KR20100071252A

KR20100071252A - Bottom plate polarizer and in-plane switching mode liquid crystal display comprising the same

Info

Publication number: KR20100071252A
Application number: KR1020080129900A
Authority: KR
Inventors: 김봉춘
Original assignee: 동우 화인켐 주식회사
Priority date: 2008-12-19
Filing date: 2008-12-19
Publication date: 2010-06-29

Abstract

PURPOSE: A lower plate polarizer and an in-plane switching mode liquid crystal display comprising the same are provided to improve a contrast feature at the front and a tilted angle. CONSTITUTION: Protective layers(13,23) are located in the side opposite to a liquid crystal cell of a polarizer(11,21) of an upper plate polarizer(20) and a lower plate polarizer. In the upper plate polarizer, an isotropy protective layer(24) is laminated on the liquid crystal cell of the polarizer. In the lower plate polarizer, a negative C plate(16), a positive biaxial A plate(14), and the polarizer are successively laminated from the liquid crystal cell. The absorption axis(12) of the lower plate polarizer is orthogonal to the absorption axis(22) of the upper plate polarizer.

Description

Lower plate polarizer and planar switching mode liquid crystal display including the same {BOTTOM PLATE POLARIZER AND IN-PLANE SWITCHING MODE LIQUID CRYSTAL DISPLAY COMPRISING THE SAME}

The present invention is applied to the planar switching (IN-PLANE SWITCHING) applying a negative C plate and a positive biaxial A plate having a specific optical property from the liquid crystal cell side, and a polarizer laminated in the order of the polarizer and the protective layer from the liquid crystal cell side to ensure a wide viewing angle (IN-PLANE SWITCHING) The present invention relates to a mode liquid crystal display device.

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. Twisted nematic (TN) and vertical alignment (VA) modes are different in the direction of the liquid crystal and the electric field. 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 polarizers, it is possible to display a dark state relatively superior to other modes in the non-driven state. In addition, when the transmission axis of the lower plate and the slow axis direction of the liquid crystal molecules coincide with each other at the front side, a change in polarization state occurs at the slope, but since the transmittance of the upper plate polarizer is maintained at the same polarization state in the electric field, the neutral is maintained. Since one color can be maintained and the transmittance is maintained as described above, it is possible to display a relatively excellent black state compared to other modes.

The planar switching mode liquid crystal display device generally obtains a relatively wide viewing angle compared to other modes without using an optical film, and thus has an image quality and a viewing angle uniform 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. Therefore, in the planar switching mode liquid crystal display (IPS-LCD), in order to secure a wide viewing angle, an isotropic protective layer (isotropic TAC) is used between the polarizer (PVA) and the liquid crystal cell to eliminate elliptical polarization due to TAC. It is pointed out that it is difficult to secure a wide viewing angle because the light leakage phenomenon occurs because the absorption axis of the polarizer is still not compensated for by improving the color.

Accordingly, a new polarizer configuration capable of mass production is urgently required by easily manufacturing a composite polarizer including a phase difference film by using a roll-to-roll production form 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 a method of changing the configuration of the compensation film by the lower polarizing plate containing a retardation film having a variety of laminated structure and retardation value design to match the absorption axis of the upper polarizing plate to the polarization plane of the polarized light passing through the lower polarizing plate By doing the polarizer absorption axis compensation of the lower plate to secure a wider viewing angle than the conventional, and to propose a lower plate polarizing plate that can be produced using a roll-to-roll production mode. Specifically, by using a negative polarizing plate in which a negative C plate and a positive biaxial A plate having a specific optical property and a polarizer and a protective layer are laminated in this order from the liquid crystal cell side in the planar switching mode liquid crystal display device, contrast at the front and inclination angles is used. The present invention provides a planar switching mode liquid crystal display device which can improve characteristics and minimize color change due to a change in viewing angle in a dark state, thereby providing a wide viewing angle than in the prior art.

The present invention is a lower plate polarizing plate for planar switching (IPS) mode in which a negative C plate, a positive biaxial A plate, a polarizer, and a protective layer are stacked from a liquid crystal cell side, and the negative C plate has a thickness direction phase difference value Rth. 70 to 170 nm; The positive biaxial A plate is characterized by a lower polarizing plate configured such that the front phase difference value (R0) is 90 to 140 nm, the refractive index ratio (NZ) is -1.2 ≤ NZ ≤ -0.01, and the slow axis is parallel to the absorption axis of the adjacent polarizer. There is this.

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

The planar switching mode liquid crystal display device according to the present invention applies a negative C plate and a positive biaxial A plate having a specific optical property from the liquid crystal cell side, and a lower polarizing plate stacked in the order of the polarizer and the protective layer, thereby providing perfect arm in all directions. By realizing the state, it is possible to have a wider viewing angle than in the prior art, and mass production is easy.

The present invention relates to a lower polarizing plate capable of realizing a dark state at an entire viewing angle by compensating for light leakage in a liquid crystal cell when applied to an area switching mode liquid crystal display. The lower plate polarizing plate is formed by laminating the negative C plate, the positive biaxial A plate, the polarizer, and the protective layer in order from the liquid crystal cell side.

As used herein, the term “negative C plate” refers to a positive optical element whose refractive index distribution satisfies nx = ny> nz. In reality, it is difficult to manufacture nx = ny in the manufacturing process of the plate, that is, nx and ny are exactly the same negative C plate, so in the art, in general, nx and ny are not only identical but also substantially the same as negative C plate. I handle it. Preferably, in the case where the difference is substantially the same, the difference between Nx and Ny is preferably maintained within a range of 10 nm / thickness. In addition, the term “positive biaxial A plate” refers to a negative biaxial optical element satisfying Nz> Nx> Ny, and is also called a “positive B plate”. In this case, the negative bi-axial optical element in the present invention refers to a material whose refractive index decreases in the stretching direction.

The negative C plate disposed on the lower polarizing plate has a thickness direction phase difference value (Rth) of 70 to 170 nm and a thickness direction phase difference value (Rth) is preferable in order to exhibit better wide viewing angle characteristics in consideration of the phase difference expression range in process. It is 80-160 nm, More preferably, it is good to maintain 90-150 nm of thickness direction phase difference values (Rth).

Such a negative C plate may be manufactured by a method generally used in the art, such as a stretching and casting method, and is not limited to the manufacturing method as long as it has the optical properties.

The positive biaxial A plate (positive B plate) laminated on the lower surface of the negative C plate from the liquid crystal cell side has a front phase difference value R0 of 90 to 140 nm and a refractive index ratio NZ of -1.2 ≤ NZ ≤ -0.01. In order to exhibit better optical viewing angle characteristics in consideration of the phase difference expression range in the process, the front phase difference value R0 is preferably 95 to 135 nm, and the refractive index ratio (NZ) is -1.1 to -0.1, more preferably. The front phase difference value R0 is 100 to 130 nm, and the refractive index ratio NZ is preferably maintained at -1 to -0.2. Such a positive biaxial A plate may be a structure in which polymethyl methacrylate (PMMA), polystyrene (PS) and polymethyl methacrylate (PMMA) are sequentially stacked or at least one or more layers of modified polycarbonate (PC). have. 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.

Said negative C plate and positive biaxial A plate can be applied to this invention without being limited to a material as long as it satisfy | fills the optical characteristic of the range which this invention limits independently of each other. 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 lower polarizing plate 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 In-Plane-Switching (Super-In-Plane-Switching) and FFS (Fringe-Field-Switching). In the IPS-LCD of the present invention, the liquid crystal orientation is FFS (Fringe-Field-Switching), and the absorption axis of the polarizer of the upper polarizing plate is parallel to the absorption axis.

The top plate polarizer 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 lower polarizer and the polarizer absorption axis of the upper polarizer are orthogonal to each other.

The isotropic protective layer and the protective layer constituting the upper polarizing plate, and the material forming the protective layer constituting the lower polarizing plate may be used independently of each other commonly 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) It may be used that is prepared as selected from. In this case, it is preferable that the isotropic protective layer has a front phase difference (RO) and a thickness direction phase difference (Rth) of less than 10 nm, preferably, an absolute value of less than 2 nm, and the protective layers of the upper and lower polarizing plates are optically based on the difference in refractive index. Since the property does not affect the viewing angle, the refractive index property is not particularly limited in the present invention.

The retardation films such as the negative C plate, the positive biaxial A plate, and the isotropic protective layer of the upper polarizing plate constituting the lower polarizing plate may have a z-axis in the thickness direction and a x-axis in the direction of the large in-plane refractive index, as shown in FIG. When the 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, the front phase difference R0 defined by Equation 2 below, and It is specified by the refractive index ratio NZ defined by Equation 3 below. At this time, the characteristics of the retardation film is determined according to the size of the refractive index. Of these, when the refractive indices in the three axial directions are different from each other, there are two optical axes that do not cause retardation. This 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 to provide a lower polarizing plate having a superior viewing angle compensation effect and a planar switching mode liquid crystal display device using the same, which can be applied to mass production rather than the conventional abstract viewing angle compensation concept. 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 0.1% or less, preferably 0.05% or less in the black state. The brightness of the brightest LCD currently produced is about 10000 nits using the vertical alignment mode (VA mode). The brightness is about 10000 nits × cos60 ° at a viewing angle of 60 °, and 0.05% of this is 2.5 nits. to be. Accordingly, the present invention is to implement the visibility of the omnidirectional transmittance of a level similar to that of the VA mode, which is relatively superior to the IPS mode while realizing the visibility of the omnidirectional transmittance equal to or higher than that of the liquid crystal display 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 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 has an isotropic protective layer 24 laminated on the liquid crystal cell side of the polarizer 21, and the lower polarizing plate 10 has a negative C plate 16, a positive biaxial A plate 14, and a lower polarizing plate 10. The polarizer 21 is laminated | stacked in order.

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, and more preferably about 380 nm in the configuration of the present invention. 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 = (n _e -n _o ) × d

Where n _e represents the extraordinary refractive index of the liquid crystal, n _o represents the normal ray refractive index, and d represents the cell gap; Note. Δn and d are scalars, not vectors.

The negative C plate constituting the lower polarizing plate 10 may use a thickness direction phase difference value Rth of 70 to 170 nm. In addition, the positive biaxial A plate may have a front phase difference value (R0) of 90 to 140 nm and a refractive index ratio (NZ) of -1.2 ≤ NZ ≤ -0.01, and the slow axis absorbs adjacent polarizers in front of the viewer side. It is configured to be parallel to the axis. 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 to be 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 22 and the liquid crystal cell 30 of the upper polarizing plate 20. 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 due to the refractive index does not affect the viewing angle. Do not.

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 upper polarizing plate 20, the directions of the protective layer 23 and the isotropic protective layer 24 have no influence on optical performance, so roll to roll production is possible, and in the case of the lower polarizing plate 20, the protective layer (13), irrespective of the direction of the negative C plate 16, roll-to-roll production is possible only by matching the MD directions with respect to the polarizer 11 and the positive biaxial A plate 14. Specifically, the absorption axis 12 of the polarizer 11 in the lower polarizing plate 10 is in the MD direction, which is the MD PVA through the MD direction stretching from the PVA fabric used as a material of the polarizer when giving a polarizing function in the polarizing plate Direction and the iodine dyeing, the direction of light absorption becomes the MD direction. Since the negative C plate 16 has almost the same Nx and Ny, since there is no slow axis in the vertical direction of the film plane, there is no difference in optical properties according to the bonding angle, so the bonding is performed by a roll to roll process. It is possible. In addition, the positive biaxial A plate 14 imparts a phase difference through the stretching in the vertical direction to the MD direction of the film having a negative refractive index characteristic of the refractive index becomes smaller with respect to the stretching direction, wherein the slow axis 15 is in the MD direction Formed and the refractive index in the MD direction becomes Nx. In the above case, the size of Nx is almost unchanged because the length of Nx is fixed in the MD direction during stretching, but the size of Nz is increased because the size of Ny decreases and the thickness direction shrinks because the vertical direction of the MD direction is stretched. . Therefore, NZ value becomes smaller than 0, and the direction of slow axis 15 becomes MD direction.

In the present invention, the absorption axis 12 of the lower polarizing plate 10 and the polarizer 11 should be located in the vertical direction when 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 15 of the positive biaxial A plate of the present invention has the slowest light passing by the retardation film when the light enters the positive biaxial A plate 15 in the normal direction. The axis refers to the axis with the largest refractive index, which is distinguished from the optical axis in which no phase difference occurs when passing through the retardation film. 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 is a planar switching mode liquid crystal display device arranged in the configuration of FIG. 1 using a film having an optical property of the present invention, which is a human being in the coordinate system defined by FIG. 6 on a Poincare Sphere. It shows the change in polarization state at the time θ = 60 ° and Φ = 45 ° at the wavelength of light 550 nm which is brightly felt. Specifically, using 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 is a positive biaxial A plate 14. While passing through the negative C plate 16, the FFS liquid crystal cell 30, and the isotropic protective layer 24, the polarization state on the Poincare Sphere (Poincare Sphere) changes in the form of polarization states 2, 3, 4, and 5. Specifically, the light polarized in the polarization state 1 becomes the polarization states 2 and 3 by the positive biaxial A plate 14 and the negative C plate 16, and the light passing through the FFS liquid crystal cell 30 is the polarization state 4. After passing through the isotropic protective layer 24, as described above, the polarizer becomes orthogonal to the polarized state 5 in which light does not leak and the viewing angle does not become narrow.

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, the effect was applied to the LCD simulation program TECH WIZ LCD 1D (man system, KOREA) 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 stacked on a TECH WIZ LCD 1D (man system, KOREA) with a structure as shown in FIG. 1. Referring to the structure of Figure 1 in detail.

The backlight unit 40 , the lower polarizing plate 10, the liquid crystal cell 30, and the upper polarizing plate 20 are sequentially stacked. The lower polarizing plate 10 has a negative C plate 16 and a positive biaxial property from the liquid crystal cell side. The A plate 14, the polarizer 11, and the protective layer 13 are configured in this order, and the upper polarizing plate 20 is an isotropic protective layer 24, a polarizer 21, and a protective layer 23 from the liquid crystal cell side. It was organized in order.

At this time, the polarizers 11 and 21 are imparted to the polarizer through stretching and dyeing, and the polarizing plates 10 and 20 are perpendicular to each other on both sides of the FFS mode liquid crystal cell 30 (Wooo9000, HITACHI, JAPAN). To be placed. Referring to FIG. 2, the absorption axis 22 of the upper polarizing plate 20 and the alignment direction 31 of the liquid crystal included in the liquid crystal cell 30 are described with reference to the absorption axis 22 of the polarizer 21 of the upper polarizing plate 20. ) And the absorption axis 12 of the polarizer 11 of the lower polarizing plate 10 are orthogonal to each other, and the absorption axis 22 of the polarizer 21 of the upper polarizing plate 20 and the alignment direction 31 of the liquid crystal are parallel to each other. Are arranged.

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 20.

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).

Optical characteristics caused by the difference in the internal refractive index according to the direction of each film is 589.3nm in the light source, the negative C plate 16 has a thickness direction phase difference (Rth) of 149nm; The positive biaxial A plate 14 has a front phase difference R0 of 101 nm and a refractive index ratio NZ of -0.99; As the isotropic protective layer 24, 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 the positive biaxial A plate 16 is parallel to the absorption axis 12 of the adjacent polarizer 11.

The negative C plate 16 uses triacetyl cellulose (TAC, IPI, Germany), and the positive biaxial A plate 14 has a negative refractive index property between two polymethyl methacrylates (PMMA). PS was placed in the retardation film (I-Film, Optes, Japan) sequentially. In addition, triacetyl cellulose (TAC) having an optical property having an Rth of 50 nm with respect to 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 Wooo9000 model (HITACHI, JAPAN) was used.

The optical components were stacked as shown in FIG. 1 and subjected to simulation of visibility omnidirectional transmittance. As a result, the results as shown in FIG. 7 were obtained. FIG. 7 illustrates the distribution of omnidirectional permeability when displaying a black on the screen. The scale ranges from 0% to 0.05% of the transmittance, and the area exceeding 0.05% of the permeability when displaying cancer is red and transmittance. Lower areas are indicated in blue. In this case, the wider the range of blue in the center, the wider the viewing angle. This is because it shows a change in polarization state such as a red path on the plane of Fig. 5 in the inclined plane.

Example 2

In the same manner as in Example 1, except that the negative C plate 16 had a thickness direction phase difference (Rth) of 91 nm at a light source of 589.3 nm; The positive biaxial A plate 14 was arranged with a front phase difference R0 of 131 nm and a refractive index ratio NZ of -0.21 to manufacture an in-plane switching (IPS) liquid crystal display device.

The results of the simulation of visibility and omnidirectional transmittance of the planar switching liquid crystal display are shown in FIG. 8. This is because it shows a change in polarization state such as the blue path on the plane of Fig. 5 on the inclined plane.

Example 3

In the same manner as in Example 1, except that the negative C plate 16 had a thickness direction phase difference (Rth) of 159 nm at a light source of 589.3 nm; The positive biaxial A plate 14 was arranged such that the front phase difference R0 was 101 nm and the refractive index ratio NZ was -0.99 to manufacture an in-plane switching (IPS) liquid crystal display device.

The results of the simulation of visibility and omnidirectional transmittance of the planar switching liquid crystal display are shown in FIG. 9.

Example 4

In the same manner as in Example 1, except that the negative C plate 16 had a thickness direction phase difference (Rth) of 85 nm at a light source of 589.3 nm; The positive biaxial A plate 14 was arranged such that the front phase difference R0 was 131 nm and the refractive index ratio NZ was -0.21 to manufacture an in-plane switching (IPS) liquid crystal display device.

The results of the simulation of visibility and omnidirectional transmittance of the planar switching liquid crystal display are shown in FIG. 10.

Example 5

In the same manner as in Example 1, except that the negative C plate 16 had a thickness direction phase difference (Rth) of 160 nm at a light source of 589.3 nm; The positive biaxial A plate 14 was arranged such that the front phase difference R0 was 91 nm and the refractive index ratio NZ was -1.1 to manufacture a planar switching (IPS) liquid crystal display device.

The results of the simulation of visibility and omnidirectional transmittance of the planar switching liquid crystal display are shown in FIG. 11.

Example 6

In the same manner as in Example 1, except that the negative C plate 16 had a thickness direction phase difference (Rth) of 81 nm at a light source of 589.3 nm; The positive biaxial A plate 14 was arranged such that the front phase difference R0 was 139 nm and the refractive index ratio NZ was -0.1 to manufacture a planar switching (IPS) liquid crystal display device.

The results of the simulation of visibility and omnidirectional transmittance of the planar switching liquid crystal display are shown in FIG. 12.

Comparative Example 1

In the configuration of Example 1, the negative C plate 16 and the positive biaxial A plate 14 were removed and an isotropic protective film was replaced to manufacture a planar switching (IPS) liquid crystal display device as shown in FIG. 13.

As a result of performing visibility visibility omnidirectional transmittance simulation of the planar switching liquid crystal display device, a result as shown in FIG. 14 was obtained.

7 of the first embodiment is wider blue portion in the center than in Figure 14 it can be seen that a wider viewing angle is implemented. In addition, the maximum omnidirectional transmittance is calculated as 0.03% for the optimization value in Example 1, 0.34% in the case of Comparative Example 1, which can be seen that Comparative Example 1 is about 11 times greater than the omnidirectional maximum transmittance.

Comparative Example 2

In the same manner as in Example 1, the negative C plate 16 had a thickness direction phase difference (Rth) of 60 nm at a light source of 589.3 nm; The positive biaxial A plate 14 was arranged such that the front phase difference R0 was 140 nm and the refractive index ratio NZ was -0.2 to manufacture a planar switching (IPS) liquid crystal display device.

The simulation results of the visibility of the planar switching liquid crystal display were shown in FIG. 15, and it was confirmed that the viewing angle was narrow due to high transmittance of the inclined plane in the black state.

Comparative Example 3

In the same manner as in Example 1, except that the negative C plate 16 has a thickness direction phase difference (Rth) of 180 nm at a light source of 589.3 nm; The positive biaxial A plate 14 was arranged such that the front phase difference R0 was 150 nm and the refractive index ratio NZ was -0.5 to manufacture an in-plane switching (IPS) liquid crystal display device.

The simulation results of the visibility of the planar switching liquid crystal display device were as shown in FIG. 16, and it was confirmed that the viewing angle was narrow due to high transmittance of the inclined plane in the black state.

Comparative Example 4

In Embodiment 1, the position of the negative C plate 16 and the positive biaxial A plate 14 are changed to form an area switching (IPS) liquid crystal display device.

The simulation results of the visibility of the planar switching liquid crystal display device were shown in FIG. 17, and it was confirmed that the viewing angle was narrow due to high transmittance of the inclined plane 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 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,

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

FIG. 5 shows a change in polarization state capable of viewing angle compensation at θ = 60 ° and Φ = 45 ° of the present invention on a Poincare Sphere.

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

7 is a simulation result of the visibility of the omnidirectional transmittance of Example 1 according to the present invention,

8 is a simulation result of the visibility of the visibility of Example 2 according to the present invention,

9 is a simulation result of the visibility of the omnidirectional transmittance of Example 3 according to the present invention,

10 is a simulation result of the visibility of the visibility of Example 4 according to the present invention,

11 is a simulation result of the visibility of the omnidirectional transmittance of Example 5 according to the present invention,

12 is a result of simulating the visibility of omnidirectional transmittance of Example 6 according to the present invention,

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

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

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

16 is a result of simulating the visibility omnidirectional transmittance of Comparative Example 3 of the present invention,

17 is a simulation result of the visibility of omnidirectional transmittance of Comparative Example 4 of the present invention.

Claims

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

The negative C plate has a thickness direction phase difference value Rth of 70 to 170 nm;

The positive biaxial A plate has a front phase difference value (R0) of 90 to 140 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 negative C plate and the positive biaxial A plate are independently of each other triacetylcellulose (TAC), cycloolefin polymer (COP), cycloolefin copolymer (COC), polyethylene terephthalate (PET), polypropylene (PP), polycarbonate (PC), polysulfone (PSF) and polymethyl methacrylate (PMMA) is a lower plate polarizer made of one selected from the group consisting of.

The lower plate polarizer 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 lower polarizing plate according to claim 1, wherein at least one layer of the positive biaxial A plate is a modified polycarbonate (PC).

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 lower polarizing plate 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 lower polarizing plate of claim 1.

7. The liquid crystal display device according to claim 6, wherein the luminous transmittance omnidirectional maximum transmittance satisfies a compensation relationship of 0.1% 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 top polarizer stacked in a protective layer order.

The method of claim 8, 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).

The liquid crystal display of claim 6, wherein the liquid crystal cell is configured such that a liquid crystal alignment direction is parallel to an absorption axis of the upper polarizing plate.