KR102590987B1 - Polarizing Plate - Google Patents

Abstract

This application relates to a polarizing plate. One purpose of this application is to provide a polarizer that can be applied to a display device and secure a high CR (Contrast Ratio) even at an inclination angle and ensure uniform color in all directions of the inclination angle. In one example, the polarizing plate of the present application may be applied to a so-called planar switching mode liquid crystal panel, and the planar switching mode liquid crystal panel may be a liquid crystal panel having a non-contact alignment film.

Description

Polarizing Plate

This application relates to a polarizing plate.

Liquid Crystal Display (LCD) can be divided into Twisted Nematic (TN) mode, Vertical Alignment (VA) mode, and In-Plane Switching (IPS) mode. The TN (Twisted Nematic) mode described above is a liquid crystal display with a relatively simple structure, but has a problem in that the viewing angle is limited because the arrangement of the liquid crystal is asymmetrical depending on the viewing angle.

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

Typically, a liquid crystal display includes a liquid crystal panel, and the liquid crystal panel includes a liquid crystal material 200 between two opposingly arranged substrates 101 and 102 as shown in FIG. 3 . As shown in the drawing, the edges of the two substrates 101 and 102 are sealed with a so-called sealant 300, and a liquid crystal material is placed between them. Liquid crystal alignment films 401 and 402 are present on the surfaces of the substrates 101 and 102 facing the liquid crystal material, and the orientation direction of the liquid crystal alignment films 401 and 402 is determined depending on the mode of the liquid crystal panel. Polarizers 501 and 502 are usually attached to both sides of such a liquid crystal panel.

The liquid crystal alignment films 401 and 402 are so-called rubbing alignment films, and films to which alignment is imparted through rubbing treatment are mainly used. Recently, non-contact alignment films such as so-called photo-alignment films have also been applied.

Conventionally, various optical structures have been proposed to compensate for the so-called in-plane switching mode, and most of these optical structures are designed taking into account the asymmetry of the liquid crystal panel itself.

In other words, the rubbing alignment film applied conventionally has a large pre-tilt angle above a certain level, so the liquid crystal materials have asymmetry above a certain level. Therefore, most conventional optical compensation structures also take into account the asymmetry of the liquid crystal panel.

However, recently applied non-contact alignment films (e.g., photo-alignment films, etc.) have little pretilt or have very small angles, so the liquid crystal panel has more symmetry, and the conventional optical compensation structure is appropriate for these new liquid crystal panels. There is a problem where it cannot be applied properly.

This application relates to a polarizing plate. One purpose of this application is to provide a polarizer that can be applied to a display device and secure a high CR (Contrast Ratio) even at an inclination angle and ensure uniform color in all directions of the inclination angle. In one example, the polarizing plate of the present application may be applied to a so-called planar switching mode liquid crystal panel, and the planar switching mode liquid crystal panel may be a liquid crystal panel having a non-contact alignment film.

Unless otherwise specified, the reference wavelength for optical properties such as retardation, refractive index and/or refractive index anisotropy mentioned in this specification is approximately 550 nm.

In this specification, the term in-plane retardation is an optical characteristic defined by Equation 1 below, the thickness direction retardation is an optical characteristic defined by Equation 2 below, and the Nz coefficient is an optical characteristic defined by Equation 3 below.

[Formula 1]

R _in = d × (n _x - n _y )

[Formula 2]

R _th = d × (n _z - n _y )

[Formula 3]

Nz = (n _x - n _z ) / (n _x - n _y )

In Equations 1 to 3, R _in is the in-plane retardation, R _th is the thickness direction retardation, d is the thickness of the layer, n _x is the refractive index in the slow axis direction of the layer, n _y is the refractive index in the fast axis direction of the layer, n _z is the refractive index in the thickness direction of the layer.

In the above, the term layer is the layer of the object of measurement of the in-plane retardation, the thickness direction retardation and/or the Nz coefficient, and therefore, for example, the layer in the above formulas for calculating the in-plane retardation, the thickness direction retardation and the Nz coefficient of the retardation layer. is the phase difference layer.

The terms vertical, horizontal, perpendicular and parallel that define angles in this specification mean vertical, horizontal, perpendicular and parallel in a practical sense, approximately within ±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 term inclination angle referred to in this specification is defined as follows unless otherwise specified. In FIG. 2, when the plane formed by the The angle formed as shown in FIG. 2 is defined as the inclination angle (the inclination angle at point P in FIG. 2 is Θ). In FIG. 2, when the plane formed by the At this time, the angle formed with respect to the relevant x-axis as shown in Figure 2 is defined as the east angle (the east angle at point P in Figure 2 is Φ).

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

In the polarizing plate of the present application, the first and second retardation layers 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 refers to a direction from the polarization layer to the first or second retardation layer, and the term upper refers to the opposite direction. In one example, the lower portion may coincide with the direction from the polarizer to the display device when the polarizer of the present application is applied to the liquid crystal display device.

As used herein, the term polarizing layer refers to a film, sheet, or device having a reflective or absorptive polarization function. The polarizing layer is a functional element that can extract light vibrating in one direction from incident light vibrating in multiple directions.

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

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

There is no particular limitation on the thickness of the applied absorbing polarizing layer, and it may have the thickness of a known polarizing layer. Typically, the thickness of the polarizing layer may range from approximately 0.5 um to 30 um.

First and second retardation layers exist below the polarizing layer of the polarizing plate of the present application. In one example, in the polarizing plate, the first retardation layer is present below the polarizing layer, and the second retardation layer is present below the first retardation layer, so as shown in FIG. 3, the polarizing layer 300, the first The first phase difference layer 100 and the second phase difference layer 200 may be stacked in the above order. Hereinafter, the structure shown in FIG. 3 may be referred to as the first structure of the present application.

In one example, the present application designs the optical characteristics of each phase difference layer as follows with the above positional relationship, and applies it to a display device, especially a liquid crystal display device in IPS (In-Plane Switching) mode with a non-contact alignment layer. It is possible to provide a polarizer that can secure a high CR (Contrast Ratio) even at tilt angles and ensure uniform color in all directions of tilt angles.

In the first structure, the first phase difference layer has a thickness direction phase difference (based on a wavelength of 550 nm) within a range of approximately 20 to 90 nm. In other examples, the thickness direction retardation is about 25 nm or more, about 30 nm or more, 35 nm or more, 40 nm or more, 45 nm or more, 50 nm or more, 55 nm or more, 60 nm or more, 65 nm or more, 70 nm or more, or 75 nm or more. , 85 nm or less, 80 nm or less, 75 nm or less, 70 nm or less, 65 nm or less, 60 nm or less, 55 nm or less, 50 nm or less, 45 nm or less, 40 nm or less, or 35 m or less.

In the first structure of the present application, a second retardation layer exists below the first retardation layer of the polarizer. The second retardation layer may be in contact with the first retardation layer, or another element may exist between the first and second retardation layers.

In the first structure, a phase difference layer having an Nz coefficient in the range of 0.4 to 1 according to Equation 3 may be applied as the second phase difference layer. In other examples, the Nz coefficient is approximately 0.45 or more, 0.5 or more, 0.55 or more, 0.6 or more, 0.65 or more, 0.7 or more, or 0.75 or more, or approximately 0.95 or less, 0.9 or less, 0.85 or less, 0.8 or less, or 0.75 or less. It may be about 0.7 or less, 0.65 or less, 0.6 or less, or 0.55 or less. The Nz coefficient is a measure of the biaxiality of the retardation layer, and the retardation layer having an Nz coefficient in the range described above reduces the light leakage phenomenon of the polarizer at an inclination angle, and is combined with the first retardation layer to form a liquid crystal display device. The purpose of this application can be effectively achieved, such as by widening the viewing angle.

In the first structure, the second phase difference layer has an in-plane phase difference in the range of approximately 150 nm to 200 nm based on a wavelength of 550 nm. In other examples, the in-plane phase difference is 151 nm or more, 152 nm or more, 153 nm or more, 154 nm or more, 155 nm or more, 156 nm or more, 157 nm or more, 158 nm or more, 159 nm or more, 160 nm or more. Abnormality, 161 nm or more, 162 nm or more, 163 nm or more, 164 nm or more, 165 nm or more, 166 nm or more, 167 nm or more, 168 nm or more, 169 nm or more, 170 nm Abnormal degree, 171 nm or more, 172 nm or more, 173 nm or more, 174 nm or more or 175 nm or more, 195 nm or less, 194 nm or less, 193 nm or less, 192 nm or less, 191 Below nm, below 190 nm, below 189 nm, below 188 nm, below 187 nm, below 186 nm, below 185 nm, below 184 nm, below 183 nm, below 182 nm, 181 It may be below nm, below 180 nm, below 179 nm, below 178 nm, below 177 nm, below 176 nm, or below 175 nm.

In the arrangement of the polarizing plate as described above, the slow axis of the second retardation layer may be parallel to the absorption axis of the polarizing layer. In the above, the term parallel means substantially parallel and includes the axes forming an angle within the range of approximately 170 degrees to 190 degrees. As described above, by making the slow axis of the second retardation layer and the absorption axis of the polarizing layer parallel to each other, the optical path can be controlled to achieve the effect desired by the present application.

In other examples, the angle of the axis is approximately 171 degrees or more, 172 degrees or more, 173 degrees or more, 174 degrees or more, 175 degrees or more, 176 degrees or more, 177 degrees or more, 178 degrees or more, 179 degrees or more, or 180 degrees or more, or 189 degrees. It may be 188 degrees or less, 187 degrees or less, 186 degrees or less, 185 degrees or less, 184 degrees or less, 183 degrees or less, 182 degrees or less, 181 degrees or less, or 180 degrees or less.

In another example, in the polarizing plate, the second retardation layer is present below the polarizing layer, and the first retardation layer is present below the second retardation layer, so that the polarizing layer 300 is formed as shown in FIG. 4. , the second phase difference layer 200 and the first phase difference layer 100 may be stacked in the above order. Hereinafter, the structure of FIG. 4 may be referred to as the second structure of the present application.

In another example, the present application designs the optical characteristics of each retardation layer as follows with the above positional relationship to be applied to a display device, particularly an IPS (In-Plane Switching) mode liquid crystal display device with a non-contact alignment layer. When applied, it is possible to provide a polarizer that can secure a high CR (Contrast Ratio) even at an inclination angle and ensure uniform color in all directions of the inclination angle.

In the second structure of the present application, a retardation layer having an Nz coefficient in the range of 0.4 to 1 according to Equation 3 is applied as the second retardation layer. In other examples, the Nz coefficient is about 0.45 or more, about 0.5 or more, about 0.99 or less, 0.98 or less, 0.97 or less, 0.96 or less, 0.95 or less, 0.94 or less, 0.93 or less, 0.92 or less, It may be about 0.91 or less, 0.9 or less, 0.89 or less, 0.88 or less, 0.87 or less, 0.86 or less, 0.85 or less, 0.84 or less, 0.83 or less, 0.82 or less, 0.81 or less, or 0.8 or less. The Nz coefficient is a measure of the biaxiality of the retardation layer, and the retardation layer having an Nz coefficient in the range described above reduces the light leakage phenomenon of the polarizer at an inclination angle, and is combined with the first retardation layer to form a liquid crystal display device. The purpose of this application can be effectively achieved, such as by widening the viewing angle.

In the second structure, the second phase difference layer has an in-plane phase difference in the range of approximately 160 nm to 250 nm based on a wavelength of 550 nm. In other examples, the in-plane phase difference is about 165 nm or more, about 170 nm or more, 176 nm or more, 177 nm or more, 178 nm or more, 179 nm or more, 180 nm or more, 181 nm or more, or 182 nm or more. , 183 nm or more, 184 nm or more, 185 nm or more, 186 nm or more, 187 nm or more, 188 nm or more, 189 nm or more, 190 nm or more, 191 nm or more, 192 nm or more. , about 193 nm or more, about 194 nm or more, or about 195 nm or more, or about 245 nm or less, about 240 nm or less, about 235 nm or less, about 230 nm or less, about 225 nm or less, about 220 nm or less, about 215 nm or less. , 214 nm or less, 213 nm or less, 212 nm or less, 211 nm or less, 210 nm or less, 209 nm or less, 208 nm or less, 207 nm or less, 206 nm or less, 205 nm or less. , 204 nm or less, 203 nm or less, 202 nm or less, 201 nm or less, 200 nm or less, 199 nm or less, 198 nm or less, 197 nm or less, 196 nm or less, or 195 nm or less. You can.

In the second structure, the first phase difference layer has a thickness direction phase difference (based on a wavelength of 550 nm) in the range of approximately 40 to 100 nm. In other examples, the thickness direction retardation is about 45 nm or more, about 50 nm or more, 55 nm or more, 60 nm or more, 65 nm or more, or 70 nm or more, or about 95 nm or less, about 90 nm or less, 85 nm or less, or 80 nm or less. , may be 75 nm or less or 70 nm or less.

In the arrangement of the polarizing plate as described above, the slow axis of the second retardation layer may be perpendicular to the absorption axis of the polarizing layer. In the above, the term vertical means substantially vertical and includes the axes forming an angle within the range of approximately 80 degrees to 100 degrees. In the above arrangement, the optical path can be controlled to achieve the effect desired by the present application by making the slow axis of the second phase difference side and the absorption axis of the polarization layer perpendicular to each other.

In other examples, the angle of the axis is approximately 81 degrees or more, 82 degrees or more, 83 degrees or more, 84 degrees or more, 85 degrees or more, 86 degrees or more, 87 degrees or more, 88 degrees or more, 89 degrees or more, or 90 degrees or more, 99 degrees. Below, it may be 98 degrees or less, 97 degrees or less, 96 degrees or less, 95 degrees or less, 94 degrees or less, 93 degrees or less, 92 degrees or less, 91 degrees or less, or 90 degrees or less.

The first retardation layer of the first and/or second structure may be a layer that does not substantially have an in-plane retardation layer. The in-plane phase difference (based on a 550 nm wavelength) of this first phase difference layer is, for example, approximately 10 nm or less, 9 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 less than or equal to 1 nm, or substantially 0 nm.

In the case of the first retardation layer, as described above, it has substantially no in-plane retardation, and therefore the arrangement of its slow axis does not significantly affect the performance of the polarizer. However, when a slow axis is present in the first retardation layer, its arrangement may be perpendicular or horizontal to the absorption axis of the polarizing layer.

It is effective for the first phase difference layer of the first and/or second structure to have a phase difference based on a wavelength of 550 nm within the range described above and to exhibit wavelength dispersion characteristics designed to be within a predetermined range. For example, the first phase difference layer may have a dispersion coefficient of 1 or less according to Equation 4 below.

[Formula 4]

Dispersion coefficient = R _th (450)/R _th (550)

In Equation 4, R _th (450) is the thickness direction retardation based on the 450 nm wavelength of the first retardation layer, and R _th (550) is the thickness direction retardation based on the 550 nm wavelength of the first retardation layer.

If the first phase difference layer exhibits dispersion characteristics of the thickness direction phase difference in the above range, an appropriate level of compensation function can be exhibited depending on the wavelength in the visible light region through a combination with the above-mentioned phase difference value and the second phase difference layer described later, Accordingly, the luminance and color characteristics desired in this application can be effectively secured.

In other examples, the dispersion coefficient is 0.99 or less, 0.98 or less, 0.97 or less, 0.96 or less, 0.95 or less, 0.94 or less, 0.93 or less, 0.92 or less, 0.91 or less, or 0.90 or less, or 0.1 or more, 0.2 or more, 0.3 or more, 0.4 or more, It may be 0.5 or more, 0.6 or more, 0.7 or more, 0.8 or more, 0.81 or more, 0.82 or more, 0.83 or more or 0.84 or more, 0.85 or more, about 0.86 or more, about 0.87 or more, about 0.88 or more, about 0.89 or more, or about 0.9 or more.

The second phase difference layer of the first and/or second structure may also have dispersion characteristics designed to be within a predetermined range. The second phase difference layer may have a dispersion coefficient of 1 or less according to Equation 5 below.

[Formula 5]

Dispersion coefficient = R _in (450)/R _in (550)

In Equation 5, R _in (450) is the in-plane retardation based on the 450 nm wavelength of the second retardation layer, and R _in (550) is the in-plane retardation based on the 550 nm wavelength of the second retardation layer.

The degree of dispersion of the in-plane phase difference is controlled as described above, and the second phase difference layer, in which the in-plane phase difference and Nz coefficient are controlled, is combined with the first phase difference layer at a predetermined position to perform an appropriate compensation function depending on the wavelength for light in the visible light region. Achieves an effect suitable for the purpose of this application.

In other examples, the dispersion coefficient is 0.99 or less, 0.98 or less, 0.97 or less, 0.96 or less, 0.95 or less, 0.94 or less, 0.93 or less, 0.92 or less, 0.91 or less, or 0.90 or less, or 0.1 or more, 0.2 or more, 0.3 or more, 0.4 or more, It may be 0.5 or more, 0.6 or more, 0.7 or more, 0.8 or more, 0.81 or more, 0.82 or more, 0.83 or more, or 0.84 or more.

The polarizing plate may include other elements above and/or below the polarizing layer and the first and second retardation layers. However, the polarizing plate may include only the first and second retardation layers as the retardation layer. That is, the polarizing plate may further include only a so-called isotropic layer, excluding the polarizing layer and the first and second retardation layers. The isotropic layer referred to in this specification is a substantially isotropic layer, and even if the layer has a certain degree of phase difference, it can be treated as an isotropic layer as long as the phase difference is sufficient to not damage the optical structure designed for the polarizer. In one example, the term isotropic layer referred to in this application is a layer in which the in-plane retardation and the thickness direction retardation are simultaneously 20 nm or less. In other examples, the phase difference is 19 nm or less, 18 nm or less, 17 nm or less, 16 nm or less, 15 nm or less, 14 nm or less, 13 nm or less, 12 nm or less, 11 nm or less, 10 nm or less, 9 nm or less, It may be 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, 1 nm or less, or 0 nm. Therefore, on the contrary, a layer in which any one of the in-plane retardation and the thickness direction retardation exceeds 20 nm may be treated as a retardation layer in the present application.

As the first and second retardation layers, various types of retardation layers can be used without limitation as long as they satisfy the above-mentioned characteristics.

Typically, the retardation layer is a liquid crystal film or liquid crystal polymer film formed by orienting and polymerizing a polymerizable liquid crystal compound (so-called RM (Reactive Mesogen)), or a stretched polymer film to which optical anisotropy is imparted by stretching such as uniaxial or biaxial stretching. Any of the above known retardation layers can be used as long as they are applied and the characteristics described above are satisfied.

A variety of polymerizable liquid crystal compounds (so-called reactive mesogens (RM)) that can be applied to the production of liquid crystal films are also known, and methods for manufacturing liquid crystal films by applying them are also known. As the above polymerizable liquid crystal compounds, so-called polymerizable nematic liquid crystal compounds and polymerizable smectic liquid crystal compounds are known. Although it is effective to apply such a polymerizable liquid crystal compound from the viewpoint of ease of controlling the dispersion coefficient, other types of films can also be applied as long as they satisfy the requirements of the present application.

Examples of the stretched polymer film include polyolefin films such as polyethylene films or polypropylene films, cyclic olefin polymer (COP) films such as polynorbornene films, acrylic films, polyvinyl chloride films, and polyacrylic films. Cellulose ester polymer films such as ronitrile film, polysulfone film, polyacrylate film, polyvinyl alcohol film, or TAC (Triacetyl cellulose) film, PET (poly(ethylene terephthalate)) film, PC (polycarbonate) film, etc. Examples include polyester films and copolymer films of two or more monomers from among the monomers forming the polymer. In one example, a cyclic olefin polymer film or an acrylic film can be used as the polymer film. In the above, the cyclic olefin polymer includes a cyclic olefin ring-opening polymer such as norbornene or a hydrogenated product thereof, an addition polymer of a cyclic olefin, a copolymer of a cyclic olefin and another comonomer such as alpha-olefin, or the above polymer or Examples include, but are not limited to, graft polymers obtained by modifying a copolymer with unsaturated carboxylic acid or its derivatives.

In one example, the first retardation layer is a so-called vertically aligned liquid crystal film, and a liquid crystal layer containing a polymerized vertically aligned polymerizable liquid crystal compound can be applied, or a film showing desired physical properties among the stretched polymer films can be applied. there is.

In one example, the second retardation layer is a so-called horizontally oriented liquid crystal film, and a liquid crystal layer containing a polymerized horizontally oriented polymerizable liquid crystal compound can be applied, or a film showing desired physical properties among the stretched polymer films can be applied. there is.

There is no particular limitation on the thickness of the first and second retardation layers, and an appropriate type may be selected within a range that can exhibit the desired retardation.

The types of the first and second retardation layers are controlled as described above and combined at a predetermined position to provide appropriate compensation according to the wavelength for light in the visible light region, resulting in excellent CR (Contrast Ratio), color, and visual characteristics even at inclination angles. A polarizer that can be maintained can be provided.

The polarizing plate of the present application may include various additional elements in addition to the elements described above. Types of these layers include, but are not limited to, other polymer films such as polarizing layer protective films, alignment films, release layers, hard coating layers, low-reflection layers, anti-reflection layers, adhesive layers, or adhesive layers. The specific type of each layer is not particularly limited, and for example, various types used in the industry to construct a polarizing plate having a desired optical function can be used without limitation.

In order to ensure appropriate performance, the polarizing plate of the present application includes the polarizing layer protective film attached to one side of the polarizing layer, and the first and second retardation layers are directly applied to the other side of the polarizing layer without a protective film. It can have a structure attached in order. Additionally, a pressure-sensitive adhesive layer or adhesive layer that can attach the polarizer to the display device may be present below the second retardation layer.

The present application also relates to a display device. An exemplary display device may include the polarizer.

The specific type of display device including the polarizer is not particularly limited. The device may be, for example, a liquid crystal display device such as a reflective or transflective liquid crystal display, or an organic light emitting device.

The arrangement form of the polarizer in the display device is not particularly limited, and for example, known forms may be adopted.

As mentioned above, among various display devices, the polarizer can be applied to an IPS (In-Plane Switching) mode liquid crystal display device to enable effective optical compensation, especially in an IPS mode liquid crystal display with a non-contact alignment film (photo-alignment film, etc.) applied. It can be applied effectively. In one example, the polarizer may be applied as a viewer-side polarizer of the liquid crystal display. The meaning of the viewer-side polarizer is as known, and for example, in two polarizers applied to a liquid crystal display, the polarizer disposed close to the backlight is the back-side polarizer, and the other polarizer, that is, the polarizer disposed farther from the backlight among the two polarizers. The polarizer is a back side polarizer. In the present application, for example, the polarizer as described above can be effectively applied to a liquid crystal display in which the in-plane retardation of the liquid crystal layer during horizontal alignment is in the range of approximately 100 to 500 nm and approximately 200 to 450 nm based on a 550 nm wavelength. there is.

The configuration of the IPS mode liquid crystal display to which the polarizer of the present application is applied is not particularly limited. That is, the polarizer can be applied in a known IPS mode liquid crystal display according to a known application method of the polarizer, and the applicable IPS liquid crystal display mode also includes the so-called O mode or E mode, and is not particularly limited.

Such a liquid crystal display typically includes two substrates arranged opposite each other; a liquid crystal layer located between the two substrates; And a liquid crystal panel in IPS (in-plane switching) mode including a liquid crystal alignment layer disposed between the liquid crystal layer and at least one of the two substrates, and a polarizer attached to both sides of the liquid crystal panel, The above-described polarizing plate can be used as a polarizing plate disposed on at least one side of the polarizing plate. In this case, the polarizer may be, for example, an upper polarizer or a viewer-side polarizer. That is, a liquid crystal display usually includes a liquid crystal panel, a polarizer attached to both sides of the liquid crystal panel, and a backlight unit (BLU) disposed adjacent to one of the two polarizers, with one of the two polarizers adjacent to the backlight unit. The disposed polarizer is generally called a lower polarizer, and the other polarizer is called an upper polarizer, and this upper polarizer becomes the viewer-side polarizer.

The polarizer of the present application can be applied as a viewer-side polarizer as described above, but the application location is not limited thereto.

In addition, when the polarizer of the present application is applied as a viewer-side polarizer, a known polarizer may be applied as the lower polarizer without particular limitation, but the first and second phase differences are present between the polarizer layer of the lower polarizer and the polarizer layer of the upper polarizer. It is effective that no other retardation layer exists except for the liquid crystal layer of the liquid crystal panel.

Meanwhile, in the above structure, the liquid crystal alignment film is usually two layers on each opposing surface of two substrates arranged opposite each other. These liquid crystal alignment films have a so-called pretilt angle of 1 degree or less, 0.9 degrees or less, 0.8 degrees or less, 0.7 degrees or less, 0.6 degrees or less, 0.5 degrees or less, 0.4 degrees or less, 0.3 degrees or less, 0.2 degrees or less, 0.1 degrees or less, or It may be around 0 degrees. Methods for checking such a pretilt angle are known, and for example, the Crystal Rotation method can be applied.

The type of the liquid crystal alignment film as described above is not particularly limited, and non-contact alignment films such as photo-alignment films usually exhibit the above-mentioned pretilt angle.

Other components of the liquid crystal display, for example, the type of substrate or liquid crystal material, and the method of constructing the liquid crystal display using them are not particularly limited, and known conventional methods can be applied.

The present application is particularly applicable to display devices such as LCDs in relatively symmetrical IPS mode, and can provide a polarizer that can maintain excellent CR (Contrast Ratio), color, and viewing characteristics even at an inclination angle.

1 and 2 are diagrams showing an exemplary structure of a polarizing plate of the present application.
Figure 3 is a diagram for explaining the structure of the liquid crystal panel.
Figure 4 is a diagram for explaining the inclination angle and the east inclination angle.
5 to 18 are diagrams showing the results of evaluating the performance of the polarizer of the example.

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

In the following examples and comparative examples, unless otherwise specified, the symbol R _th represents the phase difference in the thickness direction of the retardation layer based on a wavelength of 550 nm, and R _in represents the phase difference in the thickness direction of the retardation layer based on a wavelength of 550 nm, unless specifically specified otherwise. represents the in-plane phase difference of the phase difference layer, and Nz means the value obtained according to Equation 3.

Example 1

As a liquid crystal panel, the cell gap is about 3.1μm, the birefringence (Δn) of the liquid crystal layer for light with a wavelength of 550 nm is 0.11, the dielectric anisotropy is Δε>0, and the pretilt angle is 0°. IPS (In -plane switching mode liquid crystal panel was applied. The luminance and minimum contrast ratio values at all inclination angles were evaluated for an IPS-LCD manufactured by attaching an upper polarizer (viewer-side polarizer) and a lower polarizer to both sides of the liquid crystal panel, respectively. As an upper polarizer, a first retardation layer and a second retardation layer are sequentially laminated on one side of a polarizing layer (a typical PVA (poly(vinyl alcohol)) polarizing layer), and an isotropic TAC (triacetyl cellulose) film (Fuji Co., Ltd.) is applied to the other side. , thickness: 40μm) was used, and as the lower polarizer, an isotropic TAC (Triacetyl cellulose) film (Fuji, thickness: 40μm) was applied to both sides of the polarizing layer (a typical PVA (poly(vinyl alcohol)) polarizing layer). ) was used. The upper polarizer was attached so that first and second retardation layers existed between the polarizer layer and the liquid crystal panel. As the first retardation layer, the thickness direction retardation (R _th ) for light of 550 nm wavelength is 30 nm, and the dispersion coefficient (R _th (450)/R _th (550) according to Equation 4) is 0.9. A liquid crystal film was used, and as the second retardation layer, the Nz value according to Equation 3 is about 0.5, the in-plane retardation (R _in ) for a 550 nm wavelength is about 192 nm, and the dispersion coefficient according to Equation 5 is about 0.84. A stretched polymer film was used. For the IPS-LCD manufactured as described above, the maximum luminance and minimum contrast ratio values in all directions and tilt angles were evaluated using TechWiz LCD 1D equipment. The evaluation results are summarized in Table 1 and shown in [Figure 5].

Example 2.

As the second retardation layer, the Nz value according to Equation 3 is 0.5, the in-plane retardation (R _in ) for light with a wavelength of 550 nm is 192 nm, and the dispersion coefficient according to Equation 5 is about 0.9, excluding the use of a stretched polymer film. Then, an IPS LCD was manufactured and evaluated in the same manner as Example 1. The evaluation results are summarized in Table 1 and shown in [Figure 6].

Example 3.

As the first retardation layer, R _th is 50 nm and a vertically aligned liquid crystal film with a dispersion coefficient of 0.9 according to Equation 4 is used, and as the second retardation layer, the Nz value is 0.6, R _in is 185 nm, and in Equation 5 An IPS-LCD was manufactured and evaluated in the same manner as in Example 1, except that a stretched polymer film with a dispersion coefficient of 0.84 was used. The evaluation results are summarized in Table 1 and shown in [Figure 7].

Example 4.

As a second retardation layer, an IPS-LCD was manufactured and evaluated in the same manner as in Example 3, except that a stretched polymer film with an Nz value of 0.6, R _in of 185 nm, and a dispersion coefficient of 0.9 according to Equation 5 was applied. proceeded. The evaluation results are summarized in Table 1 and shown in [Figure 8].

Example 5.

As a first retardation layer, R _th is 60 nm, a vertically aligned liquid crystal film with a dispersion coefficient of 0.9 according to Equation 4 is used, and as a second retardation layer, a Nz value is 0.7, R _in is 170 nm, and the dispersion coefficient according to Equation 5 is used. An IPS-LCD was manufactured and evaluated in the same manner as in Example 1, except that a stretched polymer film with a value of 0.84 was applied. The evaluation results are summarized in Table 1 and shown in [Figure 9].

Example 6.

As the first retardation layer, R _th is 80 nm, a vertically aligned liquid crystal film with a dispersion coefficient of 0.9 according to Equation 4 is used, and as a second retardation layer, an Nz value is 0.8, R _in is 156 nm, and the dispersion coefficient according to Equation 5 is used. An IPS-LCD was manufactured and evaluated in the same manner as in Example 1, except that a stretched polymer film with a value of 0.84 was used. The evaluation results are summarized in Table 1 and shown in [Figure 10].

Example 7.

The luminance and minimum contrast ratio values at all inclination angles were evaluated for an IPS-LCD manufactured by attaching an upper polarizer (viewer-side polarizer) and a lower polarizer to both sides of the same liquid crystal panel as in Example 1, respectively. As an upper polarizer, a second retardation layer and a first retardation layer are sequentially laminated on one side of a polarizing layer (a typical PVA (poly(vinyl alcohol)) polarizing layer), and an isotropic TAC (triacetyl cellulose) film (Fuji Co., Ltd.) is placed on the other side. , thickness: 40μm) was used, and as the lower polarizer, an isotropic TAC (Triacetyl cellulose) film (Fuji, thickness: 40μm) was applied to both sides of the polarizing layer (a typical PVA (poly(vinyl alcohol)) polarizing layer). ) was used. The upper polarizer was attached so that the second and first retardation layers existed between the polarizer layer and the liquid crystal panel.

As the first retardation layer, a vertically aligned liquid crystal film was used, with R _th being 50 nm and a dispersion coefficient of 0.9 according to Equation 4. The Nz value of the second retardation layer was 0.5, R _in was 211 nm, and dispersion according to Equation 5. A stretched polymer film with a coefficient of 0.84 was used. The results of evaluation in the same manner as Example 1 are summarized in Table 1 and shown in [FIG. 11].

Example 8.

As a second retardation layer, an IPS-LCD was manufactured and evaluated in the same manner as in Example 7, except that a stretched polymer film with an Nz value of 0.5, R _in of 211 nm, and a dispersion coefficient of 0.9 according to Equation 5 was applied. did. The evaluation results are summarized in Table 1 and shown in [Figure 12].

Example 9.

As the first retardation layer, R _th is 60 nm, a vertically aligned liquid crystal film with a dispersion coefficient of 0.9 according to Equation 4 is used, and as a second retardation layer, an Nz value is 0.6, R _in is 206 nm, and the dispersion coefficient according to Equation 5 is used. An IPS-LCD was manufactured and evaluated in the same manner as in Example 7, except that a stretched polymer film with a value of 0.84 was applied. The evaluation results are summarized in Table 1 and shown in [Figure 13].

Example 10.

As a second retardation layer, an IPS-LCD was manufactured and evaluated in the same manner as in Example 9, except that a stretched polymer film with an Nz value of 0.6, R _in of 206 nm, and a dispersion coefficient of 0.9 according to Equation 5 was used. did. The evaluation results are summarized in Table 1 and shown in [Figure 14].

Example 11.

As the first retardation layer, R _th is 80 nm, a vertically aligned liquid crystal film with a dispersion coefficient of 0.9 according to Equation 4 is used, and as the second retardation layer, Nz value is 0.7, R _in is 185 nm, dispersion according to Equation 5 An IPS-LCD was manufactured and evaluated in the same manner as in Example 7, except that a stretched polymer film with a coefficient of 0.84 was used. The evaluation results are summarized in Table 1 and shown in [Figure 15].

Example 12.

As a second retardation layer, an IPS-LCD was manufactured and evaluated in the same manner as in Example 11, except that a stretched polymer film with an Nz value of 0.7, R _in of 185 nm, and a dispersion coefficient of 0.9 according to Equation 5 was applied. did. The evaluation results are summarized in Table 1 and shown in [Figure 16].

Example 13.

As the first retardation layer, R _th was 90 nm and a vertically aligned liquid crystal film with a dispersion coefficient of 0.9 according to Equation 4 was applied, and as the second retardation layer, the Nz value was 0.8, R _in was 175 nm, and the dispersion coefficient according to Equation 5 was applied. An IPS-LCD was manufactured and evaluated in the same manner as in Example 7, except that a stretched polymer film with a value of 0.84 was applied. The evaluation results are summarized in Table 1 and shown in [Figure 17].

Example 14.

As a second retardation layer, an IPS-LCD was manufactured and evaluated in the same manner as in Example 13, except that a stretched polymer film with an Nz value of 0.8, R _in of 175 nm, and a dispersion coefficient of 0.9 according to Equation 5 was applied. did. The evaluation results are summarized in Table 1 and shown in [Figure 18].

The evaluation results are shown when applying the design values of the first and second retardation films according to the conditions in Table 1 below.

[Table 1]

10: Polarizer
101: upper polarizer, 102: lower polarizer
100: Polarizing layer
201: first phase difference layer
202: second phase difference layer
301, 302: substrate
400: liquid crystal material
500: Sealant
601, 602: liquid crystal alignment film

Claims (14)

Polarizing layer;
A first retardation layer located below the polarizing layer, having a thickness direction retardation in the range of 20 to 90 nm based on a 550 nm wavelength according to Equation 2 below, and a dispersion coefficient of 1 or less according to Equation 4 below; and
It is located below the first retardation layer, and the Nz coefficient according to Equation 3 below is in the range of 0.5 to 0.95, and the in-plane retardation is in the range of 150 to 200 nm based on a 550 nm wavelength. Side Polarizer:
[Formula 2]
R _th = d × (n _z - n _y )
[Formula 3]
Nz = (n _x - n _z )/(n _x - n _y )
[Formula 4]
Dispersion coefficient = R _th (450)/R _th (550)
In Equations 1 and 2, R _th is the retardation in the thickness direction, d is the thickness of the retardation layer, n _x is the refractive index in the slow axis direction of the retardation layer, n _y is the refractive index in the fast axis direction of the retardation layer, and n _z is the retardation It is the refractive index in the thickness direction of the layer, and in Equation 4, R _th (450) is the thickness direction retardation based on the 450 nm wavelength of the first retardation layer, and R _th (550) is the retardation in the thickness direction based on the 550 nm wavelength of the first retardation layer. It is the phase difference in the thickness direction. The polarizing plate of claim 1, wherein the slow axis of the second retardation layer and the absorption axis of the polarizing layer are horizontal. Polarizing layer;
A second retardation layer located below the polarizing layer, having an Nz coefficient in the range of 0.4 to 0.95 according to Equation 3 below, and an in-plane retardation in the range of 160 to 250 nm based on a 550 nm wavelength; and
It is located below the second retardation layer, and has a thickness direction retardation according to Equation 2 below in the range of 40 to 100 nm based on a 550 nm wavelength, and a first retardation layer having a dispersion coefficient of 1 or less according to Equation 4 below,
Excluding the polarizing layer and the first and second retardation layers, a viewer-side polarizer further comprising only an isotropic layer having an in-plane retardation and a thickness direction retardation of 20 nm or less:
[Formula 2]
R _th = d × (n _z - n _y )
[Formula 3]
Nz = (n _x - n _z )/(n _x - n _y )
[Formula 4]
Dispersion coefficient = R _th (450)/R _th (550)
In Equations 1 and 2, R _th is the retardation in the thickness direction, d is the thickness of the retardation layer, n _x is the refractive index in the slow axis direction of the retardation layer, n _y is the refractive index in the fast axis direction of the retardation layer, and n _z is the retardation It is the refractive index in the thickness direction of the layer, and in Equation 4, R _th (450) is the thickness direction retardation based on the 450 nm wavelength of the first retardation layer, and R _th (550) is the retardation in the thickness direction based on the 550 nm wavelength of the first retardation layer. It is the phase difference in the thickness direction. The polarizing plate of claim 3, wherein the slow axis of the second retardation layer and the absorption axis of the polarizing layer are perpendicular. The polarizing plate according to claim 1 or 3, wherein the in-plane retardation of the first retardation layer is 10 nm or less based on a wavelength of 550 nm. delete The polarizer according to claim 1 or 3, wherein the second retardation layer has a dispersion coefficient of 1 or less according to the following equation 5:
[Formula 5]
Dispersion coefficient = R _in (450)/R _in (550)
In Equation 5, R _in (450) is the in-plane retardation based on the 450 nm wavelength of the second retardation layer, and R _in (550) is the in-plane retardation based on the 550 nm wavelength of the second retardation layer. The polarizing plate according to claim 1 or 3, wherein the first retardation layer is a liquid crystal layer or a stretched polymer film containing a polymerized vertically aligned polymerizable liquid crystal compound. The polarizing plate according to claim 1 or 3, wherein the second retardation layer is a liquid crystal layer containing a polymerized horizontally aligned polymerizable liquid crystal compound or a stretched polymer film. The polarizing plate according to claim 1 or 3, wherein the retardation layer includes only the first and second retardation layers. Liquid crystal panel in planar switch mode; and the polarizer of claim 1 or 3 disposed on at least one surface of the liquid crystal panel. The liquid crystal display device according to claim 11, wherein the liquid crystal alignment layer has a pretilt angle of 1 degree or less. Liquid crystal panel in planar switch mode; and the polarizer of claim 1 or 3 disposed on a viewing side of the liquid crystal panel. The liquid crystal display device according to claim 13, wherein the liquid crystal alignment film has a pretilt angle of 1 degree or less.