KR20100060092A

KR20100060092A - Upper plate polarizer and in-plane switching mode liquid crystal display comprising the same

Info

Publication number: KR20100060092A
Application number: KR1020080118532A
Authority: KR
Inventors: 김봉춘
Original assignee: 동우 화인켐 주식회사
Priority date: 2008-11-27
Filing date: 2008-11-27
Publication date: 2010-06-07

Abstract

PURPOSE: An upper plate polarizing plate and a LCD device for in plane switching mode including and upper plate of polarizing upper plate are provided to maintain absorbing axes between polarizers of an upper plate polarizing plate and a lower plate polarizing plate on a slope by an orthogonal state, thereby preventing light leakage. CONSTITUTION: A positive axial A plate(24), a positive biaxial A plate(25), a polarizer(21) and a protection layer(23) are successively laminated from a liquid crystal cell side in orders, in an upper plate polarizing plate for IPS(In Plane Switching) mode(20). A front phase difference value of a positive uniaxial A plate is 80-130nm. A slow phase axis of the positive axial A plate is parallel to an absorption axis(22) of an adjacent polarizer. The front phase difference value of the positive biaxial A plate is 40-90nm.

Description

UPPER PLATE POLARIZER AND IN-PLANE SWITCHING MODE LIQUID CRYSTAL DISPLAY COMPRISING THE SAME

The present invention provides a planar switching in which a positive uniaxial A plate and a positive biaxial A plate having specific optical properties from a liquid crystal cell side, and a polarizer stacked in the order of a polarizer and a protective layer are applied to the top plate to secure a wide viewing angle (IN−). PLANE SWITCHING, hereinafter referred to as 'IPS').

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. Therefore, a technology for securing a wide viewing angle by applying a functional optical film such as a liquid crystal driving mode and a retardation film has emerged. In particular, a liquid crystal display device using an IPS mode as a dual liquid crystal driving mode improves the viewing angle characteristics. It is well known that it has an excellent effect.

In the field switching mode (IPS mode), a liquid crystal is driven by using a lateral electric field. In modes such as twisted nematic (TN) and vertical alignment (VA), the direction of the liquid crystal and the electric field is different. While vertically formed [vertical alignment] between the upper and lower plates, the IPS mode uses a horizontally oriented liquid crystal to form the direction of the electric field parallel to the liquid crystal array direction.

In the plane switching mode, since the liquid crystal molecules have a substantially horizontal and uniform arrangement on the substrate surface in the non-driven state, the optical characteristics of the liquid crystal when the transmission axis of the lower plate and the direction of the fast axis of the liquid crystal molecules coincide with each other at the front side. Since the transmission axis and the fastening axis of the liquid crystal coincide on the slope, even if the light passing through the lower polarizing plate passes through the liquid crystal, the polarization state does not change and the liquid crystal layer can pass through the liquid crystal layer as it is. By arranging the planar polarizing plates, a certain dark state can be displayed in the non-driven state. 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 device is mainly used in high-end models of 18 inches or more.

Conventional liquid crystal display device using a plane switching mode requires a polarizing plate for polarizing light on the outside of the liquid crystal cell containing a liquid crystal, a protective film made of a triacetyl cellulose (TAC, Triacetylcellulose) film on one side or both sides of the polarizing plate It is provided in order to protect this polarizer 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 triacetylcellulose on the inclined surface instead of the front surface, and the elliptically polarized light is amplified in the liquid crystal cell. At the same time, there is a problem in that light has various colors.

Moreover, in recent years, as image display devices such as large TVs using the planar switching mode method have been manufactured, wide viewing angle characteristics are required. In the planar switching mode liquid crystal display (IPS-LCD), an isotropic protective layer is used instead of the TAC film between the polarizer PVA and the liquid crystal cell to secure a wide viewing angle, thereby eliminating elliptical polarization due to triacetylcellulose. However, it is still pointed out that it is difficult to secure a wide viewing angle because light leakage occurs because the absorption axis of the polarizer is not compensated on the inclined surface.

Accordingly, a new polarizer configuration capable of mass production is urgently needed by easily manufacturing a composite polarizer including a phase difference film by using a roll-to-roll production mode with various compensation configurations to secure an excellent wide viewing angle.

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

Accordingly, the present invention is to compensate for the absorption axis of the polarizer of the lower plate by the upper polarizing plate containing a retardation film having a variety of laminated structure and retardation value design as a method of changing the compensation film to secure a wider viewing angle than the conventional The present invention is directed to a top plate polarizer that can be manufactured using a roll-to-roll mode of production. Specifically, the positive polarization A plate and positive biaxial A plate having a specific optical property from the liquid crystal cell side, and an upper plate polarizing plate in which a polarizer and a protective layer are laminated in this order are used in the planar switching mode liquid crystal display device, so that the front and inclination angles are used. The present invention provides a planar switching mode liquid crystal display device that provides a wider viewing angle than that of the prior art because it can improve contrast characteristics and minimize light leakage due to a change in viewing angle in a dark state.

The present invention is a top plate polarizing plate for a planar switching (IPS) mode stacked in the order of a positive uniaxial A plate, a positive biaxial A plate, a polarizer and a protective layer from the liquid crystal cell side, wherein the positive uniaxial A plate has a front phase difference value ( R0) is from 80 to 130 nm, the refractive index ratio (NZ) is 0.9 ≤ NZ ≤ 1.1, and the slow axis is parallel to the absorption axis of the adjacent polarizer; The positive biaxial A plate is characterized by a top plate polarizer configured to have a front phase difference value (R0) of 40 to 90 nm, a refractive index ratio (NZ) of -1.2 ≤ NZ ≤ -0.01, and a slow axis parallel to an absorption axis of an adjacent polarizer. have.

In addition, the present invention has another feature in an on-plane switching (IPS) mode liquid crystal display including the upper polarizing plate.

The planar switching mode liquid crystal display according to the present invention applies a positive uniaxial A plate and a positive biaxial A plate having a specific optical property from the liquid crystal cell side, and a top polarizing plate laminated in the order of a polarizer and a protective layer. By enabling the implementation of the dark state can have a wider viewing angle than conventional, mass production is easy.

The present invention relates to a top polarizer for compensating for light leakage in a liquid crystal cell when applied to a planar switching mode liquid crystal display device to enable a dark state at a full viewing angle. Such a top plate polarizing plate is formed by laminating a positive uniaxial A plate, a positive biaxial A plate, a polarizer and a protective layer in this order from the liquid crystal cell side.

The term 'positive uniaxial A plate' of the present specification refers to a positive uniaxial optical element whose theoretical refractive index distribution satisfies nx> ny = nz. In reality, it is difficult to make ny = nz in the manufacturing process of the plate, that is, ny and nz produce exactly the same positive uniaxial A plate. I handle it with A plate. Preferably, when substantially the same, the range of 10Nz-9Ny <Nx for Nz> Ny and 11Ny-10Nz <Nx for Ny> Nz may be maintained. The negative biaxial optical element satisfying nz> nx> ny is also referred to as a 'positive B plate'. The negative optical element herein refers to a material whose refractive index decreases in the stretching direction.

The positive uniaxial A plate disposed on the upper polarizing plate preferably has a front phase difference (R0) of 80 to 130 nm, a refractive index ratio (NZ) of 0.9 ≤ NZ ≤ 1.1, and a better wide viewing angle characteristic. It is preferable that the value R0 is 90 to 120 nm, the refractive index ratio NZ is 1.0, more preferably the front phase difference value R0 is 100 to 110 nm, and the refractive index ratio NZ is 1.0. The slow axis of this positive uniaxial A plate is configured to be parallel to the absorption axis of the adjacent polarizer on the viewing side.

The positive biaxial A plate (positive B plate) stacked on the positive uniaxial A plate upper surface from the liquid crystal cell side has a front phase difference value R0 of 40 to 90 nm and a refractive index ratio NZ of -1.2 to -0.01. In order to exhibit better wide viewing angle characteristics, the front phase difference value R0 is preferably 45 to 85 nm, the refractive index ratio NZ is -1.1 to -0.1, and more preferably the front phase difference value R0 is 50. It is good to maintain -1 to -0.2 which is -80 nm and which is the refractive index ratio (NZ) which can be made process stable. Such a positive biaxial A plate has a structure in which polymethyl methacrylate (PMMA), polystyrene (PS) and polymethyl methacrylate (PMMA) are sequentially stacked or modified polycarbonate (PC) on at least one side of a positive biaxial A plate. ) May be further laminated. The slow axis of this positive biaxial A plate is configured to be parallel to the absorption axis of the adjacent polarizer on the viewing side.

The positive uniaxial A plate and the positive biaxial A plate described above can be applied to the present invention without being limited to materials as long as they each independently satisfy the optical characteristics within the range defined by the present invention. Specifically, triacetyl cellulose (TAC), cycloolefin polymer (COP), cycloolefin copolymer (COC), polyethylene terephthalate (PET), polypropylene (PP), polycarbonate (PC) , polysulfone (PSF) and poly Methyl methacrylate (PMMA) can be used that is prepared from the one selected from the group consisting of.

A top plate polarizer manufactured according to the present invention is laminated to form an in-plane switching (IPS) mode liquid crystal display device. In this case, the liquid crystal display of the present invention includes aligning the liquid crystal in a multi-domain or dividing it into multiple regions by a voltage applied thereto. According to the mode of an active matrix driving electrode including an electrode pair, an LCD may be classified into super-in-plane-switching (IPS) and fringe-field-switching (FFS). However, the IPS-LCD of the present invention is super-in-plane-switching (IPS), and the liquid crystal alignment is parallel to the absorption axis of the polarizer of the lower polarizing plate.

The lower polarizing plate configuration of the planar switching mode liquid crystal display is generally used in the art, and uses an isotropic protective layer applied to secure a wide viewing angle. Specifically, the liquid crystal cell is configured in the order of an isotropic protective layer, a polarizer and a protective layer, and the polarizer absorption axis of the upper polarizer and the polarizer absorption axis of the lower polarizer are orthogonal to each other.

The isotropic protective layer constituting the lower polarizing plate and the protective layer, and the material forming the protective layer constituting the upper polarizing plate may be used independently of each other generally used in the art, specifically triacetyl cellulose (TAC) , Cycloolefin polymer (COP), cycloolefin copolymer (COC), polyethylene terephthalate (PET), polypropylene (PP), polycarbonate (PC) , polysulfone (PSF) and polymethyl methacrylate (PMMA) Any one prepared from the group can be used. In this case, the isotropic protective layer is preferably less than 10nm, preferably less than 2nm each of the front phase difference (RO) and the thickness direction phase difference (Rth), the protective layer of the upper and lower polarizing plates of the optical characteristics according to the refractive index difference Since it does not affect the refractive index characteristics in the present invention is not particularly limited.

The retardation films such as the positive uniaxial A plate, the positive biaxial A plate, and the isotropic protective layer of the lower plate polarizing plate constituting the upper polarizing plate, the z-axis in the thickness direction, the x-axis in the direction of the large in-plane refractive index as shown in FIG. When the vertical direction is referred to as the y-axis, when the refractive index corresponding to each direction is Nx, Ny, and Nz, the thickness direction phase difference Rth defined by Equation 1 below and the front phase difference R0 defined by Equation 2 below And the refractive index ratio NZ defined by the following equation (3). In this case, the characteristics of the retardation film are determined according to the size of 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 that do not cause retardation, which is called a biaxial retardation film. Optical properties of each film to be implemented in the present invention is a property of the light source 589.3nm, the light source range is a reference when referring to the optical properties in general, the value when the light source 589.3nm when there is no special description of the light source Say

Rth = [(Nx + Ny) / 2-Nz] × d

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

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

As described above, the present invention is not intended to provide a conventional abstract viewing angle compensation concept, but to provide a top polarizer and a planar switching mode liquid crystal display device using the same, which can be substantially applied to mass production and have a superior viewing angle compensation effect. The planar switching liquid crystal display device configured under the optical condition of the present invention satisfies the compensating relationship of the luminous transmittance omnidirectional maximum transmittance of 0.05% or less, preferably 0.02% or less. The value of 0.05% or less is a range of maximum permeability of the general planar switching liquid crystal display device, which is similar and improved. Generally, the value is less than 0.1%. It is enough.

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

1 is a perspective view illustrating a basic structure of an IPS-LCD according to the present invention.

In the IPS mode LCD according to the present invention, the lower polarizer 10, the liquid crystal cell 30, and the upper polarizer 20 are stacked in the order of the backlight unit 40, and the lower polarizer 10 and the upper polarizer ( The protective layers 13 and 23 are positioned opposite to the liquid crystal cell of the polarizers 11 and 21 of the 20. The upper polarizing plate 20 is stacked in the order of the positive uniaxial A plate 24, the positive biaxial A plate 25, and the polarizer 21 from the liquid crystal cell side, and the lower polarizing plate 10 is formed of the polarizer 11. The isotropic protective layer 14 is laminated on the liquid crystal cell side.

More specifically, the lower polarizing plate 10 includes a horizontally oriented liquid crystal cell 30 filled with a liquid crystal having a positive dielectric anisotropy (Δε> 0) between two glass substrates, and an upper polarizing plate 20. In one of the glass substrates of the liquid crystal cell 30, an active matrix drive electrode including an electrode pair is formed on an adjacent surface of the liquid crystal cell 30.

The liquid crystal cell 30 has a panel retardation value (Δn × d) defined by Equation 4 below in a range of 300 to 400 nm at a wavelength of 589 nm of the planar switching liquid crystal display device, and more preferably in the configuration of the present invention. Is preferably about 315 nm. When the voltage is applied to the IPS-LCD panel, the light is linearly polarized in the horizontal direction after passing through the lower polarizing plate 10 and passed through the liquid crystal cell 30 to be linearly polarized in the vertical direction so as to become bright. This is because the retardation value of the liquid crystal cell 30 of the panel should be half wavelength of 589 nm (the brightest monochromatic light felt by a person). At this time, it may be adjusted to be slightly longer or shorter than the half wavelength in order to be white (White Color).

Δn × d = (ne-no) × d

Where ne is the extraordinary refractive index of the liquid crystal, no is the normal ray refractive index, and d is the cell gap; Note. Δn and d are scalars, not vectors.

The positive uniaxial A plate constituting the upper polarizing plate 20 may have a front phase difference value R0 of 80 to 130 nm and a refractive index ratio NZ of 0.9 ≤ NZ ≤ 1.1, and the slow axis absorbs adjacent polarizers. It is configured to be parallel to the axis.

The positive biaxial A plate may have a front phase difference value (R0) of 40 to 90 nm and a refractive index ratio (NZ) of -1.2 ≤ NZ ≤ -0.01, and the slow axis is an absorption axis of light polarizer adjacent to the viewer side. It is configured to be parallel to. In a specific embodiment, polymethyl methacrylate (PMMA), polystyrene (PS) and polymethyl methacrylate (PMMA) are made of a three-layered film sequentially arranged through extrusion at a time and perpendicular to the MD direction. It is prepared by stretching. In this case, the change of the refractive index through the stretching is mainly generated in the polystyrene (PS) layer and acts as a protective layer polymethyl methacrylate (PMMA) to protect the brittle polystyrene (PS) layer.

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

FIG. 2 shows the relationship between the alignment direction of the liquid crystal and the absorption axis. The alignment direction 31 and the lower plate polarizer 10 and the upper plate which show the direction in which the liquid crystals are arranged when viewed from the viewer side (the opposite side of the backlight unit) are shown in FIG. The absorption axes 12 and 22 of the polarizing plate 20 are shown.

In the lower polarizing plate 10 and the upper polarizing plate 20, polyvinyl alcohol (PVA) layers 11 and 21, which are polarizers having polarization functions through stretching and dyeing, are positioned, respectively, and polyvinyl alcohol (PVA) of the lower polarizing plate. In the polyvinyl alcohol (PVA) layer 21 of the layer 11 and the upper polarizing plate 21, protective films 13 and 23 are positioned on opposite sides of the liquid crystal cell 30, respectively. At this time, the protective film 13 of the lower polarizing plate 10 and the protective film 23 of the upper polarizing plate 20 are not particularly limited in the present invention because the optical properties according to the refractive index does not affect the viewing angle. .

The upper polarizing plate 20 and the lower polarizing plate 10 of the present invention are manufactured by applying a roll to roll method which is easy to mass produce. Figure 4 is a schematic diagram illustrating the MD direction in the roll-to-roll manufacturing process with reference to this as follows.

The upper and lower polarizing plates 10 and 20 are made of a combination of various optical films, and each optical film is in a roll state before being bonded to the composite polarizing plate. The direction in which the film is unwound or wound in the roll is called MD (Machine Direction) direction. In the case of the lower polarizing plate 10, the directions of the protective layer 13 and the isotropic protective layer 14 have no influence on optical performance, so roll to roll production is possible, and in the case of the upper polarizing plate 20, the protective layer It is irrelevant to the (23) direction, and roll to roll production is possible by only matching the MD directions of the polarizer 21, the positive uniaxial A plate 24, and the positive biaxial A plate 25. Specifically, the absorption axis 22 of the polarizer 21 in the upper polarizing plate 20 is in the MD direction. When the polarizing plate is applied to the polarizer, the PVA fabric used as the material of the polarizer is aligned with MD in the MD direction through the MD direction drawing and iodine dyeing, so that the absorption direction of the light becomes the MD direction, and the positive uniaxial A plate ( 24 is a slow axis (27) is the MD direction through the MD direction stretching using a film having a positive refractive index property of the refractive index with respect to the stretching direction, the positive biaxial A plate 25 is the stretching direction By using a film having a negative refractive index property that the refractive index is reduced with respect to the MD direction is performed in the plane orthogonal direction to the MD direction to give a phase difference, the slow axis (26) is the MD direction. In this case, the refractive index ratio is Nz (thickness direction)> Nx (MD direction)> Ny, which is applied to the film material having negative refractive index in the vertical direction of the MD direction to impart a phase difference. As there is almost no change in length, Nx is fixed and Ny direction is stretched, so the size becomes smaller, and the thickness decreases through stretching, and Nz becomes larger.

In addition, the present invention should be located in the vertical direction when the absorption axis 12 of the lower polarizer 10, the polarizer 11 is viewed from the viewing side. Specifically, when the absorption axis 12 of the lower polarizing plate 10 near the backlight unit 40 is in the vertical direction, light passing through the lower polarizing plate 10 is polarized in the horizontal direction, which is the liquid crystal cell 30 of the panel. When the light passes through the light, the light passes in the vertical direction and passes through the upper polarizing plate 20 on the side of the visual viewer whose absorption axis is in the horizontal direction. At this time, the person wearing the polarized sunglasses having the absorption axis in the horizontal direction (the absorption axis of the polarized sunglasses is in the horizontal direction) at the viewer can recognize the light emitted from the liquid crystal display. If the absorption axis 12 of the lower polarizing plate 10 near the backlight unit 40 is in the horizontal direction, a problem occurs in that an image is not visible to a person wearing polarized sunglasses. In addition, in the case of a large liquid crystal display device, in order to make the image visible from the viewer's side, in view of the fact that a human's field of view is wider than a vertical direction, a general liquid crystal display device except for a special purpose liquid crystal display device such as an advertisement is used. Since the field of view is wider in the horizontal direction than in the vertical direction, it is manufactured in the form of 4: 3 or 16: 9.

The slow axis 27 of the positive uniaxial A plate and the slow axis 26 of the positive biaxial A plate of the present invention are light positive positive uniaxial A plate 24 and positive biaxial A When the plate 25 is incident in the normal direction, it means the axis through which the light passes slowly by the retardation film, which means the axis having the largest refractive index, and this does not cause a phase difference when passing through the retardation film. It is distinguished from the optical axis. When the liquid crystal displays black, the absorption axes 12 and 22 of the polarizing plates 10 and 20 that are orthogonal to the viewer's front face cannot be kept in an orthogonal state due to their geometrical characteristics on a slope other than the front side, so that light leaks. And the light narrows the viewing angle. According to the present invention, since the optical system can keep the absorption axes 12 and 22 in the orthogonal state from the slope between the polarizers 11 and 21 of the upper and lower polarizing plates 10 and 20, the viewing angle is narrow without narrowing the light. You won't lose. The light does not leak in the phase difference value condition of the present invention can be explained through the Poincare sphere (Poincare sphere).

5 and 6 are planar switching mode liquid crystal display devices arranged in the configuration of FIG. 1 using the film having the optical properties of the present invention, in the coordinate system defined by FIG. 7 on Poincare Sphere. It shows the change in polarization state at the time θ = 60 ° and Φ = 45 ° of the wavelength of light of 550 nm that humans feel the brightest. Referring to the configuration of FIG. 1, the light passing through the polarizer 11 on the backlight side 40 is polarized in the polarization state 1 on the Poincare Sphere, and the isotropic protective layer 14 and the IPS liquid crystal cell ( 30) in the form of polarization states 2, 3, 4, and 5 on the Poincare Sphere while passing through the positive uniaxial A plate 24 and the positive biaxial A plate 25. Specifically, the light passing through the polarizer 11 of the lower polarizing plate 10 is polarized in the polarization state 1, passes through the isotropic protective layer 14 with little phase difference, and becomes the polarization state 2, and the polarization state 3 is the IPS liquid crystal cell Since the fast axis of (30) and the polarization direction of polarization state 2 almost coincide with each other, the polarization state 4 is a polarization state changed by positive uniaxial A plate 24, and is positive biaxiality. In the polarization state 5 after passing through the A plate, the state becomes a state where the polarizers are orthogonal as mentioned above, so that light does not leak and the viewing angle is widened.

In the following, the effect on the realization of the dark state at the viewing angle when the voltage is applied by the above configuration is summarized in the Examples and Comparative Examples. 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 Examples 1 to 6 and Comparative Examples 1 to 4 were applied to the LCD simulation program TECH WIZ LCD 1D (man system, KOREA) to perform a simulation to compare the wide viewing angle effect.

Example 1

Measurement data of each optical film, a liquid crystal cell, and a backlight according to the present invention were laminated 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.

The backlight unit 40 , the lower polarizing plate 10, the liquid crystal cell 30, and the upper polarizing plate 20 are sequentially stacked, and the lower polarizing plate 10 has a protective layer 13 and a polarizer from the backlight unit 40 side. (11) and the isotropic protective layer 14, the upper polarizing plate 20 is a positive uniaxial A plate 24, a positive biaxial A plate 25, a polarizer 21 and a protection from the liquid crystal cell side. In the order of layer 23.

At this time, the polarizers 11 and 21 were imparted with the function of the polarizers by stretching and dyeing, and the polarizing plates 10 and 20 were disposed on both sides of the IPS mode liquid crystal cell 30 so that absorption axes were perpendicular to each other. Referring to FIG. 2, the absorption axis 12 of the lower plate polarizer 10 and the alignment direction 31 of the liquid crystal included in the liquid crystal cell 30 are described with reference to the absorption axis and the lower plate of the polarizer 21 of the upper plate polarizer 20. Absorption axes of the polarizing plate 11 are perpendicular to each other, and the absorption axis of the polarizer 11 of the lower polarizing plate and the alignment direction 31 of the liquid crystal are arranged in parallel.

In addition, protective layers 13 and 23 are arranged on opposite surfaces of the liquid crystal cell 30 of the polarizer 11 of the lower polarizing plate 10 and the polarizer 21 of the upper polarizing plate. Between the liquid crystal cell 30 and the polarizer 21 of the upper polarizing plate 20, the positive uniaxial A plate 24 and the positive biaxial A plate 25 are arranged in order from the liquid crystal cell 30 to the lower polarizer 10. An isotropic protective layer 14 is arranged between the polarizer 11 and the liquid crystal cell 30.

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

First, the polarizers 11 and 21 of the lower polarizing plate 10 and the upper polarizing plate 20 are dyed iodine in the stretched PVA to impart a polarizer function. The degree of polarization is 99.9% or more, and the visibility of light 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).

The optical characteristics caused by the difference in the internal refractive indexes along the direction of each film were 589.3 nm in the light source, and the positive uniaxial A plate 24 had a front phase difference R0 of 101 nm and a refractive index ratio NZ of 1; The positive biaxial A plate 25 has a frontal phase difference R0 of 79 nm and a refractive index ratio NZ of -0.21; As the isotropic protective layer 14, a front phase difference (R0) of 0 nm and a thickness direction phase difference (Rth) of 0 nm were used. At this time, the direction of the slow axis of each of the positive uniaxial A plate and the positive biaxial A plate 25 is parallel to the absorption axis 22 of the adjacent polarizer 21.

The positive uniaxial A plate 24 uses a cycloolefin polymer (COP, Zeonor, Optes, Japan), and the positive biaxial A plate 25 is negative between two polymethylmethacrylates (PMMA). After the triple co-extrusion to arrange the PS having the refractive index characteristics, the retardation film (I-Film, Optes, Japan) was sequentially placed through stretching. In addition, triacetyl cellulose (TAC) having an optical property of Rth of 50 nm with respect to the incident light 589.3 nm was used as the outer protective layers 13 and 23 of the upper and lower polarizing plates 10 and 20, respectively. As the backlight unit 50, actual measurement data mounted on a 32-inch TV LC320WX4 model (LG PHILIPS LCD) was used.

As a result of laminating each optical component as shown in FIG. 1 and performing visibility omnidirectional transmittance simulation, the results as shown in FIG. 8 were obtained. FIG. 8 illustrates the distribution of visibility of permeability in the case of displaying the black on the screen, and the range on the scale ranges from 0% to 0.02% of the transmittance. Low permeability areas are indicated in blue. At this time, it was confirmed that the wider the range of blue in the center, the wider the viewing angle. This is because the polarization state of the Pohang Care sphere is shown at the same time as FIG. 5.

Example 2

In the same manner as in Example 1, the positive uniaxial A plate 24 has a front phase difference R0 of 109 nm, a refractive index NZ of 1, and the positive biaxial A plate 25 has a front phase difference at a light source of 589.3 nm. A planar switching (IPS) liquid crystal display device was manufactured by arranging (R0) at 51 nm and refractive index ratio (NZ) at -0.99.

As a result of the visibility and omnidirectional transmittance simulation of the planar switching liquid crystal display, a similar pattern to that of FIG. 8 of Example 1 is shown. This is because the polarization state of the Pohang Care sphere is shown at the same time as FIG.

Example 3

In the same manner as in Example 1, the positive uniaxial A plate 24 has a front phase difference (R0) of 95 nm and a refractive index (NZ) of 1 at a light source of 589.3 nm. Prepared.

10 shows the simulation results of the visibility of the planar switching liquid crystal display device.

Example 4

In the same manner as in Example 2, the positive biaxial A plate 25 has a front phase difference (R0) of 46 nm and a refractive index (NZ) of -1.09 at a light source of 589.3 nm. Was prepared.

11 illustrates the simulation results of the visibility of the planar switching liquid crystal display.

Example 5

In the same manner as in Example 1, except that the positive uniaxial A plate 24 has a front phase difference R0 of 81 nm and a refractive index NZ of 1 at a light source of 589.3 nm, and the positive biaxial A plate 25 A front phase difference (RO) of 89 nm and a refractive index (NZ) of -0.02 were disposed so as to manufacture a planar switching (IPS) liquid crystal display device.

12 illustrates the simulation results of the visibility of the planar switching liquid crystal display device.

Example 6

In the same manner as in Example 4, the positive biaxial A plate 25 has a front phase difference (R0) of 41 nm and a refractive index (NZ) of -1.19 at a light source of 589.3 nm. Was prepared.

13 shows the simulation results of visibility of the planar switching liquid crystal display device.

Comparative Example 1

In the configuration of Example 1, the positive uniaxial A plate 24 and the positive biaxial A plate 25 were removed, and the planar switching (IPS) liquid crystal display device as shown in FIG. 14 was manufactured by replacing the isotropic protective film.

As a result of conducting simulation of visibility and omnidirectional transmittance of the planar switching liquid crystal display, a result as shown in FIG. 15 was obtained.

In FIG. 8 of the first embodiment, the blue portion of the center is wider than that of FIG. 15, so that a wider viewing angle is realized. In addition, the omnidirectional maximum transmittance is calculated as 0.0193%, 0.34% in the case of Comparative Example 1, the optimization value in Example 1, which can be seen that the comparative example 1 is about 17.16 times larger than the maximum transmittance of Example 1.

Comparative Example 2

In the same manner as in Example 1, except that the positive uniaxial A plate 24 has a front phase difference R0 of 100 nm refractive index ratio NZ of 1 and the positive biaxial A plate 25 has a front phase difference of 58 nm at a light source. The planar switching (IPS) liquid crystal display device was manufactured by arranging that R0) is 100 nm and the refractive index ratio (NZ) is -1.

As a result of the simulation of the visibility of the planar switching liquid crystal display device as shown in FIG. 16, it can be seen that the viewing angle is narrow because the transmittance of the inclined plane is high in the black state.

Comparative Example 3

In the same manner as in Example 1, the positive uniaxial A plate 24 has a front phase difference R0 of 140 nm refractive index ratio NZ of 1 and the positive biaxial A plate 25 has a front phase difference of 58 nm at a light source. The planar switching (IPS) liquid crystal display device was manufactured by arranging that R0) is 80 nm and the refractive index ratio (NZ) is -0.2.

As a result of the simulation of the visibility of the planar switching liquid crystal display device as shown in FIG. 17, it can be seen that the viewing angle is narrow due to high transmittance of the inclined plane in the black state.

Comparative Example 4

Instead of stacking the positive uniaxial A plate 24 and the positive biaxial A plate 25 on the liquid crystal cell side of the polarizer in the configuration of Example 1, the positive biaxial A plate 24 and the positive uniaxial A The planar switching (IPS) liquid crystal display was manufactured by arranging the plates in the order of stacking 25.

As a result of the simulation of the visibility of the planar switching liquid crystal display device as shown in FIG. 18, it can be seen that the viewing angle is narrow because the transmittance of the inclined plane is high in the black state.

As described above, the planar switching liquid crystal display device according to the present invention can provide a good image quality for all the time, it can be applied to a liquid crystal display that requires high viewing angle characteristics.

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

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

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

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

FIG. 5 illustrates the change in polarization state at the time of θ = 60 degrees and Φ = 45 degrees in Example 1 according to the present invention on a Poincare sphere.

Figure 6 shows the change in polarization state on the Poincare Sphere (θ = 60 degrees, Φ = 45 degrees) of Example 2 according to the present invention,

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

8 is a simulation result of the visibility of the omnidirectional transmittance of Example 1 of the present invention,

9 is a simulation result of the visibility of the omnidirectional transmittance of Example 2 of the present invention,

10 is a simulation result of the visibility of the omnidirectional transmittance of Example 3 of the present invention,

11 is a simulation result of the visibility of the omnidirectional transmittance of Example 4 of the present invention,

12 is a simulation result of the visibility of omnidirectional transmittance of Example 5 of the present invention,

13 is a simulation result of the visibility of the omnidirectional transmittance of Example 6 of the present invention,

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

15 is a simulation result of the visibility of the omnidirectional transmittance of Comparative Example 1 of the present invention,

16 is a simulation result of the visibility of the omnidirectional transmittance of Comparative Example 2 of the present invention,

17 is a simulation result of the visibility of the omnidirectional transmittance of Comparative Example 3 of the present invention,

18 is a result of simulating the visibility of omnidirectional transmittance of Comparative Example 4 of the present invention.

Claims

A top plate polarizing plate for planar switching (IPS) mode, which is laminated in the order of a positive uniaxial A plate, a positive biaxial A plate, a polarizer and a protective layer from a liquid crystal cell side,

The positive uniaxial A plate has a front phase difference value (R 0) of 80 to 130 nm, a refractive index ratio (NZ) of 0.9 ≦ NZ ≦ 1.1, and a slow axis is parallel to an absorption axis of an adjacent polarizer;

The positive biaxial A plate has a front phase difference value (R0) of 40 to 90 nm, a refractive index ratio (NZ) of -1.2 ≤ NZ ≤ -0.01, and a slow axis configured to be parallel to an absorption axis of an adjacent polarizer.

The method of claim 1, wherein the positive uniaxial A plate and the positive biaxial A plate are independently of each other triacetylcellulose (TAC), cycloolefin polymer (COP), cycloolefin copolymer (COC), polyethylene terephthalate (PET), A top plate polarizing plate made of one selected from the group consisting of polypropylene (PP), polycarbonate (PC) , polysulfone (PSF), and polymethyl methacrylate (PMMA).

The upper polarizing plate of claim 1, wherein the positive biaxial A plate has a structure in which polymethyl methacrylate (PMMA), polystyrene (PS), and polymethyl methacrylate (PMMA) are sequentially stacked.

The upper polarizing plate according to claim 1, wherein the positive biaxial A plate is further laminated with a modified polycarbonate (PC) on at least one side thereof.

The method of claim 1, wherein the protective layer is triacetyl cellulose (TAC), cycloolefin polymer (COP), cycloolefin copolymer (COC), polyethylene terephthalate (PET), polypropylene (PP), polycarbonate (PC) , A top plate polarizer made of one selected from the group consisting of polysulfone (PSF) and polymethyl methacrylate (PMMA).

An in-plane switching (IPS) mode liquid crystal display comprising the upper polarizing plate of claim 1.

The liquid crystal display of claim 6, wherein the liquid crystal cell has a phase difference value of 300 to 400 nm at a wavelength of 589 nm.

The liquid crystal display device according to claim 6, wherein the luminous transmittance omnidirectional maximum transmittance satisfies a compensation relationship of 0.05% or less.

7. An isotropic protective layer according to claim 6, wherein the front phase difference (R0) and the thickness direction phase difference (Rth) are respectively less than 10 nm from the liquid crystal cell side; Polarizer; And a lower polarizing plate stacked in a protective layer order.

The method of claim 9, wherein the isotropic protective layer and the protective layer are independently of each other triacetyl cellulose (TAC), cycloolefin polymer (COP), cycloolefin copolymer (COC), polyethylene terephthalate (PET), polypropylene (PP) And polycarbonate (PC) , polysulfone (PSF), and polymethyl methacrylate (PMMA).

7. The liquid crystal display device according to claim 6, wherein the liquid crystal cell is configured such that the liquid crystal alignment direction is parallel to the absorption axis of the lower polarizing plate.