeing it with a dichroic dye (e.g., containing iodine or potassium iodide as an iodine-containing substance). The polarizer substrate film may include, but is not limited to, a polyvinyl alcohol film or a derivative thereof. The polarizer may be manufactured by a conventional method known to those skilled in the art.

[0101] The polarizer can have a thickness of 1 μm to 40 μm, specifically 15 μm to 30 μm, and more specifically 17 μm to 20 μm. A thickness in this range can be used for a polarizing plate.

[0102] The polarizing plate of the present invention includes a polyvinyl alcohol-based film and a polarizer manufactured by the manufacturing process described in detail below, which makes it easy for the polarizing plate to satisfy Formulas 1 and 2, and preferably Formulas 3 and 4 in addition to Formulas 1 and 2.

[0103] The polyvinyl alcohol-based film can be any conventional polyvinyl alcohol-based film known to those skilled in the art.

[0104] In one embodiment, the polyvinyl alcohol-based film contains hydrophilic and hydrophobic functional groups, and the hydrophobic functional groups are present in addition to the hydroxyl (OH) groups, which are hydrophilic functional groups present in the polyvinyl alcohol-based film.

[0105] The hydrophobic functional group is present in one or more of the main chain and side chain of the polyvinyl alcohol resin constituting the polyvinyl alcohol film. The "main chain" refers to the part that forms the main skeleton of the polyvinyl alcohol resin, and the "side chain" refers to the skeleton connected to the main chain. Preferably, the hydrophobic functional group may be present in the main chain of the polyvinyl alcohol resin.

[0106] Polyvinyl alcohol resins incorporating hydrophilic and hydrophobic functional groups can be prepared by polymerizing one or more vinyl ester monomers, such as vinyl acetate, vinyl formate, vinyl propionate, vinyl butyrate, vinyl pivalate, and isopropyl acetate, with a monomer providing a hydrophobic functional group. Preferably, the vinyl ester monomer can include vinyl acetate. The monomer providing the hydrophobic functional group can include a monomer providing a hydrocarbon repeating unit, such as ethylene or propylene.

[0107] The polyvinyl alcohol film may have a thickness of 50 μm or less, for example, 10 μm to 50 μm. Within this range, the film may not melt or break during stretching.

[0108] The polarizer can be produced by subjecting the polyvinyl alcohol-based film to the following dyeing, stretching, crosslinking, color-complementing, and drying steps, which will be described in detail below. The order of the dyeing, stretching, and crosslinking steps may be changed depending on the type of polyvinyl alcohol-based film and the manufacturing process of the polarizer.

[0109] The dyeing step includes treating the polyvinyl alcohol-based film in a dyeing bath containing a dichroic substance. In the dyeing step, the polyvinyl alcohol-based film is immersed in the dyeing bath containing a dichroic substance. The dichroic substance-containing dyeing bath contains an aqueous solution containing a dichroic substance and boric acid. By containing both the dichroic substance and the boron compound in the dyeing bath, the polyvinyl alcohol-based film is dyed, and breakage of the polyvinyl alcohol-based film may not occur even when stretched under the stretching conditions described in detail below.

[0110] The dichroic substance may contain, as iodine, one or more of potassium iodide, hydrogen iodide, lithium iodide, sodium iodide, zinc iodide, lithium iodide, aluminum iodide, lead iodide, and copper iodide. The dichroic substance may be contained in the dyeing bath, preferably in the dyeing solution, at a concentration of 0.5 mol / ml to 10 mol / ml, preferably 0.5 mol / ml to 5 mol / ml. Within this range, the effect of enabling uniform dyeing can be achieved.

[0111] The boron compound can help prevent melting and rupture of the polyvinyl alcohol-based film during stretching, and can help prevent melting and rupture of the polyvinyl alcohol-based film even when stretched at a high temperature and a high stretch ratio in the stretching process performed after the dyeing process.

[0112] The boron compound may include one or more of boric acid and borax. The boron compound may be contained in the dyeing bath, preferably in the dyeing aqueous solution, in an amount of 0.1 to 5% by weight, preferably 0.3 to 3% by weight. Within this range, melting and breakage do not occur during the stretching process, and high reliability can be achieved.

[0113] The temperature of the dyeing solution is preferably 20° C. to 50° C., specifically 25° C. to 40° C. The dyeing step can be carried out by immersing the polyvinyl alcohol film in the dyeing bath for 30 to 120 seconds, specifically 40 to 80 seconds.

[0114] The stretching step involves stretching the dyed polyvinyl alcohol film at a stretching ratio of 5.7 times or more, for example, 5.7 to 7 times, and at a stretching temperature of 57°C or more, for example, 57 to 65°C.

[0115] The stretching step is carried out by either wet stretching or dry stretching. Preferably, the stretching step includes wet stretching in order to apply a boron compound in the stretching step. Wet stretching involves uniaxially stretching the polyvinyl alcohol-based film in the mechanical direction in an aqueous solution containing a boron compound.

[0116] The boron compound may contain one or more of boric acid and borax, preferably boric acid. The boron compound may be contained in the stretching bath, preferably in the stretching aqueous solution, at 0.5% to 10% by weight, preferably 1% to 5% by weight. Within this range, melting and fracture do not occur during the stretching process, and high reliability can be achieved.

[0117] The crosslinking process is performed to strengthen the adsorption of the dichroic material in the stretched polyvinyl alcohol film. The crosslinking solution used in the crosslinking process contains a boron compound. The boron compound not only strengthens the adsorption of the dichroic material, but also helps improve the reliability of the polarizer even when exposed to thermal shock.

[0118] The boron compound may contain one or more of boric acid and borax. The boron compound may be contained in the crosslinking bath, preferably in the crosslinking aqueous solution, at 0.5% by weight to 10% by weight, preferably 1% by weight to 5% by weight. Within this range, melting and breakage do not occur during the stretching process, and high reliability can be achieved. The temperature of the crosslinking bath solution is preferably 20°C to 50°C, specifically 25°C to 40°C. The crosslinking process can be carried out by immersing the polyvinyl alcohol film in the crosslinking bath for 30 to 120 seconds, specifically 40 to 80 seconds.

[0119] The color-complementing step can improve the durability of the polarizer. The color-complementing bath can contain a color-complementing solution containing more than 0% by weight and 10% by weight or less, preferably 1% to 4.5% by weight, of potassium iodide. The color-complementing solution can be kept at 20°C to 50°C, specifically 25°C to 40°C. The color-complementing treatment can be carried out by immersing the polyvinyl alcohol film in the color-complementing bath for 5 to 50 seconds, specifically 5 to 20 seconds.

[0120] The drying step can be performed by treating the polyvinyl alcohol film after the color complementing step at 30° C. to 80° C., preferably 40° C. to 80° C., for 2 minutes or less, preferably 1 minute to 2 minutes. The drying step can be performed by hot air drying or the like, but is not limited thereto.

[0121] The ratios of Formula 1 and Formula 2 of the present invention can be realized by adjusting the conditions in the complementary color process and the drying process in the manufacturing process of the polarizer. The ratios of Formula 3 and Formula 4 of the present invention can be realized by adjusting the conditions in the complementary color process and the drying process in the manufacturing process of the polarizer.

[0122] Before the dyeing process, the polyvinyl alcohol film may be further subjected to one or more of a water washing process and a swelling process.

[0123] The water washing step involves washing the polyvinyl alcohol film with water to remove foreign matter adhering to the polyvinyl alcohol film.

[0124] The swelling step can facilitate dyeing and stretching of the dichroic material by immersing the polyvinyl alcohol film in a swelling bath at a predetermined temperature range. The swelling step can include treatment at 15°C to 35°C, preferably 20°C to 30°C, for 30 to 50 seconds.

[0125] The polarizer can have a polarization degree of 99.996% or higher.

[0126] The polarizing plate may include one or more second protective layers laminated on another surface of the polarizer.

[0127] 2nd protective layer The second protective layer is disposed on the light exit surface of the internal light polarizer and acts on the light exiting from the polarizer, thereby improving image quality and protecting the polarizer.

[0128] The second protective layer can include a protective film or a protective coating layer.

[0129] The protective film may be an optically transparent film, such as a film made of one or more resins, including cellulose-based films including triacetyl cellulose (TAC), polyester-based films including polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate (PEN), and polybutylene naphthalate, cyclic polyolefin-based films, polycarbonate-based films, polyethersulfone-based films, polysulfone-based films, polyamide-based films, polyimide-based films, polyolefin-based films, polyarylate-based films, polyvinyl alcohol-based films, polyvinyl chloride-based films, and polyvinylidene chloride-based films. Specifically, TAC and PET films may be used. The protective coating layer may be formed from one or more of a thermosetting coating layer composition and a photocurable coating layer composition.

[0130] In one embodiment, the second protective layer can be a retardation film.

[0131] In one specific example, the second protective layer has an in-plane retardation (Re) at a wavelength of 550 nm of 3,000 nm or more, specifically 5,000 nm to 15,000 nm, more specifically 5,000 nm to 12,000 nm, which can improve the front brightness ratio and suppress rainbow unevenness.

[0132] In one specific example, the second protective layer has a thickness direction retardation (Rth) of 6,000 nm or more, specifically 6,000 nm to 15,000 nm, more specifically 6,000 nm to 12,000 nm, at a wavelength of 550 nm. Within this range, effects such as suppressing unevenness due to non-uniform birefringence and improving the viewing angle characteristics of a liquid crystal display device can be achieved.

[0133] In one specific example, the degree of biaxiality (NZ) of the second protective layer at a wavelength of 550 nm can be 2.5 or less, specifically 1.0 to 2.2, more specifically 1.2 to 2.0, and most specifically 1.4 to 1.8. Within this range, effects such as suppressing unevenness due to non-uniform birefringence and maintaining the mechanical strength of the film can be achieved.

[0134] In one embodiment, the second protective layer can be a film made of the above-mentioned material and stretched at a predetermined stretch ratio, so that the protective layer has a slow axis and a fast axis in the in-plane direction.

[0135] In one embodiment, the second protective layer may have an in-plane axis with a low refractive index in the machine direction (MD) of the second protective layer and an in-plane axis with a high refractive index in the transverse direction (TD) of the second protective layer, in which case the second protective layer may be a TD uniaxially stretched protective film.

[0136] In another embodiment, the second protective layer may have an in-plane axis with a low refractive index in the cross direction (TD) of the second protective layer, and an in-plane axis with a low refractive index in the mechanical direction (MD) of the second protective layer, in which case the second protective layer may be an MD uniaxially stretched protective film.

[0137] In another embodiment, the second protective layer may have an in-plane axis of low refractive index that is tilted relative to the width direction of the second protective layer, and an in-plane axis of high refractive index that is tilted relative to the mechanical direction of the second protective layer, in which case the second protective layer may be a MD and TD biaxially oriented film or a MD and TD biaxially oriented coating layer.

[0138] In one embodiment, the second protective layer can comprise a TD uniaxially or biaxially stretched protective film having the above-mentioned low refractive index axis and high refractive index axis in the in-plane direction.

[0139] In TD uniaxial stretching, the second protective layer can be produced by a stretched film manufacturing method that includes stretching a melt-extruded, unstretched film resin in the TD direction alone by 100% to 200%, preferably 120% to 140%, of the TD width of the original resin. Stretching can be performed by one or more of dry stretching and wet stretching, and the stretching temperature can be (Tg-20)°C to (Tg+50)°C, based on the glass transition temperature (Tg) of the protective film resin, specifically 70°C to 250°C, more specifically 80°C to 200°C, and even more specifically 100°C to 200°C. The same stretching effect can be achieved across the board within this range.

[0140] The second protective layer may have a thickness of 100 μm or less, specifically more than 0 μm and 100 μm or less, and more specifically 10 μm to 90 μm, and can be used in polarizing plates within this range.

[0141] The second protective layer may further include a functional coating layer formed on at least one surface thereof, which may be a hard coating layer, an anti-fingerprint layer, an anti-reflection layer, a low-reflection layer, an anti-glare layer, a primer layer, or the like.

[0142] In one specific example, the second protective layer may have higher light transmittance at wavelengths of 390 nm, 400 nm, 410 nm, 420 nm, and 550 nm than the polarizer at the same wavelengths.

[0143] For example, the retardation layer may have a light transmittance of 45% to 62%, preferably 48% to 60%, at a wavelength of 390 nm. For example, the retardation layer may have a light transmittance of 70% to 90%, preferably 72% to 85%, at a wavelength of 400 nm. For example, the retardation layer may have a light transmittance of 75% to 95%, preferably 80% to 90%, at a wavelength of 410 nm. For example, the retardation layer may have a light transmittance of 75% to 95%, preferably 80% to 92%, at a wavelength of 420 nm. For example, the retardation layer may have a light transmittance of 80% to 95%, preferably 83% to 92%, at a wavelength of 550 nm.

[0144] The second protective layer can be attached to the polarizer with an adhesive or pressure-sensitive adhesive layer. The adhesive or pressure-sensitive adhesive layer can be formed of a photocurable or thermosetting adhesive or pressure-sensitive adhesive. The thickness of the adhesive or pressure-sensitive adhesive layer can be 1 μm to 30 μm, for example, 2 μm to 10 μm, or 2 μm to 3 μm.

[0145] 2 is a cross-sectional view of a polarizing plate according to an embodiment of the present invention. Referring to FIG. 2, the polarizing plate may include a polarizer 10, a retardation layer 20 laminated on the lower surface of the polarizer 10, and a second protective layer 30 laminated on the upper surface of the polarizer 10.

[0146] The optical display device of the present invention includes the polarizer of the present invention. In one embodiment, the optical display device can include an IPS or FFS mode liquid crystal display device.

[0147] A liquid crystal display device includes a liquid crystal panel, a polarizing plate of the present invention laminated on the light-exiting surface of the liquid crystal panel, and a polarizing plate (light source-side polarizing plate) disposed on the light-incident surface of the liquid crystal panel. The polarizing plate disposed on the light-incident surface may include polarizing plates commonly known to those skilled in the art. The polarizing plate of the present invention can be used as a viewer-side polarizing plate. However, the present invention is not limited thereto, and the polarizing plate of the present invention can be used as a viewer-side polarizing plate or a light source-side polarizing plate.

[0148] The liquid crystal panel changes the orientation of the liquid crystal depending on whether or not a voltage is applied, and as a result, can emit light emitted from a light source.

[0149] The liquid crystal panel may include a pair of substrates and a liquid crystal layer as a display medium between the substrates. One substrate (color filter substrate) may be provided with a color filter and a black matrix, and the other substrate (active matrix substrate) may be provided with switching elements (e.g., TFTs) that control the electro-optical properties of the liquid crystal, as well as signal lines and pixel lines that apply gate signals to the switching elements, but is not limited thereto.

[0150] In one embodiment, the liquid crystal panel can employ an IPS or FFS mode liquid crystal, which can improve the viewing angle characteristics of the liquid crystal display device.

[0151] The LCD device includes a light source on the lower surface of the light source-side polarizer. The light source may include a light source having a continuous emission spectrum. For example, the light source may be a white LED light source, a quantum dot (QD) light source, or a metal fluoride red phosphor light source, specifically KSF (K2SiF6:Mn 4+ ) phosphor or KTF (K2TiF6:Mn 4+ ) phosphor-containing light sources, etc. [Example]

[0152] The present invention will be described in more detail with reference to preferred examples below. However, the following examples are provided to aid in understanding the present invention and are not intended to limit the scope of the present invention.

[0153] Example 1 (1) Polarizer manufacturing A polyvinyl alcohol film (VF-TS #4500, Kuraray, thickness 45 μm) washed with water at 25° C. was subjected to a swelling treatment in a swelling bath of water at 30° C.

[0154] The film that had passed through the swelling bath was treated for 65 seconds in a dyeing bath at 30°C containing an aqueous solution containing 1 mol / ml potassium iodide and 1 wt% boric acid. The film that had passed through the dyeing bath was stretched at an MD uniaxial stretching ratio of 5.7 times in a wet stretching bath containing an aqueous solution at 60°C containing 3 wt% boric acid. The film that had passed through the wet stretching bath was treated for 65 seconds in a crosslinking bath containing an aqueous solution at 25°C containing 3 wt% boric acid.

[0155] The film that had passed through the crosslinking bath was treated for 10 seconds in a color complementing bath containing a color complementing solution, which was an aqueous solution containing 4.5 wt% of potassium iodide at 30°C. The film that had passed through the color complementing bath was washed with water and dried with hot air at 80°C for 1 minute to produce a polarizer (thickness: 17 μm).

[0156] (2) Preparation of the retardation layer A retardation layer (ZRD40SL, Fuji, thickness: 40 μm, Re: 0 nm, Rth: -5 nm at a wavelength of 550 nm, triacetyl cellulose-based, negative C layer) was prepared. The retardation layer was a single layer.

[0157] (3) Manufacture of polarizing plates A photocurable adhesive (epoxy resin adhesive) was applied to both sides of the prepared polarizer. A PET film (thickness: 85 μm, polyethylene terephthalate film with an anti-glare layer formed on the upper surface, AGSR12D-PET, DNP) was attached to the upper surface of the polarizer as a second protective layer. The prepared retardation layer was placed on the lower surface of the polarizer to prepare a polarizing plate laminated in the order of second protective layer-adhesive layer-polarizer-adhesive layer-retardation layer. The slow axis of the retardation layer forms an angle of 0° when the light absorption axis of the polarizer is taken as 0°.

[0158] Example 2 A polarizing plate was manufactured in the same manner as in Example 1, except that when manufacturing the polarizer in Example 1, the film was treated for 10 seconds in a color-complementing bath containing a color-complementing solution, which was an aqueous solution containing 4.0 wt% potassium iodide at 30°C, and the film that had passed through the color-complementing bath was washed with water and dried with hot air at 65°C for 1 minute to manufacture a polarizer.

[0159] Example 3 A polarizing plate was manufactured in the same manner as in Example 1, except that when manufacturing the polarizer in Example 1, the film was treated for 10 seconds in a color-complementing bath containing a color-complementing solution, which was an aqueous solution containing 3.5 wt% potassium iodide at 30°C, and the film that had passed through the color-complementing bath was washed with water and dried with hot air at 45°C for 1 minute to manufacture a polarizer.

[0160] Comparative Example 1 A polarizing plate was manufactured in the same manner as in Example 1, except that the polarizer was manufactured by treating the film in a color-complementing bath containing a color-complementing solution, which was an aqueous solution containing 4.5 wt % potassium iodide at 30°C, for 10 seconds, washing the film after passing through the color-complementing bath, and drying it with hot air at 85°C for 1 minute.

[0161] Comparative Example 2 A polarizing plate was manufactured in the same manner as in Example 1, except that when manufacturing the polarizer in Example 1, the film was treated for 10 seconds in a color complementing bath containing a color complementing solution, which was an aqueous solution containing 6.0 wt% potassium iodide at 30°C, and the film that had passed through the color complementing bath was washed with water and dried with hot air at 85°C for 1 minute to manufacture a polarizer.

[0162] Comparative Example 3 A polarizing plate was manufactured in the same manner as in Example 1, except that when manufacturing the polarizer in Example 1, the film was treated for 10 seconds in a color-complementing bath containing a color-complementing solution, which was an aqueous solution containing 5.0% potassium iodide at 30°C, and the film that had passed through the color-complementing bath was washed with water and dried with hot air at 95°C for 1 minute to manufacture a polarizer.

[0163] Manufacturing of light source side polarizer A polarizer was fabricated in the same manner as described above. A triacetyl cellulose (TAC) film (KC4CT1SW, Konica Minolta Opto, Inc., thickness: 40 μm) was attached to the upper surface of the fabricated polarizer, and a polyethylene terephthalate (PET) film (Toyobo Co., Ltd., thickness: 80 μm, Re: 8400 nm, Rth: 9800 nm at a wavelength of 550 nm) was attached to the lower surface of the polarizer to fabricate a light source side polarizing plate.

[0164] LCD module manufacturing The polarizers manufactured in the above examples and comparative examples were attached to the light-exiting surface of an IPS liquid crystal-containing liquid crystal panel using an adhesive layer. The negative C layer side of the polarizer was attached to the liquid crystal panel. The light-source-side polarizer manufactured above was attached to the light-incident surface of an IPS liquid crystal-containing liquid crystal panel using an adhesive layer to manufacture a liquid crystal module. The TAC film of the light-source-side polarizer was attached to the liquid crystal panel.

[0165] The polarizing plates of the examples and comparative examples were evaluated according to Table 1 below, and the results are shown in Table 1 below and in FIGS.

[0166] (1) Light transmittance of polarizing plate (unit: %): The polarizing plates manufactured in the examples and comparative examples were placed in a light transmittance measuring device V-7100, and light was transmitted from the retardation layer side to the polarizer side, but in the normal direction to the in-plane direction of the polarizing plate, to obtain the single light transmittance at wavelengths of 390 nm, 400 nm, 410 nm, 420 nm, and 550 nm. The ratios of Equations 1 to 4 were calculated using the measured single light transmittances.

[0167] (2) Left and right visual perception at an azimuth angle of 60°: LCD modules were manufactured using the polarizers manufactured in the examples and comparative examples. Using EZ-Contrast XL-88 equipment, the color coordinates x and y were determined at (45°, 60°) and (135°, 60°) by specifying a left image (left-side viewing angle) of 135° and a right image (right-side viewing angle) of 45° in a black color azimuth angle of 60°. The distance between (45°, 60°) and (135°, 60°) was calculated as △(x, y).

[0168] (3) Left and right visual perception at an azimuth angle of 45°: LCD modules were manufactured using the polarizers manufactured in the examples and comparative examples. Using EZ-Contrast XL-88 equipment, the color coordinates x and y were calculated for (45°, 45°) and (135°, 45°) by specifying a left image (left-side viewing angle) of 135° and a right image (right-side viewing angle) of 45° in the black color azimuth angle of 45°. The distance between (45°, 45°) and (135°, 45°) was calculated as △(x, y).

[0169] [Table 1]

[0170] *Formula 1: TS390 / TS550

[0171] *Formula 2: TS400 / TS550

[0172] *Formula 3: TS410 / TS550

[0173] *Formula 4: TS420 / TS550

[0174] As shown in Table 1, the polarizing plate of the present invention was excellent in reducing the difference in visual perception or color perception between the left and right sides.

[0175] This can be seen in Figures 3, 5, and 6. As shown in Figure 3, the difference in color perception between the image viewed from the left and right was small. Also, as shown in Figures 5 and 6, it was confirmed that △(x, y) was reduced compared to the comparative example.

[0176] On the other hand, the polarizing plate of the comparative example, which does not satisfy the mathematical formula 1 and mathematical formula 2 of the present invention, had a larger difference in visual perception or color perception between the left and right sides compared to the polarizing plate of the present invention. This can be seen in Figures 4, 5, and 6. As shown in Figure 4, the difference in color perception between the image viewed from the left side and the image viewed from the right side was larger than in Figure 3. In addition, as shown in Figures 5 and 6, it was confirmed that △(x, y) was relatively larger compared to the examples.

[0177] Simple variations or modifications of the present invention can be easily implemented by those skilled in the art, and all such variations and modifications can be considered to be included within the scope of the present invention.

Claims

1. A polarizing plate including a polarizer and a retardation layer laminated on one surface of the polarizer, the retardation layer has an in-plane retardation of 0 nm to 10 nm and a thickness direction retardation of −30 nm to −3 nm at a wavelength of 550 nm, The polarizing plate has a light transmittance ratio of more than 0.445 and less than 0.470 as expressed by the following formula 1, and a light transmittance ratio of more than 0.710 and less than 0.730 as expressed by the following formula 2: [Formula 1] Light transmittance ratio = TS390 / TS550 [Formula 2] Light transmittance ratio = TS400 / TS550 (In the above formulas 1 and 2, TS550 is the light transmittance of the polarizing plate at a wavelength of 550 nm (unit: %), TS390 is the light transmittance of the polarizing plate at a wavelength of 390 nm (unit: %), TS400 is the light transmittance (unit: %) of the polarizing plate at a wavelength of 400 nm.

2. 2. The polarizing plate according to claim 1, wherein the polarizing plate has a light transmittance of 10% to 20% at a wavelength of 390 nm and a light transmittance of 25% to 35% at a wavelength of 400 nm.

3. The polarizing plate of claim 1, wherein the light transmittance ratio of the following formula 3 is greater than 0.795 and less than 0.805, and the light transmittance ratio of the following formula 4 is greater than 0.835 and less than 0.850: [Formula 3] Light transmittance ratio = TS410 / TS550 [Formula 4] Light transmittance ratio = TS420 / TS550 (In the above formulas 3 and 4, TS550 is the light transmittance of the polarizing plate at a wavelength of 550 nm (unit: %), TS410 is the light transmittance of the polarizer at a wavelength of 410 nm (unit: %), TS420 is the light transmittance (unit: %) of the polarizing plate at a wavelength of 420 nm.

4. 2. The polarizing plate according to claim 1, wherein the polarizing plate has a light transmittance of 33% to 35% at a wavelength of 410 nm, and a light transmittance of 36% to 38% at a wavelength of 420 nm.

5. The polarizing plate according to claim 1 , wherein the retardation layer is a negative C layer or a positive C layer.

6. The polarizing plate according to claim 1 , wherein the retardation layer has a higher light transmittance than the polarizer at wavelengths of 390 nm, 400 nm, 410 nm, 420 nm, and 550 nm.

7. The retardation layer has a light transmittance of 45% to 62% at a wavelength of 390 nm, a light transmittance of 70% to 90% at a wavelength of 400 nm, a light transmittance of 75% to 95% at a wavelength of 410 nm, and a light transmittance of 75% to 95% at a wavelength of 420 nm. The polarizing plate according to claim 1.

8. The polarizing plate according to claim 1 , wherein the retardation layer comprises a film or coating layer containing a polymer having a positive intrinsic birefringence.

9. 2. The polarizing plate according to claim 1, wherein the retardation layer is a triacetyl cellulose (TAC)-based, cyclic olefin polymer (COP)-based, or cyclic olefin copolymer (COC)-based layer.

10. The polarizing plate according to claim 1 , wherein the retardation layer has a thickness ratio of 90% or more of the total thickness of the retardation layers (total thickness of layers) laminated on the lower surface of the polarizer.

11. 2. The polarizing plate according to claim 1, wherein the slow axis of the retardation layer is inclined from −5° to 5° when the light absorption axis of the polarizer is taken as 0°.

12. The polarizing plate according to claim 1 , further comprising a second protective layer laminated on another surface of the polarizer.

13. The polarizing plate according to claim 12 , wherein the second protective layer has an in-plane retardation of 3,000 nm or more at a wavelength of 550 nm.

14. An optical display device comprising the polarizer according to any one of claims 1 to 13.

Images