KR101486748B1 - Upper plate polarizer and in-plane switching mode liquid crystal display comprising the same - Google Patents

Abstract

The present invention relates to a polarizing plate comprising a negative biaxial A plate having a specific optical property from a liquid crystal cell side, a positive biaxial A plate, a top polarizer polarized in the order of a polarizer and a protective layer, And more particularly to a planar switching mode liquid crystal display device capable of securing a wide viewing angle and facilitating mass production of a polarizing plate composed of a composite.

Plane switching mode, liquid crystal display, polarizer

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to an upper plate polarizer, and a planar switching mode liquid crystal display including the upper plate polarizer,

The present invention relates to a negative biaxial A plate and a positive biaxial A plate having a specific optical property from a liquid crystal cell side and a positive biaxial A plate so that a wide viewing angle can be ensured and a polarizing plate laminated in the order of a polarizer and a protective layer, PLANE SWITCHING, hereinafter referred to as IPS) mode liquid crystal display.

2. Description of the Related Art A liquid crystal display (LCD) is widely used as a popular image display device. However, despite its many excellent properties, a narrow viewing angle has been pointed out as a typical drawback. Accordingly, techniques for securing a wide viewing angle by applying a functional optical film such as a liquid crystal driving mode and a retardation film have appeared. In addition, a liquid crystal display device in which a liquid crystal driving mode (IPS mode) It has been widely known that it has an excellent effect on the surface of the substrate.

In a surface switching mode (IPS mode), liquid crystal is driven using a transverse electric field. In modes such as TN (Twisted Nematic) and VA (Vertical Alignment), liquid crystal and electric field directions [Vertical alignment] between the upper and lower substrates, while the IPS mode uses the horizontally oriented liquid crystal to form the direction of the electric field parallel to the liquid crystal alignment direction.

Since the liquid crystal molecules in the plane switching mode have a substantially horizontal and uniform arrangement on the substrate surface in the non-driven state, when the transmission axis of the lower plate and the fast axis direction of the liquid crystal molecules coincide with each other, Even if the light passing through the lower plate polarizer passes through the liquid crystal, it does not cause a change in the polarization state, so that it can pass through the liquid crystal layer in its original state. As a result, It is possible to display a certain degree of darkness in the non-driving state by arranging the polarizing plates on the surface. Such a planar switching mode liquid crystal display device is generally capable of obtaining a wide viewing angle without using an optical film, ensuring a natural transmissivity, and having an image quality and a viewing angle uniform over the entire screen. Therefore, the surface switching mode liquid crystal device is used as a main type in an advanced model of 18 inch or more.

Conventionally, in a liquid crystal display device using a planar switching mode, a polarizing plate for polarizing light is required on the outside of a liquid crystal cell containing a liquid crystal, and a protective film made of triacetylcellulose (TAC) Is provided for protecting the polarizer (PVA). In this case, when the liquid crystal represents the black state, the light polarized by the polarizer provided on the lower plate is elliptically polarized by triacetylcellulose on the inclined surface, not on the front surface, and the elliptically polarized light is polarized in the liquid crystal cell There is a problem that the light has various colors simultaneously with the light leakage.

In addition, since an image display device such as a large-sized TV using a surface switching mode is manufactured, a wide viewing angle characteristic is required. Therefore, in order to secure a wide viewing angle in an IPS-LCD, an isotropic protective layer is used instead of a TAC film between a polarizer (PVA) and a liquid crystal cell to eliminate elliptical polarization caused by triacetyl cellulose, However, it is pointed out that it is difficult to secure a wide viewing angle because the compensation of the absorption axis of the polarizer is not performed on the inclined plane, and light leakage phenomenon occurs.

Therefore, a new polarizing plate structure capable of mass production is desperately required by easily producing a composite polarizing plate including a retardation film by using a roll-to-roll production mode together with various compensation structures for securing an excellent optical viewing angle.

The present invention improves the problem that it is difficult to realize a perfect wide viewing angle in a dark state due to a light leakage phenomenon that occurs due to the absorption axis compensation of a polarizer of a conventional IPS mode liquid crystal display device using a conventional isotropic protection layer.

Accordingly, it is an object of the present invention to compensate the polarizer absorption axis of the lower plate by using the upper plate polarizer including the retardation film having various lamination structures and the retardation value design as a method of changing the structure of the compensation film to secure a wider viewing angle And a top plate polarizer capable of being manufactured using a roll-to-roll production mode. Specifically, by using a negative biaxial A plate having a specific optical property from the liquid crystal cell side, a positive biaxial A plate, and a polarizer and a protective layer, which are stacked in this order on a liquid crystal display device of plane switching mode, And to provide a planar switching mode liquid crystal display device that provides a wider viewing angle than a conventional liquid crystal display device because light leakage caused by a change in viewing angle can be minimized in a dark state.

The present invention relates to a top plate polarizing plate for a planar switching (IPS) mode in which a negative biaxial A plate, a positive biaxial A plate, a polarizer and a protective layer are laminated in that order from the liquid crystal cell side, wherein the negative biaxial A plate has a front retardation value R0) is from 20 to 110 nm, the refractive index ratio (NZ) is from 1.01 to 3.5, the slow axis is parallel to the absorption axis of the adjacent polarizer; The positive biaxial A plate is characterized by a top plate polarizer having a front retardation (R0) of 40 to 120 nm, a refractive index ratio (NZ) of -1.2 to -0.01 and a slow axis parallel to the absorption axis of the adjacent polarizer .

In addition, the present invention is further characterized in that the IPS mode liquid crystal display device including the upper plate polarizer.

The planar switching mode liquid crystal display device according to the present invention includes a negative biaxial A plate having a specific optical property and a positive biaxial A plate and a polarizer and a protective layer laminated in this order from the liquid crystal cell side, By making it possible to realize a dark state, it is possible to have a wider viewing angle than in the prior art, and mass production is easy.

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a top plate polarizer capable of compensating a light leakage in a liquid crystal cell when applied to a liquid crystal display device of a surface switching mode, thereby enabling a dark state at a wide viewing angle. This top plate polarizer is composed of a negative biaxial A plate, a positive biaxial A plate, a polarizer and a protective layer laminated in this order from the liquid crystal cell side.

The 'NEGATIVE BIAXIAL A plate' in this specification refers to a positive biaxial optical element theoretically satisfying a refractive index distribution of nx> ny> nz and is also referred to as a 'negative B plate'. Here, the positive optical element means a material having a large refractive index in the stretching direction.

Also, 'POSITIVE BIAXIAL A plate' refers to a negative biaxial optical element satisfying nz> nx> ny, which is also referred to as a 'positive B plate'. Here, the negative optical element refers to a material whose refractive index decreases in the stretching direction.

The negative biaxial A plate disposed on the top plate polarizing plate preferably has a front retardation value (R0) of 20 to 110 nm and a refractive index ratio (NZ) of 1.01 to 3.5. When it is desired to exhibit better optical viewing angle characteristics, (R0) of 25 to 105 nm and a refractive index ratio (NZ) of 1.1 to 3.2, more preferably a front retardation value (R0) of 30 to 100 nm and a refractive index ratio (NZ) of 1.2 to 3 . The slow axis of such a negative biaxial A plate is configured to be parallel to the absorption axis of the adjacent polarizer at the viewer side.

The positive biaxial A plate (positive B plate) laminated on the upper surface of the negative biaxial A plate from the liquid crystal cell side has a front retardation value R0 of 40 to 120 nm and a refractive index ratio NZ of -1.2 to -0.01 The frontal retardation value R0 is preferably 45 to 115 nm and the refractive index ratio NZ is preferably -1.1 to -0.1, more preferably the frontal retardation value R0 is 50 To 110 nm, and the refractive index ratio (NZ) is preferably maintained at -1 to -0.2. Such a positive biaxial A plate may be a structure in which polymethylmethacrylate (PMMA), polystyrene (PS) and polymethylmethacrylate (PMMA) are sequentially laminated or a structure in which at least one layer is modified polycarbonate (PC) . The slow axis of this positive biaxial A plate is configured to be parallel to the absorption axis of the adjacent polarizer at the viewer side.

The negative biaxial A plate and the positive biaxial A plate are not limited to the materials and can be applied to the present invention as long as they satisfy the optical properties within the limits defined by the present invention. Specifically, a triacetyl cellulose (TAC), a cycloolefin polymer (COP), a cycloolefin copolymer (COC), polyethylene terephthalate (PET), polypropylene (PP), polycarbonate (PC), polysulfone (PSF) and a poly Methyl methacrylate (PMMA) may be used.

(IPS) mode liquid crystal display device is constructed by laminating a top plate polarizer manufactured according to the present invention. At this time, the liquid crystal display of the present invention includes aligning the liquid crystal in a multi-domain or dividing the liquid crystal into multiple regions by a voltage applied thereto. The liquid crystal display device is classified into IPS (In-Plane-Switching), Super-In-Plane-Switching (IPS), and Fringe-Field-Switching (FFS) according to the mode of the active matrix driving electrode including the electrode pairs The IPS-LCD of the present invention is Super-In-Plane-Switching (IPS), and the liquid crystal alignment is parallel to the absorption axis of the polarizer of the lower polarizer.

The lower panel polarizer of the planar switching mode liquid crystal display device is generally used in the art, and an isotropic protective layer is applied to secure a wide viewing angle. Specifically, the liquid crystal cell is composed of an isotropic protective layer, a polarizer and a protective layer in this order, and the polarizer absorption axis of the upper plate polarizer and the polarizer absorption axis of the lower plate polarizer are mutually orthogonal.

The isotropic protective layer and the protective layer constituting the lower plate polarizing plate and the material forming the protective layer constituting the upper plate polarizing plate may be independently of one another and those generally used in the art may be applied. Specifically, triacetyl cellulose (TAC) (COP), cycloolefin copolymer (COC), polyethylene terephthalate (PET), polypropylene (PP), polycarbonate (PC) , polysulfone (PSF) and polymethylmethacrylate Can be used. Preferably, the isotropic protective layer has a front retardation (RO) and a thickness direction retardation (Rth) of less than 10 nm, preferably less than 2 nm, and the protective layer of the upper plate and the lower plate polarizer has an optical characteristic according to a difference in refractive index, The refractive index characteristics are not particularly limited in the present invention.

The retardation films such as the negative biaxial A plate constituting the top plate polarizer and the isotropic protective layer of the positive biaxial A plate and the bottom plate polarizer are arranged such that the thickness direction is defined as a z-axis, the direction having a large in- And the vertical direction is a y-axis, the refractive indices corresponding to the respective directions are Nx, Ny, and Nz, the thickness direction retardation (Rth) defined by the following equation (1) ) And a refractive index ratio (NZ) defined by the following equation (3). At this time, the characteristics of the retardation film are determined according to the refractive index, and there are two optical axes (biaxial retardation film) in which there is no retardation when the birefringence indexes are different from each other. Since the optical characteristics of each film to be implemented by the present invention are physical properties at a light source of 589.3 nm and the light source range is a standard when referring to optical characteristics in general, when there is no special description about a light source, the value at a light source of 589.3 nm .

Rth = [(Nx + Ny) / 2-Nz] xd

(Where Nx and Ny are surface refractive indices Nx > = Ny, Nz is refractive index in the thickness direction of the film, and d is the thickness of the film)

R0 = (Nx - Ny) xd

(Where Nx and Ny are the surface refractive indexes of the retardation film and d is the thickness of the film, where Nx > = Ny)

NZ = (Nx - Nz) / (Nx - Ny) = Rth / R0 + 0.5

(Where Nx and Ny are surface refractive indices Nx > = Ny, Nz is refractive index in the thickness direction of the film, and d is the thickness of the film)

As described above, the present invention is not a conventional abstract viewing angle compensation concept, but rather a top plate polarizer which can be practically applied to mass production and has a better viewing angle compensation effect, and a planar switching mode liquid crystal display device using the same. The surface-switched liquid crystal display device constructed in accordance with the optical condition of the present invention satisfies the compensation relationship of the maximum visual sensitivity transmittance of 0.05% or less, preferably 0.02% or less. The value of 0.02% or less is a similar and improved value in the range of the omnidirectional maximum transmittance of a general plane switching liquid crystal display device. In general, it is not a dark room in a range of 0.1% Respectively.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a perspective view showing a basic structure of a planar switching liquid crystal display (IPS-LCD) according to the present invention.

The IPS mode liquid crystal display device according to the present invention is manufactured by stacking the lower plate polarizer 10, the liquid crystal cell 30 and the upper plate polarizer 20 in this order from the backlight unit 40 side to the lower plate polarizer 10 and the upper plate polarizer The protective layers 13 and 23 are located on the opposite sides of the liquid crystal cell of the polarizers 11 and 21 of the liquid crystal display panel 20. The upper plate polarizer 20 is laminated in the order of a negative biaxial A plate 24, a positive biaxial A plate 25 and a polarizer 21 from the liquid crystal cell side and the lower plate polarizer 10 is laminated in the order of the polarizer 11 And an isotropic protective layer 14 is laminated on the liquid crystal cell side.

More specifically, it comprises a lower plate polarizer 10, a horizontally aligned liquid crystal cell 30 filled with liquid crystal having a positive dielectric constant anisotropy (DELTA epsilon > 0) between the two glass substrates, and a top plate polarizer 20, An active matrix drive electrode including an electrode pair is formed on an adjacent surface of the liquid crystal cell 30 in any one of the glass substrates of the liquid crystal cell 30.

In the liquid crystal cell 30, the panel retardation value (DELTA n x d) defined by the following Equation 4 is in the range of 300 to 400 nm at a wavelength of 589 nm of the surface switching liquid crystal display device, It is preferably about 315 nm. In order to allow the IPS-LCD panel to pass through the liquid crystal cell 30 after passing through the lower polarizer plate 10 and linearly polarized in the horizontal direction, the IPS- This is because the retardation value of the liquid crystal cell 30 of the panel must be a half wavelength of 589 nm (the brightest monochromatic light the human senses). At this time, it may be adjusted to be slightly longer or shorter than half wavelength so as to become white color.

Δn × d = (ne-no) × d

(Where ne is the extraordinary ray refraction index of the liquid crystal, no is the normal ray refraction index, d is the cell gap, note Δn, d is a scalar rather than a vector)

The negative biaxial A plate 24 constituting the upper plate polarizer 20 may have a front retardation value R0 of 20 to 110 nm and a refractive index ratio NZ of 1.01 to 3.5. Is configured to be parallel to the absorption axis of the adjacent polarizer at the front side of the viewer side.

The positive biaxial A plate 25 may have a front retardation value R0 of 40 to 120 nm and a refractive index ratio NZ of -1.2 to -0.01. The slow axis may be a front face Is parallel to the absorption axis of the adjacent polarizer.

In a specific embodiment, a three-layer structure is formed by sequentially extruding polymethylmethacrylate (PMMA), polystyrene (PS), and polymethylmethacrylate (PMMA) . At this time, the change of the refractive index through the stretching mainly acts as a protective layer of polymethylmethacrylate (PMMA) in order to protect the brittle polystyrene (PS) layer generated in the polystyrene (PS) layer.

The absorption axis 12 of the lower plate polarizer 10 and the absorption axis 22 of the upper plate polarizer 20 are arranged perpendicular to each other and the absorption axis 12 of the lower plate polarizer 10 and the absorption axis 22 of the upper plate polarizer 20 are included in the liquid crystal cell 30 The alignment directions 31 of the liquid crystals are arranged in parallel with each other.

Fig. 2 shows the relationship between the alignment direction of the liquid crystal and the absorption axis. The alignment direction 31 indicates the direction in which the liquid crystal is arranged when viewed from the viewer side (opposite to the backlight unit), the lower plate polarizer 10, (22) of the polarizing plate (20).

Polyvinyl alcohol (PVA) layers 11 and 21, which are polarizers imparted with a polarizing function through stretching and dyeing, are placed on the lower plate polarizer 10 and the upper plate polarizer 20, and polyvinyl alcohol (PVA) Protective films 13 and 23 are disposed on the opposite side of the liquid crystal cell 30 in the polyvinyl alcohol (PVA) layer 11 and the top plate polarizer. Since the protective film 13 of the lower polarizer 10 and the protective film 23 of the upper polarizer 20 do not affect the viewing angle due to the difference in refractive index, the refractive index characteristics of the present invention are not particularly limited .

The upper plate polarizer 20 and the lower plate polarizer 10 of the present invention are manufactured by applying a roll-to-roll method which is easy to mass-produce. FIG. 4 is a schematic view for explaining the MD direction in the normal roll-to-roll manufacturing process. Referring to FIG.

The upper plate and lower plate polarizers 10 and 20 are made of a combination of various optical films, and each optical film exists in a roll state before being bonded to the composite polarizer plate. The direction in which the film is unwound or wound in this roll is referred to as the MD (Machine Direction) direction. In the case of the lower plate polarizer 10, the direction of the protective layer 13 and the isotropic protective layer 14 does not affect the optical performance and roll-to-roll production is possible. In the case of the top plate polarizer 20, (Roll To Roll) production is possible if the MD direction of the polarizer 21, the negative biaxial A plate 24, and the positive biaxial A plate 25 are matched only with each other, . Specifically, the absorption axis 22 of the polarizer 21 in the upper plate polarizer 20 is in the MD direction. This is because when the polarizing function is given by the polarizer, the PVA fabric, which is used as the polarizer material, Direction, the absorption direction of light becomes the MD direction by iodine dyeing, and the negative biaxial A plate 24 is subjected to biaxial stretching using a film having a positive refractive index property with a larger refractive index with respect to the stretching direction, Wherein the direction of the slow axis is formed in the MD direction and the positive biaxial A plate 25 is formed by using a film having a negative refractive index property with a small refractive index with respect to the stretching direction, The stretching is performed in the orthogonal direction to give a phase difference, and the slow axis 26 becomes the MD direction. At this time, the refractive index ratio becomes Nz (thickness direction) > Nx (MD direction) > Ny because if the film end having the negative refractive index characteristic is vertically stretched in the MD direction to give a retardation, Since Nx is fixed and Ny direction is stretched because there is almost no change in length in the direction of Nz, Nz becomes large because the size is small and the thickness is reduced through stretching.

Further, in the present invention, the absorption axis 12 of the polarizer 11 of the lower plate polarizer 10 should be positioned in the vertical direction when viewed from the viewer's side. Specifically, when the absorption axis 12 of the lower plate polarizer 10 close to the backlight unit 40 is vertical, light passing through the lower plate polarizer 10 is polarized in the horizontal direction, The light passes through the top plate polarizer 20 on the viewer side in which the absorption axis is in the horizontal direction. At this time, a person wearing a polarized sunglass having an absorption axis in the horizontal direction (the absorption axis of the polarized sunglasses is in the horizontal direction) on the viewer side can recognize light emitted from the liquid crystal display device. If the absorption axis 12 of the lower plate polarizer 10 close to the backlight unit 40 is in the horizontal direction, there is a problem that the image is not seen by the person wearing the polarized sunglasses. In addition, in the case of a large-sized liquid crystal display device, in order to make the image clearly visible from the viewer's view, considering that the human's field of view is wider than the vertical direction, the general liquid crystal display device except for the special- Since the main field of view is wider in the horizontal direction than in the vertical direction, it is produced in the form of 4: 3 or 16: 9.

The slow axis 26 of the negative biaxial A plate of the present invention and the slow axis 26 of the positive biaxial A plate are configured such that light is transmitted through the negative biaxial A plate 24 and the positive biaxial A plate 25, Refers to the axis through which the light is most slowly passed by the retardation film and refers to the axis having the greatest refractive index. This means that the optical axis which does not cause a phase difference when passing through the retardation film ). When the liquid crystal displays the black, the absorption axes 12 and 22 of the polarizers 10 and 20 orthogonal to the viewer-side surface can not maintain orthogonal states due to their geometrical characteristics on a slope other than the front surface, And the angle of view is narrowed by the light. Since the optical system can maintain the absorption axes 12 and 22 orthogonal to each other between the polarizers 11 and 21 of the upper and lower polarizers 10 and 20, . The absence of light leakage under the above-mentioned retardation value condition of the present invention can be explained through the Poincare sphere.

Fig. 5 is a planar switching mode liquid crystal display device arranged in the configuration of Fig. 1 using a film having optical properties according to the present invention. This liquid crystal display device is a liquid crystal display device in which, in a coordinate system defined by Fig. 6 on a Poincare Sphere, The change of the polarization state in the direction of the light θ = 60 ° and φ = 45 ° at the wavelength of 550 nm of the light felt bright is shown. 1, the light that has passed through the polarizer 11 on the backlight side 40 is polarized in the polarized state 1 on the Poincare Sphere and passes through the isotropic protective layer 14, 3, 4, and 5 on the Poincare Sphere while passing through the cell 30, the negative biaxial A plate 24, and the positive biaxial A plate 25. [ Specifically, the light having passed through the polarizer 11 of the lower plate polarizer 10 is polarized in the polarization state 1, passes through the isotropic protection layer 14 having almost no phase difference to become the polarization state 2, and the polarization state 3 becomes the IPS liquid crystal cell There is almost no change because the fast axis of the polarizing plate 30 and the polarizing direction of the polarizing state 2 are almost the same and the polarizing state 4 is the polarizing state changed by the retardation of the negative biaxial A plate 24, The polarization state 5 after passing through the A-plate becomes a state in which the polarizer is orthogonal to the state as mentioned above, so that light does not leak and the viewing angle becomes wider.

Hereinafter, the effect of implementing the dark state at the full viewing angle when the voltage is applied according to the above configuration is summarized in the embodiment and the comparative example. The present invention can be better understood by the following examples, and the following examples are intended to illustrate the present invention and are not intended to limit the scope of protection defined by the appended claims.

Example

In the following Embodiments 1 to 6 and Comparative Examples 1 to 4, simulation was performed by applying to an LCD simulation program TECH WIZ LCD 1D (Manai System, KOREA) to compare the wide viewing angle effect.

Example 1

Actual data such as each optical film, liquid crystal cell, and backlight according to the present invention were stacked on a TECH WIZ LCD 1D (MANAMA SYSTEM, KOREA) as shown in FIG. The structure of FIG. 1 will be described in detail as follows.

The backlight unit 40 , the lower plate polarizer 10, the liquid crystal cell 30 and the upper plate polarizer 20 are sequentially laminated. The lower plate polarizer 10 includes a protective layer 13, A positive biaxial A plate 25, a polarizer 21, and an isotropic protective layer 14 in this order from the side of the liquid crystal cell. Layer 23 in this order.

At this time, the polarizers 11 and 21 were given the function of a polarizer through stretching and dyeing, and the polarizers 10 and 20 were arranged orthogonal to each other on both sides of the IPS mode liquid crystal cell 30. The absorption axis 12 of the lower polarizer 10 and the alignment direction 31 of the liquid crystal contained in the liquid crystal cell 30 are referred to as an absorption axis of the polarizer 21 of the upper polarizer 20, The absorption axes of the polarizing plate 11 are orthogonal to each other and the absorption axis of the polarizer 11 of the lower plate polarizing plate and the alignment direction 31 of the liquid crystal are arranged in parallel.

Protective layers 13 and 23 are arranged on the opposite side of the liquid crystal cell 30 of the polarizer 11 of the lower plate polarizer 10 and the polarizer 21 of the upper plate polarizer. A negative biaxial A plate 24 and a positive biaxial A plate 25 are arranged between the liquid crystal cell 30 and the polarizer 21 of the upper plate polarizer 20 in the order of the liquid crystal cell 30 and the lower polarizer plate 10 The isotropic protective layer 14 is arranged between the polarizer 11 and the liquid crystal cell 30 of the liquid crystal cell 30.

On the other hand, each of the optical films and the backlight used in the embodiments of the present invention was made to have the following optical properties.

라고 할 때 하기 수학식 5 내지 9에 의해 정의된다.Polarizers 11 and 21 of the lower plate polarizer 10 and the upper plate polarizer 20 give a polarizer function by dyeing iodine on the stretched PVA and the polarizing performance of the polarizer is measured in the range of visible light of 370 to 780 nm The degree of polarization is 99.9% or more, and the visually-perceptible unit transmittance is 41% or more. The transmittance of the transmission axis according to the wavelength is denoted by TD (λ), the transmittance of the absorption axis with respect to wavelength is denoted by MD (λ), and the visibility correction value defined in JIS Z 8701: 1999

And is defined by the following equations (5) to (9).

The optical characteristics due to the difference in internal refractive indexes along the directions of the respective films are 589.3 nm for the light source, the negative biaxial A plate 24 had the frontal phase difference R0 of 79 nm and the refractive index ratio NZ of 1.19; The positive biaxial A plate 25 had a front retardation R0 of 89 nm and a refractive index ratio NZ of -0.21; The isotropic protective layer 14 used had a front retardation (R0) of 0 nm and a thickness direction retardation (Rth) of 0 nm. At this time, the direction of the slow axis of each of the negative biaxial A plate 24 and the positive biaxial A plate 25 is parallel to the absorption axis 22 of the adjacent polarizer 21.

(COP, Zeonor, Optes, Japan) is used as the negative biaxial A plate 24, and a negative biaxial A plate 25 is used as the negative biaxial A plate 24, (I-Film, Optes, Japan) were successively arranged through stretching after triple co-extrusion so that PS having refractive index characteristics were arranged. Triacetylcellulose (TAC) having optical characteristics with an Rth of 50 nm with respect to the incident light of 589.3 nm was used as the outer protective layers 13 and 23 of the upper plate and the lower plate polarizers 10 and 20, respectively. Actual data mounted on a 32-inch TV LC320WX4 model (LG.Philips LCD) was used as the backlight unit (50).

The above optical components were stacked as shown in FIG. 1, and a visual sensitivity all-round transmission test was conducted. As a result, the results shown in FIG. 7 were obtained. FIG. 7 shows the distribution of the visual sensitivity omnidirectional transmittance when displaying the black on the screen. In the range of the scale, the transmittance is 0% to 0.02%, the portion where the transmittance exceeds 0.2% Areas with low permeability are indicated in blue. At this time, as the range of the blue color in the center becomes wider, it is possible to secure a wide viewing angle by showing a wide viewing angle. This is because it indicates a change in polarization state via the point R1 on the Pouinc curry sphere in Fig.

Example 2

The negative biaxial A plate 24 had a frontal retardation R0 of 99 nm and a refractive index NZ of 1.21 at a light source of 589.3 nm and the positive biaxial A plate 25 had a front retardation (R0) of 51 nm and a refractive index ratio (NZ) of -0.99 were arranged to fabricate a planar switching (IPS) liquid crystal display device.

The visual sensitivity transmission of the surface switching liquid crystal display device was simulated. The result is shown in FIG. 8 having a pattern similar to that of FIG. 7 of the first embodiment. This is because it indicates a change in polarization state via the point R2 on the Pujiang curved spheres in Fig.

Example 3

The negative biaxial A plate 24 had a front retardation R0 of 31 nm and a refractive index NZ of 2.99 at a light source of 589.3 nm and the positive biaxial A plate 25 had a front retardation (R0) of 109 nm and a refractive index ratio (NZ) of -0.21 were fabricated to produce a planar switching (IPS) liquid crystal display device.

The visual sensitivity omni-directional transmittance simulation of the planar switching liquid crystal display device is shown in Fig. 9 having a pattern similar to that of Fig. 7 of the first embodiment. This is because it indicates a change in polarization state via the point R3 on the Pouinc curry sphere in Fig.

Example 4

The negative biaxial A plate 24 had a frontal retardation R0 of 44 nm and a refractive index NZ of 2.99 at a light source of 589.3 nm and the positive biaxial A plate 25 had a front retardation (R0) of 74 nm and a refractive index ratio (NZ) of -0.99 were arranged to fabricate a planar switching (IPS) liquid crystal display device.

As a result of simulating the visibility all-round transmission of the above-mentioned plane switching liquid crystal display device, it is shown in Fig. 10 having a pattern similar to that of Fig. 7 of the first embodiment. This is because it indicates a change in the polarization state via the point R4 on the Pouinc curry sphere in Fig.

Example 5

The negative biaxial A plate 24 had a frontal retardation R0 of 29 nm and a refractive index NZ of 3 and a positive biaxial A plate 25 at a light source of 589.3 nm, (R0) of 114 nm and a refractive index ratio (NZ) of -0.2 were fabricated to produce a planar switching (IPS) liquid crystal display device.

FIG. 11 shows the result of simulation of the visual sensitivity all-round transmission of the above-mentioned plane switching liquid crystal display device.

Example 6

The negative biaxial A plate 24 had a frontal retardation R0 of 109 nm and a refractive index NZ of 1.1 and the positive biaxial A plate 25 had a front retardation (R0) of 45 nm and a refractive index ratio (NZ) of -1 was fabricated to fabricate a planar switching (IPS) liquid crystal display device.

FIG. 12 shows the result of simulation of the visual sensitivity all-round transmission of the planar switching liquid crystal display device.

Comparative Example 1

In the structure of Example 1, the negative biaxial A plate 24 and the positive biaxial A plate 25 were removed and replaced with an isotropic protective film to produce a planar switching (IPS) liquid crystal display device as shown in FIG.

As a result of the visual sensitivity all-round transmission simulation of the above-mentioned plane switching liquid crystal display device, the results shown in Fig. 14 were obtained

FIG. 7 of the first embodiment has a wider blue area than the view of FIG. 14, which shows a wider viewing angle. In addition, the maximum transmittance in the forward direction is calculated as 0.02% in Example 1 and 0.34% in Comparative Example 1, which indicates that the maximum transmittance in all directions is about 17 times that in Example 1.

Comparative Example 2

The negative biaxial A plate 24 had a front retardation R0 of 140 nm and a refractive index NZ of 1.3 and a positive biaxial A plate 25 had a front retardation (R0) of 50 nm and a refractive index ratio (NZ) of -1 was fabricated to produce a planar switching (IPS) liquid crystal display device.

As a result of the simulation of the visual sensitivity all-round transmission of the surface switching liquid crystal display, it was confirmed that the angle of view of the slope was high and the viewing angle was narrow in the black state as shown in FIG.

Comparative Example 3

The negative biaxial A plate 24 had a frontal retardation R0 of 100 nm and a refractive index NZ of 1.2 while the positive biaxial A plate 25 had a front retardation (R0) of 20 nm and a refractive index ratio (NZ) of -1 were fabricated to produce a planar switching (IPS) liquid crystal display device.

As a result of the simulation of the visual sensitivity all-round transmission of the planar switching liquid crystal display, it was confirmed that the oblique plane transmittance was high and the viewing angle was narrow in the black state as shown in FIG.

Comparative Example 4

In place of the negative biaxial A plate 24 and the positive biaxial A plate 25 laminated in this order on the liquid crystal cell side of the polarizer in the above-mentioned first embodiment, the positive biaxial A plate 25 and the negative biaxial A Plate (24) in this order to produce a planar switching (IPS) liquid crystal display device.

As a result of the simulation of the visibility all-round transmission of the surface switching liquid crystal display, it was confirmed that the oblique plane transmittance was high and the viewing angle was narrow in the black state as shown in FIG.

As described above, the surface switching liquid crystal display device according to the present invention can provide excellent image quality for all viewing angles, and can be applied to a liquid crystal display requiring high viewing angle characteristics.

1 is a perspective view showing the structure of a planar switching liquid crystal display (IPS-LCD) according to the present invention;

2 is a schematic view for explaining the absorption axis of the polarizing plate and the alignment direction of the liquid crystal according to the present invention;

3 is a schematic view for explaining the refractive index of the retardation film according to the present invention;

4 is a schematic view showing the MD direction in the manufacturing process for explaining the stretching direction of the retardation film and the second polarizing plate according to the present invention;

Fig. 5 shows the polarization state changes on the Poincare Sphere at? = 60 deg. And? = 45 deg? Of Embodiments 1 to 4 (R1 to R4) according to the present invention;

FIG. 6 is a schematic view for explaining the expression of? And? In the coordinate system of the present invention; FIG.

7 is a simulation result of the visual sensitivity of the first embodiment according to the present invention;

8 is a simulation result of the visual sensitivity of the second embodiment according to the present invention;

9 is a simulation result of the visual sensitivity of the third embodiment according to the present invention;

10 is a simulation result of the visual sensitivity all-round transmission of the fourth embodiment according to the present invention;

11 is a simulation result of the visual sensitivity omni-directional transmittance of the fifth embodiment according to the present invention;

12 is a simulation result of the visual sensitivity of the sixth embodiment according to the present invention;

13 is a perspective view showing the structure of a planar switching liquid crystal display (IPS-LCD) including an isotropic protective film of Comparative Example 1 of the present invention;

14 is a simulation result of the visual sensitivity all-round transmission of Comparative Example 1 of the present invention;

15 is a simulation result of the visual sensitivity all-round transmission of Comparative Example 2 of the present invention;

16 is a simulation result of the visual sensitivity all-round transmission of Comparative Example 3 of the present invention;

17 is a simulation result of the visibility all-round transmission of Comparative Example 4 of the present invention.

Claims (11)

(IPS) mode laminated in the order of a negative biaxial A plate, a positive biaxial A plate, a polarizer and a protective layer from a liquid crystal cell side, Wherein the negative biaxial A plate has a front retardation value (R0) of 20 to 110 nm and a refractive index ratio (NZ) of 1.01 to 3.5, the slow axis being parallel to the absorption axis of the adjacent polarizer; Wherein the positive biaxial A plate has a front retardation (R0) of 40 to 120 nm, a refractive index ratio (NZ) of -1.2 to -0.01, and a slow axis parallel to an absorption axis of an adjacent polarizer. The method of claim 1, wherein the negative biaxial A plate and the positive biaxial A plate are independently selected from the group consisting of triacetylcellulose (TAC), cycloolefin polymer (COP), cycloolefin copolymer (COC), polyethylene terephthalate (PET) Wherein the polarizer is selected from the group consisting of polypropylene (PP), polycarbonate (PC) , polysulfone (PSF) and polymethylmethacrylate (PMMA). The top plate polarizing plate according to claim 1, wherein the positive biaxial A plate is a structure in which polymethylmethacrylate (PMMA), polystyrene (PS), and polymethylmethacrylate (PMMA) are sequentially laminated. The top plate polarizing plate according to claim 1, wherein the positive biaxial A plate is at least one layer of modified polycarbonate (PC). The method of claim 1, wherein the protective layer is a triacetyl cellulose (TAC), a cycloolefin polymer (COP), a cycloolefin copolymer (COC), polyethylene terephthalate (PET), polypropylene (PP), polycarbonate (PC), (PSF) and polymethylmethacrylate (PMMA). ≪ RTI ID = 0.0 > 11. < / RTI > A surface-switched (IPS) mode liquid crystal display comprising the top plate polarizer of claim 1. The liquid crystal display according to claim 6, wherein the liquid crystal cell has a retardation value in the range of 300 to 400 nm at a wavelength of 589 nm. The liquid crystal display device according to claim 6, wherein the compensating relationship satisfies a maximum transmittance of the visual sensitivity omnidirectional omission of 0.05% or less. 7. The liquid crystal display device according to claim 6, further comprising: an isotropic protection layer having a front retardation (R0) and a thickness retardation (Rth) of less than 10 nm from the liquid crystal cell side; A polarizer; And a protective layer laminated in this order on the lower polarizer plate. The method of claim 9, wherein the isotropic protective layer and the protective layer are independently selected from the group consisting of triacetylcellulose (TAC), cycloolefin polymer (COP), cycloolefin copolymer (COC), polyethylene terephthalate (PET) , Polycarbonate (PC) , polysulfone (PSF), and polymethylmethacrylate (PMMA). The liquid crystal display device according to claim 6, wherein the liquid crystal cell is configured such that the liquid crystal alignment direction is parallel to the absorption axis of the lower plate polarizer.

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