Polarizing plate and optical display including the same

Abstract

The present invention relates to a polarizing plate and an optical display including the polarizing plate. The polarizing plate includes a polarizer; and a first phase difference layer and a second phase difference layer sequentially stacked on the lower surface of the polarizer, wherein the first phase difference layer has a biaxiality (NZ) less than 0 at a wavelength of 550nm and is a non-liquid crystal layer, and the second phase difference layer has a biaxiality (NZ) greater than 1 at a wavelength of 550nm.

Description

[0001] Related Applications

[0002] This application claims the benefit of Korean Patent Application No. 10-2020-0113234 filed on September 4, 2020, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference in its entirety. Technical Field

[0003] The present invention relates to a polarizing plate and an optical display comprising the polarizing plate. Background Art

[0004] Due to the reflection of external light, the organic light emitting diode display may suffer from the degradation of visibility and contrast. To solve this problem, the organic light emitting diode display may use polarizing plates, each of which includes a polarizer and a retardation film, thereby realizing an anti-reflection function by preventing the reflected external light from leaking therefrom.

[0005] Polarizing plates are intended to reduce lateral reflectivity and front reflectivity. To this end, polarizing plates generally include two retardation layers on the lower surface of the polarizer. In recent years, as the trend of improving thickness reduction and processability of polarizing plates has increased, it is necessary to improve thickness reduction and processability while reducing its reflectivity. On the other hand, there is a technology for reducing reflectivity by a pattern layer on the lower surface of the polarizer. However, since the pattern layer needs to have a predetermined thickness and height, the pattern layer is not suitable for the thickening trend of the polarizing plate and requires an additional process, thereby deteriorating processability.

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

[0007] One aspect of the present invention is to provide a polarizing plate having a good thickness reduction effect while significantly reducing the front reflectivity and the lateral reflectivity.

[0008] Another aspect of the present invention is to provide a polarizing plate ensuring good processability.

[0009] A further aspect of the present invention is to provide a polarizing plate capable of improving black visibility.

[0010] Still another aspect of the present invention is to provide an optical display including the polarizing plate.

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

[0012] 1. The polarizing plate comprises a polarizer; and a first phase difference layer and a second phase difference layer stacked in sequence on the lower surface of the polarizer, wherein the first phase difference layer has a biaxiality (NZ) less than 0 at a wavelength of 550nm and is a non-liquid crystal layer, and the second phase difference layer has a biaxiality (NZ) greater than 1 at a wavelength of 550nm.

[0013] 2. In 1, the first phase difference layer may have a biaxiality (NZ) greater than or equal to -3 and less than 0 at a wavelength of 550 nm, and the second phase difference layer may have a biaxiality (NZ) greater than 1 and less than or equal to 2 at a wavelength of 550 nm.

[0014] 3. In 1 and 2, the first phase difference layer may have a greater absolute out-of-plane retardation Rth than the second phase difference layer at a wavelength of 550 nm.

[0015] 4. In 1-3, the first phase difference layer may have an Rth of -250 nm to -50 nm at a wavelength of 550 nm, and the second phase difference layer may have an Rth of 40 nm to 150 nm at a wavelength of 550 nm.

[0016] 5. In 1-4, a stack of the first phase difference layer and the second phase difference layer or a stack including the first phase difference layer and the second phase difference layer may be stacked on the lower surface of the polarizer and may have an Rth of -150 nm to -10 nm at a wavelength of 550 nm.

[0017] 6. In 1-5, the first phase difference layer may have a greater absolute in-of-plane retardation (Re) than the second phase difference layer at a wavelength of 550 nm.

[0018] 7. In 1-6, the first phase difference layer may have Re of 100 nm to 270 nm at a wavelength of 550 nm, and the second phase difference layer may have Re of 70 nm to 160 nm at a wavelength of 550 nm.

[0019] 8. In 1-7, the first phase difference layer may have negative (-) birefringence, and the second phase difference layer may have positive (+) birefringence.

[0020] 9. In 1-8, the first phase difference layer may have an Rth / d of -50 nm / μm to -10 nm / μm (Rth represents the out-of-plane retardation of the first phase difference layer at a wavelength of 550 nm (unit: nm), and d represents the thickness of the first phase difference layer (unit: μm)).

[0021] 10. In 1-9, the first phase difference layer may exhibit positive dispersion, and the second phase difference layer may exhibit positive dispersion.

[0022] 11. In 1-10, the first phase difference layer may have a thickness of 15 μm or less, and the second phase difference layer may have a thickness of 10 μm or more.

[0023] 12. In 1-11, the first phase difference layer may include at least one selected from the group consisting of a cellulose ester compound or a polymer thereof and an aromatic compound or a polymer thereof.

[0024] 13. In 12, the aromatic compound may include a polystyrene compound including a moiety represented by Formula 2:

[0025]

[0026] in is the attachment site of the atom; R 1 , R 2 and R 3 Each is independently a hydrogen atom, an alkyl group, a substituted alkyl group or a halogen; each R is independently a substituent on the styrene ring; and n is an integer from 0 to 5, indicating the number of substituents on the styrene ring.

[0027] 14. In 13, the moiety of Formula 2 may include halogen.

[0028] 15. In 1-14, the first phase difference layer may be directly formed on the lower surface of the second phase difference layer without an adhesive layer therebetween.

[0029] 16. In 1-15, the second phase difference layer may be a non-liquid crystal layer.

[0030] 17. In 1-16, the first phase difference layer may have a slow axis tilted at an angle of +5° to +25° or at an angle of -25° to -5° relative to the transmission axis of the polarizer, and the second phase difference layer may have a slow axis tilted at an angle of +50° to +80° or at an angle of -80° to -50° relative to the transmission axis of the polarizer.

[0031] 18. In 1-17, the polarizing plate may further include a protective layer formed on an upper surface of the polarizer.

[0032] 19. In 1-18, the polarizing plate may further include a third phase difference layer including a positive C layer having an out-of-plane retardation Rth of -300 nm to 0 nm at a wavelength of 550 nm.

[0033] 20. In 19, the third phase difference layer can be stacked between the polarizer and the first phase difference layer or stacked on the lower surface of the second phase difference layer.

[0034] 21. In 1-20, the polarizing plate may further include a layer containing a light absorber.

[0035] 22. In 21, the light absorber-containing layer may contain 0.001 wt % to 6 wt % of a light absorber having a maximum absorption wavelength of 380 nm to 450 nm.

[0036] 23. In 21, the layer containing the light absorber can be formed on the upper surface of the protective layer formed on the upper surface of the polarizer, between the polarizer and the protective layer, between the polarizer and the first phase difference layer, between the polarizer and the first phase difference layer, between the first phase difference layer and the second phase difference layer, and / or on the lower surface of the second phase difference layer.

[0037] The optical display according to the present invention includes the polarizing plate according to the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 is a cross-sectional view of a polarizing plate according to one embodiment of the present invention.

[0039] Figure 2 is a cross-sectional view of a polarizing plate according to another embodiment of the present invention.

[0040] Figure 3 is a cross-sectional view of a polarizing plate according to another embodiment of the present invention. DETAILED DESCRIPTION

[0041] Hereinafter, 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 implemented in different ways and is not limited to the following embodiments.

[0042] In the accompanying drawings, components not related to the description are omitted in order to clearly describe the present invention, and the same components will be represented by the same reference numerals throughout the specification. Although the length, thickness or width of each component may be exaggerated for understanding in the accompanying drawings, the present invention is not limited thereto. Herein, spatially related terms such as "upper" and "lower" are defined with reference to the accompanying drawings. Therefore, it should be understood that the term "upper surface" can be used interchangeably with the term "lower surface".

[0043] Herein, "in-plane retardation Re", "out-of-plane retardation Rth" and "biaxiality (NZ)" are represented by equations A, B and C, respectively:

[0044] Re=(nx-ny)×d,--------------------------------(A)

[0045] Rth=((nx+ny) / 2-nz)×d,-----------------------(B)

[0046] NZ=(nx-nz) / (nx-ny),-------------------------------(C)

[0047] Where nx, ny, nz are the refractive indices of the corresponding optical device in the slow axis direction, fast axis direction and thickness direction at the measurement wavelength, and d is its thickness (unit: nm). In equation AC, the measurement wavelength can be 450nm, 550nm or 650nm.

[0048] Herein, “short wavelength dispersion” refers to Re(450) / Re(550), and “long wavelength dispersion” refers to Re(650) / Re(550), wherein Re(450), Re(550) and Re(650) refer to the in-plane retardation (Re) of a single phase difference layer or a stack of phase difference layers at wavelengths of about 450 nm, about 550 nm and about 650 nm, respectively.

[0049] As used herein to indicate angles, "+" indicates a clockwise direction about a reference, and "-" indicates a counterclockwise direction about a reference.

[0050] As used herein to indicate a specific numerical range, the phrase "X to Y" means "greater than or equal to X and less than or equal to Y (X≤ and ≤Y)."

[0051] The present invention relates to a polarizing plate, which includes a first phase difference layer and a second phase difference layer stacked sequentially on the lower surface of a polarizer. The polarizing plate according to the present invention can reduce the positive reflectivity and the lateral reflectivity at any wavelength, and can improve the circular polarization degree and processability of the lateral side by eliminating the adhesive layer between the first phase difference layer and the second phase difference layer while achieving the thickness reduction of the polarizing plate. In one embodiment, the polarizing plate may have a circular polarization degree of 65% or more, for example, 65%-75%, a front reflectivity of 0.25% or less, for example, 0%-0.25%, and a lateral reflectivity of 0.55% or less, for example, 0%-0.55%. Within this range, the polarizing plate can improve the screen quality without screen imbalance between the front and the side. Although the polarizing plate may also include a pattern layer on the lower surface of the polarizer, the polarizing plate according to the present invention can achieve thickness reduction and processability improvement even without a pattern layer by achieving the effect of the present invention.

[0052] Next, refer to Figure 1 A polarizing plate according to one embodiment of the present invention is described.

[0053] refer to Figure 1The polarizing plate according to this embodiment includes a polarizer 110, a protective layer 140 stacked on an upper surface of the polarizer 110, and a first phase difference layer 120 and a second phase difference layer 130 stacked on a lower surface of the polarizer 110 in a prescribed order from the polarizer 110.

[0054] The first phase difference layer and the second phase difference layer

[0055] The first phase difference layer 120 has a biaxiality (NZ) less than 0 at a wavelength of 550 nm, and the second phase difference layer 130 has a biaxiality (NZ) greater than 1 at a wavelength of 550 nm. By using the first phase difference layer 120 and the second phase difference layer 130 satisfying the above biaxiality, the polarizing plate can achieve a significant improvement in screen quality by significantly reducing the lateral reflectivity.

[0056] Specifically, the first phase difference layer 120 can have a biaxiality (NZ) of -3 to less than 0 at a wavelength of 550 nm, for example, -2, -1.9, -1.8, -1.7, -1.6, -1.5, -1.4, -1.3, -1.2, -1.1, -1.0, -0.9, -0.8, -0.7, -0.6, -0.5, -0.4, -0.3, -0.2, -0.1, -0.05 or -0.01, preferably -2 to -0.05. The second phase difference layer 130 may have a biaxiality (NZ) greater than 1 to 3, for example, 1.05, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9 or 2, preferably 1.05 to 2, specifically 1.05 to 1.5, at a wavelength of 550 nm.

[0057] The first phase difference layer 120 may have a greater absolute out-of-plane retardation Rth at a wavelength of 550 nm than the second phase difference layer 130. As described below, the stack of the first phase difference layer 120 and the second phase difference layer 130 has a negative (-) Rth at a wavelength of 550 nm, whereby the polarizing plate can significantly reduce the lateral reflectivity, thereby significantly improving the screen quality of the display device.

[0058] The first phase difference layer 120 has a negative (-) Rth at a wavelength of 550nm, and the second phase difference layer 130 has a positive (+) Rth at a wavelength of 550nm. Therefore, the stack of the first phase difference layer 120 and the second phase difference layer 130 is an anti-reflection film and has a negative (-) Rth at a wavelength of 550nm, thereby significantly improving the lateral reflectivity. Compared with a polarizing plate in which a single phase difference layer or a phase difference layer stack is stacked on the lower surface of a polarizer and has a positive (+) Rth at a wavelength of 550nm, a polarizing plate in which the stack of the first phase difference layer and the second phase difference layer has a negative (-) Rth at a wavelength of 550nm can further reduce the lateral reflectivity, thereby further improving the screen quality of the display device.

[0059] In one embodiment, the stack of the first phase difference layer 120 and the second phase difference layer 130 or the stack of the first phase difference layer 120 and the second phase difference layer 130 stacked on the lower surface of the polarizer and including the first phase difference layer 120 and the second phase difference layer 130 can have an Rth of -150nm to -10nm at a wavelength of 550nm, for example, -150nm, -140nm, -130nm, -120nm, -110nm, -100nm, -90nm, -80nm, -70nm, -60nm, -50nm, -40nm, -30nm, -20nm or -10nm, specifically -80nm to -20nm, more specifically -70nm to -25nm. Within this range, the polarizing plate can significantly reduce the chromatic aberration between the lateral reflectivity of the display device and the azimuth of its side surface.

[0060] The first phase difference layer 120 can have an Rth of -250nm to -50nm at a wavelength of 550nm, for example, -250nm, -240nm, -230nm, -220nm, -210nm, -200nm, -190nm, -180nm, -170nm, -160nm, -150nm, -140nm, -130nm, -120nm, -110nm, -100nm, -90nm, -80nm, -70nm, -60nm or -50nm, specifically -150nm to -60nm, more specifically -130nm to -80nm. Within this range, the first phase difference layer allows the stack of the first phase difference layer and the second phase difference layer to easily reach the above Rth value at a wavelength of 550nm while reducing the lateral reflectivity of the display device.

[0061] The second phase difference layer 130 may have an Rth of 40 nm to 150 nm, for example, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, 110 nm, 120 nm, 130 nm, 140 nm or 150 nm, specifically 45 nm to 100 nm, more specifically 50 nm to 70 nm at a wavelength of 550 nm. Within this range, the second phase difference layer allows the stack of the first and second phase difference layers to easily reach the above Rth value at a wavelength of 550 nm while reducing the lateral reflectivity of the display device.

[0062] The first phase difference layer 120 may be formed of at least one first material having negative (-) birefringence.

[0063] In this article, "having negative birefringence" means that since the elongation of the unstretched film or coating formed by coating and drying the corresponding material increases when the unstretched film or coating is stretched, the in-plane retardation Re of the unstretched film or coating increases at a wavelength of 550nm, while its out-of-plane retardation Rth at a wavelength of 550nm decreases (that is, Rth becomes a negative value (-), and the absolute value of Rth increases). Using the first phase difference layer 120 formed of at least one first material having negative birefringence, the stack of the first phase difference layer and the second phase difference layer can easily achieve the above Rth value at a wavelength of 550nm.

[0064] The second phase difference layer 130 may be formed of at least one second material having positive (+) birefringence.

[0065] In this article, "having positive birefringence" means that since the elongation of the unstretched film or coating formed by coating and drying the corresponding material increases when the unstretched film or coating is stretched, the in-plane retardation Re and out-of-plane retardation Rth of the unstretched film or coating at a wavelength of 550nm will increase (that is, Rth becomes a positive value (+), and the absolute value of Rth increases). By using the second phase difference layer 130 formed of at least one second material having positive birefringence, the stack of the first phase difference layer and the second phase difference layer can easily achieve the above Rth value at a wavelength of 550nm.

[0066] The first phase difference layer 120 may have a greater absolute in-plane retardation Re at a wavelength of 550 nm than the second phase difference layer 130. With this structure, the polarizing plate can further reduce the lateral reflectivity of the display device.

[0067] The first phase difference layer 120 may have a Re of 100 nm to 270 nm, for example, 100 nm, 110 nm, 120 nm, 130 nm, 140 nm, 150 nm, 160 nm, 170 nm, 180 nm, 190 nm, 200 nm, 210 nm, 220 nm, 230 nm, 240 nm, 250 nm, 260 nm or 270 nm, specifically 100 nm to 200 nm, more specifically 150 nm to 180 nm, at a wavelength of 550 nm. Within this range, the first phase difference layer 120 can ensure the thickness reduction of the polarizing plate and the optimal Rth of the laminate by reducing the amount of material used for the polarizing plate.

[0068] The second phase difference layer 130 may have an Re of 70 nm to 160 nm, for example, 70 nm, 80 nm, 90 nm, 100 nm, 110 nm, 120 nm, 130 nm, 140 nm, 150 nm or 160 nm, specifically 80 nm to 130 nm, at a wavelength of 550 nm. Within this range, the second phase difference layer 130 can ensure the thickness reduction of the polarizing plate and the optimal Rth of the laminate by reducing the amount of material used for the polarizing plate.

[0069] The first phase difference layer 120 exhibits positive dispersion, while the stacked body of the first phase difference layer 120 and the second phase difference layer 130 exhibits negative dispersion, thereby reducing the lateral reflectivity.

[0070] The first phase difference layer 120 may have a short wavelength dispersion of 1-1.2 and a long wavelength dispersion of 0.9-1. Within this range, the polarizing plate can reduce the reflectivity of the front and lateral sides during use. Preferably, the first phase difference layer has a short wavelength dispersion of 1-1.1 and a long wavelength dispersion of 0.95-1.

[0071] In one embodiment, the first phase difference layer 120 may have an in-plane delay of 130 nm to 250 nm, preferably 150 nm to 230 nm, more preferably 160 nm to 220 nm at a wavelength of 450 nm, and an in-plane delay of 120 nm to 240 nm, preferably 140 nm to 220 nm, more preferably 150 nm to 210 nm at a wavelength of 650 nm. Within this range, the first phase difference layer can easily achieve the desired short wavelength dispersion and the desired long wavelength dispersion.

[0072] The second phase difference layer 130 exhibits positive dispersion, and the stacked body of the first phase difference layer 120 and the second phase difference layer 130 exhibits negative dispersion, thereby reducing the lateral reflectivity.

[0073] The second phase difference layer 130 may have a short wavelength dispersion of 1-1.1 and a long wavelength dispersion of 0.96-1. Within this range, the wavelength dispersion difference between the first phase difference layer and the second phase difference layer can be reduced to improve the circular polarization degree at each wavelength, thereby increasing the reflectivity.

[0074] In one embodiment, the second phase difference layer 130 may have an in-plane delay of 80nm to 120nm, preferably 85nm to 115nm, more preferably 90nm to 110nm at a wavelength of 450nm, and an in-plane delay of 80nm to 110nm, preferably 85nm to 105nm at a wavelength of 650nm. Within this range, the second phase difference layer can easily achieve short wavelength dispersion and long wavelength dispersion as described above.

[0075] The first phase difference layer 120 is a non-liquid crystal layer. Herein, the "non-liquid crystal layer" may refer to a layer formed of a composition not containing at least one selected from a liquid crystal polymer and a liquid crystal copolymer. Liquid crystal polymers and liquid crystal copolymers refer to materials formed of mesogen compounds and may have stripe, rod, and disk shapes, but are not limited thereto.

[0076] The first phase difference layer 120 may have a thickness of 15 μm or less, specifically 0 μm to 15 μm or less, more specifically 3 μm to 15 μm. Within this range, the first phase difference layer 120 may have a thin thickness and achieve the above retardation.

[0077] As described above, the stack of the first phase difference layer 120 and the second phase difference layer 130 can be formed by coating and drying the composition of the first phase difference layer 120 on the upper surface of the second phase difference layer 130 to form a coating of the first phase difference layer 120, and then stretching the coating and the second phase difference layer at the same time. Generally speaking, each layer of the first phase difference layer 120 and the second phase difference layer 130 is formed of a liquid crystal film or a liquid crystal polymer, which requires an adhesive layer or a bonding layer between the first phase difference layer and the second phase difference layer, thereby deteriorating the productivity of the polarizing plate and failing to suppress the influence of the adhesive layer or the bonding layer. On the other hand, when the first phase difference layer is formed by coating a composition containing a liquid crystal polymer on the upper surface of the second phase difference layer, the polarizing plate requires a separate alignment layer to align the liquid crystal, resulting in separation problems between the first phase difference layer and the alignment layer and between the alignment layer and the second phase difference layer.

[0078] In one embodiment, the polarizing plate according to the present invention may not have an alignment layer.

[0079] In one embodiment, the first phase difference layer 120 may be directly formed on the upper surface of the second phase difference layer 130. Herein, “directly formed” means that neither an adhesive layer nor a bonding layer is interposed between the first phase difference layer 120 and the second phase difference layer 130.

[0080] According to the present invention, the first phase difference layer 120 composed of a non-liquid crystal layer can prevent the above problems and improve the processability of the polarizing plate while reducing the thickness of the polarizing plate. According to the present invention, the first phase difference layer 120 is formed of the following first material, so that the non-liquid crystal layer of the first phase difference layer 120 satisfies the above Rth at a wavelength of 550nm.

[0081] In one embodiment, the second phase difference layer 130 may be a non-liquid crystal layer. The second phase difference layer 130 is composed of a non-liquid crystal layer, which is beneficial to the manufacture of the first phase difference layer 120 and / or the first phase difference layer 120 and the second phase difference layer 130 .

[0082] The second phase difference layer 130 may have a greater thickness than the first phase difference layer 120 .

[0083] The second phase difference layer 130 may have a thickness of 10 μm or more, specifically 10 μm to 30 μm. Within this range, the coating layer can ensure uniform coating while serving as a support for achieving uniform retardation across the entire width of the polarizing plate.

[0084] In one embodiment, the second phase difference layer 130 may include a stretched polymer film formed by a light-transmitting resin. For example, the second phase difference layer 130 may be selected from cellulose resins, including triacetyl cellulose (TAC), polyester resins, including polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate (PEN), polybutylene naphthalate, etc., cyclic polyolefin (COP) resin, polycarbonate resin, polyether sulfone resin, polysulfone resin, polyamide resin, polyimide resin, polyolefin resin, polyarylate resin, polyvinyl alcohol resin, polyvinyl chloride resin, polyvinylidene chloride resin and acrylic resin. It is preferred that the second phase difference layer 130 may include a stretched cyclic polyolefin, polycarbonate or acryl film. The cyclic polyolefin (COP) film can provide a favorable effect in improving the front reflectivity of the polarizing plate according to the present invention.

[0085] The first phase difference layer 120 may have a thickness of -50nm / μm to -10nm / μm, for example, -50nm / μm, -49nm / μm, -48nm / μm, -47nm / μm, -46nm / μm, -45nm / μm, -44nm / μm, -43nm / μm, -42nm / μm, -41nm / μm, -40nm / μm, -39nm / μm, -38nm / μm, -37nm / μm, -36nm / μm, -35nm / μm, -34nm / μm, -33nm / μm, -32nm / μm, -31nm / μm, -30nm / μm, -29nm / μm, -28nm / μm, -27nm / μm, -26nm / μm, -25nm / μm, -24nm / μm, nm / μm, -23nm / μm, -22nm / μm, -21nm / μm, -20nm / μm, -19nm / μm, -18nm / μm, -17nm / μm, -16nm / μm, -15nm / μm, -14nm / μm, -13nm / μm, -12nm / μm, -11nm / μm or -10nm / μm, preferably -40nm / μm to -20nm / μm, more preferably -35nm / μm to -25nm / μm of Rth / d (Rth represents the out-of-plane delay of the first phase difference layer at a wavelength of 550nm (unit; nm), d represents the thickness of the first phase difference layer (unit: μm). Within this range, the polarizing plate can be easily manufactured while ensuring thickness uniformity in the process of forming the coating.

[0086] According to the present invention, the first phase difference layer is formed by a composition containing a first material satisfying the above-mentioned Rth / d range instead of a typical liquid crystal film, whereby the stack of the first phase difference layer and the second phase difference layer has a negative Rth at a wavelength of 550 nm, thereby eliminating the adhesive layer between the first phase difference layer and the second phase difference layer, while improving the processability of the polarizing plate and achieving a significant reduction in lateral reflectivity and thickness.

[0087] The first phase difference layer 120 may be formed of a composition of the first phase difference layer, the composition comprising at least one selected from a cellulose ester compound or a polymer thereof and an aromatic compound or a polymer thereof as described below. The first phase difference layer 120 may comprise at least one selected from a cellulose ester compound or a polymer thereof and an aromatic compound or a polymer thereof as described below. The cellulose ester compound or a polymer thereof and the aromatic compound or a polymer thereof described below may be suitable for manufacturing the first phase difference layer according to the present invention.

[0088] The composition of the first phase difference layer can achieve a first phase difference layer having an Rth / d (Rth represents the out-of-plane delay of the first phase difference layer at a wavelength of 550nm (unit: nm), and d represents its thickness (unit: μm)) of -50nm / μm to -10nm / μm, preferably -40nm / μm to -20nm / μm, and more preferably -35nm / μm to -25nm / μm. Within this range, the polarizing plate can be easily manufactured while ensuring thickness uniformity during the process of forming the coating.

[0089] The cellulose ester compound may include at least one selected from the group consisting of a cellulose ester resin, a cellulose ester oligomer, and a cellulose ester monomer.

[0090] The cellulose ester compound may include a condensation product obtained by a reaction between a hydroxyl group on cellulose ester and a carboxylic acid or a carboxylic anhydride.

[0091] The cellulose ester compound may be regioselectively substituted or randomly substituted. Regioselectivity can be determined by measuring the C13NMR on the cellulose ester. 6 , C 3 and C 2 The cellulose ester compound can be measured by a typical method by reacting a cellulose solution with at least one C 1 -C 20 The acylating agent is contacted for a sufficient contact time to provide a cellulose ester having the desired degree of substitution and the desired degree of polymerization.

[0092] Preferably, the acylating agent comprises at least one linear or branched C 1 -C 20 Alkyl or aryl carboxylic acid anhydride, acyl halide, diketone or acetoacetate. The example of carboxylic acid anhydride can include acetic anhydride, propionic anhydride, butyric anhydride, isobutyric anhydride, valeric anhydride, caproic anhydride, 2-ethylhexanoic anhydride, nonanoic anhydride, lauric anhydride, palmitic anhydride, stearic anhydride, benzoic anhydride, substituted benzoic anhydride, phthalic anhydride and isophthalic anhydride. The example of acyl halide can include acetyl chloride, propionyl chloride, butyryl chloride, caproyl chloride, 2-ethylhexanoyl chloride, lauroyl chloride, palmitoyl chloride, benzoyl chloride, substituted benzoyl chloride and stearyl chloride. The example of acetoacetate can include methyl acetoacetate, ethyl acetoacetate, propyl acetoacetate, butyl acetoacetate and tert-butyl acetoacetate. Most preferably, the acylating agent includes straight or branched C 2 -C 9 Alkyl carboxylic anhydrides such as acetic anhydride, propionic anhydride, butyric anhydride, 2-ethylhexanoic anhydride, nonanoic anhydride and stearic anhydride.

[0093] Preferred cellulose ester compounds include, for example, cellulose acetate (CA), cellulose acetate propionate (CAP), and cellulose acetate butyrate (CAB), but are not limited thereto.

[0094] In one embodiment, the cellulose ester compound may contain at least two acyl substituents. At least one acyl group may include an aromatic substituent, and in the cellulose ester compound, the relative degree of substitution (RDS) may be arranged in the order of C6>C2>C3. C6 represents the degree of substitution of the 6th carbon in the cellulose ester, C2 represents the degree of substitution of the 2nd carbon in the cellulose ester, and C3 represents the degree of substitution of the 3rd carbon in the cellulose ester. The aromatic compound may include benzoate or substituted benzoate.

[0095] In another embodiment, the cellulose ester compound may include a regioselectively substituted cellulose ester compound having (a) a plurality of chromophore-acyl substituents and (b) a plurality of pivaloyl substituents.

[0096] The cellulose ester compound may have a hydroxyl degree of substitution of about 0.1 to about 1.2 and a chromophore-acyl degree of substitution of about 0.4 to about 1.6; the difference between the sum of the chromophore-acyl degree of substitution on the 2nd carbon in the cellulose ester compound and the chromophore-acyl degree of substitution on the 3rd carbon in the cellulose ester compound and the chromophore-acyl degree of substitution on the 6th carbon in the cellulose ester compound may be in the range of about 0.1 to about 1.6; and the chromophore-acyl group may be selected from (i), (ii), (iii) and (iv):

[0097] (i)(C 6 -C 20 ) aryl-acyl, wherein the ss aryl group is unsubstituted or substituted with 1-5 R 1 replace;

[0098] (ii) heteroaryl, wherein heteroaryl is a five- to ten-membered ring having 1 to 4 heteroatoms selected from N, O and S, and is unsubstituted or substituted with 1 to 5 R 1 replace;

[0099] (iii)

[0100] Where aryl is C 1 -C 6 Aryl, and is unsubstituted or substituted with 1-5 R 1 Replacement; and

[0101] (iv)

[0102] wherein heteroaryl is a five to ten membered ring having 1 to 4 heteroatoms selected from N, O and S, and is unsubstituted or substituted by 1 to 5 R 1 replace,

[0103] R 1 are independently nitro, cyano, (C1 -C 6 ) alkyl, halogenated (C 1 -C 6 ) alkyl, (C 6 -C 20 )Aryl-CO 2 -、(C 6 -C 20 ) aryl, (C 1 -C 6 ) alkoxy, halogenated (C 1 -C 6 ) alkoxy, halogen, a five- to ten-membered heteroaryl group having 1 to 4 heteroatoms selected from N, O and S, or

[0104] In one embodiment, the chromophore-acyl group may be an unsubstituted or substituted benzoyl group, or an unsubstituted or substituted naphthyl group.

[0105] In one embodiment, the chromophore-acyl group may be selected from the group consisting of:

[0106]

[0107]

[0108]

[0109] Where * indicates the point of attachment of the chromophore-acyl substituent to the oxygen of the cellulose ester.

[0110] In another embodiment, the cellulose ester compound may include an ester polymer having acyl units, wherein at least some of the hydroxyl groups of the sugar monomers constituting the cellulose are 2 Hydroxyl, C 3 Hydroxyl or C 6 Hydroxyl] is unsubstituted or substituted, as shown in Formula 1:

[0111]

[0112] Here, n is an integer of 1 or greater.

[0113] The cellulose ester polymer or acyl unit substituents may include halogen, nitro, alkyl (e.g., C 1 -C 20 alkyl), alkenyl (e.g., C 2 -C 20 alkenyl), cycloalkyl (e.g., C 3 -C 10 Cycloalkyl), aryl (e.g., C 6 -C 20 aryl), heteroaryl (e.g., C3 -C 10 Aryl), alkoxy (e.g., C 1 -C 20 These substituents may be the same as or different from each other.

[0114] In this context, "acyl" may refer to RC(=O)-* (* is the attachment site, R is C 1 -C 20 Alkyl, C 3 -C 20 Cycloalkyl, C 6 -C 20 Aryl or C 7 -C 20 The "acyl" group is coupled to the cellulose ring via an ester bond (via an oxygen atom) in the cellulose.

[0115] Herein, for convenience, "alkyl", "alkenyl", "cycloalkyl", "aryl", "heteroaryl", "alkoxy" and "acyl" refer to non-halogen-based compounds. The composition of the first phase difference layer may include cellulose ester polymer alone or a mixture of cellulose ester polymers.

[0116] Herein, "halogen" refers to fluorine (F), Cl, Br or I, preferably F.

[0117] A "halogen-containing functional group" is an organic functional group containing at least one halogen, and may include aromatic, aliphatic or alicyclic functional groups. For example, a halogen-containing functional group may refer to a halogen-substituted C 1 -C 20 Alkyl, halogen substituted C 2 -C 20 Alkenyl, halogen substituted C 2 -C 20 Alkynyl, halogen substituted C 3 -C 10 Cycloalkyl, halogen substituted C 1 -C 20 Alkoxy, halogen-substituted acyl, halogen-substituted C 6 -C 20 Aryl or halogen substituted C 7 -C 20 Aralkyl groups include, but are not limited to, aralkyl groups.

[0118] "Halogen-substituted acyl" may be R'-C(=O)-* (* is the attachment site, R' is the halogen-substituted C 1 -C 20 Alkyl, halogen substituted C 3 -C 20 Cycloalkyl, halogen substituted C 6 -C20 Aryl or halogen substituted C 7 -C 20 The "halogen-substituted acyl group" can be coupled to the ring of cellulose via an ester bond (via an oxygen atom) in cellulose.

[0119] Preferably, the composition of the first phase difference layer includes a cellulose ester polymer substituted with an acyl group, a halogen or a halogen-containing functional group. More preferably, the halogen is fluorine. The halogen may be present in the cellulose ester polymer in an amount of 1 wt% to 10 wt%. Within this range, the composition allows for easy formation of a positive C-plate phase difference layer having the characteristics of the present invention and can improve ellipticity.

[0120] In order to form the first phase difference layer, the cellulose ester polymer can be prepared by a typical method known to those skilled in the art, or can be obtained from commercially available products. For example, a cellulose ester polymer having an acyl group as a substituent can be prepared by reacting trifluoroacetic acid or trifluoroacetic anhydride with a sugar monomer or a polymer of sugar monomers constituting cellulose represented by Formula 1, by reacting trifluoroacetic acid or trifluoroacetic anhydride with it, and then reacting an acylating agent (e.g., an anhydride of a carboxylic acid, or a carboxylic acid) with it, or reacting trifluoroacetic acid or trifluoroacetic anhydride and an acylating agent with it.

[0121] The aromatic compound includes a phenyl group, and may include a polystyrene compound or a fluorobenzene or difluorobenzene structure, but is not limited thereto. In one embodiment, the polystyrene compound may include a moiety represented by Formula 2:

[0122]

[0123] in is the attachment site of the atom,

[0124] R 1 , R 2 and R 3 are each independently a hydrogen atom, an alkyl group, a substituted alkyl group or a halogen;

[0125] R is each independently a substituent on the styrene ring; and

[0126] n is an integer of 0 to 5 indicating the number of substituents on the styrene ring.

[0127] Examples of the substituent R on the styrene ring may include an alkyl group, a substituted alkyl group, a halogen, a hydroxyl group, a carboxyl group, a nitro group, an alkoxy group, an amino group, a sulfonate group, a phosphate group, an acyl group, an acyloxy group, a phenyl group, an alkoxycarbonyl group, and a cyano group.

[0128] The moiety of Formula 2 may contain a halogen.

[0129] In one embodiment, R 1 , R2 and R 3 At least one of them may be hydrogen or halogen, preferably hydrogen or fluorine.

[0130] Each of the first phase difference layer 120 and the second phase difference layer 130 has a slow axis and a fast axis, and by adjusting the angle between the slow axis of the first phase difference layer 120 and the slow axis of the second phase difference layer 130 , the lateral reflectivity and the front reflectivity of the display device can be further reduced.

[0131] The angle between the slow axis of the first phase difference layer 120 and the slow axis of the second phase difference layer 130 can be in the range of 30°-60°, for example, 30°, 35°, 40°, 45°, 50°, 55° or 60°, specifically 40°-55°. Within this range, the polarizing plate can further improve the front reflectivity and the lateral reflectivity.

[0132] Although Figure 1 Not shown, the first phase difference layer 120 may be adhered to the polarizer 110 by an adhesive layer or a bonding layer. The adhesive layer may be formed of, for example, at least one of a photocurable adhesive and a pressure sensitive adhesive (PSA), but is not limited thereto. The bonding layer may be formed of a water-based adhesive or a photocurable adhesive, but is not limited thereto.

[0133] Next, a method of forming a stacked body of the first phase difference layer 120 and the second phase difference layer 130 will be described.

[0134] The laminate of the first phase difference layer and the second phase difference layer can be formed by applying the composition of the first phase difference layer on an unstretched or partially stretched film of the second phase difference layer to form a coating layer, and then stretching the coating layer and the unstretched or partially stretched film of the second phase difference layer.

[0135] The partially stretched film of the second phase difference layer can be prepared by stretching the unstretched film of the second phase difference layer in the machine direction (MD), the transverse direction (TD) or the oblique direction. The oblique direction may refer to a direction of 40°-50°, specifically 45°, relative to the MD of the unstretched film of the second phase difference layer. Herein, the unstretched film may be stretched to 1.5-4 times, specifically 2-3 times, of its initial length.

[0136] The coating of the composition of the first phase difference layer can be performed by any method known to those skilled in the art, for example, by using Meyer bar coating, die coating, spin coating, etc.

[0137] The laminate of the unstretched or partially stretched film of the second phase difference layer and the coating layer can be stretched in MD, TD or a direction inclined relative to the MD of the unstretched or partially stretched film. Herein, the laminate can be stretched to 1.1-3 times, specifically 1.5-2.5 times.

[0138] The stretching may be achieved by dry stretching and / or wet stretching. Each of the dry stretching and the wet stretching may be performed by any method as long as the retardation of each of the first phase difference layer and the second phase difference layer can be achieved thereby.

[0139] polarizer

[0140] Polarizer 110 is used to convert natural light or polarized light into polarized light by linear polarization in a specific direction, and can be made of a polymer film mainly containing polyvinyl alcohol resin. Specifically, polarizer 110 can be made by dyeing the polymer film with iodine or dichroic dye and then stretching the film on MD. Specifically, by swelling, dyeing, stretching and cross-linking, it is possible to produce a polarizer. Alternatively, the polarizer 110 may include a polyene-based polarizer.

[0141] The polarizer 110 may have a total transmittance of 41% or more, for example, 41%-45%, and a polarization degree of 99% or more, for example, 99%-100%. Within this range, the polarizer can improve the anti-reflection performance of the polarizing plate by combining with the first phase difference layer and the second phase difference layer.

[0142] The polarizer 110 may have a thickness of 30 μm or less, specifically greater than 0 μm to 30 μm, more specifically 2 μm to 20 μm, and even more specifically 4 μm to 10 μm. Within this range, the polarizer can be used for a polarizing plate.

[0143] The polarizer 110 has an absorption axis and a transmission axis, wherein the absorption axis corresponds to the MD of the polarizer 110 and the transmission axis corresponds to the TD of the polarizer 110 .

[0144] By adjusting the angle between the transmission axis of the polarizer 110 and the slow axis of the first phase difference layer 120 and the angle between the transmission axis of the polarizer 110 and the slow axis of the second phase difference layer 130 , the polarizing plate can further reduce the front reflectivity and the lateral reflectivity.

[0145] Based on the transmission axis of the polarizer 110, the slow axis of the first phase difference layer 120 is tilted at an angle of +5° to +25° or -5° to -25°, specifically +5° to +20° or -20° to -5°. Within this range, the polarizer can reduce the front reflectivity and lateral reflectivity of the display device.

[0146] The slow axis of the second phase difference layer 130 is tilted at an angle of +50° to +80° or -80° to -50°, specifically +55° to +75° or -75° to -55°, relative to the transmission axis of the polarizer 110. Within this range, the polarizing plate can reduce the front reflectivity and lateral reflectivity of the display device.

[0147] Protective layer

[0148] The protective film 140 is formed on the upper surface of the polarizer 110 to protect the polarizer from the external environment while improving the mechanical strength of the polarizing plate. The protective layer 140 may include a protective film or a protective coating.

[0149] The protective film 140 is used to protect the polarizer from the external environment and can be an optically transparent film formed of, for example, at least one selected from cellulose resins including triacetyl cellulose (TAC), polyester resins including polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate (PEN), polybutylene naphthalate, etc., cyclic polyolefin resins, polycarbonate resins, polyether sulfone resins, polysulfone resins, polyamide resins, polyimide resins, polyolefin resins, polyarylate resins, polyvinyl alcohol resins, polyvinyl chloride resins, and polyvinylidene chloride resins. Specifically, the protective film may be a TAC film or a PET film.

[0150] The protective coating may be comprised of at least one of a thermosetting composition and a photocurable composition of the coating.

[0151] The protective film 140 may have a thickness of about 70 μm or less, specifically greater than 0 μm-70 μm, more specifically 5 μm-70 μm, and even more specifically 15 μm-45 μm. Within this range, the protective film can be used for a polarizing plate.

[0152] Although Figure 1 Not shown, a functional coating may be further formed on the upper surface of the protective film 140 to provide additional functions to the polarizing plate. For example, the functional coating may include a hard coating, an anti-fingerprint layer, an anti-reflection layer, etc. These functional coatings may be stacked alone or in combination.

[0153] The protective layer 140 may be directly formed on the polarizer 110, or may be formed on the polarizer 110 through an adhesive layer. The adhesive layer may be composed of a water-based or ultraviolet curable adhesive, but is not limited thereto.

[0154] Although Figure 1 A polarizing plate including a protective layer is shown, but the polarizing plate according to the present invention may omit the protective layer as long as the performance of the polarizing plate is not affected by the omission of the protective layer. Figure 11 is not shown, an adhesive layer or an adhesive layer may be formed on the lower surface of the second phase difference layer 130 to stack the polarizing plate on a panel or the like.

[0155] Next, a polarizing plate according to another embodiment will be described.

[0156] In the polarizing plate according to the present embodiment, as described above, the polarizer, the first phase difference layer, and the second phase difference layer are sequentially stacked on the lower surface of the protective layer, and the primer layer is further formed on the upper surface of the second phase difference layer.

[0157] The primer layer is formed on the upper surface of the second phase difference layer. Preferably, the primer layer is directly formed on the upper surface of the second phase difference layer so that the first phase difference layer exhibits high adhesion to the second phase difference layer. In addition, the primer layer can prevent the second phase difference layer from being adhered during the roll-to-roll process, thereby promoting the formation of a stack of the second phase difference layer and the first phase difference layer. Specifically, when the second phase difference layer is a cyclic polyolefin film, it may be adhered, making it difficult to form the second phase difference layer thereon by a roll-to-roll process, and the formation of the primer layer can improve the processability when forming the second phase difference layer.

[0158] Now, the primer layer will be described in detail.

[0159] The primer layer may contain particles. Adjusting the size of the particles in the primer layer can improve the adhesion of the first phase difference layer to the second phase difference layer and the processability when forming a stack of the first phase difference layer and the second phase difference layer.

[0160] In one embodiment, the average particle size (D50) of the particles is less than the thickness of the primer layer and can be, for example, in the range of 1nm-500nm, preferably 100nm-300nm. Within this range, the primer layer can prevent the second phase difference layer from being adhered, and can improve the adhesion of the first phase difference layer to the second phase difference layer. The particles can have a spherical or non-spherical shape, but are not limited thereto. Preferably, the particles have a spherical shape. The particles may include a material selected from silicon oxide (e.g., silicon dioxide) and titanium oxide (e.g., TiO 2 ), but not limited to.

[0161] In the primer layer, the particles may be present in an amount of 1 wt%-30 wt%, specifically 3 wt%-20 wt%. Within this range, the primer layer can prevent the second phase difference layer from being stuck when the second phase difference layer is wound on a roller, and can improve the adhesion between the first phase difference layer and the second phase difference layer.

[0162] The primer layer can be formed by coating a composition including particles and a curable resin, and then curing. The curable resin may include at least one selected from a thermosetting resin and a light curable resin, but is not limited thereto. For example, the curable resin may include a modified or unmodified olefin resin, such as an acrylic resin, an ethylene resin, and a propylene resin, but is not limited thereto.

[0163] The primer layer may have a thickness of 100 nm to 500 nm, specifically 150 nm to 300 nm, which is greater than the average particle size of the particles. Within this range, the primer layer can prevent the adhesion of the second phase difference layer, can increase the adhesion of the first phase difference layer, and can allow the polarizing plate to be reduced in thickness.

[0164] Next, a polarizing plate according to another embodiment will be described.

[0165] The polarizing plate of this embodiment includes the protective layer, the polarizer, the first phase difference layer, and the second phase difference layer described above, and further includes a third phase difference layer.

[0166] In one embodiment, the polarizing plate includes a polarizer, a first phase difference layer, and a second phase difference layer, which are sequentially stacked on a lower surface of the protective layer as described above, and further includes a third phase difference layer between the polarizer and the first phase difference layer.

[0167] In another embodiment, the polarizing plate includes a polarizer, a first phase difference layer, and a second phase difference layer, which are sequentially stacked on the lower surface of the protective layer as described above, and further includes a third phase difference layer stacked on the lower surface of the second phase difference layer.

[0168] The third phase difference layer may include a positive C phase difference layer, which satisfies the relationship: nz>nx≒ny (nx, ny and nz are the refractive indices of the third phase difference layer in the slow direction, fast direction and thickness direction respectively at a wavelength of 550nm).

[0169] In one embodiment, the third phase difference layer may have an out-of-plane delay of -300nm to 0nm, for example, -150nm to 0nm, -130nm to -10nm or -100nm to -30nm at a wavelength of 550nm. The third phase difference layer may have an in-plane delay of 0nm to 10nm, for example, 0nm to 5nm at a wavelength of 550nm. Within this range, the polarizing plate can achieve a reduction in lateral reflectivity.

[0170] In one embodiment, the third phase difference layer may be composed of a liquid crystal layer. The liquid crystal layer may be formed of any typical material known to those skilled in the art, as long as the liquid crystal layer can achieve the above-mentioned out-of-plane retardation.

[0171] In another embodiment, the third phase difference layer may be formed of the composition for the first phase difference layer.

[0172] refer to Figure 2 According to another embodiment, a polarizing plate includes a polarizer 110, a protective layer 140 stacked on an upper surface of the polarizer 110, and a first phase difference layer 120, a second phase difference layer 130, and a third phase difference layer 150 stacked on a lower surface of the polarizer 110 in a prescribed order from the polarizer 110.

[0173] The polarizing plate of the present invention may contain the following light absorber. The light absorber may be present in at least one of the protective layer, the polarizer, the first phase difference layer, the second phase difference layer, the third phase difference layer, the primer layer, the functional coating layer, the adhesive layer and the bonding layer, which are present or may be present in the polarizing plate. Alternatively, the light absorber may be present as a light absorber-containing layer in the polarizing plate.

[0174] Next, a polarizing plate according to still another embodiment will be described.

[0175] The polarizing plate of this embodiment further includes a layer containing a light absorber. That is, the polarizing plate of this embodiment includes: a polarizer; a first phase difference layer and a second phase difference layer, which are sequentially stacked on the lower surface of the polarizer, and further includes a layer containing a light absorber. The details of the polarizer, the first phase difference layer and the second phase difference layer are the same as above.

[0176] The layer containing the light absorber contains a light absorber with a maximum absorption wavelength of 380nm to 450nm. When the first phase difference layer and the second phase difference layer are laminated in the polarizing plate, the light absorber helps to improve the black visibility of the front side. Black visibility can be measured by typical methods known to those skilled in the art. For example, the module of the optical display is made by attaching the polarizing plate to the upper surface of the organic light emitting diode panel via the layer containing the light absorber, and using a spectrophotometer DMS 803 (instrument Systems) in the direction from the polarizing plate to the front side (0.05°) to irradiate with light and measure the light reflected and leaked from the polarizing plate and the organic light emitting diode panel to obtain the black visibility color values ​​a* and b* of the front side according to the CIE 1976a*b* standard. Herein, it is preferred that the color values ​​a* and b* are in the range of 0≤|a*|+|b*|≤2.5. Specifically, a* can be in the range of -2.5 to 2.5, and b* can be in the range of -2.5 to 2.5. Within this range, improvement in front black visibility can be confirmed.

[0177] Herein, "maximum absorption wavelength" refers to the wavelength at which the absorbance reaches a maximum value when measured in a light absorber solution diluted to a density of 10 mg / L in chloroform. Preferably, the maximum absorption wavelength of the light absorber-containing layer is 380 nm to 450 nm, more preferably 390 nm to 400 nm.

[0178] In one embodiment, the light absorber-containing layer may have a light transmittance of 10% or less, for example, 0%-10%, or 5% or less at a wavelength of 380nm-450nm. Within this range, the polarizing plate can improve the visual sensitivity of front reflection.

[0179] The light absorber can be selected from any light absorber, as long as the light absorber can achieve the above-mentioned maximum absorption wavelength. Specifically, the light absorber can include at least one selected from indole, phenylbenzotriazole, triazine, quinone, dihydroindole and indocyanine light absorbers. In the polarizing plate of the present invention, these light absorbers can further improve the black visibility of the front side.

[0180] In the layer containing the light absorber, the light absorber may be present in an amount of 0.001 wt%-6 wt%, such as 0.1 wt%-6 wt%, specifically 0.3 wt%-5 wt%. Within this range, the light absorber can improve black visibility and reliability of the front side without seeping out or affecting the retardation values ​​of the first phase difference layer and the second phase difference layer.

[0181] The light absorber-containing layer may be an adhesive layer or a non-adhesive layer depending on the type of base resin forming the light absorber-containing layer. In one embodiment, the light absorber-containing layer may be an adhesive layer through which the polarizing plate can be attached to a panel or the like.

[0182] The light absorber-containing layer may have a thickness of 20 μm or less, specifically greater than 0 μm-20 μm, 1 μm-20 μm, or 5 μm-15 μm. Within this range, the light absorber-containing layer can be used for the polarizing plate.

[0183] The light absorber-containing layer may be formed on the upper surface of the protective layer, between the polarizer and the protective layer, between the polarizer and the first phase difference layer, between the first phase difference layer and the second phase difference layer, and / or on the lower surface of the second phase difference layer.

[0184] refer to Figure 3 According to another embodiment, a polarizing plate includes a polarizer 110, a protective layer 140 stacked on an upper surface of the polarizer 110, and a first phase difference layer 120, a second phase difference layer 130, and a layer 160 containing a light absorber stacked on a lower surface of the polarizer 110 in a prescribed order from the polarizer 110.

[0185] The optical display according to the present invention may include the polarizing plate according to various embodiments of the present invention. For example, the optical display may include an organic light emitting diode (OLED) display and a liquid crystal display.

[0186] In one embodiment, an OLED display may include: an OLED panel including a flexible substrate; and a polarizing plate according to the present invention stacked on the OLED panel.

[0187] In another embodiment, the OLED display device may include: an OLED panel including a non-flexible substrate; and a polarizing plate according to the present invention stacked on the OLED panel.

[0188] Next, the present invention will be described in more detail with reference to Examples. However, it should be noted that these Examples are provided for illustration only and should not be construed in any way as limiting the present invention.

[0189] Example 1

[0190] A polyvinyl alcohol film (PS#60, pre-stretched thickness: 60 μm, Kuraray Co., Ltd., Japan) was stretched to 6 times its original length in an iodine aqueous solution at 55° C. so that the thick polarizer had a light transmittance of 43%.

[0191] The coating layer is formed by depositing a composition of the first phase difference layer (a non-liquid crystal composition containing a fluorine-containing polystyrene compound, negative (-) birefringence, Eastman Co., Ltd.) on the upper surface of a cyclic polyolefin (COP) film (ZD film, positive (+) birefringence, Zeon Co., Ltd.) stretched at an angle of 45° to a predetermined thickness, and then drying. The composition can achieve Rth / d=-26nm / μm.

[0192] The laminate of the coating layer and the COP film is stretched in the MD direction of the COP film, thereby preparing a laminate of a first phase difference layer and a second phase difference layer, wherein the second phase difference layer is stacked on the lower surface of the first phase difference layer.

[0193] The polarizing plate was prepared by stacking a polarizer and a protective film (triacetyl cellulose film, KA25-HC, Fuji film Co., Ltd.) in the order described above on the upper surface of the first phase difference layer.

[0194] Embodiment 2-4

[0195] The polarizing plate was prepared in the same manner as in Example 1, except that the retardation and / or thickness of each of the first and second phase difference layers were changed as listed in Table 1 while the first phase difference layer was formed using the same material as in Example 1.

[0196] Example 5

[0197] A polarizing plate was produced in the same manner as in Example 1 except that a third phase difference layer (positive C layer, Re=0.2 nm and Rth=-30 nm at 550 nm) was additionally stacked on the lower surface of the second phase difference layer.

[0198] Example 6

[0199] A composition including a (meth)acrylic binder resin, a light absorber (maximum absorption wavelength: 391 nm, Bonasorb UA3912, indole compound, Orient Chemical Co., Ltd.), and an isocyanate curing agent (Coronate L) was prepared.

[0200] A polarizing plate was prepared in the same manner as in Example 1, except that a layer containing a light absorber (thickness: 10 μm, light absorber content: 1.25 wt % in the light absorber-containing layer) was further formed by coating the prepared composition on the lower surface of the second phase difference layer to a predetermined thickness and then curing the composition.

[0201] Comparative Example 1

[0202] The first phase difference layer was formed using a liquid crystal film (negative birefringence, thickness: 2 μm, Fuji Film Co., Ltd.), the second phase difference layer was formed using a liquid crystal film (positive birefringence, thickness: 2 μm, Fuji Film Co., Ltd.), and the adhesive layer (thickness: 6.5 μm) was formed using a (meth)acrylic adhesive resin.

[0203] Then, a polarizing plate was manufactured in the same manner as in Example 1, except that the protective film, the polarizer, the liquid crystal film of the first phase difference layer, the adhesive layer (thickness: 6.5 μm), and the liquid crystal film of the second phase difference layer were sequentially stacked in the stated order.

[0204] Comparative Example 2

[0205] A laminate including a phase difference layer (second phase difference layer) on the lower surface of a cyclic polyolefin film (first phase difference layer) was prepared by coating a phase difference layer composition (containing a fluorine-containing cellulose compound, negative birefringence) on the lower surface of a cyclic polyolefin (COP) film (ZD film, positive birefringence, Zeon Co., Ltd.) stretched at an angle of 70° to a predetermined thickness, and then drying and stretching the laminate obliquely with reference to the MD of the film. The phase difference layer composition can achieve Rth / d=-5.7nm / μm.

[0206] A polarizing plate was prepared in the same manner as in Example 1 by attaching a polarizer and a triacetyl cellulose film as a protective film to the upper surface of the cyclic polyolefin film.

[0207] Comparative Example 3

[0208] A polarizing plate was prepared in the same manner as in Example 1, except that the material (negative birefringent liquid crystal, Fuji Film Co., Ltd.), the retardation and the thickness of the second phase difference layer were changed as listed in Table 1, and a (meth) acrylic adhesive resin was used to form an adhesive layer (thickness: 6.5 μm) between the first phase difference layer and the second phase difference layer while the first phase difference layer was formed using the same material as in Example 1.

[0209] Comparative Example 4

[0210] A polarizing plate was prepared in the same manner as in Example 1 by stacking a protective film, a polarizer, a first phase difference layer, an adhesive layer, and a second phase difference layer in sequence, except that the material (positive birefringent polymer film, Zeon Co., Ltd.), the retardation and thickness of each layer of the second phase difference layer and the first phase difference layer were changed as listed in Table 1 and a (meth)acrylic adhesive resin was used to form the adhesive layer (thickness: 6.5 μm).

[0211] The retardation Re, Rth, and NZ of each of the first to third phase difference layers were measured at a wavelength of 550 nm using an Axoscan polarimeter (AxoMetric Co., Ltd.).

[0212] The polarizing plates prepared in Examples and Comparative Examples were evaluated for the following properties.

[0213] (1) Degree of circular polarization (unit: %): The circular polarization degree was measured by passing light through a polarizing plate at the front side (0°) using an Axoscan polarimeter. Then, the circular polarization degree was measured by passing light through a polarizing plate at the lateral side (60°) while rotating the polarimeter 360 degrees. The results are shown in Table 1.

[0214] (2) Reflectivity (unit: %): The reflectivity was measured using a goniometer (DMS 803, Instrument Systems Inc. (Konica Minolta Group) of Japan). After measuring the white plate provided to the goniometer, the brightness and contrast were measured using the angle scanning function. Each of the polarizing plates prepared in the embodiments and comparative embodiments was attached to a flexible panel (P30 Pro, Huawei Co., Ltd.) by a pressure-sensitive adhesive, and then the front and side reflectivities were measured. Here, θ was measured at intervals of 5°, and the reflectivity was determined by obtaining the spectral transmittance / reflectivity (SCE) values ​​of the incident light from the front (0°) and the side (60°).

[0215] Table 1

[0216]

[0217]

[0218] *Angle 1: The angle between the slow axis of the first phase difference layer and the transmission axis of the polarizer

[0219] *Angle 2: The angle between the slow axis of the second phase difference layer and the transmission axis of the polarizer

[0220] *Total Rth: Rth of the laminate stacked on the lower surface of the polarizing plate at a wavelength of 550nm

[0221] *(-): negative birefringence, (+): positive birefringence

[0222] *Rth / d: Rth / d of the first retardation layer

[0223] As shown in Table 1, the polarizing plate according to the present invention exhibits significantly low front and lateral reflectivity, and achieves reduced thickness and good processability by removing the adhesive layer. In contrast, the polarizing plate of the comparative example has high front and lateral reflectivity and suffers from low processability due to the presence of the adhesive layer.

[0224] Therefore, the present invention provides a polarizing plate having a good effect in thickness reduction while significantly reducing the front reflectivity and the lateral reflectivity. The present invention provides a polarizing plate that ensures good processability. The present invention provides a polarizing plate capable of improving black visibility. The present invention provides an optical display including the polarizing plate.

[0225] Although some embodiments have been described herein, it should be understood that various modifications, changes, variations, and equivalent embodiments may be made by those skilled in the art without departing from the spirit and scope of the invention.

Claims

1. A polarizing plate, comprising: polarizer; and a first phase difference layer and a second phase difference layer sequentially stacked on a lower surface of the polarizer, The first phase difference layer has a biaxiality NZ greater than or equal to -2 and less than 0 at a wavelength of 550 nm and is a non-liquid crystal layer, and the second phase difference layer has a biaxiality NZ greater than 1 and less than or equal to 2 at a wavelength of 550 nm, A stack of the first phase difference layer and the second phase difference layer or a stack including the first phase difference layer and the second phase difference layer is stacked on a lower surface of the polarizer and has an out-of-plane retardation Rth of -80 nm to -20 nm at a wavelength of 550 nm. 2 . The polarizing plate according to claim 1 , wherein the first phase difference layer has a greater absolute out-of-plane retardation Rth than the second phase difference layer at a wavelength of 550 nm. 3 . The polarizing plate according to claim 1 , wherein the first phase difference layer has an Rth of −250 nm to −50 nm at a wavelength of 550 nm, and the second phase difference layer has an Rth of 40 nm to 150 nm at a wavelength of 550 nm. 4 . The polarizing plate according to claim 1 , wherein the first phase difference layer has a larger absolute in-plane retardation Re than the second phase difference layer at a wavelength of 550 nm. 5 . The polarizing plate according to claim 1 , wherein the first phase difference layer has Re of 100 nm to 270 nm at a wavelength of 550 nm, and the second phase difference layer has Re of 70 nm to 160 nm at a wavelength of 550 nm. 6 . The polarizing plate according to claim 1 , wherein the first phase difference layer has negative (−) birefringence, and the second phase difference layer has positive (+) birefringence. 7 . The polarizing plate according to claim 1 , wherein the first phase difference layer has an Rth / d of −50 nm / μm to −10 nm / μm, Rth represents the out-of-plane retardation of the first phase difference layer at a wavelength of 550 nm, and its unit is nm, and d represents the thickness of the first phase difference layer, and its unit is μm. 8 . The polarizing plate according to claim 1 , wherein the first phase difference layer exhibits positive dispersion, and the second phase difference layer exhibits positive dispersion. 9 . The polarizing plate according to claim 1 , wherein the first phase difference layer has a thickness of 15 μm or less, and the second phase difference layer has a thickness of 10 μm or more. 10 . The polarizing plate according to claim 1 , wherein the first phase difference layer comprises at least one selected from the group consisting of a cellulose ester compound or a polymer thereof and an aromatic compound or a polymer thereof.

11. The polarizing plate of claim 10, wherein the aromatic compound comprises a polystyrene compound including a moiety represented by Formula 2: in It is the attachment site of the atom; R 1, R 2 and R 3 are each independently a hydrogen atom, an alkyl group, a substituted alkyl group or a halogen; R is each independently a substituent on the styrene ring; and n is an integer of 0 to 5, indicating the number of substituents on the styrene ring. 12 . The polarizing plate according to claim 11 , wherein the moiety of Formula 2 comprises a halogen. 13 . The polarizing plate according to claim 1 , wherein the first phase difference layer is directly formed on a lower surface of the second phase difference layer without an adhesive layer therebetween. The polarizing plate according to claim 1 , wherein the second phase difference layer is a non-liquid crystal layer.

15. The polarizing plate according to claim 1, wherein the polarizer has a slow axis tilted at an angle of +5° to +25° or at an angle of -25° to -5° relative to the transmission axis of the polarizer, and the second phase difference layer has a slow axis tilted at an angle of +50° to +80° or -80° to -50° relative to the transmission axis of the polarizer.

16. The polarizing plate according to claim 1, further comprising: a protective layer on an upper surface of the polarizer. 17 . The polarizing plate according to claim 1 , further comprising: a third phase difference layer comprising a positive C layer having an out-of-plane retardation Rth of −300 nm to 0 nm at a wavelength of 550 nm. 18 . The polarizing plate according to claim 17 , wherein the third phase difference layer is stacked between the polarizer and the first phase difference layer or stacked on a lower surface of the second phase difference layer.

19. The polarizing plate according to claim 1, further comprising: a layer containing a light absorber. 20 . The polarizing plate according to claim 19 , wherein the light absorber-containing layer comprises 0.001 wt % to 6 wt % of a light absorber having a maximum absorption wavelength of 380 nm to 450 nm.

21. The polarizing plate according to claim 19, wherein the light absorber-containing layer is formed on the upper surface of the protective layer formed on the upper surface of the polarizer, between the polarizer and the protective layer, between the polarizer and the first phase difference layer, between the first phase difference layer and the second phase difference layer, and / or on the lower surface of the second phase difference layer.

22. An optical display comprising the polarizing plate according to any one of claims 1 to 21.

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