KR102513842B1 - Polarizing Plate - Google Patents

Abstract

This application relates to a polarizing plate and its use. The present application is applied to a display device such as an IPS mode LCD to provide a polarizing plate capable of preventing a decrease in contrast ratio (CR) at an inclination angle and excellently maintaining color and visual characteristics.

Description

Polarizing Plate {Polarizing Plate}

This application relates to a polarizing plate.

A liquid crystal display (LCD) can be largely classified into a rotation mode such as a twisted nematic (TN) mode and a birefringence mode such as a vertical alignment (VA) or in-plane switching (IPS) mode according to a driving method. The TN (Twisted Nematic) mode is an LCD having a relatively simple structure, but has a problem in that the viewing angle is limited because the arrangement of liquid crystals is asymmetrical according to the viewing angle.

VA (Vertical Alignment) and IPS (In-Plane Switching) modes have been studied to compensate for the disadvantages of the TN mode, and the IPS mode is particularly advantageous for implementing a wide viewing angle.

In the IPS mode, which is also called a two-dimensional switching mode, light leakage may occur in a black display state depending on a viewing angle, and CR (Contrast Ratio) may decrease, and a specific color may be recognized depending on a direction, and luminous characteristics may deteriorate.

This application relates to a polarizing plate. One object of the present application is to provide a polarizing plate that can be applied to a display device such as an LCD to solve problems of contrast ratio (CR) degradation, color shift, and visual impairment that may occur at an inclination angle.

The reference wavelength of optical properties such as retardation, refractive index and/or refractive index anisotropy referred to in this specification is approximately 550 nm unless otherwise specified.

In this specification, the terms vertical, horizontal, orthogonal, and parallel to define angles are vertical, horizontal, orthogonal, and parallel in a practical sense, within approximately ±10 degrees, within ±9 degrees, within ±8 degrees, within ±7 degrees, It may include errors within ±6 degrees, within ±5 degrees, within ±4 degrees, within ±3 degrees, within ±2 degrees, or within ±1 degrees.

The terms inclination angle and inclination angle referred to in this specification are defined as follows unless otherwise specified. In FIG. 1, when the plane formed by the x-axis and the y-axis is referred to as a reference plane (eg, the reference plane may be a display surface on which an image is displayed on a display device), the z-axis, which is the normal of the reference plane, is as shown in FIG. The formed angle is defined as an inclination angle (the inclination angle at point P in FIG. 1 is θ). When the plane formed by the x-axis and the y-axis in FIG. 1 is referred to as a reference plane (for example, the reference plane may be a display surface on which an image is displayed on a display device), when the x-axis of the reference plane is 0 degrees, the corresponding x-axis An angle formed as shown in FIG. 1 is defined as an azimuth angle or an azimuth angle (the azimuth angle or the azimuth angle at point P in FIG. 1 is φ).

The polarizing plate of the present application may include at least a polarizing layer and a dye layer. In the above, the polarization layer may be an absorption type or a reflection type polarization layer, and in one example may be an absorption type linear polarization layer. Accordingly, the absorption type polarization layer may have a transmission axis formed in one direction and an absorption axis formed in a different direction. In general, the transmission axis and the absorption axis of the absorption type polarization layer are perpendicular to each other.

In the polarizing plate of the present application, the vertical alignment dye layer may be located on one side of the polarizing layer, and specifically, may be located below the polarizing layer. In this specification, the term lower means a direction from the polarization layer to the homeotropic dye layer, and upper means the opposite direction. In one example, the lower portion may coincide with a direction from the polarizer to the display device when the polarizer of the present application is applied to a display device such as an LCD.

In this specification, the term polarization layer refers to a film, sheet, or device having a reflection-type or absorption-type polarization function. The polarization layer is a functional element capable of extracting light vibrating in one direction from incident light vibrating in several directions.

As the absorption-type polarization layer in the present application, an absorption-type linear polarization layer may be used. As such a polarization layer, a poly(vinyl alcohol) (PVA) polarization layer is typically known, but the type of polarization layer that can be applied in the present application is not limited to the PVA polarization layer. For example, as a polarization layer containing a liquid crystal host and a dichroic dye polymerized in a horizontally aligned state, a polarization layer known as a so-called coated polarization layer can also be applied in the present application.

Various polarization layers as described above are known, and methods for manufacturing or obtaining such polarization layers are also well known. In the present application, these known polarization layers may be applied without particular limitation.

There is no particular limitation on the thickness of the applied absorption-type polarization layer, and it may have a thickness of a known polarization layer. Typically, the thickness of the polarization layer may be within a range of approximately 0.5 μm to 30 μm.

In the polarizing plate of the present application, a vertical alignment dye layer is additionally positioned below the polarizing layer. The dye layer and the polarization layer may be in direct contact, or other layers such as an adhesive layer, an adhesive layer, or a retardation layer may be positioned between the dye layer and the polarization layer.

The dye layer may include a liquid crystal host and a dichroic dye guest polymerized in a homeotropic alignment state. The dye layer may be called a guest host layer in another example. The guest host layer is a layer including an aligned liquid crystal host and a dichroic dye guest aligned along the alignment direction of the liquid crystal host. Accordingly, the dye layer may include a liquid crystal host polymerized in a vertically aligned state and the alignment state is fixed, and a dichroic dye guest aligned in a vertical direction according to the alignment of the liquid crystal host.

Such a dye layer, when applied to a display device such as an in-plane switching LCD, can solve the CR (Contrast Ratio) deterioration problem that may occur at an inclination angle. In addition, color shift at an inclination angle may be suppressed through control of the absorption wavelength of the dichroic dye, and in some cases, color may be actively moved to a target position.

As a result of this action, it is possible to provide a display device with no decrease in CR at an inclination angle and excellent color characteristics or visual sensation, and this effect can be particularly excellent in a so-called in-plane switching mode (IPS mode) LCD.

The type of polymerizable liquid crystal host included in the dye layer is not particularly limited. As a compound called RM (Reactive Mesogen) in the industry, various polymerizable liquid crystal compounds that can be polymerized in a controlled alignment state and the alignment state can be fixed are known, and in this application, such a liquid crystal compound is used as the liquid crystal host can be used as Usually, such a liquid crystal compound includes a site capable of exhibiting liquid crystallinity (for example, a mesogen skeleton) and includes one or more polymerizable or curable functional groups. The polymerizable or curable functional group is usually an alkenyl group, an epoxy group, a carboxyl group, an acryloyl group, a methacryloyl group, an acryloyloxy group or a methacryloyloxy group.

In one example, in this application, as the liquid crystal host as described above, a nematic liquid crystal compound or a smectic liquid crystal compound may be applied. The liquid crystal compound is curable or polymerizable. Such a liquid crystal compound can form a homeotropic alignment structure more effectively, thereby exhibiting properties suitable for the purpose of the present application. Typically, a compound having a refractive index anisotropy within a range of about 0.02 to 0.3 may be applied as the nematic and/or smectic liquid crystal compound.

The homeotropic alignment state of the polymerizable liquid crystal host is a substantially homeotropic alignment state. Accordingly, the liquid crystal layer may have a certain degree of in-plane retardation. For example, the liquid crystal layer may have an in-plane retardation within a range of about 0 to 10 nm. In another example, the in-plane retardation may be about 9 nm or less, 8 nm or less, 7 nm or less, 6 nm or less, 5 nm or less, 4 nm or less, 3 nm or less, 2 nm or less, or 1 nm or less.

The term in-plane retardation referred to in this specification is a numerical value calculated by Equation A below.

[Formula A]

Rin = d × (nx - ny)

In Equation A, Rin is the in-plane retardation, d is the thickness of the dye layer, the liquid crystal layer or the retardation layer, nx is the refractive index in a direction parallel to the in-plane slow axis of the dye layer, the liquid crystal layer or the retardation layer, ny is the dye layer, It is the refractive index in the direction parallel to the in-plane fast axis of the liquid crystal layer or the retardation layer.

The liquid crystal layer includes a dichroic dye guest (Dichroic Dye Guest) aligned according to the orientation of the vertically aligned liquid crystal host.

In this specification, the term dye refers to a substance capable of intensively absorbing and/or transforming all or at least a part of light in the visible light region (light within a wavelength range of approximately 400 to 700 nm), and the term dichroic dye ( Dichroic Dye) may refer to a material in which light absorption and/or transformation has anisotropy.

As such a dichroic dye, any dye known to be able to be used as a so-called guest material can be applied. Examples of dichroic dyes include azo dyes, anthraquinone dyes, methine dyes, azomethine dyes, oxadine dyes, azo dyes, styryl dyes, coumarin dyes, porphyrin dyes, dibenzofuranone dyes, and tykes. Topylolophyllol-based dyes, rhodamine-based dyes, xanthene-based dyes, and/or philomethene-based dyes are known, and in the present application, appropriate types of these known dyes may be selected and used to suit the purpose.

In the present application, the dichroic dye may be a dye having a maximum absorption wavelength within a range of 450 nm to 650 nm. In another example, the maximum absorption wavelength may be 500 nm or more, 500 nm or more, 510 nm or more, 520 nm or more, 530 nm or more, or 540 nm or more, or 600 nm or less, 600 nm or less, 590 nm or less, 580 nm or less, or 570 nm or less. . For example, dyes commonly known as blue-green dyes, green dyes, or yellow-green dyes may be used in the present application. In this way, by adjusting the maximum absorption wavelength of the dichroic dye, it is possible to exhibit suitable effects in display devices such as LCD. The dye layer is a dichroic dye, and includes only dyes having a maximum absorption wavelength within a range of 450 nm to 650 nm, or, if necessary, another dye having a maximum absorption wavelength in a different wavelength band in addition to the dye. Dyes may also be included. Meanwhile, the maximum absorption wavelength of the dichroic dye may be any one of the wavelengths within the range of 450 nm to 650 nm, a wavelength within a partial range within the range, or the entire range from 450 nm to 650 nm. If necessary to have a maximum absorption wavelength within a certain range, two or more dichroic dyes may be simultaneously applied to the dye layer.

The homeotropic dye layer may have a dichroic ratio of 5 or more. The dichroic ratio of the dye layer is the absorption rate in the lateral direction of the dye layer (when the plane formed by the x-axis and the y-axis in FIG. 1 is referred to as the surface of the dye layer, the absorption rate in the direction parallel to the x-axis or y-axis direction ) by the absorption rate in the normal direction of the dye layer (absorption rate in a direction parallel to the z-axis direction when the plane formed by the x-axis and y-axis in FIG. 1 is referred to as the surface of the dye layer) or the normal line of the dye layer The absorption rate of the dye layer for linearly polarized light parallel to the direction (linearly polarized light parallel to the z-axis direction when the plane formed by the x-axis and y-axis in FIG. 1 is referred to as the surface of the dye layer) is perpendicular to the normal direction of the dye layer Value divided by the absorbance of the dye layer for linearly polarized light parallel to one direction (linearly polarized light parallel to the x-axis or y-axis direction when the plane formed by the x-axis and y-axis in FIG. 1 is referred to as the surface of the dye layer) can be defined as A method for confirming such a dichroic ratio is known, and can be predicted through, for example, a transmittance ratio described later. The dichroic ratio may be measured based on the maximum absorption wavelength of the dichroic dye included in the dye layer, and in one example, may be measured based on about 550 nm. The upper limit of the dichroic ratio is not particularly limited, but may be within a range of about 25 or less in consideration of CR at an inclination angle.

The vertical alignment dye layer is also transmittance (T ₀ ) in the normal direction of the vertical alignment dye layer (z-axis direction when the plane formed by the x-axis and y-axis in FIG. 1 is referred to as the surface of the dye layer) and the inclination angle The ratio of the transmittance (T 50 ) in the direction of 50 degrees (when the plane formed by the x-axis and the y-axis in FIG. 1 is referred to as the surface of the dye layer, the angle θ formed with the z-axis direction is 50 degrees) ( ₁₀₀ × T ₅₀ /T ₀ ) may be 85% or less. The ratio (100×T ₅₀ /T ₀ ) is, in another example, about 80% or less, 75% or less, 70% or less, 65% or less, 60% or less, or 55% or less, or 10% or more, 15% or more, 20 % or more, 25% or more, 30% or more, 35% or more, 40% or more, 45% or more, or 50% or more. Transmittance (T ₀ ) in the normal direction of the vertically aligned dye layer (in the z-axis direction when the plane formed by the x-axis and the y-axis in FIG. 1 is referred to as the surface of the dye layer) is 50% or more, 55% 60% or more, 65% or more, 70% or more, 75% or more, 80% or more, 85% or more, 90% or more, or 95% or more, or 100% or less, 95% or less, or 90% or less. The transmittance or the ratio thereof may be measured using a known transmittance measuring device, for example, an Axoscan device. The transmittance or ratio thereof may be measured based on the maximum absorption wavelength of the dichroic dye or based on a wavelength of approximately 550 nm.

Through the application of the dichroic dye having the maximum absorption wavelength, dichroic ratio, transmittance and/or transmittance ratio, it is possible to solve problems such as deterioration of CR, inappropriate movement of color and deterioration of visual sensation in a display device such as LCD.

The homeotropic dye layer (guest host layer) may include about 0.1 to 40 parts by weight of the dichroic dye based on 100 parts by weight of the polymerizable compound, and within this range, the purpose can be suitably achieved. However, the content of the dichroic dye is an example of the present application, and the specific content may be controlled to satisfy the above-described dichroic ratio, transmittance, and/or transmittance ratio.

There is no particular limitation on the thickness of the vertical alignment dye layer, and the desired effect is usually secured within the range of 1 μm to 20 μm, but this range depends on the specific application form, for example, the size of the display device to which the polarizing plate is applied. can be regulated.

The vertical alignment dye layer can be formed in a known manner. For example, the vertical alignment dye layer can be formed by applying a coating solution containing the aforementioned polymerizable liquid crystal host and a dichroic dye on an appropriate alignment surface and polymerizing the polymerizable liquid crystal host in an aligned state. there is. The orientation surface that can be applied in this manner, for example, a vertical alignment layer, is a known structure, and such a structure can be appropriately selected.

Accordingly, the polarizing plate may further include a base film supporting the homeotropic dye layer and/or an alignment layer controlling the orientation of the homeotropic dye layer. However, for example, when the vertical alignment dye layer is formed on a polarizing plate by a transfer method or the like, the base film and/or the vertical alignment dye layer may not be included.

The polarizing plate of the present application basically has the above configuration and may include additional other configurations.

For example, the polarizing plate may further include a retardation layer. The retardation layer may be located above or below the dye layer. For example, in the polarizing plate, the components are disposed in the order of the polarization layer 10, the dye layer 20, and the retardation layer 30 as shown in FIG. 2, or the polarization layer 10 and retardation layer 30 as shown in FIG. ) and the dye layer 20, or as shown in FIG. 4, the dye layer 20, the polarization layer 10, and the retardation layer 30 may be arranged in the order. In the most effective example, the polarizing plate may have a structure in which the retardation layer 30 is present on one side of the polarization layer 10 and the dye layer 20 is present on the other side, as shown in the structure of FIG. A structure in which the layer is disposed on the outermost viewing side among the polarization layer, the retardation layer and the dye layer when the polarizer is applied to the display device may be appropriate. Therefore, in this case, a pressure-sensitive adhesive layer or an adhesive layer for applying a polarizing plate to a display device is present under the retardation layer, and the overall structure of the polarizing plate is a structure of a dye layer, a polarizing layer, a retardation layer, and a pressure-sensitive adhesive layer (or adhesive layer). can be

The retardation layer may have a single-layer structure or a multi-layer structure, and the retardation layer does not contain a dichroic dye.

The retardation layer may satisfy a refractive index relationship of any one of the following general formulas 1 to 7, or may include at least one layer that satisfies such a refractive index relationship. For example, when the retardation layer has a multilayer structure, any one of individual layers constituting the multilayer structure or the entire multilayer structure may satisfy the refractive index relationship of any one of General Formulas 1 to 7 below.

[Formula 1]

nx>ny=nz (+A plate)

[Formula 2]

nx=nz>ny (-A plate)

[Formula 3]

nz>nx=ny (+C plate)

[Formula 4]

nx=ny>nz (-C plate)

[Formula 5]

nz>nx>ny (+B plate)

[Formula 6]

nx>ny>nz (-B plate)

[Formula 7]

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

In Formulas 1 to 7, nx, ny, and nz denote refractive indices in the x-axis, y-axis, and z-axis directions of the retardation layer, 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.

The retardation layer may be formed to satisfy wavelength dispersion of any one of the following general formulas 8 to 10. When the retardation layer has a multilayer structure, individual layers constituting the multilayer structure or the entire laminated structure may be formed to satisfy wavelength dispersion of any one of the following general formulas 8 to 10. The following general formula 8 may be referred to as an inverse dispersion characteristic, general formula 9 may be referred to as a regular dispersion characteristic, and general formula 10 may be referred to as a flat dispersion characteristic.

[Formula 8]

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

[Formula 9]

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

[Formula 10]

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

In the above, R(λ) may mean an in-plane retardation of light having a wavelength of λ of the retardation layer. That is, in Formulas 8 to 10, R(450), R(550), and R(650) are in-plane retardation for light of 450 nm, 550 nm, and 650 nm, respectively, and the in-plane retardation is determined by Equation A .

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, within a range of 10 nm to 200 nm. Within this thickness direction retardation range, it may be more advantageous to improve the viewing angle characteristics of the LCD air.

In one example, the retardation layer may further include a retardation layer having an in-plane retardation value greater than 0 nm, for example, within a range of 100 nm to 140 nm. In this case, compared to the +C plate, the retardation layer having the in-plane retardation value greater than 0 nm may be disposed closer to the polarization layer. A slow axis of the retardation layer may form an angle of about 80 to 100 degrees or about 90 degrees with respect to the light absorption axis of the polarization layer. For example, the retardation layer may further include a +A plate or a -B plate as the retardation layer having an in-plane retardation value of greater than 0 nm. Accordingly, the retardation layer may be a stack of +C plates and +A plates or a stack of +C plates and -B plates. An in-plane retardation of the +A plate with respect to a wavelength of 550 nm may be within a range of 80 nm to 140 nm. An in-plane retardation of the -B plate with respect to a wavelength of 550 nm may be within a range of 80 nm to 140 nm, and a thickness direction retardation with respect to a wavelength of 550 nm may be, for example, 50 nm to 150 nm. When the retardation layer further includes such a retardation layer, it may be more effective in improving LCD air viewing angle characteristics.

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

The retardation layer, which is a liquid crystal film, can be prepared by including a polymerizable or curable liquid crystal compound in a polymerized or cured state, similarly to that described for the dye layer. In one example, the +C plate may be a liquid crystal film including a liquid crystal compound in a vertically aligned state. In one example, the +A plate may be a liquid crystal film including a liquid crystal compound in a horizontally aligned state. However, unlike the dye layer, the retardation layer liquid crystal film does not contain 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 cycloolefin 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 types of monomers forming the polymer may be exemplified.

In the polarizing plate, the dye layer, the polarizing layer, and the retardation layer may be attached to each other by an adhesive or an adhesive. The dye layer and the polarization layer and the polarization layer and the retardation layer may be directly attached through an adhesive layer or a pressure-sensitive adhesive layer, respectively, or, if necessary, may be attached by additionally including a primer layer. In addition to the pressure-sensitive adhesive layer or the adhesive layer for laminating the polarization layer, the dye layer, and the retardation layer, the polarizing plate may include an additional pressure-sensitive adhesive or adhesive layer. With this layer, the polarizing plate can be attached to a liquid crystal panel or the like described later. As the pressure-sensitive adhesive or adhesive, known pressure-sensitive adhesives or adhesives such as acrylic, silicone, rubber, and urethane can be used.

This application also relates to the use of the polarizer. This application relates to, for example, a display device including the polarizing plate. The display device may be a liquid crystal display (LCD), and in one example may be an in-plane switching mode liquid crystal display (IPS LCD). 5 exemplarily shows the display device of the present application. An exemplary display device sequentially includes an upper polarizer 100, a liquid crystal panel 200, and a lower polarizer 300, and the upper polarizer may be the polarizer of the present application. In this case, if the polarizer includes the retardation layer, the retardation layer may be disposed closer to the liquid crystal panel 200 than the dye layer.

The liquid crystal panel may be an in-plane switching mode, that is, a liquid crystal panel in an IPS mode. Examples of liquid crystal panels of this type include in-plane switching (IPS) mode, fringe field switching (FFS) mode, or plane to line switching (PLS) mode liquid crystal panels.

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.

The liquid crystal panel may include a liquid crystal having a positive or negative dielectric constant anisotropy in a liquid crystal layer. The dielectric constant anisotropy of the liquid crystal layer may be appropriately selected according to a 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 retardation value in the thickness direction 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 polarizing layer. Regarding the polarization layer included in the lower polarizer, the contents described in the section on the polarizer of the present application may be equally applied. If necessary, a protective film and a retardation layer may be further included on one side of the lower polarization layer.

An absorption axis of the upper polarizer and an absorption axis of the lower polarizer may be within a range of 80 degrees to 100 degrees. The display device may further include a backlight. The backlight may be disposed below the lower polarizing plate.

In one example, an initial alignment direction of the liquid crystal of the liquid crystal layer may be parallel to or orthogonal to an absorption axis of the lower polarization layer. 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 alignment layers 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. A rubbing alignment layer or an optical alignment layer may be used as the alignment layer.

As described above, in the polarizer, the homeotropic dye layer may be located at the outermost side, and therefore, in this case, the polarization layer of the upper polarizer (polarizer of the present application) in the display device is more important in the liquid crystal panel than the homeotropic dye layer. can be located close by. In addition, the retardation layer may additionally exist between the polarization layer and the liquid crystal panel in the above state.

By applying the polarizing plate of the present application to the viewing side of the LCD, in particular, CR degradation and inappropriate shifting of color at an inclination angle can be prevented. A method of configuring the LCD is not particularly limited, and a conventional method may be applied as long as the polarizer is used.

The present application is applied to a display device such as an IPS mode LCD to provide a polarizing plate capable of preventing a decrease in contrast ratio (CR) at an inclination angle and excellently maintaining color and visual characteristics.

1 is a diagram for explaining an inclination angle and an inclination angle.
2 to 4 are views illustrating the structure of a polarizing plate by way of example.
5 is a diagram illustrating a structure of a display device by way of example.

The present application will be specifically described through examples and comparative examples below, but the scope of the present application is not limited to the following.

1. Vertical alignment of the dye layer Evaluation of anisotropic absorption properties

Using Axoscan equipment, the normal transmittance (Ts(0)) of the vertically aligned dye layer and transmittance (Ts(50) at a tilt angle of 50 degrees were evaluated, and the ratio (100×Ts(50)/Ts(0)) was At this time, the transmittance was based on a wavelength of 550 nm.

Example One.

homeotropic orientation Dye layer (guest host layer) produce

A polymerizable nematic liquid crystal compound (RMM460, Merck Co., refractive index anisotropy (based on 550 nm): 0.12) was used as a polymerizable liquid crystal host (RM: Reactive Mesogen) in the preparation of the vertical alignment dye layer, and green was used as a dichroic dye. A dye (maximum absorption wavelength: within the range of about 540 to 570 nm, manufacturer: Hayashibara, product name: G241) was used. A coating solution was prepared by mixing the polymerizable liquid crystal compound (host), the dichroic dye (guest), toluene and butyl cellosolve in a weight ratio of 20:2:47:31. Vertical alignment by applying the coating solution on the vertical alignment layer of an isotropic TAC (Triacetyl cellulose) film formed on the surface of a general vertical alignment layer, and allowing the polymerizable liquid crystal compound to be aligned, and then irradiating ultraviolet rays to polymerize the polymerizable liquid crystal compound. A dye layer was prepared. The ratio (100×Ts(50)/Ts(0)) of the liquid crystal layer was about 78.3%. The thickness of the homeotropic dye layer was about 1.5 μm, and the in-plane retardation was about 0.1 nm.

Fabrication of polarizer

As an absorption-type linear polarizing layer, a known PVA (Poly (vinyl alcohol)) polarizing film was used. In addition, as a retardation film, the in-plane retardation (=d×(nx-ny), d: thickness, nx: refractive index in the slow axis direction, ny: refractive index in the fast axis direction, based on 550 nm wavelength) is about 120 nm, and the thickness direction Phase difference (=d×(nz-ny), d: thickness, nz: refractive index in the thickness direction, ny: refractive index in the fast axis direction, based on 550 nm wavelength) of -40 nm COP (cyclic olefin polymer) film and thickness direction retardation ( =d×(nz-ny), d: thickness, nz: refractive index in the thickness direction, ny: refractive index in the fast axis direction, based on 550 nm wavelength) of about 130 nm was prepared. The vertical alignment dye layer, the PVA polarizing film, the COP film, and the vertical alignment liquid crystal film were attached in the above order, and a pressure-sensitive adhesive layer was formed under the vertical alignment liquid crystal film to prepare a polarizing plate. At this time, the slow axis of the COP film and the absorption axis of the PVA polarizing film were perpendicular to each other.

comparative example One

A polarizing plate was manufactured in the same manner as in Example 1, except that the vertical alignment dye layer was not applied.

evaluation example 1. Black at viewing angle sense of time evaluation

Using Techwiz LCD 1D, the polarizer of Example 1 or Comparative Example 1 was applied to an IPS (In-Plane Switching) LCD as an upper polarizer, and a black state was obtained for all angles (0 to 360 degrees) of an inclination angle of 60 degrees. Color coordinates were evaluated. The color coordinates of the black state are color coordinates measured with the LCD off. At this time, the polarizing plate of Example was applied so that the vertical alignment dye layer was located at the outermost side. In addition, the polarizing plate of Comparative Example was applied so that the homeotropic alignment liquid crystal film was positioned closer to the panel than the polarizing layer.

The IPS liquid crystal panel applied to the test has a cell gap of about 3.2㎛, a pretilt angle of the alignment layer of about 0 degrees, liquid crystal having positive dielectric constant anisotropy is applied, and an O mode with an in-plane retardation of about 340nm. It is an IPS liquid crystal panel. Table 1 below shows color coordinate evaluation results at a total tilt angle at an tilt angle of 60 degrees in Comparative Example 1 and Example 1. The color coordinates were evaluated using Eldim's EZ Contrast equipment according to the manufacturer's manual. As shown in Table 1, it can be seen that the color of Example 1 was improved in all directions compared to Comparative Example 1.

color coordinates x Y Example 1 0.252 0.12 Comparative Example 1 0.238 0.101

Claims (14)

polarization layer;
a vertically aligned dye layer located on one side of the polarization layer; and
Including a phase difference layer,
The dye layer includes a liquid crystal host and a dichroic dye guest polymerized in a homeotropic state,
The dichroic dye guest exhibits a maximum absorption wavelength within a wavelength range of 500 nm to 600 nm,
The dye layer includes, as the dichroic dye guest, only a dichroic dye guest exhibiting a maximum absorption wavelength within the wavelength range of 500 nm to 600 nm,
_The ratio (100×T ₅₀ /T 0 ) of the transmittance in the normal direction (T ₀ ) and the transmittance (T ₅₀ ) in the direction of an inclination angle of 50 degrees of the vertically aligned dye layer is in the range of 10% to 85%,
The retardation layer may include a +C plate; and a polarizing plate comprising a +A plate or a -B plate. The polarizing plate according to claim 1, wherein the liquid crystal host is a nematic liquid crystal host or a smectic liquid crystal host. The polarizing plate according to claim 1, wherein the homeotropic dye layer has an in-plane retardation within a range of 0 to 10 nm. The polarizing plate according to claim 1, wherein a ratio (100×T ₅₀ /T ₀ ) of transmittance in a normal direction (T ₀ ) and transmittance (T ₅₀ ) in an inclined angle of 50 degrees of the homeotropic dye layer is in a range of 10% to 80%. The polarizing plate according to claim 1, wherein the dichroic ratio of the dichroic dye is 5 or more. The polarizing plate of claim 1, wherein the dye layer includes a dichroic dye guest in an amount of 0.1 to 40 parts by weight based on 100 parts by weight of the liquid crystal host. The polarizing plate of claim 1, wherein the homeotropic dye layer has a thickness of 1 μm or more. delete The polarizing plate of claim 1 , wherein a retardation layer is disposed on one side of the polarization layer, and a homeotropic dye layer is disposed on the other side of the polarization layer on which the retardation layer is not disposed. delete delete A liquid crystal display device comprising an upper polarizing plate, an in-plane switching mode liquid crystal panel, and a lower polarizing plate in the above order, wherein the upper polarizing plate is the polarizing plate of claim 1. 13. The liquid crystal display device according to claim 12, wherein the polarization layer of the upper polarizer is located closer to the liquid crystal panel than the homeotropic dye layer. 14. The liquid crystal display device according to claim 13, further comprising a retardation layer between the polarization layer and the liquid crystal panel.

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