KR101565009B1 - Bottom 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 positive biaxial A plate having a specific optical property from a liquid crystal cell side, a negative biaxial A plate, a lower plate polarizer laminated 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 a liquid crystal display (LCD)

The present invention relates to a liquid crystal display device, a liquid crystal display device, a liquid crystal display device, a liquid crystal display device, a liquid crystal display device, and a liquid crystal display device, 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 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, By the arrangement of the polarizing plates on the lower surface, it is possible to display a relatively good dark state in the non-driving state compared to the other modes. When the transmission axis of the lower plate coincides with the direction of the slow axis of the liquid crystal molecule in the front plane, the polarized state changes at the slope, but since the polarized state of the polarizing plate at the propagation field remains the same, The color can be maintained and the transmittance can be maintained at the same level as above, so that it is possible to display a relatively good black state in comparison with other modes.

Such a phase-change-mode liquid crystal display device can obtain a relatively wide viewing angle compared to other modes without using an optical film, and thus has an advantage that the image quality and the viewing angle are 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. In order to secure a wide viewing angle, a isotropic protective layer (isotropic TAC) is used instead of a general TAC film between a polarizer (PVA) and a liquid crystal cell to eliminate elliptical polarization by TAC in a switching mode liquid crystal display (IPS- However, it is pointed out that it is difficult to obtain a wide viewing angle because the polarization axis is not compensated for the absorption axis of the polarizer and the light leakage phenomenon occurs.

Accordingly, a new polarizing plate structure capable of mass production is desperately required by easily manufacturing 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, in the present invention, the polarizing plane of the polarized light having passed through the lower plate polarizing plate by the lower plate polarizing plate including the retardation film having various lamination structures and the retardation value design is made to coincide with the absorption axis of the upper plate polarizing plate To compensate for the polarizer absorption axis of the lower plate to secure a wider viewing angle than in the prior art and to provide a lower plate polarizer that can be manufactured using a roll-to-roll production mode. Specifically, by using a lower polarizer plate in which a positive biaxial A plate having a specific optical property from the liquid crystal cell side and a negative biaxial A plate and a polarizer and a protective layer are laminated in this order on a plane switching mode liquid crystal display device, And it is possible to minimize a change in color due to a change in viewing angle in a dark state, thereby providing a liquid crystal display device with a flat switching mode that provides a wider viewing angle than the conventional one.

The present invention is a lower plate polarizing plate for a planar switching (IPS) mode in which a positive biaxial A plate, a negative biaxial A plate, a polarizer and a protective layer are laminated in this order from the liquid crystal cell side, wherein the positive biaxial A plate has a front retardation value (R0) of 20 to 120 nm and a refractive index ratio (NZ) of -2.2? NZ? -0.01, the slow axis being orthogonal to the absorption axis of the adjacent polarizer; The negative biaxial A plate is characterized by a lower plate polarizer having a front retardation (R0) of 20 to 120 nm, a refractive index ratio (NZ) of 1.01? NZ? 4, and a slow axis perpendicular 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 lower plate polarizer.

The planar switching mode liquid crystal display device according to the present invention applies a positive biaxial A plate and a negative biaxial A plate having a specific optical property from the liquid crystal cell side and a polarizer and a protective layer in this order, By making it possible to realize a perfect 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 [0002] The present invention relates to a lower plate polarizer capable of compensating for light leakage in a liquid crystal cell when applied to a liquid crystal display device of a planar switching mode, thereby realizing a dark state at a wide viewing angle. The lower plate polarizer is composed of a positive biaxial A plate, a negative biaxial A plate, a polarizer and a protective layer laminated in this order from the liquid crystal cell side.

The 'POSITIVE BIAXIAL A plate' in this specification refers to a negative biaxial optical element satisfying Nz> Nx> Ny, which is also referred to as a 'positive B plate'. Herein, the negative (-) biaxial optical element in the present invention refers to a material whose refractive index decreases in the stretching direction.

The 'NEGATIVE BIAXIAL A plate' in this specification refers to a biaxial optical element having a positive refractive index distribution satisfying Nx> Ny> Nz, and is referred to as a 'negative B plate'. Here, the positive (+) biaxial optical element in the present invention means a material having a large refractive index in the stretching direction.

The positive biaxial A plate disposed on the lower polarizer plate has a front retardation value (R0) of 20 to 120 nm and a refractive index ratio (NZ) of -2.2? NZ? -0.01, and a better optical viewing angle It is preferable that the front retardation value R0 is 25 to 115 nm and the refractive index ratio NZ is -2.1? NZ? -0.1, more preferably the front retardation value R0 is 30 to 110 nm , It is preferable that the refractive index ratio (NZ) be maintained at -2? NZ? -0.2, and it is most preferable that the refractive index ratio (NZ) maintains -2? NZ? -1.0. The slow axis of this positive biaxial A plate is configured to be orthogonal to the absorption axis of the adjacent polarizer on the viewer side. Such a positive biaxial A plate may have 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 have.

The negative biaxial A plate laminated on the positive biaxial A plate from the liquid crystal cell side has a front retardation value (RO) of 20 to 120 nm, a refractive index ratio (NZ) of 1.01? NZ? 4, It is preferable that the front retardation value R0 is 25 to 115 nm and the refractive index ratio NZ is 1.1? NZ? 3.7, more preferably the front retardation value R0 ) Is 30 to 110 nm, and the refractive index ratio (NZ) is preferably 1.2? NZ? 3.5. The slow axis of the negative biaxial A plate is configured to be orthogonal to the absorption axis of the adjacent polarizer on the viewer side.

The positive biaxial A plate and the negative biaxial A plate are not limited to materials and can be applied to the present invention as long as they satisfy the optical properties within the range defined by the present invention independently of each other. 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) may be used.

(IPS) mode liquid crystal display device is constructed by laminating the lower plate polarizer produced 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. In a liquid crystal display device, in-plane switching (IPS) is classified into Super-In-Plane-Switching (FIPS) and Fringe-Field-Switching (FFS) according to modes of active matrix driving electrodes including electrode pairs , The IPS-LCD of the present invention has a liquid crystal alignment by FFS (Fringe-Field-Switching) parallel to the absorption axis of the polarizer of the top plate polarizer.

The top plate 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 polarizer is composed of an isotropic protective layer, a polarizer and a protective layer in this order from the liquid crystal cell side, and the polarizer absorption axis of the lower plate polarizer and the polarizer absorption axis of the upper plate polarizer are mutually orthogonal.

Materials for forming the isotropic protective layer and the protective layer constituting the upper plate polarizer and the protective layer constituting the lower polarizer can be applied independently of one another and those commonly used in the art can be applied. Specifically, triacetylcellulose (TAC) (COP), cycloolefin copolymer (COC), polyethylene terephthalate (PET), polypropylene (PP), polycarbonate (PC), polysulfone (PSF) and polymethylmethacrylate Can be used. Preferably, the isotropic protection layer has a front retardation (RO) and a thickness direction retardation (Rth) of less than 10 nm, preferably an absolute value of less than 2 nm, and the protective layer of the upper plate and the lower plate polarizer is optically Since the characteristics do not affect the viewing angle, the refractive index characteristics are not particularly limited in the present invention.

The positive biaxial A plate constituting the lower polarizer plate and the retardation film such as the isotropic protective layer of the negative biaxial A plate and the upper plate polarizer are arranged such that the thickness direction is the z axis, the direction in which the in-plane refractive index is large is the x axis, 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. In the case where the refractive indices in the three axial directions are different from each other, there are two optical axes in which no retardation occurs, and this is called a biaxial retardation film. 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 intended to suggest a lower plate polarizing plate which can be practically applied to mass production and has a better viewing angle compensating effect than the conventional concept of viewing angle compensation, and a planar switching mode liquid crystal display using the same. The planar switching liquid crystal display device constructed in accordance with the optical condition of the present invention satisfies the compensation relationship of the maximum transmittance of the visual sensitivity omnidirectional in the dark state of 0.1% or less, preferably 0.05% or less. The front brightness of the currently produced brightest liquid crystal display device is about 10000 nits using the VA mode, and the brightness is about 10000 nits × cos 60 ° at a view angle of 60 ° slope, and 0.05% is 2.5 nits to be. Therefore, the present invention realizes visual sensitivity omnidirectional transmittance comparable to that of the IPS mode and comparable to the VA mode, while achieving a visibility omnidirectional transmittance equal to or greater than that of the liquid crystal display device using the IPS mode.

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 has an isotropic protective layer 24 laminated on the liquid crystal cell side of the polarizer 21 and the lower polarizer plate 10 has a positive biaxial A plate 16, a negative biaxial A plate 14 And a polarizer 21 are stacked in this order.

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.

The panel retardation value (DELTA n x d) defined by the following formula (4) is in the range of 300 to 400 nm at the wavelength of 589 nm, and preferably about 380 nm in the configuration of the present invention. 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 = (n _e - n _o ) × d

(Where n _e is the extraordinary ray refraction index of the liquid crystal, n _o is the normal ray refraction index, d is the cell gap, note Δ n, d is a scalar rather than a vector)

The positive biaxial A plate constituting the lower plate polarizer 10 may have a front retardation (R0) of 20 to 120 nm and a refractive index ratio (NZ) of -2.2? NZ? -0.01, So that it is orthogonal to the absorption axis. In a specific embodiment, a three-layer structure film of poly (methyl methacrylate) (PMMA), polystyrene (PS) and polymethyl methacrylate (PMMA) And stretching in the plane perpendicular to the MD direction. 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 negative biaxial A plate may have a front retardation value (R0) of 20 to 120 nm and a refractive index ratio (NZ) of 1.01? NZ? 4, and the slow axis may be orthogonal to the absorption axis of the adjacent polarizer .

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 22 of the upper plate polarizer 20 and 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. When viewed from the viewer's side (opposite to the backlight unit), the alignment direction 31 of the liquid crystal showing the direction in which the liquid crystal is aligned with the lower plate polarizer 10 And the absorption axes 12 and 22 of the top plate polarizer 20, respectively.

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 of the 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 upper plate polarizer 20, the directions of the protective layer 23 and the isotropic protective layer 24 do not affect the optical performance and roll-to-roll production is possible. In the case of the lower plate polarizer 20, And the MD direction of the polarizer 11, the slow axis 15 of the negative biaxial A plate 14 and the slow axis 17 of the positive biaxial A plate 16 If they match, roll-to-roll production is possible. Specifically, in the lower polarizer 10, the absorption axis 12 of the polarizer 11 is in the MD direction. This is because when the PVA fabric used as the polarizer material is polarized in the MD direction, Direction and stained with iodine so that the light absorption direction becomes the MD direction. The positive biaxial A plate 16 can be realized by biaxial stretching and the refractive index can be roll-to-roll bonded in the vertical direction of the MD, which is relatively in the MD direction It can be realized by stretching it a lot.

The negative biaxial A plate 14 has a positive refractive index characteristic in which the refractive index is increased with respect to the stretching direction and is uniaxially stretched in the MD direction or both in the MD and MD directions depending on the material Biaxial stretching can be realized. In the case of uniaxial stretching in the MD direction, the length in the MD direction is fixed due to the mechanical characteristics of the stretching machine, so Nx is formed in the direction perpendicular to the MD direction. During stretching, Nx becomes larger and Ny becomes smaller. 1. In the case of biaxial stretching in which both the MD direction and the MD direction are elongated, the refractive index ratio of the former when drawing a large amount in the direction perpendicular to the MD direction, and the slow axis 15 of the negative biaxial A plate 14 of the present invention ) Is a direction perpendicular to the MD direction, both of the MD direction and the MD direction, regardless of the order, may be stretched in a direction perpendicular to the MD direction relative to the MD direction, And becomes a phase difference film that can be bonded.

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 17 of the positive biaxial A plate of the present invention and the slow axis 15 of the negative biaxial A plate are such that light is incident on the negative biaxial A plate 14 and the positive biaxial When the A plate 16 is incident in the normal direction, it means the axis through which the light travels the slowest by the retardation film, which means the axis having the greatest refractive index. This means that a phase difference occurs when passing through the retardation film (Optical axis). 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 polarization state 1 on the Poincare Sphere and is incident on the negative biaxial A plate 14, 3, 4, and 5 on the Poincare Sphere while passing through the positive biaxial A plate 16, the FFS liquid crystal cell 30, and the isotropic protective layer 24. [ Specifically, the light polarized in the polarization state 1 is changed to the polarization states 2 and 3 by the negative biaxial A plate 14 and the positive biaxial A plate 16, and light passing through the FFS liquid crystal cell 30 is polarized State 4, passes through the isotropic protection layer 24, and becomes polarized state 5 in which the polarizer is orthogonal, as described above, so that light does not leak and the viewing angle is not narrowed.

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 back plate 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 positive biaxial A plate 16, The polarizer 11 and the protective layer 13 in this order from the liquid crystal cell side and the upper plate polarizer 20 is composed of an isotropic protective layer 24, a polarizer 21 and a protective layer 23 ).

At this time, the polarizers 11 and 21 are provided with the function of a polarizer through stretching and dyeing, and the polarizers 10 and 20 are arranged on both sides of the FFS mode liquid crystal cell 30 (Wooo9000, HITACHI, JAPAN) Respectively. The absorption axis 22 of the upper plate polarizing plate 20 and the alignment direction 31 of the liquid crystal contained in the liquid crystal cell 30 are referred to as an absorption axis 22 of the polarizer 21 of the upper polarizer 20 And the absorption axis 12 of the polarizer 11 of the lower plate polarizer 10 are orthogonal to each other and the absorption axis 22 of the polarizer 21 of the upper plate polarizer 20 and the alignment direction 31 of the liquid crystal are parallel .

Protective layers 13 and 23 are arranged on opposite sides of the liquid crystal cell 30 of the polarizer 11 of the lower polarizer 10 and the polarizer 21 of the upper polarizer 20, respectively.

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 the stretched PVA with iodine and the polarizing performance of the polarizer is changed from visible light ray region of 370 to 780 nm 99.9% or more, and the visible 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 resulting from the difference in internal refractive indexes according to the directions of the respective films were 589.3 nm for the light source, the positive biaxial A plate 16 had a front retardation (R0) of 80 nm and a refractive index ratio (NZ) of -0.21; The negative biaxial A plate 14 has a front retardation R0 of 90 nm and a refractive index ratio NZ of 1.21; 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 positive biaxial A plate 14 and the negative biaxial A plate 16 is orthogonal to the absorption axis 12 of the adjacent polarizer 11.

The negative biaxial A plate 14 uses a cyclopolymer olefin (COP, Zeonor, Optes, Japan) and the positive biaxial A plate 16 uses a negative biaxial A PS having refractive index characteristics was sequentially arranged on a retardation film (I-Film, Optes, Japan). The outer protective layers 13 and 23 of the upper and lower plate polarizers 10 and 20 were coated with triacetyl cellulose (TAC) having an optical property with a thickness direction retardation (Rth) of 50 nm to the incident light of 589.3 nm Respectively. Actual data mounted on a 32-inch TV Wooo 9000 model (HITACHI, JAPAN) was used as the backlight unit 50.

The above optical components were laminated as shown in FIG. 1, and a visual sensitivity omni-directional transmittance simulation was performed. As a result, the results shown in FIG. 7 were obtained. 7 shows the distribution of the visual sensitivity omnidirectional transmittance when displaying the black on the screen. In the scale range, the transmittance is in the range of 0% to 0.05%, the portion in which the transmittance exceeds 0.05% 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, on the inclined plane, the change in polarization state of the pouincure sphere like Fig. 5 (R1) is shown.

Example 2

The positive biaxial A plate 16 had a front retardation (R0) of 31 nm and a refractive index ratio (NZ) of -1.99 at a light source of 589.3 nm; The negative biaxial A plate 14 was provided with a front retardation R0 of 109 nm and a refractive index ratio NZ of 1.21 to prepare a planar switching (IPS) liquid crystal display device.

FIG. 8 shows the result of simulation of the visual sensitivity omni-directional transmittance of the planar switching liquid crystal display device. This is because on the inclined surface, the polarization state change of the pouincure spherical shape as shown in Fig. 5 (R2) is shown.

Example 3

The positive biaxial A plate 16 had a frontal retardation R0 of 109 nm and a refractive index ratio (NZ) of -0.21 at a light source of 589.3 nm. The negative biaxial A plate 14 was provided with a front retardation R0 of 31 nm and a refractive index ratio NZ of 3.49 to prepare a planar switching (IPS) liquid crystal display device.

FIG. 9 shows the result of simulation of the visual sensitivity omni-directional transmittance of the planar switching liquid crystal display device. This is because it shows the change in polarization state of the pouincure spherical surface as shown in Fig. 5 (R3) on the inclined plane.

Example 4

The positive biaxial A plate 16 had a front retardation (R0) of 50 nm and a refractive index ratio (NZ) of -1.99 at a light source of 589.3 nm; The negative biaxial A plate 14 was provided with a front retardation R0 of 40 nm and a refractive index ratio NZ of 3.49 to produce a planar switching (IPS) liquid crystal display device.

FIG. 10 shows the result of simulation of the visual sensitivity omni-directional transmittance of the planar switching liquid crystal display device. This is because, on the inclined plane, the change in the polarization state of the Poincare sphere like that shown in Fig. 5 (R4) is shown.

Example 5

The positive biaxial A plate 16 had a frontal retardation R0 of 119 nm and a refractive index ratio (NZ) of -0.21 at a light source of 589.3 nm. The negative biaxial A plate 14 was provided with a front retardation R0 of 31 nm and a refractive index ratio NZ of 3.49 to prepare a planar switching (IPS) liquid crystal display device.

FIG. 11 shows the result of simulation of the visual sensitivity omni-directional transmittance of the planar switching liquid crystal display device.

Example 6

The positive biaxial A plate 16 had a front retardation (R0) of 31 nm and a refractive index ratio (NZ) of -1.99 at a light source of 589.3 nm; The negative biaxial A plate 14 was provided with a front retardation R0 of 119 nm and a refractive index ratio NZ of 1.21 to produce a planar switching (IPS) liquid crystal display device.

FIG. 12 shows the result of simulation of the visual sensitivity omni-directional transmittance of the planar switching liquid crystal display device.

Comparative Example 1

In the structure of the first embodiment, the positive biaxial A plate 16 and the negative biaxial A plate 14 were removed to replace the isotropic protective film to produce a planar switching (IPS) liquid crystal display device as shown in FIG.

The visual sensitivity omni-directional transmittance simulation of the planar switching liquid crystal display device was performed. As a result, 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 0.21% in Example 1 and 0.34% in Comparative Example 1, which indicates that the maximum transmittance in all directions is about 14.7 times that in Example 1.

Comparative Example 2

The positive biaxial A plate 16 had a front retardation (R0) of 150 nm and a refractive index ratio (NZ) of -0.2 at a light source of 589.3 nm. The negative biaxial A plate 14 was provided with a front retardation R0 of 50 nm and a refractive index ratio NZ of 3.5 to produce a planar switching (IPS) liquid crystal display device.

The results of the visual sensitivity omni-directional transmittance simulation of the planar switching liquid crystal display device were as shown in Fig. 15, and it was confirmed that the oblique plane transmittance in the black state was high and the viewing angle was narrow

Comparative Example 3

The positive biaxial A plate 16 had a front retardation (R0) of 30 nm and a refractive index ratio (NZ) of -2 at a light source of 589.3 nm. The negative biaxial A plate 14 was provided with a front retardation R0 of 30 nm and a refractive index ratio NZ of 5 to produce a planar switching (IPS) liquid crystal display device.

The results of the visual sensitivity omni-directional transmittance simulation of the planar switching liquid crystal display device were as shown in Fig. 16, and it can be confirmed that the oblique plane transmittance in the black state is high and the viewing angle is narrow.

Comparative Example 4

(IPS) liquid crystal display device was manufactured by changing the positions of the positive biaxial A plate 16 and the negative biaxial A plate 14 in the first embodiment.

The results of the omni-directional transmittance simulation of the planar switching liquid crystal display device were as shown in Fig. 17, and it can be confirmed that the oblique plane transmittance in the black state is high and the viewing angle is narrow.

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 polarizing plate according to the present invention,

FIG. 5 is a diagram illustrating a polarization state change in the Poincare Sphere that enables viewing angle compensation at the time of? = 60 ° and? = 45 ° 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,

FIG. 8 is a result of simulating the visual sensitivity of the second embodiment according to the present invention,

FIG. 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 visibility all-round transmission of the fourth embodiment according to the present invention,

11 is a simulation result of the visibility all-round transmission 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 a 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 visibility 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 (10)

(IPS) mode laminated in the order of a positive biaxial A plate, a negative biaxial A plate, a polarizer and a protective layer from the liquid crystal cell side, Wherein the positive biaxial A plate has a front retardation value (RO) of 20 to 120 nm and a refractive index ratio (NZ) of -2.2? NZ? -1.0, the slow axis being orthogonal to the absorption axis of the adjacent polarizer; Wherein the negative biaxial A plate has a front retardation value (RO) of 20 to 120 nm, a refractive index ratio (NZ) of 1.01? NZ? 4, and a slow axis perpendicular to an absorption axis of an adjacent polarizer, The refractive index ratio (NZ) is defined by the following equation (3): " (3) " [Equation 1] Rth = [(Nx + Ny) / 2 - Nz] xd &Quot; (2) " RO = (Nx - Ny) xd &Quot; (3) " NZ = (Nx - Nz) / (Nx - Ny) = Rth / RO + 0.5 (Where Nx and Ny are refractive indices in planes, Nx > = Ny, Nz is refractive index in the thickness direction, RO is the front retardation value, Rth is the thickness direction retardation value, and d is the thickness of the film) The positive biaxial A plate and the negative biaxial A plate according to claim 1, wherein the positive biaxial A plate and the negative biaxial A plate are made of triacetylcellulose (TAC), cycloolefin polymer (COP), cycloolefin copolymer (COC), polyethylene terephthalate Wherein the polymer is selected from the group consisting of polypropylene (PP), polycarbonate (PC), polysulfone (PSF) and polymethylmethacrylate (PMMA). The lower plate polarizer of claim 1, wherein the positive biaxial A plate has a structure in which polymethylmethacrylate (PMMA), polystyrene (PS), and polymethylmethacrylate (PMMA) are sequentially laminated. The lower plate polarizer of claim 1, wherein the positive biaxial A plate is at least one or more layers of modified polycarbonate (PC). The protective layer according to claim 1, wherein the protective layer comprises at least one of triacetylcellulose (TAC), cycloolefin polymer (COP), cycloolefin copolymer (COC), polyethylene terephthalate (PET), polypropylene (PP), polycarbonate (PSF) and polymethylmethacrylate (PMMA). ≪ RTI ID = 0.0 > 11. < / RTI > A surface-switched (IPS) mode liquid crystal display comprising the lower plate polarizer of claim 1. The liquid crystal display device according to claim 6, wherein the maximum sensitivity of the visual sensitivity omnidirectional transmission satisfies a compensation relationship of 0.1% 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 upper plate polarizer. The method of claim 8, 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 top plate polarizer.

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