KR101629742B1 - In-plane switching mode liquid crystal display - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a phase switching liquid crystal display, and more particularly to a phase switching liquid crystal display having a first polarizing plate, a second polarizing plate and a liquid crystal cell, The optical characteristics of the retardation film are designed by checking the change of state, and by configuring the retardation film so that the slow axis direction, the liquid crystal alignment direction, and the absorption axis direction of the polarizer are parallel to each other, the contrast ratio can be improved on the inclined plane, It is possible to secure a wide viewing angle even if only one film is used for each of the first and second polarizing plates, and thus the thin liquid crystal display device can be mass-produced at a high yield (reduction in defect rate due to foreign matters and impurities).

Liquid crystal display, plane switching mode

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a liquid crystal display (LCD)

BACKGROUND OF THE INVENTION 1. Field of the Invention [0002] The present invention relates to a liquid crystal display device of a planar switching mode capable of securing a wide viewing angle by improving a contrast ratio on an oblique plane.

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 is pointed out as a typical drawback.

The liquid crystal display device is divided into two modes depending on the initial arrangement of the liquid crystal, the electrode structure, and the physical properties of the liquid crystal. The modes of the liquid crystal display devices most widely used today include twisted nematic (TN), vertical alignment (VA) .

The VA mode is PVA (Patterned VA), SPVA (Super PVA) and MVA (multidomain VA) depending on the domain and initial alignment of the liquid crystal. Modes are classified into Super In-plane Switching (S-IPS) and Fringe-Field Switching (FFS).

The surface switching mode has a substantially horizontal and uniform arrangement of liquid crystal molecules on the substrate surface in the non-driven state. When the transmission axis of the lower plate and the direction of the fast axis of the liquid crystal molecules coincide with each other, the transmission axis and the liquid crystal phase coincide with each other due to the optical characteristics of the liquid crystal, so that light passing through the lower plate polarizer passes through the liquid crystal It is possible to pass through the liquid crystal layer in the original state without causing a change in the polarized state of the sea. As a result, a dark state can be displayed in a non-driven state by arranging the polarizers on the upper surface and the lower surface of the substrate.

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 liquid crystal display device of the surface switching mode is used as a main type in an advanced model of 18 inch or higher class.

In a liquid crystal display device using a planar switching mode, a polarizing plate for polarizing light is required outside a liquid crystal cell containing a liquid crystal, and a protective film made of a triacetyl cellulose (TAC) film is attached to one side or both sides of the polarizing plate, 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 the TAC film on the inclined surface instead of the front surface. The elliptically polarized light has a problem that the polarized light is amplified in the liquid crystal cell, and the light has various colors simultaneously with the light leakage.

Further, in recent years, a wide angle of view characteristic has been demanded as a brand name market value such as a large-sized TV using a surface switching mode method is manufactured. Therefore, in order to secure a wide viewing angle, a isotropic protective film is placed between the polarizer (PVA) of one polarizing plate of the liquid crystal cell and the liquid crystal cell in place of the TAC film, and a polarizer PVA) and a liquid crystal cell, or a single Z-axis oriented (thickness direction oriented) film is laminated to constitute a liquid crystal display device.

As described above, the phase switching liquid crystal display device uses two layers of different optical properties on one side of a liquid crystal layer to form a three-layered thick phase retardation film (one lower flat isotropic film and two upper retardation layers) Or a Z-axis oriented film which is not economical to manufacture by using a shrink film in the manufacturing process and which necessarily includes a shrinkage process and is not easy to manufacture as a large-area film.

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

The present invention relates to a liquid crystal display device having a first polarizing plate, a second polarizing plate and a liquid crystal cell in a plane switching mode including a liquid crystal cell, wherein the optical characteristic of the retardation film is designed by confirming the change in the polarization state of the liquid crystal alignment direction The liquid crystal display device of the present invention is a liquid crystal display device of a thin flat panel type switching mode in which a slow axis direction, a liquid crystal alignment direction and an absorption axis direction of a polarizer are parallel to each other to improve a contrast ratio on a slope,

The present invention relates to a polarizing plate comprising a first polarizer laminated in this order of a protective film, a polarizer and a negative biaxial A plate; A liquid crystal cell; Wherein the absorption axes of the polarizers of the first polarizing plate and the polarizing plate of the second polarizing plate are orthogonal to each other, and the isotropic protective film has a retardation The absolute value of the thickness direction retardation value Rth is less than 10 nm and the negative biaxial A plate has a front retardation value R0 of 40 to 200 nm and a refractive index ratio NZ of 1 < NZ &lt; = 4, and the slow axis is parallel to the alignment direction of the liquid crystal and the absorption axis of the adjacent polarizer.

The phase switching film according to the present invention can secure a wide viewing angle at a level using three phase difference films and can obtain a wide viewing angle even if only one phase difference film is used for each of the first polarizing plate and the second polarizing plate So that it is possible to mass-produce a thin liquid crystal display device with high yield (reduction of defect rate due to foreign matters and impurities).

The present invention relates to a liquid crystal display device having a first polarizing plate, a second polarizing plate and a liquid crystal cell in a plane switching mode including a liquid crystal cell, wherein the optical characteristic of the retardation film is designed by confirming the change in the polarization state of the liquid crystal alignment direction A liquid crystal alignment direction and an absorption axis direction of a polarizer are parallel to each other so that a contrast ratio can be improved on a slope so that a wide viewing angle can be secured and an economical thin flat-plane switching mode liquid crystal display device can be obtained.

The configuration of the planar switching mode liquid crystal display device of the present invention will be described in detail as follows.

The surface switching mode liquid crystal display includes a first polarizing plate, a liquid crystal cell and a second polarizing plate.

The first polarizing plate is laminated in the order of the negative biaxial A plate, the polarizer and the protective film from the liquid crystal cell side, and the second polarizing plate is laminated in the order of the isotropic protective film, the polarizer and the protective film from the liquid crystal cell side. The absorption axes of the respective polarizers of the first polarizing plate and the second polarizing plate are orthogonal to each other.

The arrangement of the first polarizing plate and the second polarizing plate is changed according to the alignment direction of the liquid crystal.

If the liquid crystal alignment direction is 90 degrees (S-IPS) when the counterclockwise direction is the positive (+) direction with respect to the horizontal direction on the right side of the liquid crystal cell, the first polarizing plate is the lower polarizing plate, The polarizing plate is disposed on the top plate polarizing plate. In this case, the panel retardation value of the liquid crystal cell in the range of 300 to 330 nm is represented by the following equation (1) at a wavelength of 589 nm.

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)

If the liquid crystal alignment direction is 0 degrees (FFS) when the counterclockwise direction is the positive (+) direction with respect to the horizontal direction on the right side of the liquid crystal cell, the first polarizer plate is the top polarizer plate, The polarizing plate is disposed on the lower plate polarizing plate. In this case, the panel retardation value of the liquid crystal cell is in a range of 370 to 400 nm at a wavelength of 589 nm.

The isotropic protective film of the second polarizing plate preferably has a front retardation value RO of 0 to 5 nm and an absolute value of a thickness direction retardation value Rth of less than 10 nm and preferably a front retardation value RO and a thickness retardation value Rth ) Of less than 2 nm can be used. The range of the front retardation value RO and the thickness direction retardation value Rth is an optimum range in which actual mass production is easy and the isotropic protective film thickness suitable for the polarizing plate manufacturing process is considered.

The negative biaxial A plate of the first polarizing plate preferably has a front retardation value R0 of 40 to 200 nm and a refractive index ratio NZ of 1 to 4, preferably a front retardation R0 of 40 to 180 nm, and a refractive index ratio NZ) of 1.3 to 3.5 can be used.

At this time, if the liquid crystal cell is oriented 90 ° (S-IPS) when the counterclockwise direction is the positive (+) direction with respect to the horizontal direction of the right side of the liquid crystal cell, the negative biaxial A plate has the front retardation value (R0) Of 140 to 180 nm and a refractive index ratio (NZ) of 1.5 to 1.9 are preferably used. When the liquid crystal alignment direction is 0 degrees (FFS) when the counterclockwise direction is the positive (+) direction with respect to the right side horizontal direction of the liquid crystal cell, the front retardation value R0 is 40 to 60 nm and the refractive index ratio NZ ) Of from 2.8 to 3.2 is preferably used.

In the negative biaxial A plate of the present invention, when the refractive index ratio (NZ) is less than 1, the production is not easy and the manufacturing cost is very high. When the refractive index ratio (NZ) is more than 4, the absorption axis of the adjacent polarizer is parallel to the slow axis. There is a problem that it is difficult to realize the retardation of the film while maintaining the film. When the front retardation value R0 is less than 40 nm, there is a problem that it is difficult to obtain a uniform geographical axial direction. When the front retardation value R0 is more than 200 nm, there is a problem that the retardation of the film is difficult to realize while maintaining the wide width.

The slow axes of the negative biaxial A plates are configured to be parallel to the alignment direction of the liquid crystal and the absorption axis of the adjacent polarizer.

When the counterclockwise direction is the positive (+) direction with respect to the horizontal direction on the right side of the viewer side as shown in Fig. 1A, the first polarizer plate is disposed on the lower plate when the liquid crystal alignment direction is 90 deg., And the negative biaxial A plate and the lower plate The polarizer is configured to be parallel to the liquid crystal alignment direction 90 DEG.

As shown in FIG. 1B, when the counterclockwise direction is the positive (+) direction with respect to the horizontal direction on the right side of the viewer side, the first polarizer plate is disposed on the upper plate when the liquid crystal alignment direction is 0 °, And the top plate polarizer is configured to be parallel to 0 DEG which is the liquid crystal alignment direction.

In the present invention, the optical properties of the negative biaxial A plate and the isotropic protective film are defined by the following equations (2) to (4) for the propagation field in the visible light region.

It is the most easily obtainable optical characteristic for 589nm without mentioning the wavelength of the light source in general. Where Nx is the refractive index of the axis with the greatest 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.

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

(Where Nx and Ny are surface refractive indices Nx &gt; = 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, Nx &gt; = Ny, and d is the thickness of the film)

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

(Where Nx and Ny are the surface refractive indexes, Nx &gt; = Ny, and Nz is the refractive index in the thickness direction of the film)

In the formula (2), Rth is a thickness direction retardation value indicating a difference in refractive index in a thickness direction with respect to an in-plane average refractive index, and R0 in Equation (3) is a front retardation Phase difference value.

In Equation (4), NZ is a refractive index ratio, and accordingly, a type of a plate used as a retardation film is distinguished.

The plate types of the retardation film are as follows: 1) when the optical axis in which the retardation does not exist exists in the in-plane direction of the film; 2) C plate when the optical axis exists in the direction perpendicular to 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 referred to as a 'Positive A plate'; 2) In the case of 1 < NZ, the refractive index satisfies Nx > Ny > Nz and is called &quot; NEGATIVE BIAXIAL A PLATE &quot;; 3) In the case of 0 <NZ <1, the refractive index has a relation of Nx> Nz> Ny and is called 'Z-axis oriented film'; 4) In the case of NZ = 0, the refractive index has a relationship of Nx = Nz> Ny and is referred to as a 'negative A plate'; 5) In the case of NZ <0, the refractive index has a relation of Nz> Nx> Ny and is called 'POSITIVE BIAXIAL A PLATE'; 6) In the case of NZ = ∞, the refractive index has a relationship of Nx = Ny> Nz and is called a 'negative C plate'; 7) In the case of NZ = -∞, the refractive index has a relation of Nz> Nx = Ny and is called 'Positive C plate'.

However, it is not possible in practice to make A plates and C plates that perfectly match the theoretical definition as described above. Thus, in the general process, the A plate is divided into a rough range of the refractive index ratio and the C plate is set by setting the range of the frontal retardation to an arbitrary numerical value. Nevertheless, an arbitrary numerical setting has a limitation in applying to all materials having different refractive index display characteristics in accordance with stretching. Therefore, the retardation film according to the present invention is not limited to the plate type according to the shape of the refractive index anisotropy but the numerical values of the optical characteristics NZ, RO and Rth of the plate.

Each retardation film of the first polarizing plate and the second polarizing plate according to the present invention is made into a stretching type.

The retardation film is usually called a positive refractive index film in which the refractive index is increased in the stretching direction while giving a retardation through stretching, and a film in which the refractive index is decreased in the stretching direction is called a negative (-) refractive index property do. The retardation film having a positive refractive index is preferably a triacetylcellulose (TAC), a cycloolefin polymer (COP), a cycloolefin copolymer (COC), a polyethylene terephthalate (PET), a polypropylene (PP), a polycarbonate PC), polysulfone (PSF), and polymethyl methacrylate (PMMA). Further, the retardation film having a negative refractive index characteristic 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. The fixed-end stretching is a method of fixing the length in a direction other than the stretching direction in the film stretching process, and the free-end stretching is a method of imparting a degree of freedom in a direction other than the stretching direction in the stretching process of the film. In general, when the film is stretched, the direction other than the stretching direction shrinks, but in the case of the Z-axis oriented film, a separate shrinking process other than stretching may be required.

The direction in which the film is released in the roll state during stretching is referred to as the MD direction (machine direction), and the direction perpendicular thereto is referred to as the TD direction (transverse direction). It is said that free-direction stretching is to stretch in the MD direction, and fixed-end stretching is to stretch in the TD direction.

The type of NZ and plate are different according to the drawing method (only when the first step is applied), which is summarized as follows. 1) the positive A plate is subjected to free end stretching of a film having a positive refractive index characteristic; 2) the negative biaxial A plate is a fixed end stretched film having a positive refractive index characteristic; (3) The Z-axis oriented film is subjected to free end stretching and shrinkage of the film having positive (+) refractive index characteristics or negative (-) refractive index properties; 4) the negative A plate is free stretched film having a negative refractive index characteristic; 5) The positive biaxial A plate can be produced by fixed-end stretching a film having a negative refractive index property.

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

The isotropic protective film of the present invention is preferably produced by a casting method. In addition, it is preferable that the negative biaxial A plate is produced by applying a film having a positive refractive index property to at least one fixed end stretching. In this case, it is necessary to perform more stretching in the MD direction than in the TD direction, and the direction of the slow axis must be the MD direction. This is intended to be easily applied to a roll-to-roll process in the production of a polarizing plate.

The negative biaxial A plate is not limited to the material as long as it satisfies the optical characteristics of the present invention. Specifically, the negative biaxial A plate may be formed of triacetylcellulose (TAC), cycloolefin polymer (COP), cycloolefin copolymer (COC) Those selected from the group consisting of polyethylene terephthalate (PET), polypropylene (PP), polycarbonate (PC), polysulfone (PSF) and polymethylmethacrylate (PMMA).

Each of the polarizers of the first and second polarizing plates has a polyvinyl alcohol (PVA) layer as a polarizer imparted with a polarizing function through stretching and dyeing. The absorption axes of the first polarizing plate and the second polarizing plate are arranged to be orthogonal to each other.

Protective films are respectively disposed on the opposite sides of the liquid crystal cell in the respective polyvinyl alcohol (PVA) layers of the first polarizing plate and the second polarizing plate.

The protective film of the first polarizing plate and the second polarizing plate does not affect the viewing angle with respect to the optical characteristic depending on the refractive index difference, so that the refractive index characteristic is not particularly limited in the present invention. The materials forming the protective films of the first and second polarizing plates may be independently used from those commonly used in the art. Specifically, it is possible to use polyacetal such as triacetylcellulose (TAC), cycloolefin polymer (COP), cycloolefin copolymer (COC), polyethylene terephthalate (PET), polypropylene (PP), polycarbonate (PC) Methyl methacrylate (PMMA), and the like.

The first and second polarizing plates of the present invention can be manufactured by a process generally used in the related art. Specifically, a roll-to-roll process, a sheet to sheet process, have. It is preferable to apply a roll-to-roll process in consideration of the yield and efficiency of the production 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 since the slow axis is perpendicular to the absorption axis of the polarizing plate, the roll-to- And the like. In order to make the absorption axis of the polarizing plate orthogonal to the slow axis of the retardation film, it is most preferable to integrate the polarizing plate and the retardation film by the roll-to-roll method because the production cost can be reduced.

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

1A is laminated in the order of the first polarizing plate 10, the liquid crystal cell 30 and the second polarizing plate 20 from the backlight unit 40 side. 1B is laminated from the backlight unit 40 side in the order of the second polarizing plate 20, the liquid crystal cell 30 and the first polarizing plate 10. The liquid crystal cell of FIG. 1A is an S-IPS liquid crystal cell, and the liquid crystal cell of FIG. 1B is an FFS liquid crystal cell

The first polarizing plate 10 is laminated from the liquid crystal cell to the negative biaxial A plate 14, the polarizer 11 and the protective film 13 in this order. The second polarizing plate 20 is laminated in this order from the liquid crystal cell to the isotropic protective film 24, the polarizer 21 and the protective film 23.

The absorption axes 12 and 22 of the first polarizer 11 and the second polarizer 21 are arranged orthogonally to each other and the absorption axes 12 and 22 of the first polarizer 11 and the slow axes 15 of the negative biaxial A plate 14, The absorption axis 12 and the alignment direction 31 of the liquid crystal cell are parallel to each other.

The negative biaxial A plate 14 has a front retardation value R0 of 40 to 200 nm and a refractive index ratio NZ of 1 NZ 4 and an isotropic protective film 24 has a front retardation value RO of 0 to 5 nm , And the absolute value of the thickness direction retardation value (Rth) is less than 10 nm.

In the present invention, the absorption axis of the polarizer of the lower plate polarizer should be positioned in the vertical direction when viewed from the viewer side. Specifically, when the absorption axis of the lower plate polarizer close to the backlight unit is vertical, light passing through the lower polarizer is polarized in the horizontal direction. When the voltage of the panel passes through the applied liquid crystal cell and becomes bright, the light passes through the upper polarizer on the side of the viewer having the absorption axis in the horizontal direction. The light thus passed can be perceived by a person wearing polarized sunglasses (usually the absorption axis is in the horizontal direction) on the viewer side, and an image can be seen. However, in the case where the absorption axis of the lower plate polarizer close to the backlight unit is in the horizontal direction, there is a problem that the person wearing the polarized sunglasses does not see the image.

The effect of the viewing angle compensation of the present invention can be understood by indicating the change in polarization state when passing through each optical layer on the Pouinc curry sphere.

Since the puang curle sphere is a very useful method for expressing the change of the polarization state at a specific time, when a light proceeding at a specific time passes through each optical element in the liquid crystal display device in a liquid crystal display device displaying an image using polarized light, Change.

A specific viewpoint of the present invention is to confirm the wavelength dispersion by expressing the change in polarization state of light coming out in this direction in the semicircle coordinate system shown in Fig. 4 in the direction of Φ = 45 ° and θ = 60 ° in the pouinc curry sphere for the propagation field have.

FIG. 5 illustrates polarization states to be realized by the liquid crystal display device according to the present invention at the time of? = 45 ° and? = 60 °. Specifically, the change in the polarization state with respect to the light emerging in the front direction when the surface in the direction of? With respect to the? + 90 占 direction from the front is rotated by? To the viewer side is shown on the Pujiang curry. When the coordinates of the S3 axis indicate positive (+) polarity, the right circularly polarized light is expressed as Ex, and the polarized light component as Ey. Is slower than phase 0 and less than half the wavelength.

The liquid crystal display device of the present invention satisfies the compensation relationship in which the maximum transmittance of the visual sensitivity omnidirectional is 0.2% or less in the direction of the inclination angle (? = 60 占? = 45 占.

Hereinafter, the effect of improving the wide viewing angle by the above-described constitution is summarized in the following examples and comparative examples. 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 examples, simulation was performed in an LCD optical simulation program, TECH WIZ LCD 1D POLAR (Sanai System, KOREA), to confirm 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 laminated on a TECH WIZ LCD 1D (MANAMA SYSTEM, KOREA) with the structure shown in FIG. 1A. The structure of FIG. 1A will be described in detail as follows.

Phase switching mode liquid crystal cells (30, 30) having a liquid crystal alignment direction of 90 DEG when the first polarizing plate (10) from the backlight side and the counterclockwise direction from the right side of the viewer side in the voltage- The first polarizing plate 10 is composed of a negative biaxial A plate 14, a polarizer 11, and a protective film 13 from the liquid crystal cell 30 side And the second polarizing plate 20 was laminated from the liquid crystal cell 30 side in the order of the isotropic protective film 24, the polarizer 21 and the protective film 23 in this order.

The liquid crystal cell used for the 42 inch panel LC420WU5 of LG Display was used and the absorption of the color filter was not considered. Actual data mounted on a 32-inch TV LC320WX4 model (LG.Philips LCD) was used as the backlight unit 40. FIG.

On the other hand, each of the optical films used in the examples of the present invention has the following optical properties.

라고 할 때 하기 수학식 5 내지 9에 의해 정의된다. 여기서 S(λ)는 광원스펙트럼이며 보통 C광원을 사용한다.Polarizers 11 and 21 of the first polarizing plate 10 and the second polarizing plate 20 dye polarized iodine on the stretched PVA to give a polarizer function and the polarizing performance of the polarizer is in the range of visible light of 370 to 780 nm Visibility The degree of polarization is 99.9% or more, and the visible light 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). Where S (λ) is the light source spectrum and usually a C source is used.

The isotropic protective film 24 had a front retardation value R0 of 0 nm, a thickness retardation value Rth of 0 nm, and a negative dioptric power Rt The sex A plate 14 had a front retardation (R0) of 140 nm and a refractive index ratio (NZ) of 1.5. At this time, the absorption axis 12 of the lower polarizer 11, the slow axis 15 of the negative biaxial A plate 14, and the alignment direction 31 of the liquid crystal are configured to be parallel.

The outer protective films 13 and 23 of the first and second polarizing plates 10 and 20 were subjected to surface switching using triacetyl cellulose (TAC) having an optical property with an Rth of 50 nm with respect to the incident light of 589.3 nm Mode liquid crystal display device was manufactured.

The polarization state change of? = 45 ° and? = 60 ° in the oblique direction on the Fujian curves of the planar switching mode liquid crystal display device is shown in FIG. Specifically, when passing through the polarizer 11 of the first polarizing plate 10 on the basis of 550 nm light on the Poincare sphere, the negative biaxial A plate 14, the liquid crystal cell 30, , The isotropic protective film 24, and then the polarized state reaches the arrival point.

FIG. 6 shows a visual sensitivity transmission distribution of a liquid crystal display device in a plane-phase switching mode. In the range of scale, the transmittance is 0% to 1% Is displayed in blue. At this time, it can be seen that the wider blue range of the center makes it possible to secure a wide viewing angle.

Example 2

Phase switching mode liquid crystal display device was fabricated in the same manner as in Example 1 except that the front retardation R0 of the negative biaxial A plate 14 was 160 nm and the refractive index ratio NZ was 1.5.

The polarization state change of the Pouinc curry spherical shape according to the wavelength of the surface switching mode liquid crystal display is similar to that of FIG. 5, and the result of the visual sensitivity transmission test is shown in FIG. From the result of FIG. 7, it can be seen that it is possible to secure a wide viewing angle when the blue range is wide.

Example 3

Phase switching mode liquid crystal display device was manufactured in the same manner as in Example 1 except that the front retardation value R0 of the negative biaxial A plate 14 was 160 nm and the refractive index ratio NZ was 1.7.

The polarization state change of the Poincare sphere shape according to the wavelength of the surface switching mode liquid crystal display device is similar to that of FIG. 5, and the result of the visual sensitivity transmission test is shown in FIG. From the result of FIG. 8, it can be seen that it is possible to secure a wide viewing angle when the blue range is wide.

Example 4

Phase switching mode liquid crystal display device was manufactured in the same manner as in Example 1 except that the front retardation value R0 of the negative biaxial A plate 14 was 180 nm and the refractive index ratio NZ was 1.7.

The polarization state change of the Poincare sphere according to the wavelength of the phase change switching mode liquid crystal display is similar to that of FIG. 5, and the result of the visual sensitivity transmission is shown in FIG. From the result of FIG. 9, it can be seen that it is possible to secure a wide viewing angle when the blue range is wide.

Example 5

Phase switching mode liquid crystal display device was manufactured using the same procedure as Example 1 except that the negative retardation A plate 14 had a front retardation value R0 of 140 nm and a refractive index ratio NZ of 1.9.

The change in the polarization state of the Poincare sphere according to the wavelength of the phase change switching mode liquid crystal display is similar to that of FIG. 5, and the result of the visual sensitivity transmission is shown in FIG. It can be seen from FIG. 10 that it is possible to secure a wide viewing angle when the blue range is wide.

Example 6

The phase difference value R0 of the negative biaxial A plate 14 was 40 nm and the refractive index ratio NZ was 2.8 to obtain a liquid crystal display device according to Example 1, A display device was manufactured. In this case, the liquid crystal cell was a planar switching mode liquid crystal cell (FFS) having a liquid crystal alignment direction of 0 ° when the counterclockwise direction was set to the positive direction with respect to the horizontal direction on the right side of the viewer side in the voltage unapplied state.

The polarization state change (Φ = 45 °, θ = 60 ° oblique direction) of the Poincare sphere according to the wavelength of the planar switching mode liquid crystal display device is shown in FIG. 11 and the result of the visual sensitivity transmission is shown in FIG.

11 shows a polarization state of "start" when passing through the polarizer 21 of the second polarizing plate 20 on the Poincare Sphere with reference to light of 550 nm, and shows an isotropic protective film 24, The negative biaxial A plate 14, and the negative biaxial A plate 14 in this order.

It can be seen from FIG. 12 that it is possible to secure a wide viewing angle when the blue range is wide.

Example 7

The phase difference value R0 of the negative biaxial A plate 14 was 60 nm and the refractive index ratio NZ was 2.8 to obtain a liquid crystal display device of the present invention. A display device was manufactured. At this time, the liquid crystal cell was a plane switching mode liquid crystal cell 30 (FFS) in which the liquid crystal alignment direction was 0 ° when the counterclockwise direction was the positive (+) direction with respect to the horizontal direction on the right side of the viewer side in the voltage unmanned state .

The polarization state change of the Poincare sphere shape according to the wavelength of the surface switching mode liquid crystal display is similar to that of FIG. 11, and the result of the visual sensitivity transmission test is shown in FIG. It can be seen from FIG. 13 that it is possible to secure a wide viewing angle when the blue range is wide from the center.

Example 8

The phase difference value R0 of the negative biaxial A plate 14 is 50 nm and the refractive index ratio NZ is 3 as in the case of Embodiment 6, A display device was manufactured. In this case, the liquid crystal cell was a planar switching mode liquid crystal cell (FFS) having a liquid crystal alignment direction of 0 ° when the counterclockwise direction was set to the positive direction with respect to the horizontal direction on the right side of the viewer side in the voltage unapplied state.

The polarization state change of the Poincare sphere shape according to the wavelength of the surface switching mode liquid crystal display is similar to that of FIG. 11, and the result of the visual sensitivity transmission test is shown in FIG. It can be seen from FIG. 14 that it is possible to secure a wide viewing angle in view of the wide blue range from the center.

Example 9

The phase difference value R0 of the negative biaxial A plate 14 was 40 nm and the refractive index ratio NZ was 3.2 as in the case of Example 6, A display device was manufactured. In this case, the liquid crystal cell was a planar switching mode liquid crystal cell (FFS) having a liquid crystal alignment direction of 0 ° when the counterclockwise direction was set to the positive direction with respect to the horizontal direction on the right side of the viewer side in the voltage unapplied state.

The polarization state change of the Pouinc curry spherical shape according to the wavelength of the surface switching mode liquid crystal display is similar to that of FIG. 11, and the result of simulation of the visual sensitivity all-round transmission is shown in FIG. It can be seen from FIG. 15 that a wide viewing angle range from the center of the result shows that it is possible to secure a wide viewing angle.

Example 10

The phase difference value R0 of the negative biaxial A plate 14 was 60 nm and the refractive index ratio NZ was 3.2 as in the case of Example 6, A display device was manufactured. In this case, the liquid crystal cell was a planar switching mode liquid crystal cell (FFS) having a liquid crystal alignment direction of 0 ° when the counterclockwise direction was set to the positive direction with respect to the horizontal direction on the right side of the viewer side in the voltage unapplied state.

The polarization state change of the Pouinc curry spherical shape according to the wavelength of the surface switching mode liquid crystal display device is similar to that of FIG. 11, and the result of the visual sensitivity transmission test is shown in FIG. From the result of FIG. 16, it can be seen that it is possible to secure a wide viewing angle when the blue range is wide.

As described above, the planar 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.

1A and 1B are perspective views showing a structure of a planar switching liquid crystal display (IPS-LCD and FFS-LCD) according to the present invention,

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

3 is a schematic view 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,

FIG. 4 is a schematic view for explaining the expression of? And? In the coordinate system of the present invention,

5 is a graph showing a change in polarization state according to Example 1 of the present invention on a pouinc curry in the direction of an inclination angle (? = 60 占? = 0 占)

6 is a graph showing a result of simulation of a visibility omnidirectional transmission according to Embodiment 1 of the present invention,

FIG. 7 shows a result of simulation of a visibility omnidirectional transmission according to a second embodiment of the present invention,

8 shows a result of a simulation of a visibility omnidirectional transmission according to a third embodiment of the present invention,

FIG. 9 shows a result of simulation of a visual sensitivity omnidirectional transmission according to the fourth embodiment of the present invention,

10 shows the result of the simulation of the visibility omnidirectional transmission according to the fifth embodiment of the present invention,

11 is a graph showing a change in polarization state according to Example 6 of the present invention in a pouinc curry in the direction of an inclination angle (? = 60 占? = 0 占)

FIG. 12 shows a result of simulation of a visibility omnidirectional transmission according to Embodiment 6 of the present invention,

FIG. 13 shows the result of the simulation of the visibility omnidirectional transmission according to the seventh embodiment of the present invention,

FIG. 14 shows a result of a simulation of a visibility omnidirectional transmission according to an eighth embodiment of the present invention,

FIG. 15 shows a result of a visual sensitivity transmission test according to the ninth embodiment of the present invention,

FIG. 16 shows a result of a simulation of a visibility omnidirectional transmission according to the tenth embodiment of the present invention.

Claims (7)

A first polarizer laminated in this order on a protective film, a polarizer and a negative biaxial A plate; A liquid crystal cell; An isotropic protective film, a polarizer, and a protective film in this order, The absorption axes of the respective polarizers of the first polarizing plate and the second polarizing plate are orthogonal to each other, The isotropic protective film has a front retardation value (RO) of 0 to 5 nm, an absolute value of a thickness direction retardation value (Rth) of less than 10 nm, The negative biaxial A plate has a surface phase difference (R0) of 40 to 200 nm and a refractive index ratio (NZ) of 1 < NZ & Mode liquid crystal display device. The isotropic protective film of claim 1, wherein the absolute value of the front retardation value (RO) and the thickness direction retardation value (Rth) is less than 2 nm, Wherein the negative biaxial A plate has a front retardation value (R0) of 40 to 180 nm and a refractive index ratio (NZ) of 1.3 to 3.5. [2] The method according to claim 1, wherein the first polarizer is a lower plate polarizer, the second polarizer is a top plate polarizer, Wherein the liquid crystal cell has a liquid crystal alignment direction of 90 DEG when the counterclockwise direction is set to the positive (+) direction with respect to the horizontal direction on the right side of the viewer side. 4. The liquid crystal display according to claim 3, wherein the liquid crystal cell has a panel retardation value in the range of 300 to 330 nm at a wavelength of 589 nm. [3] The liquid crystal display according to claim 1, wherein the first polarizer is a top plate polarizer, the second polarizer is a bottom plate polarizer, Wherein the liquid crystal cell has a liquid crystal alignment direction of 0 DEG when the counterclockwise direction is a positive (+) direction with respect to a horizontal direction on the right side of the viewer side. The liquid crystal display according to claim 5, 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 negative biaxial A plate of claim 1 wherein the negative biaxial A plate is selected from the group consisting of triacetylcellulose (TAC), cycloolefin polymer (COP), cycloolefin copolymer (COC), polyethylene terephthalate (PET), polypropylene (PC), polysulfone (PSF), and polymethyl methacrylate (PMMA).

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