Polarizing plate and optical display device

Abstract

Provided are a polarizing plate and an optical display device comprising same, the polarizing plate comprising: a polarizer; a retardation layer laminated on the lower surface of the polarizer; and an upper protective layer laminated on the upper surface of the polarizer, wherein the polarizing plate has an orthogonal transmittance of 1% or less at a wavelength of 600 nm, the retardation layer comprises a cholesteric liquid crystal layer, an angle formed by the slow axis at a wavelength of 450 nm with respect to the slow axis at a wavelength of 550 nm of the cholesteric liquid crystal layer is 5° or less, an angle formed by the slow axis at a wavelength of 650 nm with respect to the slow axis at a wavelength of 550 nm of the cholesteric liquid crystal layer is 5° or less, and the upper protective layer has a total haze of 5 to 25%.

Description

Polarizing plate and optical display device

[0001] This relates to a polarizing plate and an optical display device.

[0002] A light-emitting device display device including an organic light-emitting element includes a polarizer to improve optical characteristics. The polarizer may include a polarizer and a phase difference layer located on one side of the polarizer.

[0003] The above phase difference layer may be a single-layer phase difference layer. Alternatively, the above phase difference layer may be a laminate of an inverse wavelength dispersive phase difference layer and a positive C phase difference layer to improve reflective color. When a polarizer having the above laminate is applied to an optical display device, the screen may appear red and blue depending on the type of panel for the optical display device and the pixel arrangement of the optical display device. Therefore, it may be desirable to prevent the screen of the optical display device from appearing red and blue.

[0004] The background technology of the present invention is disclosed in Korean Published Patent No. 10-2013-0103595, etc.

[0005] The objective of the present invention is to provide a polarizing plate that, when applied to an optical display device, prevents blue and red from being visible as reflected colors from the side and allows green to be visible, thereby minimizing the difference in reflected colors between the left and right sides.

[0006] The objective of the present invention is to provide a polarizing plate that increases the reflectance by 8 degrees when applied to a panel.

[0007] One aspect of the present invention is a polarizing plate.

[0008] The above polarizing plate includes a polarizer, a phase difference layer laminated on the lower surface of the polarizer, and an upper protective layer laminated on the upper surface of the polarizer, wherein the polarizing plate has an orthogonal transmittance of 1% or less at a wavelength of 600 nm, the phase difference layer includes a cholesteric liquid crystal layer, the angle formed by the ground axis at a wavelength of 450 nm with respect to the ground axis at a wavelength of 550 nm of the cholesteric liquid crystal layer is 5° or less, the angle formed by the ground axis at a wavelength of 650 nm with respect to the ground axis at a wavelength of 550 nm of the cholesteric liquid crystal layer is 5° or less, and the upper protective layer has a total haze of 5 to 25%.

[0009] Another aspect of the present invention is an optical display device.

[0010] The above optical display device includes the polarizing plate of the present invention.

[0011] The present invention provides a polarizing plate that minimizes the difference in reflected color according to the viewing angle direction by ensuring that blue and red are not visible as reflected colors from the side and green is visible when applied to an optical display device.

[0012] When the above-described polarizing plate of the present invention is applied to a panel, a polarizing plate is provided that increases the reflectance by 8° and reduces the dispersion of reflected colors.

[0013] FIG. 1 is a cross-sectional view of a polarizing plate according to one embodiment of the present invention.

[0014] FIG. 2 is a cross-sectional view of a polarizing plate of another embodiment of the present invention.

[0015] FIG. 3 is a cross-sectional view of a polarizing plate of another embodiment of the present invention.

[0016] Figure 4 shows an exemplary cholesteric-oriented liquid crystal layer.

[0017] Figure 5 shows the results of the reflection color a* and b* values ​​when the polarizer of Example 1 is applied.

[0018] Figure 6 shows the results of the reflection color a* and b* values ​​when the polarizer of Example 5 is applied.

[0019] Figure 7 shows the results of the reflection color a* and b* values ​​when the polarizer of Reference Example 1 (conventional polarizer) is applied.

[0020] In Figures 5 to 7, ■ is the color coordinate of the reflection color a* and b* values ​​at 8° side, ▲ is at 30° side, ● is at 45° side, and ★ is at 60° side.

[0021] Embodiments of the present application will be described in more detail with reference to the attached drawings. However, the technology disclosed in the present application is not limited to the embodiments described herein and may be embodied in other forms. The embodiments introduced herein are provided merely to ensure that the disclosed content is thorough and complete and to ensure that the spirit of the present application is sufficiently conveyed to those skilled in the art. In the drawings, the dimensions, such as the width or thickness of the components, are shown slightly enlarged to clearly represent the components of each device, and the dimensions, such as the width or thickness of the components, are not limited to the scope of the present invention. In a plurality of drawings, the same reference numerals refer to substantially identical components.

[0022] In this specification, "upper" and "lower" are defined based on the drawings, and depending on the viewing perspective, "upper" may be changed to "lower" and "lower" to "upper." Additionally, terms referred to as "on" or "on" may include not only the direct upper portion but also cases where other structures are interposed in between. Conversely, terms referred to as "directly on," "immediately on," or "directly formed" indicate the absence of other structures, such as intermediate bodies.

[0023] The terms used herein are for describing exemplary embodiments only and are not intended to limit the invention. The singular expression includes the plural expression unless the context clearly indicates otherwise.

[0024]

[0025] In this specification, the "in-plane phase difference (Re)" of the cholesteric liquid crystal layer is determined by measuring the Mueller matrix at Sin x M = Sout for each wavelength and calculating the result to obtain the slow axis and Re.

[0026] S : Stockes Vector ,

[0027] M : Mueller matrix ,

[0028] Sout : out of Sources vector

[0029] The "measurement wavelength" of the above-mentioned in-plane phase difference can be a wavelength of 450 nm, 550 nm, or 650 nm.

[0030] In this specification, the ground axis is the axis with the highest refractive index among the in-plane directions of the optical element, and the true axis is the axis with the lowest refractive index among the in-plane directions of the optical substrate.

[0031] In this specification, "(meth)acrylic" means acrylic and / or methacrylic.

[0032] In the present specification, when describing a numerical range, "X to Y" means X or greater and Y or less (X ≤ and ≤Y).

[0033] An anti-reflection polarizer may include a polarizer and an inverse wavelength dispersive phase difference layer and a positive C layer laminated on one surface of the polarizer.

[0034] When the above anti-reflection polarizer is applied to an optical display device, depending on the type or phase difference of the above inverse wavelength dispersive phase difference layer, blue light and red light may not be completely absorbed, so there may be a phenomenon where the screen appears blue and / or red when viewed from the side.

[0035] Figure 7 shows the results of the reflection color a* and b* values ​​when a laminate of a conventional inverse wavelength dispersive phase difference layer and a positive C layer is applied.

[0036] Referring to Fig. 7, it can be seen that the reflection color values ​​a* and b* are concentrated in blue and red according to the azimuth angles of 8°, 30°, 45° and 60°.

[0037] Generally, the above phenomenon is not easily visible in large-area optical display devices. However, in small-area optical display devices such as notebook PCs or tablet PCs, the above phenomenon can be easily visible.

[0038] A polarizing plate of one embodiment of the present invention can make the phenomenon of appearing blue and red depending on the angle greenish when applied to an optical display device.

[0039] Therefore, when the above polarizing plate is applied to an optical display device, the phenomenon where the reflected color value becomes blue and red is eliminated, and the entire color becomes green, thereby minimizing the difference in reflected color value according to the viewing angle direction.

[0040] In this regard, when the above polarizing plate is applied to an optical display device, the reflection color value a* is -2.5 to 2 and the reflection color value b* is -2 to 3 within the entire viewing angle, specifically the side incidence angle of 8°, and the reflection color value a* is 0 or less and the reflection color value b* is 0 or more at the side incidence angle of 60°.

[0041] In addition, the above polarizer can increase the reflectance by 8° and reduce the dispersion of reflected colors when applied to a panel.

[0042] The above polarizer includes a cholesteric liquid crystal layer as a phase difference layer located between a polarizer and a panel for an optical display device, and adjusts the angle formed by the ground axis at a wavelength of 450 nm with respect to the ground axis at a wavelength of 550 nm of the cholesteric liquid crystal layer and the angle formed by the ground axis at a wavelength of 650 nm with respect to the ground axis at a wavelength of 550 nm of the cholesteric liquid crystal layer, adjusts the orthogonal transmittance at a wavelength of 600 nm of the polarizer, and adjusts the total haze of the upper protective layer laminated on the other side of the polarizer.

[0043] According to one embodiment, the polarizing plate comprises a polarizer, a phase difference layer laminated on the lower surface of the polarizer, and an upper protective layer laminated on the upper surface of the polarizer, wherein the polarizing plate has an orthogonal transmittance of 1% or less at a wavelength of 600 nm, the phase difference layer comprises a cholesteric liquid crystal layer, the angle formed by the ground axis at a wavelength of 450 nm with respect to the ground axis at a wavelength of 550 nm of the cholesteric liquid crystal layer is 5° or less, the angle formed by the ground axis at a wavelength of 650 nm with respect to the ground axis at a wavelength of 550 nm of the cholesteric liquid crystal layer is 5° or less, and the upper protective layer has a total haze of 5 to 25%.

[0044] In one embodiment, the phase difference layer is positioned between the polarizer and the panel for the optical display device, and the lower surface of the polarizer may be a surface into which light from the panel for the optical display device is incident.

[0045]

[0046] Light transmittance of a polarizer

[0047] The above polarizer has an orthogonal transmittance (Tc) of 1% or less at a wavelength of 600 nm. Since the orthogonal transmittance at a wavelength of 600 nm is 1% or less among several wavelengths, when external light is incident on the polarizer, the degree of absorption of green light is increased, thereby preventing the phenomenon where the reflected color value becomes blue and red, and making it easy to ensure that the reflected color value becomes green overall.

[0048] The above orthogonal transmittance can be measured by conventional methods known to those skilled in the art.

[0049] In one embodiment, the polarizer may have an orthogonal transmittance of 0 to 1%, 0 to 0.5%, 0.1 to 0.5%, or 0.3 to 0.5% at a wavelength of 600 nm.

[0050] The orthogonal transmittance at the wavelength of 600 nm can be determined by the cholesteric liquid crystal layer as well as by a protective layer, an adhesive layer, etc. that may be included in the polarizer, but it can be mainly achieved by controlling the orthogonal transmittance at the wavelength of 600 nm of the polarizer.

[0051] The method for controlling the orthogonal transmittance of the above polarizer at a wavelength of 600 nm is explained in more detail below.

[0052] The above polarizer may have a single light transmittance (Ts) of 40 to 47%, for example, 42 to 46% at a wavelength of 550 nm. Within this range, it may be easy to implement the effect of the above-described polarizer.

[0053] The above polarizer may have a single light transmittance of 3% or less at a wavelength of 380 nm, for example, 0 to 3%. Within this range, damage to the light-emitting element caused by external light can be suppressed.

[0054] A single light transmittance of 3% or less at the above wavelength of 380 nm can be achieved by adding a UV absorber to one or more of the polarizer, cholesteric liquid crystal layer, and protective layer among the polarizer.

[0055] Cholesteric liquid crystal layer

[0056] The inventors have confirmed that although the orthogonal transmittance of the above polarizer at a wavelength of 600 nm is 1% or less, thereby increasing the absorption of green light and making the entire screen appear green, there are limitations.

[0057] The above cholesteric liquid crystal layer can increase the degree of absorption of green light so that the reflection color value of the entire screen becomes green and there is no difference in reflection color value between the left side and the right side.

[0058] Specifically, the angle formed by the ground axis at a wavelength of 450 nm with respect to the ground axis at a wavelength of 550 nm of the cholesteric liquid crystal layer (hereinafter referred to as angle A) is 5° or less, and the angle formed by the ground axis at a wavelength of 650 nm with respect to the ground axis at a wavelength of 550 nm of the cholesteric liquid crystal layer (hereinafter referred to as angle B) is 5° or less.

[0059] Here, angle A is the absolute value of the angle formed by the ground axis at a wavelength of 450 nm with respect to the ground axis at a wavelength of 550 nm of the cholesteric liquid crystal layer, so it can be 0° or greater and 5° or less.

[0060] Here, angle B is the absolute value of the angle formed by the ground axis at a wavelength of 650 nm with respect to the ground axis at a wavelength of 550 nm of the cholesteric liquid crystal layer, so it can be 0° or greater and 5° or less.

[0061] When the above angle A is 5° or less and the above angle B is 5° or less, the degree of absorption of green light can be increased so that the reflection color value becomes green across the entire screen and there is no difference in the reflection color value between the left side and the right side.

[0062] If the above angle A is 5° or less but the above angle B is greater than 5°, there may be a problem where the side reflectance increases and the side reflectance color is skewed toward Reddish and Bluish.

[0063] If the above angle B is 5° or less but the above angle A is greater than 5°, there may be a problem where the lateral reflectance increases and the lateral reflective color is skewed toward Reddish and Bluish.

[0064] In one embodiment, the angle A may be 0° to 5°, for example, greater than 0° and less than or equal to 5°, 0° to 4.5°, or 2° to 4.5°. In one embodiment, the angle B may be 0° to 5°, for example, greater than 0° and less than or equal to 5°, for example, 0° to 3°, or 0° to 1°. Within the above range, the manufacturing of the polarizer may be easy.

[0065] In one embodiment, at least one of the angle A and the angle B may be greater than 0°.

[0066] The ground axis at a wavelength of 450 nm, the ground axis at a wavelength of 550 nm, and the ground axis at a wavelength of 650 nm of the above cholesteric liquid crystal layer can each be measured using an Axoscan measuring instrument, and from this, angles A and B can be obtained.

[0067] The above angles A and B can be realized by using a chiral agent in the process of manufacturing the cholesteric liquid crystal layer and by controlling the content of the chiral agent. This is explained in detail below.

[0068] The above cholesteric liquid crystal layer may have different ground axes at a wavelength of 450 nm, 550 nm, and 650 nm. That is, the angles formed by the ground axes at wavelengths of 450 nm, 550 nm, and 650 nm with respect to the light absorption axis of the polarizer may be different.

[0069] In one embodiment, the cholesteric liquid crystal layer may satisfy the relationship of Equation 1 below: In this case, there may be an effect of reducing lateral reflectance and making the reflected color greenish.

[0070] [Equation 1]

[0071] A450 > A550 ≥ A650

[0072] (In the above Equation 1,

[0073] A450 is the absolute value of the angle formed by the ground axis of the cholesteric liquid crystal layer with respect to the absorption axis of the polarizer at a wavelength of 450 nm.

[0074] A550 is the absolute value of the angle formed by the ground axis of the cholesteric liquid crystal layer with respect to the absorption axis of the polarizer at a wavelength of 550 nm.

[0075] A650 is the absolute value of the angle formed by the ground axis of the cholesteric liquid crystal layer with respect to the absorption axis of the polarizer at a wavelength of 650 nm).

[0076] In one embodiment, the cholesteric liquid crystal layer may satisfy the relationship of Equation 1-1 below:

[0077] [Equation 1-1]

[0078] A450 > A550 > A650

[0079] (In the above Equation 1,

[0080] A450, A550, and A650 are as defined in Equation 1 above).

[0081] In the above Equation 1, A450 can be 45 to 50°, for example 46 to 49°, 47 to 49°, A550 can be 44 to 47°, for example 44 to 46°, 45 to 46°, and A650 can be 43 to 46°, for example 44 to 46°, 45 to 46°. Within the above range, the above-described angles A and B can be easily reached.

[0082] In one embodiment, the cholesteric liquid crystal layer may satisfy the relationship of Equation 2 below: In this case, there may be an effect of reducing lateral reflectance and making the reflective color greenish.

[0083] [Equation 2]

[0084] B450 < B550 < B650

[0085] (In the above Equation 2,

[0086] B450 is the in-plane phase difference of the cholesteric liquid crystal layer at a wavelength of 450 nm,

[0087] B550 is the in-plane phase difference of the cholesteric liquid crystal layer at a wavelength of 550 nm,

[0088] B650 is the in-plane phase difference of the cholesteric liquid crystal layer at a wavelength of 650 nm)

[0089] In the above Equation 2, B450 can be 100 to 150 nm, for example, 100 to 140 nm, 100 to 130 nm; B550 can be 110 to 160 nm, for example, 110 to 150 nm, 120 to 145 nm; and B650 can be 120 to 170 nm, for example, 120 to 160 nm, 130 to 160 nm. Within the above range, the manufacture of the cholesteric liquid crystal layer can be easy.

[0090] The above cholesteric liquid crystal layer may have a thickness of 10㎛ or less, for example, greater than 0㎛ and less than or equal to 10㎛.

[0091] The above cholesteric liquid crystal layer may include a cholestericly oriented liquid crystal (CLC) region. The CLC region may be a liquid crystal region with a helical structure in which the directionators of liquid crystal molecules are oriented in layers while twisting along a helical axis.

[0092] Figure 4 shows an exemplary cholesteric-oriented liquid crystal layer.

[0093] Referring to FIG. 4, the CLC has a helical structure in which the directioners of the liquid crystal molecules (n in FIG. 4) are oriented in layers while twisting along the helical axis (H in FIG. 4). In the structure of the CLC, the distance (P in FIG. 4) until the directioners of the liquid crystal molecules complete a 360-degree rotation is referred to as the "pitch." In this specification, the term "CLC region" may refer to the region where the directioners of the CLC complete a 360-degree rotation. The directioners of the liquid crystal molecules may refer to the direction of the ground axis. For example, in the case of a discotic liquid crystal, the directioners of the liquid crystal molecules may refer to the normal direction of the disc, and in the case of a rod-shaped liquid crystal, they may refer to the direction of the major axis of the rod shape.

[0094] The above-mentioned cholesteric liquid crystal layer can be obtained by fixing the cholesteric liquid crystal phase. The structure fixing the cholesteric liquid crystal phase is preferably a structure in which the orientation of the liquid crystal compound in the cholesteric liquid crystal phase is supported. Typically, it is preferable to have a structure in which a polymerizable liquid crystal compound is oriented in the cholesteric liquid crystal phase, then polymerized and cured by UV irradiation, heating, etc., to form a non-fluid layer, and simultaneously transformed into a state in which the orientation does not change due to external factors or external forces. Furthermore, in the structure fixing the cholesteric liquid crystal phase, it is sufficient that the optical properties of the cholesteric liquid crystal phase are maintained, and the liquid crystal compound does not need to exhibit liquid crystallization. For example, the polymerizable liquid crystal compound may lose its liquid crystallization properties by becoming a high molecular weight through a curing reaction.

[0095] Materials used for forming the above-mentioned cholesteric liquid crystal structure may include liquid crystal compositions containing a liquid crystal compound. It is preferable that the liquid crystal compound be a polymerizable liquid crystal compound.

[0096] A liquid crystal composition containing a polymerizable liquid crystal compound further includes a surfactant, a chiral agent, and a polymerization initiator, etc.

[0097] The polymerizable liquid crystal compound may be a rod-shaped liquid crystal compound or a disc-shaped liquid crystal compound. Examples of polymerizable groups include acryloyl groups, methacryloyl groups, epoxy groups, and vinyl groups. By curing the polymerizable liquid crystal compound, the orientation of the liquid crystal compound can be fixed. The liquid crystal compound having polymerizable groups is preferably a monomer or a relatively low molecular weight liquid crystal compound with a degree of polymerization of less than 100.

[0098] The above disc-shaped liquid crystal compound may preferably be a compound having a triphenylene structure, for example. On the other hand, since a disc-shaped liquid crystal compound having a 3-substituted benzene structure has a higher Δn than a triphenylene structure and can widen the selective reflection wavelength range, it can be appropriately selected as needed.

[0099] The above rod-shaped liquid crystal compounds preferably include azomethines, azoxys, cyanobiphenyls, cyanophenyl esters, benzoic acid esters, cyclohexane carboxylic acid phenyl esters, cyanophenylcyclohexane, cyano-substituted phenylpyrimidines, alkoxy-substituted phenylpyrimidines, phenyldioxanes, trans, and alkenyl cyclohexyl benzonitriles.

[0100] One or more of the above chiral agents may be used among levorotatory chiral agents and right-handed chiral agents. Preferably, the above chiral agent may be a levorotatory chiral agent.

[0101] The chiral agent may be included in an amount of 1 to 4 parts by weight, for example, 3 to 4 parts by weight, per 100 parts by weight of the polymerizable liquid crystal compound. Within this range, the cholesteric liquid crystal layer described above can be easily reached. The angles A and B of the cholesteric liquid crystal layer may be controlled according to the content of the chiral agent.

[0102] Phase difference layer

[0103] The above phase difference layer may consist solely of the above cholesteric liquid crystal layer.

[0104] The above phase difference layer may further include the cholesteric liquid crystal layer and a lower protective layer formed on at least one surface of the cholesteric liquid crystal layer.

[0105] The above lower protective layer may include one or more of an optically transparent protective film or a protective coating layer. The protective film may include, but is not limited to, a film formed from one or more of a cellulose ester resin including triacetylcellulose (TAC), a cyclic polyolefin resin including amorphous cyclic polyolefin (COP), a polycarbonate resin, a polyester resin including polyethylene terephthalate (PET), a polyethersulfone resin, a polysulfone resin, a polyamide resin, a polyimide resin, an acyclic-polyolefin resin, a poly(meth)acrylate resin including polymethyl methacrylate resin, a polyvinyl alcohol resin, a polyvinyl chloride resin, and a polyvinylidene chloride resin.

[0106] The protective coating layer may be formed from an active energy beam curable resin composition comprising an active energy beam curable compound and a polymerization initiator. The active energy beam curable compound may include one or more of a cationic polymerizable curable compound, a radical polymerizable curable compound, a urethane resin, and a silicone-based resin.

[0107] The lower protective layer may be a phase-less film or have an in-plane phase difference within a predetermined range. For example, the protective layer may have an in-plane phase difference of less than 5000 nm, or greater than or equal to 5000 nm, 120 to 160 nm, or 5 nm to 0 nm at a wavelength of 550 nm. Within the above range, the polarizer can be protected without affecting the effect of the cholesteric liquid crystal layer.

[0108] The lower protective layer may have a thickness of 10㎛ or less, 5㎛ to 300㎛, 5㎛ or less, or 5㎛ to 200㎛. Within the above range, it may be used in a polarizer.

[0109] In one embodiment, the lower protective layer has a low moisture permeability, which can further enhance the durability of the polarizer after exposure to high temperature and high humidity. For example, the lower protective layer has a moisture permeability of 1 g / m² 2 .day or more, e.g., 1g / m² 2 .day to 100g / m² 2 It can be .day. Within the above range, the durability of the polarizer is good and the protective layer can be easily manufactured.

[0110] polarizer

[0111] Polarizers can contribute to lowering reflected color and reflectance across the entire viewing angle by linearly polarizing light incident from external light or phase difference laminates.

[0112] The polarizer may have a polarization degree of 99% or higher. By simultaneously satisfying the above polarization degree and single light transmittance (Ts), the reflectance can be significantly reduced when the polarizer is laminated in a phase difference laminate. The above "single light transmittance" refers to the single light transmittance (Ts) measured in the visible light region, for example, at a wavelength of 400 nm to 700 nm, and can be measured by conventional methods known to those skilled in the art. The above "polarization degree" can be measured by conventional methods known to those skilled in the art. Specifically, the polarization degree may be 99% to 99.9999%.

[0113] The polarizer may have an orthogonal transmittance of 1% or less at a wavelength of 600 nm. Within the above range, the orthogonal transmittance at a wavelength of 600 nm of the polarizer described above can be easily reached.

[0114] The polarizer can have a thickness of 5㎛ to 40㎛. Within this range, it can be used in a polarizing plate.

[0115] The light absorption axis of the polarizer can be the stretching direction, for example, the machine direction (MD) of the polarizer, when manufacturing the polarizer from a polyvinyl alcohol-based film.

[0116] The polarizer may include a polyvinyl alcohol-based polarizer manufactured by uniaxially stretching a polyvinyl alcohol-based film. In one embodiment, the polarizer may be manufactured by dyeing, stretching, crosslinking, and color correction processes of a polyvinyl alcohol-based film.

[0117] In order to manufacture a polarizer having an orthogonal transmittance of 1% or less at the above wavelength of 600 nm, the polarizer can be manufactured by the following method.

[0118] The polyvinyl alcohol-based film can be a conventional polyvinyl alcohol-based film known to those skilled in the art.

[0119] In one embodiment, the polyvinyl alcohol-based film contains hydrophilic functional groups and hydrophobic functional groups. The hydrophobic functional group is additionally present in addition to the hydrophilic functional group, the hydroxyl group (OH group), present in the polyvinyl alcohol-based film.

[0120] Hydrophobic functional groups are present in one or more of the main chain and side chains of the polyvinyl alcohol-based resin constituting the polyvinyl alcohol-based film. The "main chain" refers to a portion forming the main framework of the polyvinyl alcohol-based resin, and the "side chain" refers to a framework connected to the main chain. Preferably, hydrophobic functional groups may be present in the main chain of the polyvinyl alcohol-based resin.

[0121] Polyvinyl alcohol-based resins having hydrophilic and hydrophobic functional groups introduced can be prepared by polymerizing one or more vinyl ester monomers, such as vinyl acetate, vinyl formate, vinyl propionate, vinyl butyrate, vinyl pivalate, and isopropene acetic acid, with a monomer providing a hydrophobic functional group. Preferably, the vinyl ester monomer may include vinyl acetate. The monomer providing the hydrophobic functional group may include a monomer providing a hydrocarbon repeating unit, such as ethylene or propylene.

[0122] The polyvinyl alcohol-based film may have a thickness of 50 μm or less, for example, 10 to 50 μm. Within the above range, there may be no melting or breakage of the film during film stretching.

[0123] The dyeing process includes treating a polyvinyl alcohol-based film in a dyeing tank containing a dichroic substance. In the dyeing process, the polyvinyl alcohol-based film is immersed in a dyeing tank containing a dichroic substance. The dyeing tank containing a dichroic substance includes an aqueous solution containing a dichroic substance and boric acid. By including the dichroic substance and a boron compound together, the dyeing tank dyes the polyvinyl alcohol-based film, and even if the polyvinyl alcohol-based film is stretched under the stretching conditions described above, the polyvinyl alcohol-based film may not break.

[0124] The dichroic substance may include one or more of potassium iodide, hydrogen iodide, lithium iodide, sodium iodide, zinc iodide, lithium iodide, aluminum iodide, lead iodide, and copper iodide as iodine. The dichroic substance may be included in the dyeing tank, preferably in the dyeing solution, at a concentration of 0.5 to 10 mol / ml, preferably 0.5 to 5 mol / ml. Within the above range, the effect of enabling uniform dyeing may be achieved.

[0125] Boron compounds can help prevent melting and rupture of polyvinyl alcohol-based films during the stretching process of polyvinyl alcohol-based films. Boron compounds can help prevent melting and rupture of the film even when the polyvinyl alcohol-based film is stretched at high temperatures and high stretch ratios during the stretching process performed after the dyeing process.

[0126] The boron compound may include one or more of boric acid and borax. The boron compound may be included in the dye fixation tank, preferably in an aqueous dye fixation solution, at a concentration of 0.1 to 5 weight%, preferably 0.3 to 3 weight%. Within this range, there may be no melting or breakage during the stretching process, and high reliability may be achieved.

[0127] It may be preferable to set the temperature of the dyeing solution to 20°C to 50°C, specifically 25°C to 50°C. The dyeing process can be carried out by immersing a polyvinyl alcohol-based film in a dyeing tank for 30 seconds to 120 seconds, specifically 40 seconds to 80 seconds.

[0128] The stretching process includes stretching the dyed polyvinyl alcohol-based film at a stretching ratio of 5.7 times or more, for example, 5.7 times to 7 times, at a stretching temperature of 57°C or more, for example, 57°C to 65°C.

[0129] The stretching process is performed in either wet stretching or dry stretching. Preferably, the stretching process includes wet stretching to apply a boron compound during the stretching process. Wet stretching involves uniaxially stretching a polyvinyl alcohol-based film in a mechanical direction in an aqueous solution containing a boron compound.

[0130] The boron compound may include one or more of boric acid and borax, preferably boric acid. The boron compound may be included in the drawing bath, preferably in an aqueous drawing solution, at a concentration of 0.5 to 10 weight%, preferably 1 to 5 weight%. Within this range, there may be no melting or breakage during the drawing process, and high reliability may be achieved.

[0131] A crosslinking process is performed to strengthen the adsorption of dichroic substances on polyvinyl alcohol-based films that have undergone a stretching process. The crosslinking solution used in the crosslinking process contains a boron compound. The boron compound can help improve reliability even when the polarizer is subjected to thermal shock while strengthening the adsorption of the aforementioned dichroic substances.

[0132] The boron compound may include one or more of boric acid and borax. The boron compound may be included in the crosslinking agent, preferably in an aqueous crosslinking solution, at a concentration of 0.5 to 10 weight%, preferably 1 to 5 weight%. Within this range, there may be an effect of achieving high reliability without melting or breakage during the stretching process. The temperature of the crosslinking agent solution may preferably be 20°C to 55°C, specifically 25°C to 55°C. The crosslinking process may be performed by immersing the polyvinyl alcohol-based film in the crosslinking agent for 30 to 120 seconds, specifically 40 to 80 seconds.

[0133] The complementary color process can improve the durability of the polarizer. The complementary color bath may include a complementary color solution containing more than 0% by weight and less than or equal to 10% by weight of potassium iodide, preferably 1% to 5% by weight, and more preferably 3% to 5% by weight. The complementary color solution may preferably be at a temperature of 20°C to 50°C, specifically 25°C to 50°C. The complementary color treatment may be performed by immersing a polyvinyl alcohol-based film in the complementary color bath for 5 to 50 seconds, specifically 5 to 20 seconds.

[0134] The drying process can be performed by treating the polyvinyl alcohol-based film after the color correction process at 30°C to 80°C, preferably 40°C to 80°C, for 2 minutes or less, preferably 1 minute to 2 minutes. The drying process may be performed by hot air drying, but is not limited thereto.

[0135] In one embodiment, a polarizer having an orthogonal transmittance of 1% or less at a wavelength of 600 nm can be realized by controlling conditions during the stretching process in the polarizer manufacturing process, such as the stretching ratio and stretching temperature. In another embodiment, a polarizer having an orthogonal transmittance of 1% or less at a wavelength of 600 nm can be realized by controlling conditions during the complementary color process and drying process in the polarizer manufacturing process.

[0136] Before the dyeing process treatment, the polyvinyl alcohol-based film may additionally include one or more of a washing process and a swelling process.

[0137] The washing process involves washing the polyvinyl alcohol-based film with water to remove foreign substances adhering to the polyvinyl alcohol-based film.

[0138] The swelling process can facilitate the dyeing and stretching of dichroic materials by immersing a polyvinyl alcohol-based film in a swelling bath within a predetermined temperature range. The swelling process may include treatment at 15°C to 35°C, preferably 20°C to 30°C, for 30 to 50 seconds.

[0139] Upper protective layer

[0140] The upper protective layer has a total haze of 5 to 25%.

[0141] If the total haze of the upper protective layer is less than 5%, there may be a problem with no haze expression.

[0142] If the total haze of the upper protective layer exceeds 25%, there may be a problem with reduced screen visibility due to sparkling.

[0143] Preferably, the total haze of the upper protective layer can be 10 to 25%. Within this range, the reflection color dispersion is lowered and may not affect the effect of the cholesteric liquid crystal layer.

[0144] The internal haze of the upper protective layer can be 3 to 15%, for example 5 to 15%, or 5 to 10%.

[0145] The external haze of the upper protective layer can be 2 to 10%, for example, 2 to 8%, or 2 to 5%.

[0146] The upper protective layer may include a substrate layer and an anti-glare layer laminated on one surface of the substrate layer. The anti-glare layer may enable the upper protective layer to easily reach the entire haze described above.

[0147] The above substrate layer may include an optically transparent protective film. The protective film may include, but is not limited to, a film formed from one or more of the following: a cellulose ester resin including triacetylcellulose (TAC), etc.; a cyclic polyolefin resin including amorphous cyclic polyolefin (COP), etc.; a polycarbonate resin; a polyester resin including polyethylene terephthalate (PET), etc.; a polyethersulfone resin; a polysulfone resin; a polyamide resin; a polyimide resin; an acyclic-polyolefin resin; a poly(meth)acrylate resin including polymethyl methacrylate resin, etc.; a poly(meth)acrylate resin; a polyvinyl alcohol resin; a polyvinyl chloride resin; and a polyvinylidene chloride resin.

[0148] The above substrate layer may have a thickness of 80㎛ or less, for example, 20㎛ to 80㎛. Within this range, it may be used as an upper protective layer.

[0149] The anti-glare layer comprises particles, and the particles may have an average particle size D50 of 0.1 to 10 μm. Within this range, the total haze can be easily reached, and the light transmittance does not become excessively high, so it can be used in a polarizer. For example, the average particle size D50 of the particles may be 0.1 to 10 μm or 1 to 8 μm.

[0150] According to one embodiment, the particles may include one or more of organic particles, inorganic particles, and organic-inorganic particles. The organic particles may include one or more of polymethyl methacrylate and polystyrene particles.

[0151] The above inorganic particles may include one or more of silica, zirconia, and titania. Preferably, silica may be used.

[0152] The anti-glare layer may have a thickness of 10 μm or less, for example, from 0.1 μm to 10 μm. Within this range, the total haze can be easily reached, and the light transmittance does not become excessively high, so it can be used in a polarizer.

[0153] The anti-glare layer may include the particles and a cured product of a resin that impregnates the particles to form the anti-glare layer. The resin may include one or more types of a thermosetting resin and a UV-curing resin.

[0154] FIGS. 1 to 3 are cross-sectional views of a polarizing plate according to one embodiment of the present invention.

[0155] The polarizer comprises a polarizer 100, an upper protective layer 200 laminated on the upper surface of the polarizer 100, and a phase difference layer 300A laminated on the lower surface of the polarizer 100, wherein the phase difference layer 300A may be a cholesteric liquid crystal layer 310.

[0156] The polarizer comprises a polarizer 100, an upper protective layer 200 laminated on the upper surface of the polarizer 100, and a phase difference layer 300B laminated on the lower surface of the polarizer 100, and the phase difference layer 300B may include a cholesteric liquid crystal layer 310 and a lower protective layer 320 laminated sequentially from the polarizer 100.

[0157] The polarizer comprises a polarizer 100, an upper protective layer 200 laminated on the upper surface of the polarizer 100, and a phase difference layer 300C laminated on the lower surface of the polarizer 100, and the phase difference layer 300C may include a lower protective layer 320 and a cholesteric liquid crystal layer 310 laminated sequentially from the polarizer 100.

[0158] Although not shown in FIGS. 1 to 3, each layer may be laminated by an adhesive layer or an adhesive layer.

[0159] Optical display device

[0160] The optical display device of the present invention includes the polarizing plate of the present invention.

[0161] The above optical display device may include a light-emitting element display device. The light-emitting element may be one or more of an organic light-emitting element, an inorganic light-emitting element, or an organic-inorganic light-emitting element.

[0162]

[0163] Hereinafter, the structure and operation of the present invention will be explained in more detail through preferred embodiments of the present invention. However, these are presented as preferred examples of the present invention and should not be interpreted in any way as limiting the present invention.

[0164]

[0165] Example 1

[0166] (1) Manufacturing of a polarizer

[0167] A polyvinyl alcohol film (VF-TS #4500, Kuraray, thickness 45 µm) washed with water at 25 ℃ was swollen in a swelling bath of water at 50 ℃.

[0168] The film that passed through the swelling bath was treated for 65 seconds in a dyeing bath at 50°C containing an aqueous solution containing 1 mol / ml of potassium iodide and 1 wt% of boric acid. The film that passed through the dyeing bath was stretched at a stretching ratio of 5.7 times in a wet stretching bath containing an aqueous solution at 60°C containing 3 wt% of boric acid. The film that passed through the wet stretching bath was treated for 65 seconds in a crosslinking bath containing an aqueous solution at 55°C containing 3 wt% of boric acid.

[0169] The film that passed through the crosslinking bath was treated for 10 seconds in a color-correcting bath containing a color-correcting solution, which is a 50°C aqueous solution containing 4.5% by weight of potassium iodide. The film that passed through the color-correcting bath was washed with water and hot-air dried at 80°C for 1 minute to produce a polarizer (thickness: 17 μm).

[0170] (2) Manufacturing of polarizing plates

[0171] A triacetylcellulose film having an anti-glare layer (containing silica particles with an average particle size D50 of 5 μm) formed on one side was prepared as the upper protective layer of a polarizer. The upper protective layer has a total haze of 10%, an internal haze of 6%, and an external haze of 4%.

[0172] A film was prepared in which a cholesteric liquid crystal layer was formed on one side of a triacetylcellulose film. The cholesteric liquid crystal layer comprises a rod-shaped liquid crystal compound and a levorotatory chiral agent. The levorotatory chiral agent is included in an amount of 3 parts by weight per 100 parts by weight of the rod-shaped liquid crystal compound.

[0173] The upper protective layer was laminated to the upper surface of the polarizer manufactured above using an adhesive.

[0174] A polarizing plate was manufactured by laminating a film having a cholesteric liquid crystal layer formed on one side of the triacetylcellulose film onto the lower surface of the polarizer manufactured above.

[0175] The above lamination was laminated such that the angle formed by the ground axis in the in-plane direction of the cholesteric liquid crystal layer at a wavelength of 550 nm with respect to the light absorption axis of the polarizer is as shown in Table 1 below. In this way, the angle formed by the ground axis of the cholesteric liquid crystal layer at wavelengths of 450 nm and 650 nm, respectively, with respect to the light absorption axis of the polarizer can be the value shown in Table 1 below.

[0176]

[0177] Example 2

[0178] In Example 1, a polarizing plate was manufactured in the same manner as in Example 1, except that the content of the chiral agent was changed to 3.2 parts by weight for 100 parts by weight of the rod-shaped liquid crystal compound and angles A and B were changed.

[0179]

[0180] Example 3

[0181] In Example 1, a polarizing plate was manufactured in the same manner as in Example 1, except that the content of the chiral agent was changed to 3.3 parts by weight for 100 parts by weight of the rod-shaped liquid crystal compound and angles A and B were changed.

[0182]

[0183] Example 4

[0184] A polarizing plate was manufactured in the same manner as in Example 1, except that a triacetylcellulose film having an anti-glare layer (containing silica particles with an average particle size D50 of 3 μm) formed on one side was used as the upper protective layer. The upper protective layer has a total haze of 5%, an internal haze of 3%, and an external haze of 2%.

[0185]

[0186] Example 5

[0187] A polarizing plate was manufactured in the same manner as in Example 1, except that a triacetylcellulose film having an anti-glare layer (containing silica with an average particle size D50 of 8 μm) formed on one side was used as the upper protective layer. The upper protective layer has a total haze of 25%, an internal haze of 15%, and an external haze of 10%.

[0188]

[0189] Comparative Example 1

[0190] In Example 1, a polarizing plate was manufactured in the same manner as in Example 1, except that the content of the chiral agent was changed to 6 parts by weight for 100 parts by weight of the rod-shaped liquid crystal compound and angles A and B were changed.

[0191]

[0192] Comparative Example 2

[0193] In Example 1, a polarizing plate was manufactured in the same manner as in Example 1, except that the content of the chiral agent was changed to 0.1 parts by weight for 100 parts by weight of the rod-shaped liquid crystal compound and angles A and B were changed.

[0194]

[0195] Comparative Example 3

[0196] A polarizing plate was manufactured in the same manner as in Example 1, except that a triacetylcellulose film having an anti-glare layer (containing silica particles with a D50 of 0.1 μm) formed on one surface was used as the upper protective layer. The upper protective layer has a total haze of 1%, an internal haze of 0.65%, and an external haze of 0.35%.

[0197]

[0198] Comparative Example 4

[0199] A polarizing plate was manufactured in the same manner as in Example 1, except that a triacetylcellulose film having an anti-glare layer (containing silica particles with a D50 of 10 μm) formed on one side was used as the upper protective layer. The upper protective layer has a total haze of 35%, an internal haze of 21%, and an external haze of 14%.

[0200]

[0201] Reference Example 1

[0202] A polarizer was manufactured using the same method as in Example 1.

[0203] A triacetylcellulose film (Haze 15% Toppan) with an anti-glare layer formed on one side was prepared as the upper protective layer of a polarizer.

[0204] The upper protective layer was laminated to one side of the above-manufactured polarizer. A polarizing plate was manufactured by sequentially laminating an inverse wavelength dispersive phase difference layer (positive A layer, liquid crystal layer) and a positive C layer (liquid crystal layer) to the other side of the above-manufactured polarizer.

[0205]

[0206] The following evaluation was conducted using polarizers manufactured in the examples and comparisons, and the results are shown in Table 1 and Figures 5 to 7.

[0207] (1) Orthogonal transmittance of a polarizer: The polarizers prepared in the examples and comparative examples were placed in a light transmittance measuring device V-7100, and light was transmitted from the upper protective layer toward the polarizer, but the light was transmitted in a normal direction to the in-plane direction of the polarizer to obtain orthogonal light transmittance at a wavelength of 600 nm.

[0208] (2) Reflection color values ​​a* and b*: Reflection color values ​​a* and b* at 8°, 30°, 45° and 60° were obtained using the Goniometer method with Minolsata's DMS-803 instrument.

[0209] (3) Dispersion of reflection color values: (maximum value of a* - minimum value of a*) of reflection color values ​​a* and b* measured in (2) 2 + (maximum value of b - minimum value of b) 2 I obtained it.

[0210] (4) Sparkling: Sparkling was quantified as the luminance dispersion per unit area of ​​the display. The larger the luminance dispersion, the more severe the sparkling, which degrades screen visibility. After connecting the evaluation monitor to the PC for display, a haze film (200mm x 200mm) was attached to the evaluation monitor. At this time, the evaluation monitor was set to the Green screen among R / G / B. The luminance of the evaluation monitor with the haze film attached (a total of 10,000 luminance data points, 100 in each row and 100 in each row) was measured using the ACE3 Color System, a luminance measuring device. The standard deviation of the 10,000 measured luminances was quantified as the sparkling value.

[0211]

[0212] Example Comparative Example Reference Example 123451234 Orthogonal transmittance of polarizer at wavelength 600 nm 0.30.30.50.30.30.30.30.30.30.30.3 Ground axis angle* @45047.948.649.847.947.951.546.847.947.9-@55045.145.345.645.145.145.545.345.145.1-@65045.045.345.445.044.838.245.045.0-angle A2.83.34.22.82.86.43.32.82.8-angle B0.100.20.10.10.160.10.1-In-plane phase difference*@450115116118115115132116115115-@550139140141139139139140139139-@650150152153150150150142150150-Entire upper protective layer Hayes1010105251010135-@8°a*0000000000.1b*-0.2-0.3-0.2-0.2-0.2-0.3-0.3-0.3-0.2-0.3@30°a*-1-1-1-1-0.5-10.1-1-0.50.2b*00.20.30.20-0.20.20.50-1.9@45 °a*-2-2.1-2.5-2.3-2-20.5-2.5-1.50.5b*2.52.732.62.1-1-2.52.81.9-2.5@60°a*-3-3.2-3.5-3.3-2.9-30.7-3.5-2.80.7b*3.53.43.73.63.3-5.8-5.13.73.1-3.5 Reflective Color Scatter 1471501501557717017018070200sparkling 1.061.061.061.031.071.061.0611.81.2

[0213] * Ground axis angle: The angle formed by the ground axis of the cholesteric liquid crystal layer with respect to the light absorption axis of the polarizer at the corresponding wavelength.

[0214] *In-plane phase difference: In-plane phase difference of the cholesteric liquid crystal layer.

[0215]

[0216] As shown in Table 1 above, when the polarizing plate of the embodiment is applied to an optical display device, blue and red are not visible as reflected colors from the side, and green is visible, thereby minimizing the difference in reflected colors according to the viewing angle direction.

[0217] On the other hand, the polarizing plate of the comparative example showed a weak effect compared to the polarizing plate of the example.

[0218] Figure 5 shows the case where the polarizer of Example 1 is applied. Referring to Figure 5, it can be seen that the reflection color value has become green overall, and that the reflection color dispersion is low.

[0219] Figure 6 shows the case where the polarizer of Example 4 is applied. Referring to Figure 5, it can be seen that the reflection color value has become green overall, and that the reflection color dispersion is low.

[0220] Figure 7 shows the case where the polarizing plate of the reference example is applied. Referring to Figure 7, it can be seen that the reflection color values ​​have become blue and red.

[0221]

[0222] Simple variations or modifications of the present invention can be easily implemented by those skilled in the art, and all such variations or modifications are considered to be within the scope of the present invention.

[0223] The present invention can be applied to polarizing plates and optical display devices, thus having industrial applicability.

Claims

1. A polarizing plate comprising a polarizer, a phase difference layer laminated on the lower surface of the polarizer, and an upper protective layer laminated on the upper surface of the polarizer, and The above polarizer has an orthogonal transmittance of 1% or less at a wavelength of 600 nm, and The above phase difference layer includes a cholesteric liquid crystal layer, and The angle formed by the ground axis at a wavelength of 450 nm with respect to the ground axis at a wavelength of 550 nm of the above-mentioned cholesteric liquid crystal layer is 5° or less, and the angle formed by the ground axis at a wavelength of 650 nm with respect to the ground axis at a wavelength of 550 nm of the above-mentioned cholesteric liquid crystal layer is 5° or less, and A polarizing plate characterized in that the upper protective layer has a total haze of 5 to 25%.

2. The polarizing plate according to claim 1, characterized in that the polarizing plate has a single light transmittance of 40 to 47% at a wavelength of 550 nm.

3. The polarizing plate according to claim 1, characterized in that the polarizing plate has a single light transmittance of 3% or less at a wavelength of 380 nm.

4. In claim 1, the angle formed by the ground axis at a wavelength of 450 nm with respect to the ground axis at a wavelength of 550 nm of the cholesteric liquid crystal layer is 0° to 5°, and A polarizing plate characterized in that the angle formed by the ground axis at a wavelength of 650 nm with respect to the ground axis at a wavelength of 550 nm of the above-mentioned cholesteric liquid crystal layer is 0° to 5°.

5. A polarizing plate according to claim 1, characterized in that at least one of angle A and angle B is greater than 0°.

6. In claim 1, the cholesteric liquid crystal layer is a polarizer satisfying the relationship of Equation 1 below. [Equation 1] A450 > A550 ≥ 4650 (In the above Equation 1, A450 is the angle formed by the ground axis of the cholesteric liquid crystal layer with respect to the absorption axis of the polarizer at a wavelength of 450 nm. A550 is the angle formed by the ground axis of the cholesteric liquid crystal layer with respect to the absorption axis of the polarizer at a wavelength of 550 nm. A650 is the angle formed by the ground axis of the cholesteric liquid crystal layer with respect to the absorption axis of the polarizer at a wavelength of 650 nm.

7. A polarizing plate according to claim 6, characterized in that in the above formula 1, A450 is 45 to 50°, A550 is 44 to 47°, and A650 is 43 to 46°.

8. In claim 1, the cholesteric liquid crystal layer is a polarizer satisfying the relationship of Equation 2 below. [Equation 2] B450 < B550 < B650 (In the above Equation 2, B450 is the in-plane phase difference of the cholesteric liquid crystal layer at a wavelength of 450 nm, B550 is the in-plane phase difference of the cholesteric liquid crystal layer at a wavelength of 550 nm, B650 is the in-plane phase difference of the cholesteric liquid crystal layer at a wavelength of 650 nm) 9. A polarizing plate according to claim 8, characterized in that in the above formula 2, B450 is 100 to 150 nm, B550 is 110 to 160 nm, and B650 is 120 to 170 nm.

10. A polarizing plate according to claim 1, characterized in that the cholesteric liquid crystal layer has a thickness of 10㎛ or less.

11. A polarizing plate according to claim 1, wherein the cholesteric liquid crystal layer comprises a polymerizable liquid crystal compound and a levorotatory chiral agent.

12. A polarizing plate according to claim 11, characterized in that the levorotatory chiral agent is included in an amount of 1 to 4 parts by weight per 100 parts by weight of the polymerizable liquid crystal compound.

13. A polarizing plate according to claim 11, characterized in that the polymerizable liquid crystal compound comprises one or more of a rod-shaped liquid crystal compound and a disc-shaped liquid crystal compound.

14. A polarizing plate according to claim 1, characterized in that the phase difference layer is composed solely of the cholesteric liquid crystal layer.

15. A polarizing plate according to claim 1, wherein the phase difference layer comprises the cholesteric liquid crystal layer and a protective layer formed on at least one surface of the cholesteric liquid crystal layer.

16. A polarizing plate according to claim 1, wherein the upper protective layer has an internal haze of 3% to 15% and an external haze of 2% to 10%.

17. A polarizing plate according to claim 1, wherein the upper protective layer comprises a substrate layer and an anti-glare layer laminated on one surface of the substrate layer, and the anti-glare layer comprises inorganic particles having an average particle size D50 of 0.1 to 10 μm.

18. An optical display device comprising a polarizing plate according to any one of claims 1 to 17.

Images