KR20110048205A - In-plane switching mode liquid crystal display - Google Patents

Abstract

PURPOSE: An in-plane switching mode liquid crystal display is provided to ensure the optical view angle by improving a contrast ration on an inclined plane. CONSTITUTION: An upper polarizing plate(10) includes a protection film, a polarizer and a first phase difference film(14) which are laminated sequentially on the plate. A lower polarizing plate comprises a liquid crystal cell(30), a second phase difference film(24), a polarizer and a protection film(13) which are sequentially laminated thereon. The absorption axes of the polarizers of the upper and lower plates are perpendicular to each other.

Description

Planar Switching Mode Liquid Crystal Display {IN-PLANE SWITCHING MODE LIQUID CRYSTAL DISPLAY}

The present invention relates to a planar switching mode liquid crystal display device capable of securing a wide viewing angle by improving contrast ratio on an inclined surface.

Liquid crystal display (LCD) is widely used as a popular image display device. However, despite its many excellent features, a narrow viewing angle is pointed out as a representative disadvantage.

The liquid crystal display is divided into modes according to the initial arrangement of the liquid crystal, the electrode structure, and the physical properties of the liquid crystal. The most commonly used modes of the liquid crystal display are twisted nematic (TN), vertical alignment (VA), and plane switching (IPS). There is this.

Also, it is divided into normal black or normal white mode according to whether light is transmitted when no voltage is applied, and VA mode is PVA (Patterned VA), SPVA (Super PVA) and MVA (Multidomain VA) according to domain and liquid crystal initial arrangement. Modes are classified into S-IPS (Super In-Plane Switching) and FFS (Fringe-Field Switching).

In the planar switching mode, the liquid crystal molecules 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 of the liquid crystal molecules coincide with each other at the front side, the light passing through the lower plate polarizer passes through the liquid crystal because the transmission axis and the liquid crystal axis of the liquid crystal coincide on the slope due to the optical characteristics of the liquid crystal. Even if the polarization state is not changed, the liquid crystal layer can pass through the liquid crystal layer as it is. As a result, a certain dark state can be displayed in the non-driven state by the arrangement of the polarizing plates on the upper and lower surfaces of the substrate.

In general, such a plane switching mode liquid crystal display can obtain a wide viewing angle without using an optical film, thereby ensuring a natural transmittance, and having a uniform image quality and viewing angle throughout the screen. Therefore, the planar switching mode liquid crystal display is mainly used in high-end models of 18 inches or more.

In the liquid crystal display device using the planar switching mode, a polarizing plate for polarizing light is required on the outside of the liquid crystal cell including the liquid crystal, and a protective film made of a triacetyl cellulose (TAC) film is formed on one or both sides of the polarizing plate. To protect the PVA). In this case, when the liquid crystal expresses a black state, the light polarized by the polarizer provided in the lower plate is elliptically polarized by the TAC film on the inclined surface instead of the front side. Elliptically polarized light has a problem in that the polarization is changed in the liquid crystal cell so that light has various colors at the same time as light leakage.

In addition, in recent years, as the image display apparatuses of large TVs using the planar switching mode are manufactured, wide viewing angle characteristics are required. Accordingly, in the planar switching mode liquid crystal display (IPS-LCD), an isotropic protective film is positioned between the polarizer (PVA) of one polarizer of the liquid crystal cell and the liquid crystal cell in order to secure a wide viewing angle, and the polarizer of the other polarizer ( PVA) and two or more retardation layers having different optical characteristics were laminated between one or more liquid crystal cells, or one Z-axis orientation (thickness orientation) film was laminated to form a liquid crystal display device.

As described above, the planar switching mode liquid crystal display uses three layers of thick retardation film (one lower isotropic film and two upper phase retardation layers) using a polarizer composite by stacking two layers having different optical properties on one side of the liquid crystal layer. In addition, a Z-axis oriented film using a shrink film in the manufacturing process is low in economic efficiency and a shrink process is necessarily included and is not easy to manufacture a large area film.

Therefore, it is difficult to reduce the thickness by using a composite polarizing plate in which three retardation films are stacked, and there is a high possibility of warpage due to temperature or humidity changes due to thickness unevenness on both sides of the liquid crystal cell. There is a problem in that it is used only in the planar switching mode of the liquid crystal display device.

The present invention is to check the change of the polarization state of the liquid crystal alignment direction by using Poincare Sphere in the planar switching mode liquid crystal display device including an upper polarizer, a lower polarizer and a liquid crystal cell to design the optical characteristics of the retardation film, In the lower polarizing plate, the slow axis of the retardation film, the direction of the absorption axis of the polarizer, and the liquid crystal alignment direction are specifically configured to improve the contrast ratio on the inclined surface, thereby securing a wide viewing angle and providing an economical thin surface switching mode liquid crystal display device. .

The present invention is a top plate polarizer laminated in the order of the protective film, the polarizer and the first retardation film; Liquid crystal cell; A planar switching mode liquid crystal display device comprising a lower polarizing plate stacked in the order of a second retardation film, a polarizer, and a protective film, wherein absorption axes of the upper polarizing plate and the lower polarizing plate are orthogonal to each other, and the liquid crystal cell is horizontal to the right side of the viewer. When the counterclockwise direction is set as the positive (+) direction, the liquid crystal alignment direction is 0 °, the first retardation film has a front retardation value R0 of 60 to 150 nm, and a refractive index ratio NZ of -2 to -1, its slow axis is orthogonal to the absorption axis of the adjacent polarizer, the second retardation film has a front retardation value (R0) of 150 to 230 nm and a refractive index ratio (NZ) of -1 to 0, its ground Provided is a planar switching mode liquid crystal display in which axes are parallel to the absorption axes of adjacent polarizers, and the sum of the front phase difference values R0 of the first retardation film and the second retardation film is 250 to 350 nm.

The planar switching mode liquid crystal display device according to the present invention can secure a wide viewing angle at a level using conventional three phase retardation films, and can secure a wide viewing angle even when only one sheet of retardation film is used for the upper and lower polarizing plates, respectively. Therefore, there is an advantage in that a thin liquid crystal display can be mass-produced in high yield (reduced defect rate due to foreign substances and impurities).

The present invention is to check the change of the polarization state of the liquid crystal alignment direction by using Poincare Sphere in the planar switching mode liquid crystal display device including an upper polarizer, a lower polarizer and a liquid crystal cell to design the optical characteristics of the retardation film, The present invention relates to an economical thin planar switching mode liquid crystal display device which can secure a wide viewing angle by specifically configuring the direction of the slow axis of the retardation film, the absorption axis of the polarizer, and the liquid crystal alignment direction in the lower polarizer to improve the contrast ratio on the inclined plane.

Hereinafter, the configuration of the planar switching mode liquid crystal display device according to the present invention will be described.

The planar switching mode liquid crystal display includes an upper polarizing plate, a liquid crystal cell, and a lower polarizing plate.

The upper polarizing plate is laminated in the order of the first retardation film, the polarizer and the protective film from the liquid crystal cell side, and the lower polarizing plate is laminated in the order of the second retardation film, the polarizer and the protective film from the liquid crystal cell side. The absorption axes of the polarizers of the upper and lower polarizing plates are perpendicular to each other.

The liquid crystal cell has a liquid crystal alignment direction of 0 ° (FFS) when the counterclockwise direction is made to the positive (+) direction based on the horizontal direction on the right side of the viewer. Range.

Δn × d = (n _e -n _o ) × d

(Where n _e represents the extraordinary refractive index of the liquid crystal, n _o represents the normal ray refractive index, and d represents the cell gap; Note. Δn, d is a scalar rather than a vector)

As the first retardation film of the upper polarizing plate, one having a front retardation value R0 of 60 to 150 nm and a refractive index ratio NZ of -2 to -1 can be used.

As the front retardation value R0 of the first retardation film is smaller, there is a problem in that the slow axis direction of the film is nonuniform and the front contrast ratio is lowered during film production. Therefore, it is necessary to find an appropriate lower limit value. 60 nm is preferable in this invention in consideration of retardation film preparation. In addition, in the present invention, when the front retardation value of the retardation film exceeds 150nm, there is a problem that a wide viewing angle cannot be realized in the configuration of the liquid crystal display device according to the present invention. In addition, when the refractive index ratio NZ is less than -2, when the slow axis is not orthogonal to the absorption axis of the adjacent polarizer and exceeds -1, the optical characteristic may not be realized in accordance with the object of the present invention.

The slow axis of this first retardation film is disposed perpendicular to the absorption axis of the adjacent polarizer.

The second retardation film of the lower polarizing plate may have a front retardation value R0 of 150 to 230 nm, a refractive index ratio NZ of -1 to 0, and preferably a refractive index ratio NZ of -1.0 to -0.3. .

If the front retardation value R0 of the second retardation film is less than 150 nm, the retardation compensation of the liquid crystal is not sufficient, so that the wide viewing angle is not easy to implement, and when the front retardation film exceeds 230 nm, the wide viewing angle is not easy to implement and manufacture. . In addition, if the refractive index ratio (NZ) is less than -1, it is not easy to manufacture only by fixed-end stretching, which requires an additional step of free-end stretching, which complicates the manufacturing process of the retardation film and has a problem in that it is not easy to implement a wide viewing angle. If the refractive index ratio (NZ) exceeds 0, there is a problem that it is difficult to implement a stable phase difference by the stretching process.

The slow axis of this second retardation film is disposed in parallel with the absorption axis of the adjacent polarizer.

The sum of the front retardation values R0 of the first retardation film and the second retardation film is preferably 250 to 350 nm, preferably 260 to 300 nm. As a result of path search using the liquid crystal display device of the present invention, the front phase difference values of the first and second retardation films for compensating the liquid crystal phase difference value of the panel should be small. It was confirmed that the implementation is not easy.

In the present invention, the optical characteristics of the first retardation film of the upper polarizing plate and the second retardation film of the lower polarizing plate are defined by Equations 2 to 4 below with respect to the electric field in the visible light region.

In general, it is the optical characteristic for 589nm which is most easily obtained when there is no mention of the wavelength of the light source. Where Nx is the refractive index of the axis with the largest refractive index in the in-plane direction, Ny is the vertical direction of Nx in the in-plane direction, and Nz is the refractive index in the thickness direction as shown in FIG. 2.

Rth = [(Nx + Ny) / 2-Nz] × d

(Where Nx and Ny are planar refractive indices Nx ≧ Ny, Nz represents the thickness direction refractive index of the film, and d represents the thickness of the film)

R0 = (Nx-Ny) × d

(Where Nx and Ny are planar refractive indices Nx ≧ Ny, and d represents the thickness of the film)

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

(Where Nx and Ny are plane refractive indices Nx ≧ Ny, and Nz represents the thickness direction refractive index of the film)

Rth in Equation 2 is a thickness retardation value representing the difference in refractive index in the thickness direction with respect to the in-plane average refractive index, and R0 in Equation 3 is a front phase which is a substantial phase difference when light passes through the normal direction (vertical direction) of the film. Phase difference value.

In addition, NZ in Equation 4 is a refractive index ratio to distinguish the type of plate used as a retardation film accordingly.

The plate type of the retardation film may include 1) an A plate in the case where an optical axis without retardation exists in the in-plane direction of the film; 2) a C plate if the optical axis is present in the vertical direction of the film plane; And 3) when there are two optical axes, it is called a biaxial plate. Specifically, 1) when NZ is 1, the refractive index has a relationship of Nx> Ny = Nz and is called 'Positive A Plate'; 2) when 1 <NZ, the refractive index satisfies Nx> Ny> Nz and is called 'NEGATIVE BIAXIAL A PLATE'; 3) when 0 <NZ <1, the refractive index has a relationship of Nx> Nz> Ny and is called 'Z-axis oriented film'; 4) When NZ = 0, the refractive index is called 'NEGATIVE A PLATE' with the relationship Nx = Nz> Ny; 5) If NZ <0, the refractive index is called 'POSITIVE BIAXIAL A PLATE' with the relationship Nz> Nx> Ny; 6) When NZ = ∞, the refractive index is called 'NEGATIVE C PLATE' with the relationship Nx = Ny> Nz; 7) In the case of NZ = -∞, the refractive index has a relationship of Nz> Nx = Ny and is called 'positive C plate'.

However, it is impossible in practice to make A and C plates that perfectly match the theoretical definition as above. In the general process, the A plate is divided into an approximate range of the refractive index ratio, and the C plate is set to an arbitrary value, respectively. Nevertheless, the arbitrary numerical setting is limited to apply to all materials having different refractive index expression characteristics due to stretching. Therefore, the retardation film according to the present invention represents not the type of plate according to the form of refractive anisotropy, but NZ, RO, and Rth, which are optical properties of the plate.

Each retardation film of the upper polarizing plate and the lower polarizing plate according to the present invention is produced in a stretched type.

The retardation film is generally referred to as a film having a high refractive index in the stretching direction to impart retardation through stretching, and a film having a small refractive index in the stretching direction is called a negative refractive index property. do. Retardation films having positive refractive index characteristics include triacetyl cellulose (TAC), cycloolefin polymer (COP), cycloolefin copolymer (COC), polyethylene terephthalate (PET), polypropylene (PP), polycarbonate ( PC), polysulfone (PSF) and polymethylmethacrylate (PMMA). In addition, the retardation film having negative refractive index characteristics may be made of modified polystyrene (PS) or modified polycarbonate (PC).

The stretching method of the retardation film is divided into fixed end stretching and free end stretching. Fixed-end stretching is a method of fixing the length of a direction other than the extending direction in the extending process of a film, and free end extending | stretching is a method of providing a degree of freedom to other directions other than the extending direction in the extending process of a film. Usually, when the film is stretched, other directions other than the stretching direction are contracted, but in the case of the Z-axis oriented film, a separate shrinkage process may be required in addition to the stretching.

The direction in which the film in the roll state is released during stretching is called the MD direction (machine direction) and the direction perpendicular thereto is called a TD direction (Transverse Direction). Free end drawing refers to stretching in the MD direction, and fixed end drawing refers to stretching in the TD direction.

The type of NZ and plate vary depending on the stretching method (only when the first process is applied). 1) the positive A plate stretches the free end of the film with positive refractive index characteristics; 2) the negative biaxial A plate fixed-stretches the film with positive refractive index characteristics; 3) the Z-axis alignment film contracts fixed end shrinkage after free end stretching of a film having a positive refractive index characteristic or a negative refractive index characteristic; 4) the negative A plate free-ends the film with negative refractive index characteristics; 5) The positive biaxial A plate can be prepared by fixed end stretching a film having negative refractive index characteristics.

In addition, the retardation film may control an optical property such as a direction of a slow axis, a retardation value, and a value of NZ by applying an additional process such as secondary stretching and additives in addition to the primary stretching as described above. The further process thereof is a process generally applied in the art and is not particularly limited in the present invention.

The first retardation film of the upper polarizing plate and the second retardation film of the lower polarizing plate of the present invention may be manufactured by applying one or more fixed end stretching of a film having negative refractive index characteristics. Preferably, the first retardation film is preferably manufactured by applying both free end stretching and fixed end stretching, and the draw ratio should be greater than free end stretching than fixed end stretching. It is good to manufacture a 2nd phase difference film applying only a fixed stage extending process. This is to easily apply to the roll-to-roll process when manufacturing the composite polarizing plate of the present invention.

The first retardation film of the upper polarizing plate and the second retardation film of the lower polarizing plate are not limited to the material as long as they satisfy the optical properties of the present invention independently of each other, more preferably modified polycarbonate (PC), modified Polystyrene (PS) and polymethyl methacrylate (PMMA) can be used that is selected from the group consisting of.

Each polarizer of the upper plate and the lower plate flat plate is positioned in a polyvinyl alcohol (PVA) layer, which is a polarizer imparted with a polarizing function through stretching and dyeing. Each absorption axis of the upper polarizing plate and the lower polarizing plate is arranged to be orthogonal to each other.

In each of the polyvinyl alcohol (PVA) layers of the upper polarizing plate and the lower polarizing plate, protective films are positioned on opposite sides of the liquid crystal cell.

The protective film of the upper polarizing plate and the lower polarizing plate is not particularly limited in the present invention because the optical properties due to the difference in refractive index does not affect the viewing angle. Materials for forming the protective film of the upper polarizing plate and the lower polarizing plate may be applied to those commonly used in the art independently of each other. Specifically, triacetyl cellulose (TAC), cycloolefin polymer (COP), cycloolefin copolymer (COC), polyethylene terephthalate (PET), polypropylene (PP), polycarbonate (PC), polysulfone (PSF) and Polymethyl methacrylate (PMMA) and the like prepared from the group consisting of can be used.

The upper polarizing plate and the lower polarizing plate of the present invention may be manufactured by a process generally applied in the art, and specifically, the manufacturing process may be a roll to roll process, sheet to sheet, or the like. . In general, it is preferable to apply a roll to roll process in consideration of yield and efficiency in the manufacturing process.

In the first polarizing plate of the present invention, the direction of the absorption axis of the PVA polarizer is always fixed in the MD direction, and the retardation film has a roll to roll process because the slow axis is perpendicular to the absorption axis of the polarizing plate. It can be prepared by application. In order to make the absorption axis of the polarizing plate and the slow axis of the retardation film orthogonal, it is most preferable to use a roll-to-roll method to lower the production cost when integrating the polarizing plate and the retardation film.

The configuration of the planar switching mode liquid crystal display of the present invention will be described with reference to FIG. 1.

FIG. 1 is stacked in the order of the lower polarizing plate 20, the FFS liquid crystal cell 30, and the upper polarizing plate 10 from the backlight unit 40 side.

The upper polarizing plate 10 is stacked in order from the liquid crystal cell to the first retardation film 14, the polarizer 11, and the protective film 13. The lower polarizing plate 20 is laminated in the order of the second retardation film 24, the polarizer 21, and the protective film 23 from the liquid crystal cell.

The absorption axes 12 and 22 of the upper polarizer 11 and the lower polarizer 21 are arranged to be orthogonal to each other. The slow axis 15 of the first retardation film 14 of the upper polarizing plate and the absorption axis 12 of the polarizer 11 adjacent to each other are arranged perpendicular to each other and the slow axis 25 of the second retardation film 24 of the lower polarizing plate. Absorption axis 22 of polarizer 21 adjacent to is parallel to each other.

The first retardation film 14 of the upper polarizing plate has a front retardation value R0 of 60 to 150 nm, the refractive index ratio NZ is -2 to -1, and the second retardation film 24 of the lower polarizing plate has a front retardation value. (R0) is 150 to 230 nm, the refractive index ratio (NZ) is -1 to 0, and the sum of the front retardation values of the first retardation film 14 and the second retardation film 24 should be 250 to 350 nm.

In the present invention, the absorption axis of the polarizer of the lower polarizing plate should be located in the vertical direction when viewed from the viewer side. Specifically, when the absorption axis of the lower polarizing plate close to the backlight unit is in the vertical direction, light passing through the lower polarizing plate is polarized in the horizontal direction. When the voltage of the panel passes through the liquid crystal cell to which the voltage is applied, the light is in the vertical direction, and the light passes through the upper polarizing plate on the viewer's side where the absorption axis is horizontal. The light passed in this way can be perceived by a person wearing polarized sunglasses (usually the absorption axis is horizontal) on the viewer's side, so that the image is visible. However, when the absorption axis of the lower polarizing plate close to the backlight unit is in the horizontal direction, a person wearing polarized sunglasses has a problem in that the image is not visible to him.

The effect of the viewing angle compensation of the present invention can be understood by showing the change in polarization state as it passes through each optical layer on the Poangaregu sphere.

The Pouangaregu is a very useful method for expressing the change of polarization state at a certain time. Therefore, the polarization state is generated when the light traveling at a specific time passes through each optical element in the liquid crystal display device. It can represent a change.

Particular view of the present invention can confirm the wavelength dispersion by expressing the change in polarization state of the light coming out in this direction in the semicircular coordinate system shown in FIG. have.

5 illustrates a polarization state to be implemented by the liquid crystal display according to the present invention at the time of Φ = 45 ° and θ = 60 °. Specifically, when the screen is rotated by θ on the Φ direction with the Φ + 90 ° direction from the front as the viewing side, the polarization state change with respect to the light emitted from the observer's front direction is shown on the Poang Kare sphere. When the coordinates of the S3 axis are positive (+) on the Poang Cure sphere, the right-handed polarized light indicates that the right-handed polarized light is the polarized horizontal component Ex and the polarized vertical component is Ey. Compared to light, the slowness of phase is greater than zero and less than half wavelength.

The liquid crystal display device of the present invention satisfies the compensating relationship of the luminous transmittance omnidirectional maximum transmittance of 0.2% or less in the inclination angle (θ = 60 °, Φ = 45 °).

Below, the wide viewing angle improvement effect by the said structure was put together in the following Example. The invention can be better understood by the following examples, which are intended to illustrate the invention and are not intended to limit the scope of protection as defined by the appended claims.

Example

In the following example, the effect of the wide viewing angle was confirmed by performing a simulation in the LCD optical simulation program TECH WIZ LCD 1D POLAR (man system, KOREA).

Example 1

Measurement data of each optical film, a liquid crystal cell, and a backlight according to the present invention were stacked on a TECH WIZ LCD 1D (man system, KOREA) with a structure as shown in FIG. 1. Referring to the structure of Figure 1 in detail.

Planar switching mode liquid crystal cells 30 and FFS whose liquid crystal alignment direction is 0 ° when the counterclockwise direction is set to the positive (+) direction with respect to the lower horizontal polarizing plate 20 from the backlight side and the right horizontal direction of the viewer side in the state where no voltage is applied. ) And the upper polarizing plate 10, and the lower polarizing plate 20 is laminated with a second retardation film 24, a polarizer 21, and a protective film 23 from the liquid crystal cell 30 side, and an upper polarizing plate ( 10) was laminated in the order of the first retardation film 14, the polarizer 11, and the protective film 13 from the liquid crystal cell side.

The liquid crystal cell was applied to LG Display's 42-inch panel LC420WU5, and the phase difference value of the liquid crystal cell was used by adjusting the thickness of the cell gap so that the light source was 589 nm to 380 nm. As the backlight unit 40, actual measurement data mounted on a 32-inch TV LC320WX4 model (LG PHILIPS LCD) was used.

On the other hand, each optical film used in the embodiment of the present invention was used to have the optical properties as follows.

라고 할 때 하기 수학식 5 내지 9에 의해 정의된다. 여기서 S(λ)는 광원스펙트럼이며 보통 C광원을 사용한다.First, the polarizers 11 and 21 of the upper polarizing plate 10 and the lower polarizing plate 20 are dyed iodine on the stretched PVA to impart a polarizer function. It is 99.9% or more, and the visibility transmittance is 41% or more. The visibility polarization and the visibility single transmittance are the TD (λ) transmittance of the transmission axis according to the wavelength, and the transmittance correction of the absorption axis according to the wavelength of MD (λ) and the visibility correction value defined in JIS Z 8701: 1999.

Is defined by the following equations (5) to (9). Where S (λ) is the light source spectrum and usually uses a C light source.

The optical characteristic caused by the difference in internal refractive index according to the direction of each film is 589.3 nm in the light source, the second retardation film 24 has a front retardation value R0 of 180 nm, a refractive index ratio NZ of -0.5, and a first phase difference. As the film 14, a front retardation value R0 of 85 nm and a refractive index ratio NZ of -2.0 were used.

At this time, the absorption axis 12 of the lower polarizer 11 and the slow axis 25 of the second retardation film 24 are disposed in parallel to each other, the absorption axis 12 of the upper polarizer 11 and the first retardation film ( The slow axis 15 of 14) was configured to be orthogonal to each other.

In addition, a planar switching mode liquid crystal display device was manufactured by using a TAC film having an optical property of Rth of 50 nm with respect to the incident light 589.3 nm as the outer protective films 13 and 23 of the upper and lower polarizing plates 10 and 20, respectively. It was.

The change in the polarization state in the tilt direction of Φ = 45 ° and θ = 60 ° in the Puan Cureg sphere of the planar switching mode liquid crystal display is shown in FIG. 5. Specifically, when passing through the polarizer 21 of the lower polarizing plate 20 on the basis of 550nm light on the Poincare Sphere, it shows the polarization state of "starting", the second retardation film 24, the FFS liquid crystal cell (30), the polarization state reaches the arrival point after passing in the order of the first retardation film (14).

FIG. 6 shows the distribution of visibility of permeability in a planar switching mode liquid crystal display device. The scale ranges from 0% to 1% of the transmittance, and a portion of the color exceeding 1% of the transmittance when displaying a dark red portion and a low transmittance portion. Is displayed in blue. In this case, the wider the blue range of the center, the wider the viewing angle. As a result, the wider the blue range from the center of FIG.

Example 2

The retardation value of the liquid crystal cell is adjusted in the same manner as in Example 1, and the thickness of the cell gap is adjusted to be 380 nm from the light source 589 nm, and the second retardation film 24 has a front retardation value R0 of 200 nm and a refractive index ratio ( NZ) is -0.3, and the first retardation film 14 has a front retardation value R0 of 70 nm and a refractive index ratio NZ of -1.9 to manufacture a planar switching mode liquid crystal display device.

The change in the polarization state of the Puan Cureg sphere according to the wavelength of the planar switching mode liquid crystal display device is similar to that of FIG. As a result of Figure 7 it can be seen that the wide viewing angle can be secured by seeing a wide range of blue from the center.

Example 3

In the same manner as in Example 1, the phase difference value of the liquid crystal cell is adjusted to the thickness of the cell gap so that the light source is from 589nm to 380nm, and the second phase difference film 24 has a front phase difference value R0 of 150nm and a refractive index ratio ( NZ) is -0.3, and the first retardation film 14 uses a front retardation value R0 of 150 nm and a refractive index ratio NZ of -1 to manufacture a planar switching mode liquid crystal display device.

The change in polarization state of the Puan Cureg sphere according to the wavelength of the planar switching mode liquid crystal display is similar to that of FIG. As a result of FIG. 8, it can be seen that a wide viewing angle can be secured by seeing a wide range of blue color from the center.

Example 4

In the same manner as in Example 1, the phase difference value of the liquid crystal cell is adjusted to the thickness of the cell gap so that the light source is from 589nm to 380nm, and the second phase difference film 24 has a front phase difference value R0 of 150nm and a refractive index ratio ( NZ) is -0.8, and the first retardation film 14 has a front phase retardation value R0 of 120 nm and a refractive index ratio NZ of -1.8 to manufacture a planar switching mode liquid crystal display device.

The change in polarization state of the Puan Cureg sphere according to the wavelength of the planar switching mode liquid crystal display device is similar to that of FIG. As a result of Figure 9 it can be seen that the wide viewing angle can be secured by seeing a wide range of blue from the center.

Example 5

In the same manner as in Example 1, the phase difference value of the liquid crystal cell is adjusted to the thickness of the cell gap so that the light source is 589nm to 400nm, the second phase difference film 24 has a front retardation value (R0) 230nm and the refractive index ratio ( NZ) is -0.3, and the first retardation film 14 uses a front retardation value R0 of 65 nm and a refractive index ratio NZ of -2 to manufacture a planar switching mode liquid crystal display device.

The change in polarization state of the Puan Cureg sphere according to the wavelength of the planar switching mode liquid crystal display device is similar to that of FIG. As a result of FIG. 10, it can be seen that the wide viewing angle can be secured by seeing a wide range of blue color from the center.

As described above, the planar switching liquid crystal display device according to the present invention can provide excellent image quality for all visual fields 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 (FFS-LCD) according to the present invention;

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

Figure 3 is a schematic diagram showing the MD direction in the manufacturing process for explaining the stretching direction of the retardation film and the polarizing plate according to the present invention,

4 is a schematic diagram for explaining what is represented by Φ, θ in the coordinate system of the present invention,

5 is a representation of the change in the polarization state according to the first embodiment of the present invention in the direction of the angle of angle (θ = 60 °, Φ = 0 °) on the Poang Cure sphere,

Figure 6 shows the visibility of the omnidirectional transmittance simulation results according to Example 1 of the present invention,

Figure 7 shows the visibility of the omnidirectional transmittance simulation results according to Example 2 of the present invention,

8 is a view showing the visibility of the omnidirectional transmittance simulation according to the third embodiment of the present invention,

9 is a view showing the visibility of the omnidirectional transmittance simulation according to the fourth embodiment of the present invention,

FIG. 10 is a view illustrating a simulation result of visibility of transmittance in accordance with Example 5 of the present invention. FIG.

Claims (7)

An upper plate polarizer laminated in the order of the protective film, the polarizer and the first retardation film; Liquid crystal cell; An on-plane switching mode liquid crystal display device comprising a lower polarizing plate stacked in order of a second retardation film, a polarizer, and a protective film. The absorption axes of the polarizers of the upper and lower polarizers are perpendicular to each other, The liquid crystal cell has a liquid crystal alignment direction of 0 ° when the counterclockwise direction is set as a positive (+) direction based on the horizontal direction on the right side of the viewer. The first retardation film has a front retardation value R0 of 60 to 150 nm, a refractive index ratio NZ of -2 to -1, and its slow axis is disposed perpendicular to the absorption axis of the adjacent polarizer, The second retardation film has a front retardation value R0 of 150 to 230 nm, a refractive index ratio NZ of -1 to 0, and its slow axis is parallel to an absorption axis of an adjacent polarizer, The planar switching mode liquid crystal display device wherein the sum of the front phase difference values (R0) of the first retardation film and the second retardation film is 250 to 350 nm. The method of claim 1, wherein the second retardation film has a refractive index ratio (NZ) of -1.0 to -0.3, The planar switching mode liquid crystal display device wherein the sum of the front phase difference values (R0) of the first retardation film and the second retardation film is 260 to 300 nm. The liquid crystal display of claim 1, wherein the liquid crystal cell has a panel retardation value in a range of 370 to 400 nm at a wavelength of 589 nm. The method of claim 1, wherein the first retardation film and the second retardation film are independently of each other triacetyl cellulose (TAC), cycloolefin polymer (COP), cycloolefin copolymer (COC), polyethylene terephthalate (PET), polypropylene ( PP), polycarbonate (PC), polysulfone (PSF) and polymethyl methacrylate (PMMA) is a liquid crystal display device which is prepared from the group consisting of. The liquid crystal display device of claim 1, wherein the first retardation film is manufactured by at least one fixed end stretching a film having negative refractive index characteristics. The liquid crystal display of claim 1, wherein the first retardation film is manufactured by free end stretching and fixed end stretching of a film having negative refractive index characteristics. The liquid crystal display device of claim 1, wherein the second retardation film is manufactured by stretching the film having a negative refractive index characteristic at least once.

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