KR20210042642A - Polarizing Plate - Google Patents

Abstract

The present application relates to a polarizing plate. The present application is to provide a polarizing plate, which can secure a high contrast ratio (CR) even at an inclination angle by being applied to a display device, and can control light leakage in a block sate. In one example, the polarizing plate of the present application may be applied to a liquid crystal panel of a so-called in-plane switching mode, and the liquid crystal panel in the in-plane switching mode may be a liquid crystal panel having a non-contact alignment layer.

Description

Polarizing Plate

This application relates to a polarizing plate.

A liquid crystal display (LCD) may be classified into a twisted nematic (TN) mode, a vertical alignment (VA), and an in-plane switching (IPS) mode. In the TN (Twisted Nematic) mode, although a liquid crystal display having a relatively simple structure, there is a problem in that the viewing angle is limited because the arrangement of liquid crystals is asymmetric according to the viewing angle.

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

In general, a liquid crystal display includes a liquid crystal panel, and the liquid crystal panel includes a liquid crystal material 200 between two substrates 101 and 102 oppositely disposed as shown in FIG. 1. As shown in the figure, the edges of the two substrates 101 and 102 are sealed with a so-called sealant 300, and a liquid crystal material is positioned therebetween. Liquid crystal alignment layers 401 and 402 are present on the surfaces of the substrates 101 and 102 facing the liquid crystal material, and the alignment directions of the liquid crystal alignment layers 401 and 402 are determined according to the mode of the liquid crystal panel. Polarizing plates 501 and 502 are usually attached to both sides of such a liquid crystal panel.

As the liquid crystal alignment layers 401 and 402, a so-called rubbing alignment layer is mainly used as an alignment layer to which alignment is imparted by a rubbing treatment. Recently, a non-contact alignment layer such as a photo-alignment layer or the like is also 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 in consideration of the asymmetry of the liquid crystal panel itself.

That is, since the conventional rubbing alignment layer has a large pre-tilt angle greater than a certain level, the liquid crystal materials have a certain level or greater asymmetry. Therefore, most of the conventional optical compensation structures also consider the asymmetry of the liquid crystal panel.

However, recently applied non-contact alignment layers (e.g., photo-alignment layers) have little or no pre-tilt, or their angles are very small, so that the liquid crystal panel has more symmetrical properties, but a conventional optical compensation structure is appropriate for such a new liquid crystal panel. There is a problem that cannot be applied properly.

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 to secure a high CR (Contrast Ratio) even at an inclination angle and control a light leakage phenomenon in a black state. In one example, the polarizing plate of the present application may be applied to a liquid crystal panel in a so-called plane switching mode, and the liquid crystal panel in a plane switching mode may be a liquid crystal panel having a non-contact alignment layer.

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

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

[Equation 1]

R _in = d × (n _x -n _y )

[Equation 2]

R _th = d × (n _z -n _y )

[Equation 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 retardation in the thickness direction, d is the thickness of the layer, n _x is the refractive index of the layer in the slow axis direction, and 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 a layer to be measured for an in-plane retardation, a thickness direction retardation, and/or an Nz coefficient, and thus, for example, a layer in the above formulas for obtaining an in-plane retardation, a thickness direction retardation, and an Nz coefficient of the retardation layer. Is the phase difference layer.

In this specification, the terms vertical, horizontal, orthogonal and parallel are vertical, horizontal, orthogonal and parallel in a practical sense, and are within approximately ±10 degrees, within ±9 degrees, within ±8 degrees, and within ±7 degrees, Errors within ±6 degrees, within ±5 degrees, within ±4 degrees, within ±3 degrees, within ±2 degrees, or within ±1 degrees may be included.

The term inclination angle referred to in the present specification is defined as follows unless otherwise specified. In FIG. 2, when the plane formed by the x-axis and y-axis 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 or a surface of a polarizing plate), the z-axis, which is the normal line of the reference plane, is The angle formed as in FIG. 2 is defined as the inclination angle (the inclination angle at point P in FIG. 2 is a plane formed by the x-axis and y-axis in FIG. 2) as a reference plane (e.g., the reference plane is an image This may be the display surface or the surface of the polarizing plate), with the reference axis as the reference axis with an arbitrary axis on the reference surface as the x-axis on the drawing, and when the angle with the reference axis is set to 0 degrees, the x-axis is The angle formed as shown in Fig. 2 is defined as the moving angle (in Fig. 2, the moving angle at point P is Φ

The polarizing plate of the present application may include at least a polarizing layer, a first retardation layer, and a second retardation layer. In the above, the polarization 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. In general, in the absorption type linear polarizing layer, the transmission axis and the absorption axis are formed perpendicular to each other.

In the present specification, the term polarizing layer refers to a film, sheet, or device having a reflective or absorbing polarizing function. The polarizing layer is a functional device capable of extracting light vibrating in one direction from incident light vibrating in several directions.

In the present application, as the polarizing layer, an absorption type linear polarizing layer may be used. As such a polarizing layer, a poly(vinyl alcohol) (PVA) 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, as a polarizing layer including a liquid crystal host and a dichroic dye polymerized in a horizontally oriented state, a polarizing layer known as a so-called coating type polarizing layer may also be applied in the present application.

Various polarizing layers as described above are known, and a method of manufacturing or obtaining such a polarizing layer is also well known. In the present application, such known polarizing layers may be applied without any particular limitation.

There is no particular limitation on the thickness of the absorption-type polarizing layer to be applied, and may have a thickness of a known polarizing layer. The thickness of the polarizing layer may be, for example, in the range of about 0.5 μm to 30 μm. In another example, about 1 μm or more, about 2 μm or more, about 3 μm or more, about 4 μm or more, about 5 μm or more, about 6 μm or more, or about 7 μm or more or about 25 μm or less, about 20 μm or less, about It may be 15 μm or less, about 10 μm or less, about 9 μm or less, about 8 μm or less, or about 7 μm or less.

The single transmittance of the absorption-type polarizing layer to be applied is not particularly limited, and may be, for example, about 20% or more. In other examples, it may be about 25% or more, about 30% or more, about 35% or more, about 40% or more, or about 95% or less. In addition, the degree of polarization of the absorption-type polarizing layer may be 95% or more in one example, and 96% or more, 97% or more, 98% or more, 99% or more, 99.1% or more, 99.2% or more, 99.3% in another example. It may be more than, 99.4% or more, 99.5% or more, 99.6% or more, 99.7% or more, 99.8% or more, 99.9% or more, 99.995% or more, 100% or less, or 99.995% or less.

In the polarizing plate of the present application, the first and second retardation layers may be positioned on one surface of the polarizing layer, and specifically, may be positioned below the polarizing layer. In the present specification, the term lower means a direction from the polarizing layer to the first or second retardation layer, and the upper portion means the opposite direction. In an example, when the polarizing plate of the present application is applied to a liquid crystal display device, the lower portion may coincide with a direction from the polarizing plate toward the display device.

In one example, in the polarizing plate, the first retardation layer is present under the polarizing layer, and the second retardation layer is present under the first retardation layer, so that the polarizing layer 300 and the second retardation layer are present as shown in FIG. 3. The first phase difference layer 100 and the second phase difference layer 200 may be stacked in the above order.

The polarizing plate of the present application has the positional relationship as described above and the optical properties of each phase difference layer are designed as follows, and is applied to a display device, particularly a liquid crystal display device in an IPS (In-Plane Switching) mode having a non-contact alignment layer, so that the inclination angle In addition, it is possible to provide a polarizing plate capable of securing a high CR (Contrast Ratio) and controlling a light leakage phenomenon in a black state.

In the present application, the first retardation layer may have an in-plane retardation of light having a wavelength of 550 nm according to Equation 1 in a range of 50 nm to 70 nm. The in-plane retardation is 51 nm or more, 52 nm or more, 53 nm or more, 54 nm or more, 55 nm or more, 56 nm or more, 57 nm or more, 58 nm or more, 59 nm or more, 60 nm or more, 61 nm or more, 62 nm or more, 63 nm or more, 64 nm or more, 65 nm or more, 66 nm or more, 67 nm or more, 68 nm or more, or 69 nm or more, or 69 nm or less, 68 nm or less, 67 nm or less, 66 nm or less, 65 nm Or less, 64 nm or less, 63 nm or less, 62 nm or less, 61 nm or less, 60 nm or less, 59 nm or less, 58 nm or less, 57 nm or less, 56 nm or less, 55 nm or less, 54 nm or less, 53 nm or less, It may be 52 nm or less or 51 nm or less.

The first retardation layer may have, for example, a retardation in a thickness direction of light having a wavelength of 550 nm in a range of about 80 to 100 nm. The retardation in the thickness direction is 81 nm or more, 82 nm or more, 83 nm or more, 84 nm or more, 85 nm or more, 86 nm or more, 87 nm or more, 88 nm or more, 89 nm or more, 91 nm or more, 92 nm or more, 93 nm or more, 94 nm or more, 95 nm or more, 96 nm or more, 97 nm or more, 98 nm or more or 99 nm or more, 99 nm or less, 98 nm or less, 97 nm or less, 96 nm or less, 95 nm or less, 94 nm or less, 93 nm or less, 92 nm or less, 91 nm or less, 90 nm or less, 89 nm or less, 89 nm or less, 88 nm or less, 87 nm or less, 86 nm or less, 85 nm or less, 84 nm or less, 83 nm or less, 82 nm or less Or 81 nm or less.

In the present application, as the first retardation layer, for example, a retardation layer in which the Nz coefficient according to Equation 3 below is in the range of -0.6 to -0.2 while showing the in-plane retardation and/or the retardation in the thickness direction in the above range. Can be applied.

[Equation 3]

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

In Equation 3, 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, and n z} is the refractive index in the thickness direction of the layer.

In another example, the Nz coefficient according to Equation 3 is -0.55 or more, -0.5 or more, -0.499 or more, -0.498 or more, -0.497 or more, -0.496 or more, -0.495 or more, -0.494 or more, -0.493 or more, -0.492 More than, -0.491 or more, -0.49 or more, -0.489 or more, -0.488 or more, -0.487 or more, -0.486 or more, -0.485 or more, -0.484 or more, -0.483 or more, -0.482 or more, -0.481 or more, -0.48 or more, -0.479 or more, -0.478 or more, -0.477 or more, -0.476 or more, -0.475 or more, -0.25 or less, -0.3 or less, -0.35 or less, -0.4 or less, -0.41 or less, -0.42 or less, -0.43 or less,- 0.44 or less, -0.45 or less, -0.46 or less, -0.47 or less, -0.471 or less, -0.472 or less, -0.473 or less, -0.474 or less, -0.475 or less, -0.476 or less, -0.477 or less, -0.478 or less, -0.479 or less , -0.48 or less, -0.481 or less, -0.482 or less, -0.483 or less, -0.484 or less, -0.485 or less, -0.486 or less, -0.487 or less, -0.488 or less, -0.489 or less, -0.49 or less, -0.491 or less,- It may be 0.492 or less, -0.493 or less, -0.494 or less, -0.495 or less, -0.496 or less, -0.497 or less, -0.498 or less, or -0.499 or less.

The polarizing plate of the present application may more effectively control a light leakage phenomenon of the polarizing plate in a so-called black state by introducing a retardation layer having an Nz coefficient in the above range.

It may be effective for the first retardation layer to exhibit a wavelength dispersion characteristic designed in a predetermined range while an in-plane retardation, a retardation in a thickness direction, and/or an Nz value based on a wavelength of 550 nm are within the above-described range. For example, the first retardation layer may have a dispersion coefficient of 1 or more and less than 1.2 according to Equation 4 below.

[Equation 4]

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

In Equation 4, R _th (450) is the retardation in the thickness direction 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.

In another example, the variance coefficient according to Equation 4 may be 1.01 or more, 1.02 or more, 1.03 or more, 1.04 or more, 1.05 or more, or 1.06 or more, or less than 1.1, less than 1.09, less than 1.08, less than 1.07, 1.06 or less, or about 1.03 or less. have.

While the first retardation layer exhibits the dispersion characteristics of the retardation in the thickness direction in the above range, a compensation function of an appropriate level according to the wavelength within the visible light region is provided through a combination of the retardation value, Nz value, and/or the second retardation layer described later. Can be expressed, and thus the properties desired in the present application can be effectively secured.

In the present application, for example, a second retardation layer may be present under the first retardation layer of the polarizing plate.

In the present application, the second retardation layer may have an in-plane retardation of light having a wavelength of 550 nm according to Equation 1 in a range of 90 nm to 115 nm. The in-plane retardation is 91 nm or more, 92 nm or more, 93 nm or more, 94 nm or more, 95 nm or more, 96 nm or more, 97 nm or more, 98 nm or more, 99 nm or more, 100 nm or more, 101 nm or more, 102 nm or more, 103 nm or more, 104 nm or more, 105 nm Or more, 106 nm or more, 107 nm or more, 108 nm or more, 109 nm or more, 110 nm or more, or 110 nm or more or 114 nm or less, 113 nm or less, 112 nm or less, 111 nm or less, 110 nm or less, 109 nm or less, 108 nm or more, 107 nm or less, Less than 106 nm, less than 105 nm, less than 104 nm, less than 103 nm, less than 102 nm, less than 101 nm, less than 100 nm, less than 99 nm, less than 98 nm, less than 97 nm, less than 96 nm, less than 95 nm, less than 94 nm, less than 93 nm, or less than 92 nm May be.

The second retardation layer may have, for example, a retardation in a thickness direction of light having a wavelength of 550 nm in a range of about -10 to 10 nm. The retardation in the thickness direction may be -9 nm or more, -8 nm or more, -7 nm or more, -6 nm or more, -5 nm or more, -4 nm or more, -3 nm or more, -2 nm or more, -1 nm or more, or It may be 0.5 nm or more, 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, 1 nm or less, or 0.5 nm or less.

In the present application, as the second retardation layer, for example, a retardation layer in which the Nz coefficient according to Equation 3 below is in the range of 0.5 to 1.5 while representing the in-plane retardation and/or the retardation in the thickness direction in the above range is applied. I can.

[Equation 3]

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

In Equation 3, 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, and n z} is the refractive index in the thickness direction of the layer.

In another example, the Nz coefficient of the second phase difference layer according to Equation 3 is 0.6 or more, 0.7 or more, 0.8 or more, 0.9 or more, 0.95 or more, or 1 or more, 1.4 or less, 1.3 or less, 1.2 or less, 1.1 or less, 1.05 or less Or it may be 1 or less.

In the present application, the second retardation layer may also have dispersion characteristics designed in a predetermined range while having the above-described in-plane retardation. The second retardation layer may have a dispersion coefficient for the in-plane retardation according to Equation 5 below, for example, in a range of greater than 0.5 and less than 1. That is, the second phase difference layer of the present application may exhibit negative dispersion characteristics.

[Equation 5]

Variance 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 dispersion coefficient for the in-plane phase difference according to Equation 5 may be greater than 0.6, greater than 0.7, greater than 0.8, greater than 0.9, less than 0.95, or less than 0.9 in another example.

In this specification, the term reverse wavelength dispersion property refers to a characteristic in which the birefringence (△) increases as the wavelength increases. In addition, the term birefringence (△ is the difference between the _{ideal refractive index (n e} ) and the normal refractive index (n _{o) (n e} -n _o ) In the case of the present application, by controlling the dispersion coefficient of the second retardation layer applied to the polarizing plate as described above, it has approximately the same retardation value in all visible light regions, thereby exhibiting an appropriate compensation effect. A polarizing plate that can be provided can be provided.

In the present application, the second phase difference layer has optical properties such as dispersion coefficient and/or in-plane retardation according to Equation 5 as described above and is combined with the above-described first phase difference layer at a predetermined position. By performing an appropriate compensation function according to the wavelength, an effect suitable for the purpose of the present application can be achieved.

In the present application, in the above arrangement of the polarizing plate, for example, the slow axis of the first retardation layer may be parallel to the absorption axis of the polarizing layer. In the above, the term parallelism is substantially parallel and means that the axes form an angle within the range of approximately 170 degrees to 190 degrees.

As described above, by making the slow axis of the first retardation layer and the absorption axis of the polarizing layer parallel to each other, and defining the angle between the slow axis of the second retardation layer and the absorption axis of the polarizing layer to be described later within a certain range, the intended effect of this application can be achieved. The optical path can be controlled so that it is possible.

In the present application, the second retardation layer may also have, for example, a slow axis parallel to the absorption axis of the polarizing layer.

In the present application, the angle between the slow axis of the first retardation layer and the absorption axis of the polarizing layer and/or the angle between the slow axis of the second retardation layer and the absorption layer of the polarizing layer may be, for example, about -10 degrees to 10 degrees. have. In the present specification, the angle between the slow axis and the absorption axis of the polarizing layer may mean a smaller angle among the angles formed by the slow axis and the absorption axis of the polarizing layer. The angle between the slow axis of the first and/or second phase difference layer and the absorption axis of the polarizing layer is, in another example, -9 degrees or more, -8 degrees or more, -7 degrees or more, -6 degrees or more, -5 degrees or more, -4 degrees or more, -3 degrees or more, -2 degrees or more, -1 degrees or more or 9 degrees or less, 8 degrees or less, 7 degrees or less, 6 degrees or less, 5 degrees or less, 4 degrees or less, 3 degrees or less, 2 degrees It may be less than or equal to 1 degree, and substantially the angle may be about 0 degrees.

The polarizing plate of the present application, for example, by controlling the optical properties of each phase difference layer and/or additional properties to be described later with the positional relationship as described above, a display device, in particular, an IPS (In-Plane Switching) mode having a non-contact alignment layer By being applied to a liquid crystal display device of, it is possible to provide a polarizing plate capable of securing a high CR (Contrast Ratio) even at an inclination angle and suppressing light leakage even in a so-called black state.

The polarizing plate of the present application may have a maximum light leakage of 1.6 cd/cm ² or less in a black state, for example. The maximum light leakage in the black state can be evaluated in a manner described below using an LCD display viewing angle polarization characteristic analyzer (ELDIM, ELDIM EZContrast 160R). In another example, 1.5 cd/cm ² or less, 1.4 cd/cm ² or less, 1.3 cd/cm ² or less, 1.2 cd/cm ² or less, 1.1 cd/cm ² or less, 1.0 cd/cm ² or less, 0.9 cd/cm ² or less, 0.8 cd/cm ² or less, 0.7 cd/cm ² or less, or 0.6 cd/cm ² or less, or 0.1 cd/cm ² or more, or 0.2 cd/cm ² or more.

The polarizing plate of the present application may include other elements above and/or below the polarizing layer and the first and second retardation layers, for example. However, the polarizing plate may include only the first and second retardation layers as retardation layers. That is, the polarizing plate may further include only a so-called isotropic layer except for the polarizing layer and the first and second retardation layers. The isotropic layer referred to in the present specification may be treated as an isotropic layer as long as it has a phase difference that does not damage the optical structure designed for the polarizing plate, even if the layer has a phase difference to some extent as a substantially isotropic layer. In one example, the term isotropic layer referred to in the present application is a layer in which the in-plane retardation and the retardation in the thickness direction are equal to or less than 20 nm. In another example, the retardation 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 retardation in the thickness direction exceed 20 nm may be treated as a retardation layer in the present application.

As the isotropic layer, for example, there may be a transparent substrate layer such as a glass or transparent plastic substrate layer. As the plastic substrate layer, a silulose substrate layer such as a DAC (diacetyl cellulose) or a TAC (triacetyl cellulose) substrate layer; A cyclo olefin copolymer (COP) substrate layer such as a norbornene derivative resin substrate layer; Acrylic substrate layer such as PMMA (poly(methyl methacrylate) substrate layer; PC (polycarbonate) substrate layer; olefin substrate layer such as PE (polyethylene) or PP (polypropylene) substrate layer); PVA (polyvinyl alcohol) substrate layer; PES (polycarbonate) substrate layer ether sulfone) base layer; PEEK (polyetheretherketone) base layer; PEI (polyetherimide) base layer; PEN (polyethylenenaphthalate) base layer; PET (polyethyleneterephthalate) base layer, such as polyester base layer; PI (polyimide) base layer; PSF (polysulfone) base layer ) Base layer: A PAR (polyarylate) base layer or a fluororesin base layer, etc. The base layer may be, for example, in the shape of a sheet or film.

As the first and second retardation layers, various types of retardation layers may be used without limitation, as long as the above-mentioned characteristics are satisfied.

In the present application, the first retardation layer may be a stretched polymer film in an example.

As the stretched 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, an acrylic film, a polyvinyl chloride film, and a polyacrylic film. Cellulose ester-based polymer films such as ronitrile film, polysulfone film, polyacrylate film, polyvinyl alcohol film or TAC (triacetyl cellulose) film, or PET (poly(ethylene terephthalate)) film or PC (polycarbonate) film, etc. A polyester film or a copolymer film of two or more monomers among the monomers forming the polymer may be used. In another example, as the stretched polymer film, a cyclic olefin polymer film or an acrylic film may be used. In the above, as the cyclic olefin polymer, a cyclic olefin ring-opening polymer such as norbornene or a hydrogenated product thereof, an addition polymer of a cyclic olefin, a copolymer of another comonomer such as a cyclic olefin and an alpha-olefin, or the polymer or Graft polymers in which the copolymer is modified with an unsaturated carboxylic acid or derivative thereof may be exemplified, but are not limited thereto.

However, in another example, the first retardation layer may be a liquid crystal polymerized layer including a polymerized vertically aligned polymerizable liquid crystal compound, and various types of retardation layers may be used without limitation if the above-described characteristics are satisfied.

In the present application, the second retardation layer may be a liquid crystal polymerization layer including a polymerized horizontal alignment polymerizable liquid crystal compound in an example.

In the liquid crystal polymerization layer, the liquid crystal compound may be included in an aligned state. The compound may be polymerized in a horizontal (homogeneous), vertical (homeotropic), tilted, spray (splay) or cholesteric (cholesteric) orientation state, for example, and included in the liquid crystal polymerization layer.

In one example, the liquid crystal compound may be included in the liquid crystal polymerization layer in a horizontally aligned state. In the present specification, the term "horizontal alignment" means that the optical axis of the liquid crystal polymerization layer containing the liquid crystal compound is about 0 to 25 degrees, about 0 to about 15 degrees, about 0 to about 10 degrees, and about 0 with respect to the plane of the liquid crystal polymerization layer. To about 5 degrees or about 0 degrees. In the present specification, the term "optical axis" may mean a slow axis or a fast axis when light passes through a corresponding region, and generally may mean a slow axis.

The liquid crystal polymerization layer may include, for example, a polymerizable liquid crystal compound, and may include the polymerizable liquid crystal compound in a polymerized form. In this specification, the term "liquid crystal polymerization layer" means a layer obtained by polymerizing a polymerizable liquid crystal compound in an aligned state. In addition, in the present specification, the term "polymerizable liquid crystal compound" may mean a compound including one or more polymerizable functional groups and including a moiety capable of exhibiting liquid crystallinity, for example, a mesogen skeleton, and the like, As such a polymerizable liquid crystal compound, a so-called polymerizable nematic liquid crystal compound, a polymerizable smectic liquid crystal compound, and the like are variously known. In addition, in the present specification, "including a polymerizable liquid crystal compound in a polymerized form" may mean a state in which the liquid crystal compound is polymerized to form a skeleton such as the main chain or side chain of the liquid crystal polymer in the liquid crystal polymerization layer. have.

It is effective to apply the polymerizable liquid crystal compound as described above to the second phase difference layer from the viewpoint of ease of adjustment of the dispersion coefficient, etc., but other types of films can be applied as long as the requirements of the present application are satisfied, and other examples In, it may be a stretched polymer film.

There is no particular limitation on the thickness of the first and second retardation layers, and may be appropriately selected within a range capable of representing a desired retardation.

The types of the first and second phase difference layers are controlled as described above, and are combined at a predetermined position, thereby performing an appropriate compensation function according to wavelength for light in the visible region, even at an inclination angle, in CR (Contrast Ratio) and black mode. A polarizing plate capable of controlling light leakage may be provided.

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

In order to secure proper performance, the polarizing plate of the present application includes the polarizing layer protective film attached to one surface of the polarizing layer, and the first and second retardation layers are directly provided without a protective film on the other surface of the polarizing layer. It can have a structure that is attached in sequence. In addition, a pressure-sensitive adhesive layer or an adhesive layer for attaching the polarizing plate to the display device may be present under the second retardation layer.

The present application also relates to a liquid crystal display device. An exemplary liquid crystal display device may include the polarizing plate.

The specific type of the liquid crystal display device including the polarizing plate 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.

In the liquid crystal display device of the present application, the arrangement form of the polarizing plate is not particularly limited, and for example, a known form may be employed.

As described above, the polarizing plate is applied to a liquid crystal display device in a plane switch (IPS, In-Plane Switching) mode among various display devices, so that effective optical compensation is possible. It can be effectively applied in liquid crystal displays.

The configuration of the liquid crystal display of the planar switch mode to which the polarizing plate of the present application is applied is not particularly limited. That is, the polarizing plate may be applied according to a known application method of a polarizing plate in a liquid crystal display of a known planar switch mode, and the planar switch mode may also include a so-called O mode or E mode, and is not particularly limited.

Such a liquid crystal display generally includes two substrates disposed opposite to each other; A liquid crystal layer positioned between the two substrates; And a liquid crystal panel in a planar switch mode including a liquid crystal alignment layer disposed between the liquid crystal layer and at least one of the two substrates, and including polarizing plates attached to both sides of the liquid crystal panel, at least of which As the polarizing plate disposed on one side, the above-described polarizing plate may be used. In the present specification, the term liquid crystal layer is a liquid crystal layer that is generally applied to an LCD and refers to a layer capable of switching alignment by an electric field signal.

In this case, the polarizing plate may be, for example, an upper polarizing plate or a viewer-side polarizing plate. That is, a liquid crystal display generally includes a liquid crystal panel, a polarizing plate attached to both sides thereof, and a backlight unit (BLU) disposed adjacent to any one of the two polarizing plates. The arranged polarizing plate may be generally referred to as a lower polarizing plate, another polarizing plate may be referred to as an upper polarizing plate, and the upper polarizing plate may be a viewer-side polarizing plate.

The polarizing plate applied to the liquid crystal display of the present application may be applied as the viewer-side polarizing plate in an example, but the application position is not limited thereto. When the polarizing plate of the present application is applied as a viewing side polarizing plate, a known polarizing plate may be applied as a lower polarizing plate without any particular limitation. However, it is effective that no other retardation layer exists between the polarizing layer of the upper polarizing plate and the polarizing layer of the lower polarizing plate except for the first and second retardation layers and the liquid crystal layer of the liquid crystal panel.

In the present application, for example, the liquid crystal panel may have an in-plane retardation of about 100 to 500 nm based on a wavelength of 550 nm when horizontally aligned. In another example, it may be within a range of about 200 nm or more, 300 nm or more, 310 nm or more, or 320 nm or more, or 400 nm or less, 390 nm or less, 380 nm or less, 370 nm or less, or 360 nm or less. The polarizing plate of the present application may be applied together with a liquid crystal panel having an in-plane retardation in the above range when horizontally aligned to provide a liquid crystal display having a desired effect.

The liquid crystal alignment layer included in the liquid crystal display of the present application may exist in, for example, two layers on each surface facing each other in the two substrates that are normally arranged oppositely in the above-described structure. The liquid crystal alignment layer has 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 , May be about 0 degrees. A method of checking such a pretilt angle is known, and for example, a Crystal Rotation method or the like may be applied.

In the present application, the kind of the liquid crystal alignment layer is not particularly limited, and a non-contact alignment layer such as a photo-alignment layer generally exhibits a pretilt angle within the above-described range.

The present application shows an excellent viewing angle compensation effect by applying a polarizing plate having the above optical properties and/or arrangement, in particular, with a liquid crystal panel in a planar switch mode including the non-contact alignment layer, and light leakage in a black state. It is possible to provide a liquid crystal display device in which development is controlled.

The present application is particularly applied to a liquid crystal display device of a relatively symmetric plane switch mode, thereby providing a polarizing plate capable of controlling light leakage in a black state while securing a high CR (Contrast Ratio) even at an inclination angle. I can.

1 is a diagram for explaining the structure of a liquid crystal panel.
2 is a diagram for describing an inclination angle and a moving angle.
3 is a diagram showing an exemplary structure of a polarizing plate of the present application.
4 to 7 are diagrams showing simulation results of maximum light leakage in a black state for a polarizing plate designed according to an embodiment.

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

One. In-plane retardation, thickness direction retardation and Nz coefficient evaluation of retardation layer

The in-plane retardation, thickness direction retardation, and Nz coefficient of each retardation layer applied in Examples or Comparative Examples were evaluated by analyzing the polarization state of transmitted light using a retardation measuring device (Jungwon Tongsang Co., Ltd., Axoscan). A method of measuring the in-plane retardation, the thickness direction retardation, and the Nz coefficient of the retardation layer using such equipment is known.

2. Evaluation of the dispersion characteristics of the retardation layer

The dispersion characteristics of each retardation layer applied to the Examples or Comparative Examples were derived through the ratio of the values by evaluating the in-plane retardation or the retardation in the thickness direction for the light having a wavelength of 450 nm and 550 nm in the manner described above.

3. Evaluation of maximum light leakage in the black state

The maximum light leakage in the black state was evaluated using an LCD display viewing angle polarization characteristic analyzer (ELDIM, ELDIM EZContrast 160R).

For the evaluation, a liquid crystal panel in a planar switch mode (cell gap: 3.2 μm, filled with a liquid crystal having positive dielectric anisotropy) to which a non-contact alignment layer (photo-alignment layer) was applied was used. The pre-tilt angle of the alignment layer (photo-alignment layer) of the liquid crystal panel was approximately within 0.3 degrees, and the pre-tilt angle was confirmed by the Crystal Rotation method.

As an upper polarizing plate, a polarizing plate prepared in Examples or Comparative Examples was attached to the liquid crystal panel as described above, and a polarizing plate already provided in the liquid crystal panel was used as the lower polarizing plate.

The liquid crystal panel configured as described above was set in a black state, and the maximum light leakage was evaluated using the analyzer.

Example 1.

When manufacturing the polarizing plate, the polarizing layer is an iodine-based PVA (Poly (vinyl alcohol)) polarizing film, which has a single transmittance (based on a 550 nm wavelength) of about 42% and a polarization degree (based on a 550 nm wavelength) of about 99.995, and A PVA film having a thickness of about 7 μm was used.

As the first retardation layer, the in-plane retardation Rin for light having a wavelength of 550 nm is 57 nm, the retardation Rth in the thickness direction is 85 nm, the Nz value according to Equation 3 is -0.491, and the dispersion coefficient according to Equation 4 is 1.06 A stretched polymer film (Okura Co., Ltd., thickness of 40 µm) of about the degree was used.

As the second retardation layer, a liquid crystal film prepared by horizontally aligning a polymerizable liquid crystal compound (Merck, RMM2032) and polymerizing in that state was applied. In the liquid crystal film, a known horizontal alignment layer was formed on one surface of an NRT (No Retardation TAC) film as a base film, a coating layer of the polymerizable liquid crystal compound was formed thereon, and after horizontal alignment under alignment conditions, ultraviolet rays were irradiated. Was prepared.

The thickness of the second retardation layer prepared as described above was about 2 μm, the in-plane retardation was 91 nm, the dispersion coefficient according to Equation 5 was 0.84, and the Nz coefficient was about 1.

As a protective film on one side of the PVA polarizing film, an NRT (No Retardation TAC) film (Fuji) having a thickness of about 40 μm was attached with an adhesive. Subsequently, the first retardation layer was attached to the other side of the PVA polarizing film, that is, the side to which the NRT film was not attached, with an adhesive, and finally, the second retardation layer was attached to the first retardation layer with an adhesive. .

Thereafter, an adhesive layer was formed under the second phase difference layer.

At this time, the first phase difference layer and the second phase difference layer are disposed so that their slow axis is parallel to the absorption axis of the polarizing layer.

As a result, a polarizing plate having a structure of an NRT film (substrate film)/PVA polarizing film (polarizing layer)/first retardation layer/second retardation layer/adhesive layer was produced.

After designing the polarizing plate as described above using the TechWiz LCD 1D equipment, the maximum light leakage in the black state was evaluated.

Examples 2 to 64.

The in-plane retardation (Rin), the thickness direction retardation (Rth) for the light of the 550 nm wavelength of the first retardation layer, the dispersion coefficient according to Equation 4, the in-plane retardation (Rin) of the second retardation layer, and the dispersion coefficient according to Equation 5 are as follows: Designed in the same manner as in Example 1, except for the ones shown in Table 1, the maximum light leakage in the black state was evaluated, and the results are shown in FIGS. 4 to 7. In FIGS. 4 to 7, +B denotes a first retardation layer, and A denotes a second retardation layer.

[Table 1]

Graphs of the results of evaluating maximum light leakage in the black state for the polarizing plates of Examples 1 to 64 are shown in FIGS. 4 to 7.

For example, the +B57/85 (1.06) graph in FIG. 4 is for Examples 1 to 4, and in the x-axis of the graph, A91 (0.84), A98 (0.84), A105 (0.84), A112 (0.84) ) Points represent the results for each of Examples 1 to 4. That is, when Rin (nm) of the first phase difference layer (+B) is 57 nm, Rth (nm) is 85 nm, and the dispersion coefficient according to Equation 4 is 1.06 (+B57/85 (1.06)), the second phase difference The maximum light leakage in the black state for the polarizing plate of Example 1 in which the Rin (nm) of the layer (A) was 91 nm and the dispersion coefficient according to Equation 5 was 0.84 (A91 (0.84) point) was about 0.8 cd/m ² , The maximum light leakage in the black state for the polarizing plate of Example 2 in which the Rin (nm) of the second retardation layer (A) is 98 nm and the dispersion coefficient according to Equation 5 is 0.84 (A98 (0.84) point) is about 0.8 cd/m ² , the maximum light leakage in the black state for the polarizing plate of Example 3 in which the Rin (nm) of the second phase difference layer (A) is 105 nm, and the dispersion coefficient according to Equation 5 is 0.84 (A105 (0.84) point) is about 1.0. cd/m ² , The maximum light leakage in the black state for the polarizing plate of Example 4 in which the Rin (nm) of the second retardation layer (A) is 112 nm and the dispersion coefficient according to Equation 5 is 0.84 (A112 (0.84) point) is It was confirmed that it was about 1.3 cd/m ^2.

Claims (11)

A polarizing layer;
A first retardation layer located under the polarizing layer, wherein the retardation in the plane for light having a wavelength of 550 nm is in the range of 50 to 70 nm, and the retardation in the thickness direction for light having a wavelength of 550 nm according to Equation 2 below is in the range of 80 to 100 nm ; And
A polarizing plate including a second retardation layer positioned under the first retardation layer and having an in-plane retardation with respect to light having a wavelength of 550 nm within a range of 90 to 115 nm:
[Equation 2]
Rth = d × (nz-ny)
In Equation 2, Rth is the retardation in the thickness direction, d is the thickness of the retardation layer, nx is the refractive index in the slow axis direction of the retardation layer, ny is the refractive index in the fast axis direction of the retardation layer, and nz is the refractive index in the thickness direction of the retardation layer. to be.
The polarizing plate of claim 1, wherein the first retardation layer has a dispersion coefficient of 1 or more and less than 1.2 according to Equation 4 below:
[Equation 4]
Variance Coefficient = Rth(450)/Rth(550)
In Equation 4, Rin (450) is the in-plane retardation with respect to the 450 nm wavelength of the first retardation layer, and Rin (550) is the in-plane retardation of the first retardation layer with respect to the 550 nm wavelength.
The polarizing plate of claim 1, wherein the second retardation layer has a dispersion coefficient of greater than 0.5 and less than 1 according to Equation 5 below:
[Equation 5]
Variance Coefficient = Rin(450)/Rin(550)
In Equation 5, Rin (450) is the in-plane retardation with respect to the 450 nm wavelength of the second retardation layer, and Rin (550) is the in-plane retardation of the second retardation layer with respect to the 550 nm wavelength.
The polarizing plate of claim 1, wherein the first retardation layer has an Nz value in the range of -0.6 to -0.2 according to Equation 3 below:
[Equation 3]
Nz = (nx-nz)/(nx-ny)
In Equation 3, nx is a refractive index of the first retardation layer in the slow axis direction, ny is a refractive index of the retardation layer in the fast axis direction, and nz is a refractive index of the first retardation layer in the thickness direction.
The polarizing plate according to claim 1, wherein a slow axis of the first retardation layer and an absorption axis of the polarizing layer are parallel.
The polarizing plate according to claim 1, wherein a slow axis of the second retardation layer and an absorption axis of the polarizing layer are parallel.
The polarizing plate according to claim 1, wherein the first retardation layer is a stretched polymer film.
The polarizing plate according to claim 1, wherein the second retardation layer is a liquid crystal polymerized layer comprising a polymerized horizontally aligned polymerizable liquid crystal compound.
The polarizing plate of claim 1, wherein the retardation layer includes only the first and second retardation layers.
Two substrates disposed opposite to each other; A liquid crystal layer positioned between the two substrates; And a liquid crystal panel in a planar switch mode including a liquid crystal alignment layer disposed between the liquid crystal layer and at least one of the two substrates. And
A liquid crystal display device comprising the polarizing plate of claim 1 disposed on at least one surface of the liquid crystal panel.
The liquid crystal display device according to claim 10, wherein the pretilt angle of the liquid crystal aligning film is less than 1 degree.

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