Polarizing plate and optical display including same

Abstract

The present invention provides a polarizing plate capable of improving a front contrast ratio and a side contrast ratio, and an optical display including the same capable of minimizing a reduction in the front contrast ratio during operation while improving the side contrast ratio. Specifically, the polarizing plate includes a polarizing film and a contrast improvement film formed on one surface of the polarizing film, in which the contrast improvement film includes a contrast improvement layer composed of a first protective layer, and includes a first resin layer and a second resin layer facing each other. The first resin layer has a patterned portion. The patterned portion has at least two optical patterns on one surface of the first resin layer facing the second resin layer and a flat portion between the optical patterns and another optical pattern immediately adjacent to the optical patterns.

Description

[0001] The present invention is a divisional application of the invention patent application with application number 201780088079.X filed on November 30, 2017 and invention name “Polarizing plate and optical display including the same”. Technical Field

[0002] The invention relates to a polarizing plate and an optical display comprising the polarizing plate. Background Art

[0003] The liquid crystal display is operated to emit light through the liquid crystal panel after receiving light from the backlight unit. Therefore, the liquid crystal display provides a good front contrast ratio (contrast ratio; CR). However, the liquid crystal display has a poor side contrast ratio. Therefore, it is necessary to increase the side contrast ratio of the liquid crystal display while minimizing the reduction of its front contrast ratio in order to improve visibility.

[0004] The liquid crystal display may also be maintained in a non-driven state. In addition, for the purpose of product display or product sales, the liquid crystal display may be displayed in a driven state or in a non-driven state. When the screen of the liquid crystal display in the non-driven state receives external light, rainbow spots or mura may be generated on the screen or reflected light may be separated, thereby causing the black visibility and appearance of the liquid crystal display to deteriorate. Black visibility means the degree of black on the screen of the liquid crystal display in the non-driven state.

[0005] Therefore, there is a need for a polarizing plate that can improve both the front contrast ratio and the side contrast ratio of a liquid crystal display when in operation while preventing the appearance of the liquid crystal display from being deteriorated when the liquid crystal display is turned off.

[0006] One example of the background art is disclosed in Japanese Unexamined Patent Publication No. 2006-251659A. Summary of the invention

[0007] [Technical issues]

[0008] An object of the present invention is to provide a polarizing plate capable of preventing the external appearance of a screen of an optical display from being deteriorated by external light when the optical display is not in operation.

[0009] Another object of the present invention is to provide a polarizing plate capable of preventing spots from being generated on a screen of an optical display due to external light while improving black visibility when the optical display is not in operation.

[0010] Another object of the present invention is to provide a polarizing plate capable of improving both the front contrast ratio and the side contrast ratio, and capable of minimizing the reduction in the front contrast ratio of an optical display during operation while improving the side contrast ratio.

[0011] [Technical solution]

[0012] According to one embodiment of the present invention, a polarizing plate includes: a polarizing film and a contrast improvement film formed on one surface of the polarizing film, wherein the contrast improvement film includes a first protective layer and a contrast improvement layer, and the contrast improvement layer includes a first resin layer and a second resin layer facing each other; the first resin layer includes a patterned portion, the patterned portion is formed on a surface of the first resin layer facing the second resin layer and includes at least two optical patterns and a flat portion (flat section) located between adjacent optical patterns; the optical pattern has a base angle (α) of 75° to 90°; the patterned portion satisfies Formula 2:

[0013] 1< P / W≤ 10 ----------- (2),

[0014] In Formula 2, P is the sum of the maximum width of the corresponding optical pattern and the width of the flat portion directly adjacent to the corresponding optical pattern (unit: micrometer), and W is the maximum width of the corresponding optical pattern (unit: micrometer),

[0015] The patterned portion satisfies at least one of the following conditions (i) and (ii):

[0016] (i) the optical pattern has a maximum width different from at least one of the optical patterns adjacent to each other; and

[0017] (ii) the flat portion has a different width from at least one of the flat portions adjacent to each other; and

[0018] The polarizing plate has a determination coefficient of black visibility of 0.985 or greater.

[0019] According to another embodiment of the present invention, an optical display comprises the polarizing plate according to the present invention.

[0020] [Beneficial Effects]

[0021] The present invention provides a polarizing plate capable of preventing the external appearance of a screen of an optical display from being deteriorated due to external light when the optical display is not in operation.

[0022] The present invention provides a polarizing plate capable of preventing spots from being generated on the screen of an optical display due to external light while improving black visibility when the optical display is not in operation.

[0023] The present invention provides a polarizing plate capable of improving the front contrast ratio and the side contrast ratio, and capable of improving the side contrast ratio while minimizing the reduction of the front contrast ratio when an optical display is operated. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is a cross-sectional view of a polarizing plate according to an embodiment of the present invention.

[0025] Figure 2 FIG. 4 is a cross-sectional view of a polarizing plate according to another embodiment of the present invention.

[0026] Figure 3 FIG. 4 is a cross-sectional view of a polarizing plate according to another embodiment of the present invention.

[0027] Figure 4 This is a curve for calculating the determination coefficient of black visibility when the optical display of Example 5 is not in operation. DETAILED DESCRIPTION

[0028] Embodiments of the present invention will be described in detail with reference to the accompanying drawings to provide a thorough understanding of the present invention to those skilled in the art. It should be understood that the present invention can be embodied in different ways and is not limited to the following embodiments. In the accompanying drawings, parts irrelevant to the description will be omitted for clarity. Similar components will be represented by similar accompanying drawing element symbols throughout this specification.

[0029] In this document, spatially relative terms such as "upper" and "lower" are defined with reference to the accompanying drawings. Thus, it will be understood that the term "upper surface" may be used interchangeably with the term "lower surface," and when an element such as a layer or film is referred to as being "on" another element, it may be directly on the other element, or there may be intervening elements. On the other hand, when an element is referred to as being "directly on another element," there are no intervening elements therebetween.

[0030] In this document, the terms "horizontal direction" and "vertical direction" respectively mean the longitudinal direction and the lateral direction of the rectangular screen of the liquid crystal display. In this document, "side" refers to an area where θ ranges from 60° to 90° in a spherical coordinate system represented by (φ, θ), wherein the front side is indicated by (0°, 0°), the left end point is indicated by (180°, 90°), and the right end point is indicated by (0°, 90°) with reference to the horizontal direction.

[0031] As used herein, the term "top part" refers to the highest part in an engraved optical pattern.

[0032] Herein, "aspect ratio" refers to the ratio of the maximum height of an optical pattern to its maximum width (maximum height / maximum width).

[0033] Herein, "pitch" means the sum of the maximum width W of an optical pattern and the width L of a flat portion.

[0034] Herein, "in-plane retardation (Re)" is a value measured at a wavelength of 550 nanometers and is expressed as Formula A:

[0035] <Formula A>

[0036] Re=(nx-ny)×d

[0037] In Formula A, nx and ny are the refractive indices on the slow axis and the fast axis of the corresponding protective layer or base layer at a wavelength of 550 nanometers, respectively, and d is the thickness of the protective layer or base layer (unit: nanometer).

[0038] As used herein, the term "(meth)acryl" refers to acryl and / or methacryl.

[0039] Herein, the term "black visibility" means the degree of black on the optical display screen when not in operation without generating spots due to external light. A higher determination coefficient of black visibility indicates better black visibility.

[0040] Herein, the "determination coefficient of black visibility" is measured on a liquid crystal display manufactured using a polarizing plate as a viewer-side polarizing plate (on which the determination coefficient of black visibility is measured), wherein a fluorescent lamp is placed at a predetermined height higher than the screen of the liquid crystal display so as to correspond to the middle position of the screen in the longitudinal direction. In a non-driving state of the liquid crystal display, the fluorescent lamp is turned on to measure the intensity of reflected light on each of the obtained pixels by dividing the screen of the liquid crystal display into pixels. The intensity (I) of the reflected light measured on each pixel is divided by the maximum value of the measured intensity (I) of the reflected light to obtain a squared value in each pixel. A curve is obtained by arranging the pixel unit positions on the x-axis and the obtained squared values ​​on the y-axis, and the curve is normalized by a statistical analysis method. According to the normalization, an exponential function (y=ae) is obtained. bx ) and residual. The residual is used as a determination coefficient for black visibility. A determination coefficient for black visibility close to 1 indicates a better exterior appearance, and a lower determination coefficient for black visibility means a larger fluctuation in the intensity of reflected light providing significant diffracted light.

[0041] The present invention is based on the characteristics of a polarizing plate including a contrast improvement layer (including a patterned portion satisfying at least one of conditions (i) and (ii)), and satisfies the following formula 2 to improve both the front contrast ratio and the side contrast ratio, and while improving the side contrast ratio, minimizes the reduction in the front contrast ratio of the optical display when it is in operation. While satisfying the following formulas 2 and 3 to prevent the generation of mottles on the screen of the optical display caused by external light, the black visibility of the optical display when it is not in operation is improved:

[0042] (i) the optical pattern has a maximum width that is different from at least one of the adjacent optical patterns; and

[0043] (ii) The flat portion has a different width from at least one of the adjacent flat portions.

[0044] In the following, reference will be made to Figure 1 A polarizing plate according to an embodiment of the present invention will be described. Figure 1 is a cross-sectional view of a polarizing plate according to an embodiment of the present invention.

[0045] refer to Figure 1 According to the embodiment, the polarizing plate 10 includes a polarizing film 300 and a contrast-improving film, and the contrast-improving film includes a contrast-improving layer 100 a and a first protective layer 200 .

[0046] In the polarizing plate 10, a contrast improvement film is stacked on the polarizing film 300. The polarizing plate 10 can be used as a viewer side polarizing plate in a liquid crystal display. In this article, the term "viewer side polarizing plate" means a polarizing plate disposed at the viewer side and opposite to the light source relative to the liquid crystal panel. The liquid crystal display is affected by external light when not in operation. The polarizing plate 10 includes a contrast improvement film described in detail below. Therefore, a liquid crystal display including a polarizing plate according to this embodiment allows external light to diffract and mix when not in operation, thereby significantly improving the black visibility of its screen. Specifically, the polarizing plate may have a determination coefficient of black visibility of 0.985 or greater than 0.985, preferably 0.985 to 1.000. The contrast improvement film of the polarizing plate 10 can improve the side contrast ratio when the liquid crystal display is in operation.

[0047] Contrast Improvement Film

[0048] The contrast-improving film is formed on the polarizing film 300. The contrast-improving film is formed on the light-emitting surface of the polarizing film 300.

[0049] The contrast improvement film is composed of a first protective layer 200 and a contrast improvement layer 100a, wherein the contrast improvement layer is a stacked structure of a first resin layer 110a and a second resin layer 120a facing each other. In the contrast improvement film, the second resin layer 120a, the first resin layer 110a and the first protective layer 200 are sequentially stacked on the polarizing film 300.

[0050] The first resin layer 110a may be formed directly on the second resin layer 120a. Herein, the expression "formed directly on" means that any adhesive layer, bonding layer, or adhesive bonding layer is not interposed between the first resin layer 110a and the second resin layer 120a. The first resin layer 110a may improve the light diffusion effect by diffusing light to reach the second resin layer 120a.

[0051] The first resin layer 110a includes a patterned portion formed on a surface thereof facing the second resin layer 120a and including an optical pattern and a flat portion disposed between adjacent optical patterns. Accordingly, the contrast improvement film can diffuse polarized light received from the polarizing film 300, thereby improving the relative brightness at the front side and improving both the front and side contrast ratios (CR). In addition, the contrast improvement film can increase the side contrast ratio while minimizing the reduction in the front contrast ratio, reduce the difference between the front contrast ratio and the side contrast ratio, and increase the contrast ratio at the same side viewing angle and the same front viewing angle.

[0052] The patterned portion may satisfy condition (i). Figure 1 , with reference to the width direction of the optical patterns of the patterned portion, the maximum width of the first optical pattern is indicated by W1, the maximum width of the second optical pattern is indicated by W2, the maximum width of the third optical pattern is indicated by W3, ..., the maximum width of the (n-2)th optical pattern is indicated by W n-2 Indicates that the (n-1)th optical pattern is composed of W n-1 Indicated by W, and the maximum width of the nth optical pattern is indicated by W n Here, n is an integer from 4 to 500,000. Figure 1 A polarizing plate including four optical patterns is shown, but it should be understood that the present invention is not limited thereto.

[0053] The patterned portion may be formed to satisfy the following Formula 1-1, Formula 1-2, and Formula 1-3, and the planar portion may have the same width (ie, L1 = L2 = L3).

[0054] <Formula 1-1>

[0055] W n-1 ≠W n

[0056] <Formula 1-2>

[0057] W n-2 ≠W n

[0058] <Formula 1-3>

[0059] W n-3 ≠W n

[0060] (Wherein, the width direction of the reference optical pattern, W n-3 Indicates the maximum width of the (n-3)th optical pattern, W n-2 Indicates the maximum width of the (n-2)th optical pattern, W n-1 indicates the maximum width of the (n-1)th optical pattern, and W n indicates the maximum width of the nth optical pattern; and n is an integer from 4 to 500,000).

[0061] Preferably, n is an integer from 5,000 to 200,000.

[0062] Preferably, in the polarizing plate, adjacent optical patterns have different maximum widths to extinguish external light through diffraction and mix the external light through the optical patterns, thereby further improving black visibility.

[0063] In one embodiment, the optical patterns may have different maximum widths.

[0064] In the patterned portion, each of the optical patterns 111 may have a base angle α of 75° to 90°. The base angle α refers to the angle between the inclined surface 112 formed in each optical pattern 111 and a straight line along the maximum width (W1, W2, W3, W4) of the optical pattern 111. Within this range, the contrast-improving film may improve the relative brightness at the front side, while improving both the front contrast ratio and the side contrast ratio, reducing the difference between the front contrast ratio and the side contrast ratio, and improving the contrast ratio at the same side viewing angle and the same front viewing angle. Although Figure 1 A structure is shown in which each of the optical patterns has the same base angle at both sides thereof, but the optical patterns may still have different base angles as long as the base angle is within the range of 75° to about 90° as described above. Preferably, the optical patterns have the same base angle.

[0065] In the patterned portion, each of the optical pattern and the flat portion directly adjacent to the corresponding optical pattern may satisfy Formula 2. With this structure, the contrast-improving film may improve the relative brightness at the front side, while improving both the front contrast ratio and the side contrast ratio, reducing the difference between the front contrast ratio and the side contrast ratio, and improving the contrast ratio at the same side viewing angle and the same front viewing angle.

[0066] <Formula 2>

[0067] 1 <P / W≤10

[0068] Wherein P is the sum of the maximum width of the corresponding optical pattern and the width of the flat portion directly adjacent to the optical pattern (unit: micrometer), and W is the maximum width of the optical pattern (unit: micrometer).

[0069] Since the optical pattern satisfies Formula 1-1, Formula 1-2, and Formula 1-3, the optical pattern of the patterned portion has different values ​​of Formula 2. When the maximum value and the minimum value of Formula 2 are [P / W]max and [P / W]min, respectively, the patterned portion may satisfy the following Formula 3, thereby significantly improving black visibility while preventing moire from being generated due to external light when the liquid crystal display is not operating.

[0070] <Formula 3>

[0071] 1.5<[P / W]max / [P / W]min<10

[0072] Wherein [P / W]max is the maximum value of P / W expressed by Formula 2, and [P / W]min is the minimum value of P / W expressed by Formula 2.

[0073] For example, [P / W]max / [P / W]min may be in a range of 1.55 to less than 10, preferably greater than 2 to less than 10. Within this range, the liquid crystal display may have a black visibility of 0.985 or greater.

[0074] Next, the optical pattern will be described in detail.

[0075] The optical pattern 111 may be an engraved optical pattern, each of which has a first surface 114 formed at a top portion thereof and at least one inclined surface 112 connected to the first surface 114. The first surface 114 is formed at the top portion of the optical pattern, and can improve the viewing angle and brightness by further diffusing light to reach the second resin layer 120a in the optical display. Therefore, the polarizing plate according to this embodiment can improve light diffusion, thereby minimizing brightness loss. Although Figure 1 A structure in which the first surface 114 is a plane and parallel to the flat portion 113 is shown, but the first surface 114 may still have fine roughness or a curved surface. In a structure in which the first surface 114 is a curved surface, the optical pattern may be implemented by a double convex lens pattern. The first surface 114 may have a width A of 0.5 micrometers to 30 micrometers, specifically 2 micrometers to 20 micrometers.

[0076] Figure 1An optical pattern is shown, the optical pattern including a flat surface and a plane inclined surface formed at the top portion thereof and having a trapezoidal cross section (e.g., a truncated prism shape having a triangular cross section, i.e., a cut-prism shape). Alternatively, the optical pattern may be an optical pattern in which the first surface is formed at the top portion thereof and the inclined surface is an arcuate surface (e.g., a stacked structure of a first resin layer and a second resin layer having a truncated biconvex (cut-lenticular lens) lens shape, or a truncated microlens (cut-micro lens) shape). Alternatively, the engraved optical pattern may have an N-sided polygonal cross section (N is an integer of 3 to 20), such as a rectangular shape or a square shape.

[0077] The optical pattern 111 may have an aspect ratio of 0.3 to 3.0, specifically 0.3 to 2.5, and more specifically 0.3 to 1.5. For example, the optical pattern 111 may have an aspect ratio of 0.3 to 1.4, such as 0.3 to 1. Within this range, the polarizing plate may improve the side contrast ratio and viewing angle in the optical display.

[0078] The optical pattern 111 may have a height H of 40 μm or less, specifically 30 μm or less, and more specifically 5 μm to 15 μm. Within this range, the polarizing plate may improve the contrast ratio, viewing angle, and brightness of the optical display without causing a moire phenomenon.

[0079] although Figure 1 The optical patterns are shown to have patterned portions of the same height, but the optical patterns of the patterned portions may still have different heights or at least one of the adjacent optical patterns may have a different height from the other optical patterns. Preferably, the optical patterns have the same height.

[0080] The maximum width (W1, W2, W3, W4) of the optical pattern 111 may be 80 micrometers or less, specifically 50 micrometers or less. The maximum width (W1, W2, W3, W4) of the optical pattern 111 may be 5 micrometers to 25 micrometers. Within this range, the polarizing plate may improve the contrast ratio, viewing angle, and brightness without causing a moire phenomenon. The difference between the maximum value and the minimum value in the maximum width of the optical pattern 111 may be 2 micrometers or more, preferably 2 micrometers to 20 micrometers, and more preferably 2 micrometers to 15 micrometers. Within this range, the polarizing plate may improve the black visibility of the optical display.

[0081] The flat portion 113 may be formed between adjacent optical patterns. When receiving light, the flat portion 113 may diffuse the light through the emission of light, thereby improving the front contrast ratio and brightness.

[0082] The ratio of the maximum width (W1, W2, W3, W4) of the optical pattern to the width L of the flat portion 113 may be 9 or less, specifically 0.10 to 3, and more specifically 0.15 to 2.6. Within this range, the polarizing plate can improve the relative brightness at the front side, can reduce the difference between the front contrast ratio and the side contrast ratio, and can improve the contrast ratio at the same side viewing angle and the same front viewing angle without causing a moire phenomenon.

[0083] The flat portion 113 may have a width L of 1 μm to 300 μm, specifically 3 μm to 50 μm, and more specifically 5 μm to 20 μm. Within this range, the contrast-improving optical film may improve the front brightness of an optical display.

[0084] In one embodiment, the optical pattern may have a maximum width of 5 micrometers to 25 micrometers, and the flat portion may have a width of 3 micrometers to 50 micrometers.

[0085] The patterned portions may have different pitches P. The pitch P is the sum of the maximum width of the corresponding optical pattern and the width of a flat portion directly adjacent to the corresponding optical pattern. The pitch P may be 0.6 times or more than 0.6 times, for example, 0.6 times to 5 times, the maximum width W of the corresponding optical pattern. Within this range, the polarizing plate may improve brightness and contrast ratio without causing moire. The pitch P may be in the range of 5 microns to 500 microns, specifically 10 microns to 25 microns. Within this range, the polarizing plate may improve brightness and contrast ratio without causing moire.

[0086] The first resin layer 110a may have a lower refractive index than the second resin layer 120a. The absolute value of the difference in refractive index between the first resin layer 110a and the second resin layer 120a may be 0.20 or less, specifically 0.05 to 0.20, and more specifically 0.10 to 0.15. Within this range, the contrast-improving film can provide a greater effect of diffusing polarized light while improving the contrast ratio. Specifically, a contrast-improving film having a refractive index difference of 0.10 to 0.15 can have an excellent effect of diffusing polarized light in an optical display, and thus improve brightness even at the same viewing angle. Figure 1 A structure is shown in which the first resin layer 110a has a higher refractive index than the second resin layer 120a. Alternatively, the first resin layer 110a may have a lower refractive index than the second resin layer 120a.

[0087] The first resin layer 110a may have a refractive index of 1.50 or more, specifically 1.50 to 1.70. Within this range, the contrast-improving film may have an excellent effect on light diffusion. The first resin layer 110a may be formed of a UV curable composition or a heat curable composition, and the UV curable composition or the heat curable composition includes (but is not limited to) at least one of (meth) acrylic acid, polycarbonate, silicone, and epoxy resin.

[0088] although Figure 1 A structure is shown in which the first resin layer 110a is directly adjacent to the first protective layer 200, but it should be understood that the present invention is not limited thereto. The first resin layer 110a may be directly formed on the first protective layer 200 or may be formed of an adhesive resin to act as an adhesive bonding layer that promotes interlayer bonding. Alternatively, an adhesive layer, a bonding layer, or an adhesive bonding layer may be further inserted between the first protective layer 200 and the first resin layer 110a.

[0089] Upon receiving light through the lower surface of the optical display, the second resin layer 120a may diffuse the light by emitting the light in various directions according to the incident angle of the light. The second resin layer 120a may be formed to directly adjoin the first resin layer 110a.

[0090] The second resin layer 120a may include a filling pattern 121 that at least partially fills the optical pattern 111. When an element is referred to as "at least partially filling" an optical pattern, the element may completely fill the optical pattern, or partially fill the optical pattern. When the filling pattern partially fills the optical pattern, the remaining space of the optical pattern may be filled with air or a resin having a certain refractive index. Specifically, the refractive index of the resin may be lower than or equal to the refractive index of the first resin layer and greater than or equal to the refractive index of the first resin layer. Although Figure 1 Although not shown in FIG. 1 , the optical pattern may extend in a stripe shape. Alternatively, the optical pattern may be formed in a dot shape. The term “dot” means that the optical pattern is dispersed.

[0091] The second resin layer 120a may have a refractive index of less than 1.52, specifically 1.35 to less than 1.50. Within this range, the contrast improvement film may have a greater light diffusion effect, may be easy to form, and may have a greater effect of diffusing polarized light while improving the contrast ratio. The second resin layer 120a may be formed of a UV curable composition or a heat curable composition containing a transparent resin. Specifically, the transparent resin may include (but not limited to) at least one of (meth) acrylic acid, polycarbonate, silicone, and epoxy resin. The transparent resin may have a light transmittance of about 90% or more after curing.

[0092] The second resin layer 120a may be a non-adhesive layer that does not exhibit adhesion. Alternatively, the second resin layer may be formed of a self-adhesive resin to act as an adhesive bonding layer that promotes inter-layer bonding or allows the elimination of a separation polarizer protective layer during inter-layer bonding, thereby enabling the thickness of the polarizing plate to be reduced. The self-adhesive bonding resin may be an acrylic acid, an epoxy resin, or a urethane resin. If the second resin layer 120a is not a self-adhesive layer, the second resin layer 120a may be bonded to the polarizing film 300 via a bonding layer. The bonding layer may be formed of a water-based bonding agent or a light-curable bonding layer.

[0093] The contrast improvement layer 100a may have a thickness of 10 μm to 100 μm, specifically 20 μm to 60 μm, and more specifically 20 μm to 45 μm. Within this thickness range, the contrast improvement layer can be sufficiently supported on the first protective layer and can be applied to optical displays.

[0094] The first protective layer 200 is a light-transmitting layer and allows light having passed through the first resin layer to pass therethrough in the optical display.

[0095] The first protective layer 200 may be a retardation film or an isotropic optical film having a certain range of retardation. In one embodiment, the first protective layer has an Re of 8,000 nanometers or more, specifically 10,000 nanometers or more, more specifically more than 10,000 nanometers, and still more specifically 10,100 nanometers to 15,000 nanometers. Within this range, the first protective layer can prevent the generation of rainbow spots while further diffusing the light diffused through the stacked structure of the first resin layer and the second resin layer. In another embodiment, the first protective layer may be an isotropic optical film having an Re of 60 nanometers or less, specifically 0 nanometers to 60 nanometers, and more specifically 40 nanometers to 60 nanometers. Within this range, the first protective layer can provide good image quality through compensation for viewing angle. Herein, the term "isotropic optical film" means a film having substantially the same nx, ny, and nz, and the expression "substantially the same" includes not only the case where nx, ny, and nz are completely the same, but also the case where an acceptable error margin exists between nx, ny, and nz. Preferably, the first protective layer may be a retardation film having Re of 8,000 nm or more, specifically 10,000 nm or more, more specifically more than 10,000 nm.

[0096] The first protective layer 200 may have a thickness of 30 micrometers to 120 micrometers, specifically 20 micrometers to 80 micrometers. Within this thickness range, the first protective film may be applied to an optical display. In the visible range, the first protective layer 200 may have a light transmittance of 80% or more, specifically 85% to 95%. The first protective layer 200 may be formed by uniaxially stretching or biaxially stretching an optically transparent resin. Specifically, the optically transparent resin may include at least one selected from the following: polyester resins including polyethylene terephthalate (PET), polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate and the like, acrylic resins, cyclic olefin polymers (COP), cellulose ester resins including triacetyl cellulose, polyvinyl acetate, polyvinyl chloride (PVC), polynorbornene resins, polycarbonate resins (PC), polyamide resins, polyacetal resins, polyphenylene ether resins, polyphenylene sulfide resins, polysulfone resins, polyethersulfone resins, polyacrylate resins, and polyimide resins. Preferably, the first protective layer includes a film formed of a polyester resin. The first protective layer may include a film formed of a modified resin. Here, the modification may include (but is not limited to) copolymerization, branching, crosslinking, and modification of molecular ends.

[0097] although Figure 1Although not shown in the figure, the protective film may include a base film and a primer layer formed on at least one surface of the base film. The base film supports the first protective layer and has a ratio of a certain range relative to the refractive index of the primer layer to improve the transmittance of the base layer. Specifically, the ratio of the refractive index of the primer layer to the refractive index of the base film (refractive index of the primer layer / refractive index of the base film) may be 1.0 or less than 1.0, specifically 0.6 to 1.0, more specifically 0.69 to 0.95, still more specifically 0.7 to 0.9, still more specifically 0.72 to 0.88. Within this range, the base layer can improve the transmittance of the first protective layer. The base film may have a refractive index of about 1.3 to about 1.7, specifically about 1.4 to about 1.6. Within this range, the base layer can be used in the first protective layer, allowing easy control of the refractive index relative to the primer layer, and improving the transmittance of the first protective layer. The base film may include a film formed by a resin as described above. The primer layer is formed between the substrate layer and the first resin layer, and strengthens the adhesion between the substrate film and the first resin layer. The primer layer may have a refractive index of about 1.0 to about 1.6, specifically about 1.1 to about 1.6, and more specifically about 1.1 to about 1.5. Within this range, the primer layer can be used for optical films and has a suitable refractive index compared to the substrate film, thereby improving the transmittance of the substrate layer. The primer layer may have a thickness of about 1 nanometer to about 200 nanometers, specifically about 60 nanometers to about 200 nanometers. Within this range, the primer layer can be used for optical films, has a suitable refractive index compared to the substrate film, and thus improves the transmittance of the substrate layer without brittleness (brittle). The primer layer may be a non-urethane primer layer without a urethane group. Specifically, the primer layer may be formed by a primer composition comprising a resin or monomer such as a polyester, a propylene group or the like. By controlling the mixing ratio (e.g., molar ratio) between these monomers, the primer layer may have a refractive index as described above. The base coating composition may further include at least one of additives such as a UV absorber, an antistatic agent, a defoaming agent, a surfactant, and the like.

[0098] Polarizing film

[0099] The polarizing film 300 may polarize and transmit light received from the liquid crystal panel and may include a polarizer.

[0100] In one embodiment, the polarizing film may include a polarizer. The polarizer is used to polarize incident light and may include a typical polarizer known to those skilled in the art. Specifically, the polarizer may include a polyvinyl alcohol-based polarizer obtained by uniaxially stretching a polyvinyl alcohol film, or a polyene-based polarizer obtained by dehydrating a polyvinyl alcohol film. The polarizer may have a thickness of about 5 microns to about 40 microns. Within this range, the polarizer can be applied to an optical display.

[0101] In another embodiment, the polarizing film may include a polarizer and a second protective layer formed on at least one surface of the polarizer. The second protective layer can prevent moisture from entering the polarizer while increasing the mechanical strength of the polarizing plate. Preferably, the second protective layer can be formed between the polarizer and the contrast improvement film.

[0102] The second protective layer may include at least one of an optically transparent protective film or a protective coating layer.

[0103] When the second protective layer is of the protective film type, the protective layer may include a protective film formed of an optically transparent resin. The protective film may be formed by melting and extruding the resin. A process of stretching the resin may be further added. The optically transparent resin may include at least one of the resins described above. The protective film may be an optically transparent liquid crystal film.

[0104] When the second protective layer belongs to the protective coating type, the second protective layer can provide excellent properties in terms of adhesion to the polarizer, transparency, mechanical strength, thermal stability, moisture barrier and durability. In one embodiment, the protective coating layer can be formed by an actinic radiation curable resin composition comprising an actinic radiation curable compound and a polymerization initiator. The actinic radiation curable compound may include at least one of a cationically polymerizable curable compound, a free radically polymerizable curable compound, a urethane resin and a silicone resin. The cationically polymerizable curable compound may be an epoxy compound having at least one epoxy group per molecule, or an oxetane compound having at least one oxetane ring per molecule. The free radically polymerizable curable compound may be a (meth) acrylic compound having at least one (meth) acryloyloxy group per molecule. The epoxy compound may include at least one of a hydrogenated epoxy compound, a chain aliphatic epoxy compound, an alicyclic epoxy compound and an aromatic epoxy compound. The free radically polymerizable curable compound can achieve a protective coating layer with excellent hardness and mechanical strength and high durability. Examples of free radical polymerizable curable compounds may include (meth)acrylate monomers having at least one (meth)acryloyloxy group per molecule, and (meth)acrylate oligomers obtained by reacting a compound containing at least two functional groups and having at least two (meth)acryloyloxy groups per molecule. Examples of (meth)acrylate monomers may include monofunctional (meth)acrylate monomers having one (meth)acryloyloxy group per molecule, difunctional (meth)acrylate monomers having two (meth)acryloyloxy groups per molecule, and multifunctional (meth)acrylate monomers having three or more (meth)acryloyloxy groups per molecule. Examples of (meth)acrylate oligomers may include urethane (meth)acrylate oligomers, polyester (meth)acrylate oligomers, and epoxy (meth)acrylate oligomers. A polymerization initiator may cure the actinic radiation curable compound. The polymerization initiator may include at least one of an optical cationic initiator and a photosensitizer.

[0105] The optical cationic initiator may include any typical optical cationic initiator known in the art. Specifically, the optical cationic initiator may include an onium salt, which includes a cation and an anion. Specifically, the cation may include diaryliodonium such as diphenyl iodide, 4-methoxydiphenyl iodide, bis(4-methylphenyl) iodide, bis(4-tert-butylphenyl) iodide, bis(dodecylphenyl) iodide, and (4-methylphenyl)[(4-(2-methylpropyl)phenyl) iodide; triarylsulfides such as triphenylsulfonium and diphenyl-4-thiophenoxyphenylsulfonium; and bis[4-(diphenyldihydrosulfanyl)phenyl]sulfide. Specifically, the anion may include hexafluorophosphate, tetrafluoroborate, hexafluoroantimonate, hexafluoroarsenate, and hexachloroantimonate. The photosensitizer may be any typical photosensitizer known in the art. Specifically, the photosensitive agent may include at least one selected from the following: thioxanthone, phosphorus, triazine, acetophenone, benzophenone, benzoin and oxime photosensitive agents. The polymerization initiator may be present in an amount of 0.01 to 10 parts by weight relative to 100 parts by weight of the actinic radiation curable compound. Within this range, the composition can be fully cured to provide good mechanical strength and adhesion to the polarizer. The actinic radiation curable resin composition may further include common additives such as silicone leveling agents, UV absorbers, antistatic agents and similar additives. The additives may be present in an amount of 0.01 to 1 parts by weight relative to 100 parts by weight of the actinic radiation curable compound. The protective coating may be a liquid crystal coating layer.

[0106] The second protective layer may have the same or different retardation, material, and thickness as the first protective layer.

[0107] The second protective layer may have a thickness of 5 micrometers to 200 micrometers, specifically 30 micrometers to 120 micrometers. The protective film type of the second protective layer may have a thickness of 50 micrometers to 100 micrometers, and the second protective layer of the protective coating type may have a thickness of 5 micrometers to 50 micrometers. Within this thickness range, the second protective layer may be applied to the optical display.

[0108] Next, we will refer to Figure 2 A polarizing plate according to another embodiment of the present invention will be described. Figure 2 FIG. 4 is a cross-sectional view of a polarizing plate according to another embodiment of the present invention.

[0109] refer to Figure 2 , the polarizing plate 20 according to this embodiment is substantially the same as the polarizing plate 10 except that the optical patterns 111 of the polarizing plate 20 have the same maximum width and satisfy the condition (ii).

[0110] Specifically, refer to Figure 2 , the polarizing plate 20 includes a contrast improvement layer 100b, and the contrast improvement layer includes a first resin layer 110b and a second resin layer 120b. When referring to the width direction of the optical pattern 111 of the patterned portion, the width of the first flat portion is indicated by L1, the width of the second flat portion is indicated by L2, the width of the third flat portion is indicated by L3, ..., the width of the (m-3)th flat portion is indicated by L m-3 Indicates that the width of the (m-2)th flat portion is L m-2 Indicates that the width of the (m-1)th flat portion is L m-1 Indicated by L m When indicated, at least one of Formula 4-1, Formula 4-2 and Formula 4-3 is established and the optical pattern 111 has the same maximum width W:

[0111] <Formula 4-1>

[0112] L m-1 ≠L m

[0113] <Formula 4-2>

[0114] L m-2 ≠L m

[0115] <Formula 4-3>

[0116] L m-3 ≠L m

[0117] (Where L m-3 Indicates the width of the (m-3)th flat portion, L m-2 Indicates the width of the (m-2)th flat portion, L m-1 Indicates the width of the (m-1)th flat portion, L m indicates the width of the m-th flat portion, and m is an integer from 4 to 500,000). Preferably, n is an integer from 5,000 to 200,000.

[0118] In one embodiment, the planar portions of the patterned portion may have different widths.

[0119] The polarizing plate 20 may satisfy Formula 3, thereby improving black visibility while suppressing moire generation when the liquid crystal display is not in operation. In addition, each of the optical patterns of the polarizing plate 20 may satisfy Formula 2 and have a base angle of 75° to 90°, thereby improving relative brightness at the front side, while improving both the front contrast ratio and the side contrast ratio, reducing the difference between the front contrast ratio and the side contrast ratio, and improving the contrast ratio at the same side viewing angle and the same front viewing angle.

[0120] The difference between the maximum value and the minimum value in the width of the flat portion 113 may be 7 micrometers or more, preferably 7 micrometers to 20 micrometers. Within this range, the polarizing plate can improve black visibility of the optical display.

[0121] In one embodiment, the optical pattern may have a maximum width of 5 micrometers to 25 micrometers, and the flat portion may have a width of 3 micrometers to 50 micrometers.

[0122] Next, we will refer to Figure 3 A polarizing plate according to another embodiment of the present invention will be described. Figure 3 FIG. 4 is a cross-sectional view of a polarizing plate according to another embodiment of the present invention.

[0123] refer to Figure 3 , except that the polarizing plate 30 satisfies all of the conditions (i) and (ii), the polarizing plate 30 according to this embodiment is substantially the same as the polarizing plate 10 .

[0124] refer to Figure 3 The polarizing plate 30 includes a contrast improvement layer 100c, and the contrast improvement layer includes a first resin layer 110c and a second resin layer 120c. The polarizing plate 30 satisfies at least one of Formula 1-1, Formula 1-2, and Formula 1-3 and at least one of Formula 4-1, Formula 4-2, and Formula 4-3.

[0125] The polarizing plate 30 may also satisfy Formula 3, thereby improving black visibility while suppressing the generation of moire when the liquid crystal display is not in operation. In addition, each of the optical patterns of the polarizing plate 30 may satisfy Formula 2 and have a base angle of 75° to 90°, thereby improving the relative brightness at the front side, improving both the front contrast ratio and the side contrast ratio, reducing the difference between the front contrast ratio and the side contrast ratio, and improving the contrast ratio at the same side viewing angle and the same front viewing angle.

[0126] The difference between the maximum value and the minimum value in the width of the optical pattern 111 may be 2 micrometers or more, preferably 2 micrometers to 20 micrometers. Within this range, the polarizing plate can improve the black visibility of the optical display. The difference between the maximum value and the minimum value in the width of the flat portion 113 may be 7 micrometers or more, preferably 7 micrometers to 20 micrometers. Within this range, the polarizing plate can improve the black visibility of the optical display.

[0127] In one embodiment, the optical pattern may have a maximum width of 5 micrometers to 25 micrometers, and the flat portion may have a width of 3 micrometers to 50 micrometers.

[0128] According to the present invention, the optical display comprises the polarizing plate according to the present invention. In one embodiment, the optical display may comprise a liquid crystal display.

[0129] The liquid crystal display may include a polarizing plate as a viewer-side polarizing plate relative to the liquid crystal panel.

[0130] In one embodiment, a liquid crystal display may include a backlight unit, a first polarizing plate, a liquid crystal panel, and a second polarizing plate, which are stacked in the stated order, wherein the second polarizing plate may include a polarizing plate according to the present invention. The liquid crystal panel may adopt a vertical alignment (VA) mode, an IPS mode, a patterned vertical alignment (PVA) mode, or a super-patterned vertical alignment (S-PVA) mode, but is not limited thereto.

[0131] [Invention Mode]

[0132] Next, the present invention will be described in more detail with reference to some examples. However, it should be understood that these examples are provided for illustration only and should not be interpreted as limiting the present invention in any way.

[0133] Example 1

[0134] A UV curable resin (SHIN-A T&C Co., Ltd., South Korea) was applied to one surface of a polyethylene terephthalate (PET) film (thickness: 80 μm, Re=14,000 nm at a wavelength of 550 nm, Toyobo Co., Ltd.) for a first protective layer. Subsequently, a film having a patterned portion including optical patterns having the same bottom angle at both sides thereof and a flat portion formed between the optical patterns was applied to the coating layer so that the optical patterns and the flat portion were formed on the coating layer, followed by curing, thereby forming an optical pattern including the optical patterns having the same bottom angle at both sides as listed in Table 1 (having the optical patterns as shown in Table 1). Figure 2 The first resin layer is a patterned portion having a trapezoidal cross-sectional shape shown in FIG. 1 and a flat portion alternately arranged. Here, the optical patterns have the same maximum width W. The optical patterns have the same maximum height H. The flat portions formed between the optical patterns have different widths L ranging from 5 micrometers to 18 micrometers. The first resin layer has a refractive index of 1.59.

[0135] A UV curable resin (Korea Shinan Co., Ltd.) was applied onto the first resin layer to form a second resin layer having a filling pattern that completely filled the optical pattern, thereby forming a contrast-improving film. The second resin layer had a refractive index of 1.47.

[0136] The polarizer was manufactured by stretching a polyvinyl alcohol film to 3 times its original length at 60°C and adsorbing iodine to the stretched film, followed by stretching the film to 2.5 times the stretched length of the film in an aqueous solution of boric acid at 40°C.

[0137] A COP film (ZEON) was bonded to one surface of the polarizer, and a PET film (thickness: 80 μm, Toyobo Co., Ltd.) was bonded to the other surface thereof through a bonding agent for polarizing plates (Z-200, Nippon Goshei) applied to both surfaces of the prepared polarizer.

[0138] An acrylic resin adhesive was applied to one surface of the second resin layer of the contrast-improving film, and the PET film bonded to the polarizer was adhered to the adhesive.

[0139] Example 2 to Example 8

[0140] Each of the polarizing plates was manufactured in the same manner as in Example 1, except that the maximum height H and maximum width W of the optical pattern, the width L of the flat portion, the minimum value of P / W, and the maximum value of P / W were changed within the ranges listed in Table 1.

[0141] Examples 9 to 16

[0142] Each of the polarizing plates was manufactured in the same manner as in Example 1, except that the maximum height H and maximum width W of the optical pattern, the width L of the flat portion, the minimum value of P / W, and the maximum value of P / W were changed within the ranges listed in Table 2.

[0143] Example 17

[0144] A polarizing plate was manufactured in the same manner as in Example 1, except that the maximum height H and maximum width W of the optical pattern, the width L of the flat portion, the minimum value of P / W, and the maximum value of P / W were changed within the ranges listed in Table 2.

[0145] Comparative Example 1

[0146] A polarizing plate was manufactured in the same manner as in Example 1, except that the optical patterns had the same maximum width of 7 micrometers and the same height of 7 micrometers, and the flat portions had the same width of 7 micrometers.

[0147] A module for a liquid crystal display was manufactured using the polarizing plates of the example and the comparative example.

[0148] Preparation Example 1: Manufacturing the First Polarizing Plate

[0149] The first polarizer was prepared by stretching a polyvinyl alcohol film to 3 times its original length at 60° C., adsorbing iodine to the stretched film, and then stretching the film to 2.5 times the stretched length of the film in an aqueous solution of boric acid at 40° C. As a base layer, a triacetyl cellulose film (thickness: 80 μm) was bonded to both surfaces of the first polarizer using a bonding agent for polarizing plates (Z-200, Goshei Co., Ltd., Japan), thereby manufacturing the first polarizing plate.

[0150] Preparation Example 2: Manufacturing a module for a liquid crystal display

[0151] The first polarizing plate of Preparation Example 1, the liquid crystal panel (PVA mode), and each of the polarizing plates prepared in the examples and comparative examples were assembled in the stated order to manufacture a module for a liquid crystal display. Each of the polarizing plates manufactured in the examples and comparative examples was used as a viewer-side polarizing plate.

[0152] Schematic characteristics of the module for a liquid crystal display are shown in Table 1 and Table 2. Each of the modules for a liquid crystal display manufactured using the polarizing plates of Examples and Comparative Examples was evaluated to achieve the following characteristics, and the evaluation results are shown in Table 1 and Table 2.

[0153] (1) Side contrast ratio in operation: A liquid crystal display was manufactured as described above. The contrast ratio of the liquid crystal display was measured with spherical coordinates (0°, 60°) using EZCONTRASTX88RC (EZXL-176R-F422A4, ELDIM).

[0154] (2) Evaluation of external appearance when not in operation: A liquid crystal display was manufactured as described above. The reflected image was photographed by turning on a three-wavelength fluorescent lamp (OSRAM) placed at a height of 30 cm above the viewer-side polarizing plate. The three-wavelength fluorescent lamp was placed to correspond to the middle position on the screen of the liquid crystal display in the longitudinal direction. The intensity (I) of the reflected light was measured in pixel units using an image analysis program (ImageJ). When the outermost edge of the three-wavelength fluorescent lamp was defined as pixel unit 0, the screen of the liquid crystal display was divided into a total of 250 pixels from pixel unit 0 in the longitudinal direction.

[0155] The intensity (I) of the reflected light measured at each pixel is divided by the maximum value of the intensity (I) of the measured reflected light (the reflected light in the pixel unit 0) to obtain the square value in each pixel. A curve is obtained by arranging the pixel unit positions on the x-axis and the obtained square values ​​on the y-axis, and the curve is normalized by a statistical analysis method. According to the normalization, the exponential function (y=ae) is obtained. bx) and the residual. The residual is used as the determination coefficient of black visibility. Figure 4 Graph showing the calculation of the determination coefficient of black visibility when the optical display of Example 5 is not operating, wherein the pixel position is indicated by the x-axis and the square value is indicated by the y-axis. Figure 4 In FIG. 5 , the solid line indicates a square value depending on the pixel position and the dotted line indicates a normalized value. A determination coefficient of black visibility close to 1 indicates a better exterior appearance and a lower determination coefficient of black visibility means a larger fluctuation in the intensity of reflected light providing significant diffracted light.

[0156] Table 1

[0157]

[0158] Table 2

[0159]

[0160] As shown in Table 1 and Table 2, the polarizing plate of the example can prevent moire from being generated on the screen of the optical display due to external light, and can improve black visibility when the optical display is not operated, while improving the side contrast ratio when the optical display is not operated.

[0161] In contrast, although the polarizing plate of Comparative Example 1 satisfied Formula 2 to provide a high side contrast ratio when the optical display was operating, the polarizing plate of Comparative Example 1 failed to satisfy Formula 3 and thus had a determination coefficient less than 0.985 in the evaluation of external appearance when not operating.

[0162] It should be understood that those skilled in the art may make various modifications, changes, alterations and equivalent embodiments without departing from the spirit and scope of the present invention.

Claims

1. A polarizing plate, comprising: polarizing film; as well as A contrast improvement film is formed on one surface of the polarizing film, The contrast improvement film includes a first protective layer and a contrast improvement layer, the contrast improvement layer includes a first resin layer and a second resin layer facing each other, the second resin layer and the first resin layer are sequentially stacked on the polarizing film, The first resin layer includes a patterned portion formed on a surface of the first resin layer facing the second resin layer, The patterned portion includes at least two engraved optical patterns and a flat portion between the engraved optical patterns adjacent to each other, The engraved optical pattern has a base angle of 75° to 90°, The patterned portion satisfies Formula 2: <Formula 2> 1 <P / W≤10 Wherein P is the sum of the maximum width of the corresponding engraved optical pattern and the width of the flat portion directly adjacent to the corresponding engraved optical pattern (in micrometers), and W is the maximum width of the corresponding engraved optical pattern (in micrometers), The patterned portion satisfies the following conditions i and ii: The condition i: the engraved optical pattern has a maximum width different from at least one of the engraved optical patterns adjacent to each other; The condition ii: the flat portion has a width different from that of at least one of the flat portions adjacent to each other; and wherein the polarizing plate has a determination coefficient of black visibility of 0.985 or greater, Each of the engraved optical patterns extends in a strip shape from the flat portion, The patterned portion satisfies Formula 3: <Formula 3> 2.38<[P / W]max / [P / W]min<3.52 Wherein [P / W]max is the maximum value of P / W represented by Formula 2, and [P / W]min is the minimum value of P / W represented by Formula 2. 2 . The polarizing plate of claim 1 , wherein the engraved optical patterns have the same height. 3 . The polarizing plate of claim 2 , wherein the engraved optical pattern has a maximum width of 5 to 25 micrometers and the flat portion has a width of 3 to 50 micrometers. 4 . The polarizing plate according to claim 2 , wherein a difference between a maximum value and a minimum value in a maximum width of the engraved optical pattern is in a range of 2 μm to 20 μm. 5 . The polarizing plate according to claim 2 , wherein a difference between a maximum value and a minimum value in a width of the flat portion is in a range of 7 μm to 20 μm. The polarizing plate according to claim 1 , wherein a pitch of the patterned portion is 0.6 to 5 times a maximum width of the engraved optical pattern. 7 . The polarizing plate of claim 1 , wherein the engraved optical pattern has an aspect ratio of 0.3 to 3.

0. 8 . The polarizing plate according to claim 1 , wherein the engraved optical patterns include optical patterns each having a first surface located at a top of the engraved optical pattern and at least one inclined surface connected to the first surface, the inclined surface being a plane or a curved surface. 9 . The polarizing plate according to claim 1 , wherein the first resin layer has a higher refractive index than the second resin layer. 10 . The polarizing plate according to claim 1 , wherein an absolute value of a difference in refractive index between the first resin layer and the second resin layer is 0.20 or less. 11 . The polarizing plate according to claim 1 , wherein in the contrast-improving film, the second resin layer directly adjoins the first resin layer, and the first resin layer directly adjoins the first protective layer. 12 . The polarizing plate according to claim 1 , wherein the first resin layer or the second resin layer is an adhesive bonding layer, and the contrast-improving film is directly formed on the polarizing film.

13. The polarizing plate according to claim 1, wherein the first protective layer has a Re represented by Formula A of 8,000 nm or more at a wavelength of 550 nm: <Formula A> Re=(nx-ny)×d Wherein nx and ny are the refractive indices on the slow axis and the fast axis of the first protective layer at a wavelength of 550 nanometers, respectively, and d is the thickness of the first protective layer, and the unit of the thickness is nanometer. The polarizing plate according to claim 1 , wherein the first protective layer is formed of a polyester resin. 15 . The polarizing plate according to claim 1 , wherein the polarizing film comprises a polarizer and a second protective layer formed on one surface of the polarizer, and the second protective layer is formed between the polarizer and the contrast-improving film.

16. An optical display comprising the polarizing plate according to any one of claims 1 to 15.

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