KR102451590B1 - Polarizing plates and liquid crystal display devices - Google Patents

Abstract

This application relates to a polarizing plate and a liquid crystal display device. The polarizing plate of the present application is applied to a liquid crystal display of a horizontal electric field method by improving the contrast ratio by reducing the luminance of the black state at the viewing angle through the use of a dichroic dye and improving the color moving from the red or yellow color to the blue color. It is possible to improve the visibility at the viewing angle.

Description

Polarizing plates and liquid crystal display devices

This application relates to a polarizing plate and a liquid crystal display device.

The horizontal electric field type liquid crystal display device refers to a liquid crystal display device in which the initial liquid crystal is aligned horizontally with the substrate and at a constant angle with respect to the electrode, and the direction of the electric field applied for driving is parallel to the substrate.

The horizontal electric field type liquid crystal display shows color in an oblique direction according to the characteristics of the panel, and thus there is a problem in that light leakage is large in the dark state (black state), and the visibility is deteriorated.

In order to improve the contrast ratio at the viewing angle to realize a display of excellent quality without distortion of image quality, a retardation film may be applied. However, it is difficult to simultaneously satisfy the luminance and the visual sensation.

Korean Patent Publication No. 2010-0106838

The present application is applied to a liquid crystal display of a horizontal electric field method through improvement of contrast ratio through reduction of luminance in black state at viewing angle through use of dichroic dye and improvement of color moving from red or yellow color to blue color at the viewing angle. It provides a polarizing plate capable of improving the visibility of the liquid crystal display device including the polarizing plate.

This application relates to a polarizing plate. 1 exemplarily shows the polarizing plate of the present application. 1 , the polarizing plate may include a polarizer 10 , a dye layer 20 disposed on one surface of the polarizer, and a retardation layer 30 disposed on a side opposite to the dye layer of the polarizer. The dye layer may include a liquid crystal compound and a dichroic dye in a vertically aligned state. The polarizing plate of the present application not only has a viewing angle compensation effect, but by applying the dye layer as described above on top of the polarizer, from the side, the absorption axis of the polarizer and the absorption axis of the dye layer are crossed, By improving the contrast ratio by reducing the luminance in the black state and improving the color moving from red or yellow to blue, an excellent visual sense can be exhibited at a viewing angle. In general, a blue color is preferred over a red or yellow color for a visual feeling in a dark room. According to the present application, it can have a more advantageous effect in that it can represent a mild blue color instead of a deep blue among blue colors.

In the present application, the terms polarizer and polarizer refer to objects that are distinct from each other. The term polarizer refers to a film, sheet, or device having a polarizing function itself, and the term polarizing plate refers to an object including the polarizer and other elements laminated on one or both surfaces of the polarizer. In the above, other elements may include, but are not limited to, the liquid crystal layer, a protective film of a polarizer, a retardation layer, an adhesive layer, an adhesive layer, a surface treatment layer, and the like.

A polarizer is a functional element capable of extracting light vibrating in one direction from incident light vibrating in multiple directions. As the polarizer, for example, a known absorption type linear polarizer can be used. As such a polarizer, a poly(vinyl alcohol) (PVA) polarizer may be exemplified.

In one example, the polarizer included in the polarizing plate may be a PVA film or sheet in which a dichroic dye or iodine is adsorbed and oriented. The PVA can be obtained by, for example, gelling polyvinyl acetate. Examples of the polyvinyl acetate include a homopolymer of vinyl acetate; and copolymers of vinyl acetate and other monomers may be exemplified. As another monomer copolymerized with vinyl acetate in the above, one or more kinds of an unsaturated carboxylic acid compound, an olefin compound, a vinyl ether compound, an unsaturated sulfonic acid compound, and an acrylamide compound having an ammonium group may be exemplified. The gelation degree of polyvinyl acetate is generally about 85 mol% to about 100 mol% or 98 mol% to 100 mol%. The degree of polymerization of polyvinyl alcohol of the linear polarizer may be generally from about 1,000 to about 10,000 or from about 1,500 to about 5,000.

The transmittance or polarization degree of the polarizer may be appropriately adjusted in consideration of the purpose of the present application. For example, the transmittance of the polarizer with respect to a wavelength of 550 nm may have a single transmittance of 40% to 55%, and a polarization degree of 65% to 99.9997%.

The dye layer may include a liquid crystal compound and a dichroic dye in a vertically aligned state. In the present application, the vertical alignment state means a state in which the director of the liquid crystal compound is vertically arranged with respect to the plane of the dye layer or the liquid crystal layer, for example, about 85 degrees to 95 degrees, preferably about 90 degrees. can In the present application, the horizontal alignment state means a state in which the directors of the liquid crystal compound are arranged parallel to the plane of the dye layer or the liquid crystal layer, for example, -5 degrees to 5 degrees, preferably about 0 degrees. can

In the present application, the director of the liquid crystal compound may mean a long axis when the liquid crystal compound has a rod shape, and may mean an axis in a direction normal to the plane of the disk when the liquid crystal compound has a discotic shape.

The dichroic dye may be aligned according to the alignment of the liquid crystal compound. Accordingly, when the liquid crystal compound is included in a vertically aligned state, the dichroic dye may also be included in a vertically aligned state. When the dichroic dye is included in a vertically aligned state, the contrast ratio and color may be improved at the viewing angle due to the anisotropic absorption characteristic at the viewing angle.

The liquid crystal compound may be a polymerizable or curable liquid crystal compound. In the present application, the polymerizable or curable liquid crystal compound may refer to a molecule including a moiety capable of exhibiting liquid crystallinity, for example, a mesogen skeleton, and at least one polymerizable or curable functional group. The polymerizable or curable functional group is not particularly limited, but for example, an alkenyl group, an epoxy group, a cyano group, a carboxyl group, an acryloyl group, a methacryloyl group, an acryloyloxy group, or a methacryloyloxy group may be exemplified. have.

The dye layer may include the liquid crystal compound in a cured state or a polymerized state. In addition, including the polymerizable liquid crystal material in a cured or polymerized state may mean a state in which the liquid crystal compound is polymerized to form a backbone such as a main chain or side chain of a liquid crystal polymer in the dye layer. The dye layer may include the liquid crystal compound in a state in which vertical alignment is fixed. Accordingly, in the dye layer, the vertical alignment state of the liquid crystal compound is not switched by the application of external energy such as an electric field.

In the present application, "dye" may mean a material capable of intensively absorbing and/or transforming light within the visible light region, for example, at least a portion or the entire range within the wavelength range of 380 nm to 780 nm, and "dichroic dye" ' may mean a material capable of anisotropic absorption of light in at least a part or the entire range of the visible light region.

In the dye layer, dichroic dyes are arranged together according to the arrangement of the liquid crystal compound, so that the dichroic dye may exhibit anisotropic light absorption characteristics with respect to an alignment direction of the dichroic dye and a direction perpendicular to the alignment direction, respectively. In one example, the dichroic dye may have a rod shape. For example, a dichroic dye is a material whose absorption rate of light varies depending on the polarization direction. If the absorption rate of light polarized in the long-axis direction is large, it is called a p-type dye, and if the absorption rate of light polarized in the short-axis direction is large, it is called an n-type dye. can be called In one example, when a p-type dye is used, polarized light vibrating in the long-axis direction of the dye is absorbed, and polarized light vibrating in the short-axis direction of the dye is absorbed and transmitted therethrough. Hereinafter, it is assumed that the dichroic dye is a p-type dye, unless otherwise specified.

As the dichroic dye, for example, a known dye known to have a property that can be arranged according to the alignment of the liquid crystal compound may be selected and used. Examples of the dichroic dye include azo dyes, anthraquinone dyes, methine dyes, azomethine dyes, oxadine dyes, azo dyes, styryl dyes, coumarin dyes, porphyrin dyes, di At least one dye selected from the group consisting of benzofuranone-based dyes, tiketophyllorophyllor-based dyes, rhodamine-based dyes, xanthene-based dyes and phylomethene-based dyes may be used. As the dichroic dye, one type of dye or a mixture of two or more types of dyes may be used within the range in which the dye layer exhibits a desired transmittance.

In the polarizing plate of the present application, the contrast ratio and color can be adjusted at the viewing angle according to the dichroic ratio of the dichroic dye. The dichroic ratio of the dichroic dye may be appropriately selected within a range capable of achieving the object of the present application. In the present application, the term "dichroic ratio" means, for example, in the case of a p-type dye, a value obtained by dividing the absorption of polarized light parallel to the long axis direction of the dye by the absorption of polarized light parallel to the direction perpendicular to the long axis direction. can

In the present specification, the dichroic ratio of the dichroic dye may be obtained by measuring the transmittance of the dye layer including the dichroic dye and the liquid crystal compound. In one example, with respect to the dye layer including the dichroic dye and the liquid crystal compound in a horizontally aligned state, among the light incident in the normal direction of the dye layer, measured for polarized light parallel to the horizontal alignment direction After measuring the transmittance (Te) and transmittance (To) for polarized light parallel to the direction of the horizontal orientation and the in-plane vertical direction, the dichroic ratio may be determined as a ratio of log10(Te)/log10(To). The dichroic ratio for a specific wavelength may be obtained by substituting values for a specific wavelength into Te and To, and the dichroic ratio for a specific wavelength range may be obtained by substituting an average value of a specific wavelength range into Te and To.

The dichroic dye may have, for example, a dichroic ratio of 5 or more. The dichroic dye is, for example, within the wavelength range of the visible region, for example, in the wavelength range of about 380 nm to 780 nm, about 400 nm to 780 nm or 600 nm to 750 nm, at least a part of the wavelength or at any one wavelength, the dichroic ratio is can be satisfied The upper limit of the dichroic ratio may be, for example, 25 or less. As the dichroic ratio of the dichroic dye increases, the panel tends to darken in a white state, so that the dichroic ratio can be appropriately adjusted within the above range according to the needs of the final product.

The dichroic dye may be included in the dye layer in an amount of 0.1 to 1 part by weight based on 100 parts by weight of the liquid crystal compound. When the content of the dichroic dye is within the above range, it may be more advantageous to improve the visual sense by improving the color of the black state at the viewing angle.

In the polarizing plate of the present application, the dichroic dye may have an absorption band within a wavelength range of 600 nm to 750 nm, specifically, a wavelength range of 600 nm to 700 nm. A dye having the above absorption band may be referred to as a long-wavelength absorption dye. In the present application, by applying a dye layer including a dichroic dye having such an absorption band on the upper portion of the polarizer, it is preferable in terms of color control because it is possible to improve the contrast ratio and move the red or yellow color to the blue region.

In the present application, the absorption band of the dichroic dye is the point at which the absorbance is highest or the transmittance when the absorbance or transmittance for a wavelength of 380 nm to 780 nm is measured with respect to the dye layer including the dichroic dye in a horizontally aligned state. may mean a wavelength band including a wavelength at a point where ? In the present application, the absorption band of the dichroic dye refers to a wavelength region in which transmittance is about 20% or less, 15% or less, 10% or less, 7% or less, 5% or less, 3% or less, or 1% or less within the entire wavelength range. can mean

In addition, a wavelength region other than the absorption band may exhibit a higher transmittance than the transmittance of the absorption band. In one example, transmittance in a wavelength region other than the absorption band may be 30% or more, 40% or more, 50% or more, 60% or more, 70% or more, or 80% or more.

In the present application, in the dichroic dye, part or the entire wavelength range of 600 nm to 750 nm may be the absorption band. In one example, the dichroic dye may have an absorption band in a part of the wavelength range of 600 nm to 750 nm. In this case, the width of the absorption band may be 20 nm or more, 40 nm or more, 60 nm or more, 80 nm or more, or 100 nm or more.

The transmittance of the dichroic dye may be transmittance measured with respect to a dye layer including the dichroic dye in a state in which it is horizontally aligned in one direction. The dye layer may further include a liquid crystal compound in a horizontally aligned state to horizontally align the dichroic dye. The transmittance is a percentage of the intensity of light transmitted through the dye layer to the intensity of light incident on the dye layer. The transmittance may mean transmittance for polarized light parallel to an axis indicating maximum absorbance or minimum transmittance with respect to the dye layer, based on light incident in a normal direction. An axis on which the dye layer exhibits maximum absorbance or minimum transmittance may be parallel to the direction of the horizontal alignment.

Since the dye layer includes the dichroic dye in a vertically aligned state, the dye layer itself included in the polarizing plate may exhibit high transmittance. In one example, the dye layer may be 90% or more in the entire wavelength range of 380 nm to 780 nm with respect to light incident in the normal direction of the dye layer.

The dichroic dye having an absorption band within the wavelength range of 600 nm to 750 nm may be a mixture of dyes exhibiting different colors or dyes having different chromophores in one dye molecule.

In one example, the dichroic dye may be a mixture of two or more dichroic dyes having different absorption bands. As a specific example, the dichroic dye may be any one of dichroic dyes having orange and red absorption bands or a mixture of the dyes. In the present application, the orange wavelength region may mean 590 nm to 620 nm, and the red wavelength region may mean about 620 nm to 750 nm. When the dichroic dye is used as a mixture as described above, it may be more advantageous to obtain a black color moving from red or yellow to blue.

The thickness of the dye layer may be appropriately adjusted in consideration of the purpose of the present application. The thickness of the dye layer may be, for example, 1 μm or more. When the thickness of the dye layer is within the above range, the vertically oriented dichroic dye may be sufficiently included, and thus it may be more advantageous to exhibit excellent contrast ratio and color at a viewing angle. In addition, when the thickness of the dye layer is too thick, the thickness direction retardation value is excessively increased due to the birefringence of the liquid crystal compound, so that the viewing angle characteristic may be deteriorated. or 1.3 μm or less.

The dye layer includes a liquid crystal compound in a vertically aligned state to induce vertical alignment of the dichroic dye. The dye layer may have a thickness direction retardation value due to the birefringence of the liquid crystal compound. The thickness direction retardation value of the dye layer may be 40 nm or more. The upper limit of the retardation value in the thickness direction of the dye layer may be, for example, 200 nm or less. When the retardation value in the thickness direction of the dye layer is within the above range, when the dichroic dye is included, it may be more advantageous to improve contrast ratio and color at a viewing angle.

In the present application, the in-plane retardation value may be defined by Equation 1 below, and the thickness direction retardation value may be defined by Equation 2 below.

[Formula 1]

Rin = (nx-ny) × d

[Equation 2]

Rth = (nz-ny) × d

In Equation 1, Rin means the in-plane retardation value, in Equation 2, Rth means the thickness direction retardation value, and nx, ny and nz are the dye layer, liquid crystal layer, A plate, B plate, The x-axis, y-axis, and z-axis refractive indices of a retardation layer such as a C plate, and d is a thickness of a retardation layer such as a dye layer, a liquid crystal layer, an A plate, a B plate, and a C plate.

In the present application, the x-axis, the y-axis and the z-axis of the retardation layer such as the dye layer, the liquid crystal layer, the A plate, the B plate, and the C plate are described. It means a direction parallel to the in-plane slow axis of retardation layers such as B plate and C plate, and the y-axis means a direction parallel to the in-plane fast axis of retardation layers such as dye layer, liquid crystal layer, A plate, B plate, and C plate. and the z-axis means the thickness direction of the retardation layer such as the dye layer, the liquid crystal layer, the A plate, the B plate, and the C plate. The x-axis and the y-axis may be orthogonal to each other in a plane. In the present application, when the dye layer, the liquid crystal layer, or the retardation layer contains rod-shaped liquid crystal molecules, the slow axis may mean the long axis direction of the rod-shaped liquid crystal molecules. It can mean direction. In the present application, while describing the optical axis of the retardation layer such as the dye layer, the liquid crystal layer, the A plate, the B plate, and the C plate, unless otherwise specified, it means a slow axis. In the present application, the refractive index of the retardation layer such as the dye layer, the liquid crystal layer, the A plate, the B plate, and the C plate is described, and unless otherwise specified, the refractive index for light having a wavelength of about 550 nm.

The dye layer may be formed by, for example, coating a composition including a liquid crystal compound and a dichroic dye on one surface of the base layer and then curing or polymerization.

The coating method of the composition on the base layer is not particularly limited, and for example, a known coating method such as roll coating, printing method, inkjet coating, slit nozzle method, bar coating, comma coating, spin coating or gravure coating, etc. It can be carried out by coating through.

The polymerization method of the composition is not particularly limited, and may be performed by a known liquid crystal compound polymerization method. For example, it may be carried out by a method of maintaining an appropriate temperature so that the polymerization reaction can be initiated or a method of irradiating an appropriate active energy ray. When maintenance at an appropriate temperature and irradiation with active energy rays are required at the same time, the process may be performed sequentially or simultaneously. In the above, the irradiation of the active energy ray may be performed using, for example, a high-pressure mercury lamp, an electrodeless lamp or a xenon lamp, etc. The polymerizable liquid crystal compound may be selected within a range in which polymerization of the liquid crystal compound can be appropriately performed.

As the base layer, a known material may be used without any particular limitation. For example, an inorganic film or a plastic film such as a glass film, a crystalline or amorphous silicon film, a quartz or indium tin oxide (ITO) film may be used. As the base layer, an optically anisotropic base layer such as an optically isotropic base layer or a retardation layer can be used. Examples of the plastic film include triacetyl cellulose (TAC); COP (cyclo olefin copolymer) such as norbornene derivatives; PMMA(poly(methyl methacrylate); PC(polycarbonate); PE(polyethylene); PP(polypropylene); PVA(polyvinyl alcohol); DAC(diacetyl cellulose); Pac(Polyacrylate); PES(poly ether sulfone); PEEK(polyetheretherketon) ); PPS (polyphenylsulfone), PEI (polyetherimide); PEN (polyethylenemaphthatlate); PET (polyethyleneterephtalate); PI (polyimide); PSF (polysulfone); In the base layer, if necessary, a coating layer of a silicon compound such as gold, silver, silicon dioxide or silicon monoxide, or a coating layer such as an anti-reflection layer may be present.

A vertical alignment layer for vertically aligning the liquid crystal compound may be formed on the base layer. As the alignment film, for example, it is a contact alignment film such as a rubbing alignment film, or an alignment film known to be capable of exhibiting alignment characteristics by a non-contact method such as irradiation of linearly polarized light, including a photo-alignment film compound, for example. can

The polarizing plate may further include a retardation layer. The retardation layer may be disposed on a side opposite to the dye layer of the polarizer. The retardation layer may be a single retardation film or a laminate of two or more retardation films. 2 exemplarily shows the structure of a polarizing plate including a laminate of two retardation films. As shown in FIG. 2 , the dye layer 20 may be disposed on one side of the polarizer 10 , and the first retardation film 301 and the second retardation film on the opposite side of the dye layer 20 of the polarizer 10 . 302 may be disposed.

According to the polarizing plate of the present application, the retardation layer does not include a dichroic dye. As will be described later, when the polarizing plate is applied to a liquid crystal display, the retardation layer may be disposed closer to the liquid crystal panel than the dye layer. If the retardation layer disposed between the polarizer and the liquid crystal panel includes a dichroic dye, there is a problem in that a contrast ratio or color at a viewing angle is rather reduced.

The retardation film may satisfy any one of the refractive index relationship of Formulas 1 to 7 below. When the retardation layer is a laminate of two or more retardation films, each retardation film may independently satisfy any one of the refractive index relationships of Formulas 1 to 7 below.

[General formula 1]

nx>ny=nz (+A plate)

[General formula 2]

nx=nz>ny (-A plate)

[General Formula 3]

nz>nx=ny (+C plate)

[General formula 4]

nx=ny>nz (-C plate)

[General formula 5]

nz>nx>ny (+B plate)

[General formula 6]

nx>ny>nz (-B plate)

[General formula 7]

nx>nz>ny (Z-axis oriented film)

In Formulas 1 to 7, nx, ny, and nz mean the refractive indices of the retardation film in the x-axis, y-axis, and z-axis directions, respectively. In the present application, the x-axis direction may mean a slow axis direction, the y-axis direction may mean a fast axis direction, and the z-axis direction may mean a thickness direction. Unless otherwise specified in the present application, the refractive index may mean a refractive index for light having a wavelength of about 550 nm.

The retardation film may be formed to satisfy the wavelength dispersibility of any one of the following general formulas 8 to 10. When the retardation layer is a laminate of two or more retardation films, each film may be independently formed to satisfy the wavelength dispersibility of any one of the following general formulas 8 to 10. The following general formula 8 may be called an inverse dispersion characteristic, general formula 9 may be called a normal dispersion characteristic, and general formula 10 may be called a flat dispersion characteristic.

[General formula 8]

R(450)/R(550) < R(650)/R(450)

[General formula 9]

R(450)/R(550) > R(650)/R(450)

[General formula 10]

R(450)/R(550) = R(650)/R(450)

In Formulas 8 to 10, R(λ) may mean a retardation value for light having a wavelength of λnm of the retardation film.

In one example, the retardation layer may include at least a +C plate. A thickness direction retardation of the +C plate with respect to a wavelength of 550 nm may be, for example, 120 nm to 150 nm. Within this thickness direction retardation range, it may be applied to a liquid crystal display device to be more advantageous in improving viewing angle characteristics.

In one example, the retardation layer may further include a retardation film having an in-plane retardation value greater than 0 nm, for example, 100 nm to 140 nm. In this case, compared to the +C plate, the retardation film having the in-plane retardation value greater than 0 nm may be disposed closer to the polarizer or disposed further away from the polarizer. For example, the retardation layer is a retardation film having an in-plane retardation value greater than 0 nm, and may further include a +A plate or a -B plate. Accordingly, the retardation layer may be a laminate of a +C plate and a +A plate or a laminate of a +C plate and a -B plate. In one example, the polarizing plate may include a polarizer, a -B plate, and a +C plate in sequence. In another example, the polarizing plate may include a polarizer, a +C plate, and a +A plate in sequence. The in-plane retardation of the +A plate with respect to a wavelength of 550 nm may be in the range of 100 nm to 140 nm. The angle between the slow axis of the +A plate and the light absorption axis of the polarizer may be in the range of -5 degrees to 5 degrees, -3 degrees to 3 degrees, or -1 degrees to 1 degree. The in-plane retardation with respect to the 550 nm wavelength of the -B plate may be in the range of 100 nm to 140 nm, and the thickness direction retardation with respect to the 550 nm wavelength may be in the range of, for example, -20 nm to -50 m. An angle between the slow axis of the -B plate and the light absorption axis of the polarizer may be in the range of 85 degrees to 95 degrees, 87 degrees to 93 degrees, 89 degrees to 91 degrees to 89.5 degrees to 90.5 degrees. When the retardation film is further included, it may be applied to a liquid crystal display device to be more advantageous in improving viewing angle characteristics.

The retardation film may be a liquid crystal film or a polymer film.

In the case of a liquid crystal film, similar to that described for the liquid crystal layer, it can be prepared by including a polymerizable or curable liquid crystal compound in a polymerized state or a cured state. In one example, the +C plate may be a liquid crystal film including the liquid crystal compound in a vertically aligned state. In one example, the +A plate may be a liquid crystal film including the liquid crystal compound in a horizontally aligned state. As described above, the retardation film does not include a dichroic dye.

In the case of a polymer film, for example, a polyolefin film such as a polyethylene film or a polypropylene film, a cyclic olefin polymer (COP) film such as a polynorbornene film, a polyvinyl chloride film, a polyacrylonitrile film, a poly A cellulose ester-based polymer film such as a sulfone film, a polyacrylate film, a polyvinyl alcohol film, or a triacetyl cellulose (TAC) film, or a copolymer film of two or more kinds of monomers among the monomers forming the polymer may be exemplified.

The dye layer, the polarizer, and the retardation layer of the polarizing plate may be attached to each other by an adhesive or an adhesive. The dye layer, the polarizer, and the polarizer and the retardation layer may be directly attached through an adhesive layer or an adhesive layer, respectively, or may be attached by additionally including a primer layer, if necessary. A pressure-sensitive adhesive or adhesive layer may be further formed on the side opposite to the polarizer of the retardation layer. Through this, the polarizing plate can be attached to a liquid crystal panel to be described later. As the pressure-sensitive adhesive or adhesive, a known pressure-sensitive adhesive or adhesive such as acrylic, silicone, rubber, or urethane may be used.

A method of attaching the dye layer and/or the retardation layer and the polarizer is not particularly limited. In one example, an adhesive or pressure-sensitive adhesive composition is coated on one side of a polarizer or a dye layer, and after laminating the polarizer and the dye layer, the composition is cured, or the adhesive or pressure-sensitive adhesive composition is applied with a polarizer by a dropping method. A method of laminating a dye layer and curing the composition may be used. The curing of the composition may be performed, for example, by irradiating an active energy ray having an appropriate intensity with an appropriate amount of light in consideration of the components included in the composition. In another example, the dye layer may be attached to the polarizer by a transfer method. In the present application, the transfer of the dye layer may refer to a process of bonding the dye layer formed on the carrier substrate to the polarizer, which is a transfer target, through an adhesive or an adhesive, and then peeling and removing the carrier substrate. Attachment of the retardation layer and the polarizer may be performed in the same manner as in the method of attaching the dye layer and the polarizer.

The present application also relates to the use of the polarizing plate. The present application relates, for example, to a liquid crystal display including the polarizing plate. 3 exemplarily shows the liquid crystal display of the present application. The exemplary liquid crystal display of the present application includes an upper polarizing plate 100, a liquid crystal panel 200, and a lower polarizing plate 300 in sequence, and the upper polarizing plate may be the polarizing plate of the present application. In this case, the retardation layer 30 may be disposed closer to the liquid crystal panel 200 than the dye layer 20 .

The liquid crystal panel may be a horizontal electric field type liquid crystal panel. In the present application, the liquid crystal panel of the horizontal electric field method means a liquid crystal panel in which the liquid crystal compound exists in a horizontally aligned state in a state in which no voltage is applied or in an initial state, and its orientation can be switched according to a horizontal electric field when a voltage is applied. can An example of the horizontal electric field type liquid crystal panel may be an in-plane switching (IPS) mode, a fringe field switching (FFS) mode, or a plane to line switching (PLS) mode liquid crystal panel.

The liquid crystal panel may include an upper substrate, a liquid crystal layer, and a lower substrate. Each of the upper and lower substrates may be a glass substrate or a plastic substrate. According to an embodiment of the present invention, the liquid crystal panel may be an IPS mode (in-plane switching mode) liquid crystal panel.

The liquid crystal layer may include a liquid crystal having a positive or negative dielectric anisotropy. The dielectric anisotropy of the liquid crystal layer may be appropriately selected according to the desired mode of the liquid crystal panel. In one example, the liquid crystal layer may include a liquid crystal panel having a positive dielectric anisotropy. In one example, the in-plane retardation value of the liquid crystal layer may be 270 nm to 330 nm, and the thickness direction retardation value may be 0 nm to -40 nm.

The upper polarizing plate may be referred to as a viewer-side polarizing plate, and the lower polarizing plate may be referred to as a rear-side polarizing plate. The lower polarizing plate may include a polarizer. For the polarizer included in the lower polarizing plate, the contents described in the section of the polarizing plate of the present application may be equally applied. If necessary, a protective film and a retardation film may be further included on one surface of the lower polarizer.

The absorption axis of the upper polarizing plate and the absorption axis of the lower polarizing plate may be in the range of 80 degrees to 100 degrees. The liquid crystal display may further include a backlight. The backlight may be disposed under the lower polarizing plate.

In one example, the initial alignment direction of the liquid crystal of the liquid crystal layer may be parallel to or perpendicular to the absorption axis of the lower polarizer. When the angles are parallel, it can be defined as an O-mode liquid crystal panel, and when the angles are orthogonal, it can be defined as an E-mode liquid crystal panel.

The upper and lower substrates of the liquid crystal panel may further include an alignment layer toward the liquid crystal layer. The alignment direction of the liquid crystal may be determined by the alignment layer. The alignment layer may be a horizontal alignment layer. As the alignment layer, a rubbing alignment layer or a photo alignment layer may be used.

By applying the polarizing plate of the present application to the viewer side, the liquid crystal display device can exhibit excellent visual sensation at the viewing angle by improving the contrast ratio through reduction of the luminance of the black state at the viewing angle and improving the color moving from red or yellow to blue. have.

In one example, in the liquid crystal display to which the dye layer is applied, a color at an inclination angle of 60 degrees and an azimuth angle of 45 degrees is based on the CIE xy color coordinate, x may be 0.230 or less, and y may be 0.100 or less. The lower limit of x may be, for example, 0.200 or more, and the lower limit of y may be, for example, 0.05 or more.

A method of configuring the liquid crystal display device as described above is not particularly limited, and a conventional method may be applied as long as the polarizing plate is used.

The present application provides a polarizing plate capable of exhibiting an excellent visual sense at a viewing angle through improvement of contrast ratio through reduction of luminance in a black state at a viewing angle and improvement of a color moving from red or yellow to blue, and a liquid crystal display including the polarizing plate can do.

1 exemplarily shows the polarizing plate of the present application.
2 exemplarily shows the polarizing plate of the present application.
3 exemplarily shows the liquid crystal display of the present application.
4 is a graph showing the transmittance of the dichroic dye of Example 1.
5 is a black color coordinates at viewing angles of Comparative Example 1 and Example 1. FIG.

Hereinafter, the present application will be specifically described through Examples according to the present application and Comparative Examples not according to the present application, but the scope of the present application is not limited by the Examples presented below.

Example One

For the viewing angle black color evaluation, a polarizing plate including a dye layer, a polarizer, and a retardation layer in sequence was prepared.

The dye layer includes a rod-shaped liquid crystal compound having a birefringence value of 0.12 and a dichroic dye in a vertically aligned state, and has a thickness of 1.1 μm. The dichroic dye is a long-wavelength absorption dye (LSB-335#14, manufactured by Hayashibara) having an absorption band within a wavelength range of 600 nm to 700 nm. 4 is a transmittance spectrum of the dichroic dye, and the dichroic ratio to a wavelength of 670 nm is 7; Te is a transmittance graph for polarized light parallel to the absorption axis of the dichroic dye, and To is a transmittance graph for polarized light perpendicular to the absorption axis of the dichroic dye. The transmittance is measured with respect to the dye layer including the rod-shaped liquid crystal compound and the dichroic dye in a state in which the dichroic dye is horizontally aligned, among the light incident in the normal direction of the dye layer, Te is measured with respect to the polarized light parallel to the horizontal alignment direction transmittance, and To denotes transmittance for polarized light parallel to the direction of the horizontal alignment and the direction perpendicular to the plane. The transmittance is a percentage of the intensity of light transmitted through the dye layer to the intensity of light incident on the dye layer. The dichroic ratio of the dichroic dye may be determined as a ratio of log10(Te)/log10(To), and the dichroic ratio for a 670nm wavelength is obtained by substituting To and Te values for a 670nm wavelength in To and Te of the above formula. can

The polarizer is a PVA-based polarizer having a polarization degree of 99.99% or more for light having a wavelength of 380 nm to 780 nm and a single transmittance of 42.5%.

The retardation layer includes a -B plate and a +C plate, and the -B plate is disposed closer to the polarizer than the +C plate. The -B plate is a COP-based film having a Rin (550) value of 120 nm and an Rth (550) value of -40 nm. The +C plate is a liquid crystal film having a Rin (550) value of 0 nm and an Rth (550) value of 130 nm.

comparative example One

Same as Example 1, except that, instead of the dye layer, a rod-shaped liquid crystal compound having a birefringence value of 0.12 is included in a vertically aligned state, and a liquid crystal layer having a thickness of 1.1 μm (not including a dichroic dye) is applied. A polarizing plate was prepared.

evaluation example 1. Black in the viewing angle tick evaluation

Techwiz LCD 1D was used to simulate black color coordinates in all directions (0° to 360°) based on an inclination angle of 60° for an in-plane switching mode liquid crystal display. The black color coordinate means the color coordinate of the electric field off state of the liquid crystal display device. The azimuth angle of 0 degrees is based on the absorption axis of the polarizer. The in-plane switching mode liquid crystal display has a structure in which a liquid crystal panel is disposed between an upper polarizer and a lower polarizer, and the lower polarizer is disposed closer to the backlight than the upper polarizer.

The polarizing plate of Example 1 or Comparative Example 1 is used as the upper polarizing plate, and the dye layer of Example or the liquid crystal layer of Comparative Example is disposed on the outer layer. The liquid crystal panel has a cell spacing of 2.9 μm, a pretilt angle of 0°, dielectric anisotropy Δε > 0, and liquid crystal birefringence Δn=0.1 at a wavelength of 550 nm. It is an IPS liquid crystal panel in O mode with Rin(550): 290 nm Rth(550): 0 nm. The lower polarizing plate is a PVA-based polarizer having a polarization degree of 99.99% or more for light having a wavelength of 380 nm to 780 nm and a single transmittance of 42.5%.

Tables 1 and 5 below are black color coordinate evaluation results at viewing angles of Comparative Example 1 (A) and Example 1 (B). Table 1 shows xy color coordinate values at an inclination angle of 60 degrees and an azimuth angle of 45 degrees, and FIG. 5 shows color shifts at the entire viewing angle. As shown in Table 1 and FIG. 5 , it can be seen that the black color was improved in Example 1 compared to Comparative Example 1 by moving the omnidirectional color coordinate region from the yellow region to the blue region.

color coordinates x y Comparative Example 1 0.238 0.101 Example 1 0.218 0.089

10: polarizer, 20: dye layer, 30: retardation layer 301: first retardation film 302: second retardation film 100: upper polarizing plate 200: liquid crystal panel 300: lower polarizing plate

Claims (14)

a polarizer, a dye layer disposed on one surface of the polarizer, comprising a liquid crystal compound and a dichroic dye in a vertically aligned state, and a retardation layer disposed on the opposite side of the dye layer of the polarizer, wherein the dye layer has a thickness of 1 μm or more, and the dichroic dye has an absorption band within a wavelength range of 600 nm to 750 nm in a horizontally oriented state, and the dichroic dye is a mixture of dyes exhibiting different colors, and absorption in a wavelength region of 590 nm to 620 nm It is a mixture of a dichroic dye having a band and a dichroic dye having an absorption band in a wavelength region of 620 nm to 750 nm, the dichroic ratio of the dichroic dye is within the range of 5 to 25, and the dichroic dye is included in a horizontally oriented state The dye layer to be used is a polarizing plate having a transmittance of 30% or more in a wavelength region other than the absorption band. The polarizing plate according to claim 1, wherein the liquid crystal compound is included in the dye layer in a cured state. delete The polarizing plate of claim 1, wherein the dichroic dye is included in the dye layer in an amount of 0.1 to 1 part by weight based on 100 parts by weight of the liquid crystal compound. The polarizing plate of claim 1 , wherein the dye layer has a transmittance of light incident in a normal direction of the dye layer of 90% or more in a wavelength range of 380 nm to 780 nm. The polarizing plate according to claim 1, wherein the thickness of the dye layer is in the range of 1 μm to 1.8 μm. The polarizing plate of claim 1 , wherein the retardation layer does not contain a dichroic dye. The polarizing plate of claim 1 , wherein the retardation layer comprises a +C plate. The polarizing plate of claim 8 , wherein the retardation layer further comprises a +A plate or a -B plate. A liquid crystal display device comprising an upper polarizing plate, a horizontal electric field type liquid crystal panel, and a lower polarizing plate sequentially, wherein the upper polarizing plate is the polarizing plate of claim 1, and the retardation layer of the polarizing plate is disposed closer to the liquid crystal panel than the dye layer. 11. The liquid crystal display of claim 10, wherein the liquid crystal panel includes an upper substrate, a liquid crystal layer, and a lower substrate in sequence, and the in-plane retardation value of the liquid crystal layer is 270 nm to 330 nm, and the thickness direction retardation value is 0 nm to -40 nm. Device. The liquid crystal display of claim 10 , wherein the absorption axis of the upper polarizing plate and the absorption axis of the lower polarizing plate are within a range of 80 degrees to 100 degrees. The liquid crystal display of claim 10 , further comprising a backlight under the lower polarizing plate. The liquid crystal display device of claim 10 , wherein, in the liquid crystal display device, a color color at an inclination angle of 60 degrees and an azimuth angle of 45 degrees is 0.230 or less and y is 0.100 or less based on CIE xy color coordinates.

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