KR20080049303A - Liquid crystal display - Google Patents

Abstract

An LCD(Liquid Crystal Display) is provided to implement a narrow viewing angle by reducing a side viewing angle by applying voltage to a sub pixel of an ECB(Electrical Controlled Birefringence) mode, thereby achieving switching between wide and narrow viewing angle modes and providing flexible viewing angle characteristics according to needs. A first common electrode(131) is formed on a first substrate(100) and made from a transparent conductor. An insulating layer(140) is formed on the first common electrode. Plural first pixel electrode lines(191a) are formed on the insulating layer and overlapped with the first common electrode. A second pixel electrode line(191b) is formed on the insulating layer, and spaced from the first pixel electrode lines. A second substrate(200) faces the first substrate. A second common electrode(270) is formed on a part of the second substrate so as to face the second pixel electrode line. A first LC layer(3) is inserted between the first substrate and the second substrate where the second common electrode is not formed. A second LC layer(30) is inserted between the first substrate and the second substrate where the second common electrode is formed. In the second substrate where the second common electrode is formed, a white color filter is formed. In the second substrate where the second common electrode is not formed, RGB(Red, Green and Blue) color filters are formed. If a wide viewing angle is necessary, a signal controller applies no voltage to a sub pixel. Therefore, an LC layer of a sub pixel area is arranged in parallel to an LC layer of a main pixel area. If a narrow viewing angle is necessary, the signal controller applies voltage to the sub pixel. Therefore, the LC layer of the sub pixel area is arranged to be vertical to the LC layer of the main pixel area.

Description

Liquid crystal display {LIQUID CRYSTAL DISPLAY}

1 is a cross-sectional view of a liquid crystal display according to an exemplary embodiment of the present invention.

2 is a schematic diagram illustrating one pixel of a liquid crystal display according to an exemplary embodiment of the present invention.

3A is a graph showing the transmittance of a liquid crystal display in PLS mode

3B is a graph showing transmittance of a liquid crystal display in ECB mode

4 is a view illustrating a driving principle for driving a subpixel of an ECB mode to implement a narrow viewing angle in the liquid crystal display of the present invention;

5 is a schematic diagram illustrating one pixel of a liquid crystal display according to another exemplary embodiment of the present invention.

<Description of Drawing>

110 and 210: insulating substrate 131: first common electrode

140: insulating films 191a and 191b: first and second pixel electrodes

100: upper display panel 200: lower display panel

270: second common electrode 3, 30: liquid crystal layer

300: liquid crystal panel assembly 600: signal control unit

The present invention relates to a liquid crystal display device.

The liquid crystal display is one of the most widely used flat panel display devices. The liquid crystal display includes two display panels on which field generating electrodes such as a pixel electrode and a common electrode are formed, and a liquid crystal layer interposed therebetween. Is applied to generate an electric field in the liquid crystal layer, thereby determining the orientation of liquid crystal molecules in the liquid crystal layer and controlling the polarization of incident light to display an image.

Among them, the vertical alignment (VA) mode liquid crystal display in which the long axis of the liquid crystal molecules are arranged perpendicular to the upper and lower display panels without an electric field applied to the display panel has a high contrast ratio.

However, there is a problem in the wide viewing angle, so that a liquid crystal display device in a patterned vertically aligned (PVA) mode, an in-plane switching (IPS) mode liquid crystal display device, and a plane to line switching are applied. Mode liquid crystal display device has been developed. In this case, the liquid crystal material may use both positive and negative dielectric anisotropy.

The viewing angle characteristic is very important in such a liquid crystal display device, and it is an important factor to make a liquid crystal panel that can be displayed normally even in a wide range. Therefore, research to obtain a clear and wide viewing angle has been continued.

However, the liquid crystal display device requires a narrower viewing angle than a wide viewing angle when using a computer for personal reasons, for example, when writing, reading a secret document, performing a work requiring security, or when using an ATM device.

Therefore, an object of the present invention is to implement a privacy protection function at the same time by enabling the switching of wide viewing angle and narrow viewing angle.

The liquid crystal display according to the exemplary embodiment of the present invention is formed on a first substrate, a first common electrode formed on the first substrate and made of a transparent conductor, an insulating film formed on the first common electrode, and formed on the insulating film. A plurality of first pixel electrodes overlapping the first common electrode, a second pixel electrode formed on the insulating layer and spaced apart from the first pixel electrode, a second substrate facing the first substrate, and the first substrate electrode A second common electrode formed on a portion of the second substrate so as to face the second pixel electrode, a first liquid crystal layer interposed between the second substrate on which the second common electrode is not formed and the first substrate, and And a second liquid crystal layer interposed between the second substrate on which the second common electrode is formed and the first substrate, wherein the second common electrode is formed. White color filters are formed on the second substrate, and red, blue, and green color filters are formed on the second substrate on which the second common electrode is not formed.

The dielectric constants of the first and second liquid crystal layers may have positive anisotropy.

The dielectric constants of the first and second liquid crystal layers may have negative anisotropy.

When voltage is applied to the first and second pixel electrodes and the first and second common electrodes, the major axis direction of the liquid crystal molecules of the first liquid crystal layer is perpendicular to the major axis direction of the liquid crystal molecules of the second liquid crystal layer. Can be.

When a voltage is applied to the second pixel electrode and the second common electrode, the major axis direction of the liquid crystal molecules of the second liquid crystal layer may be perpendicular to the first and second substrates.

An alignment layer may be further formed on inner surfaces of the first substrate and the second substrate.

DETAILED DESCRIPTION Embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention.

In the drawings, the thickness of layers, films, panels, regions, etc., are exaggerated for clarity. Like parts are designated by like reference numerals throughout the specification. When a part of a layer, film, region, plate, etc. is said to be "on" another part, this includes not only the other part being "right over" but also another part in the middle. On the contrary, when a part is "just above" another part, there is no other part in the middle.

First, a liquid crystal display according to an exemplary embodiment of the present invention will be described in detail with reference to FIG. 1.

1 is a cross-sectional view of a liquid crystal display according to an exemplary embodiment of the present invention, and FIG. 2 is a schematic diagram illustrating one pixel of the liquid crystal display according to the exemplary embodiment of the present invention.

1 and 2, a liquid crystal display according to an exemplary embodiment of the present invention includes a pixel facing a color filter capable of displaying one of primary colors such as three primary colors of red, green, and blue. A pixel including an electrode (hereinafter referred to as the main pixel A) and a pixel (hereinafter referred to as a subpixel B) provided with a pixel electrode facing a color filter capable of displaying white and black. Here, the main pixel and the sub pixel are one pixel representing one image. The main pixel is formed in a plane to line switching (PLS) mode, and the sub pixel is formed in an electrically controlled birefringence (ECB) mode. In this case, the liquid crystal molecules of the liquid crystal layer have a positive or negative dielectric anisotropy.

In order to implement the dual mode in one pixel, the rubbing directions of the two modes should be the same and the same liquid crystal should be used. Here, the PLS mode and the ECB mode may use the same liquid crystal in the same rubbing direction. In addition, as illustrated in FIG. 2, the subpixel B may be smaller than the main pixel A. FIG.

The main pixel area includes the lower panel 100, the upper panel 200, and the liquid crystal layer 3 formed between them. The lower panel 100 and the upper panel 200 face substantially parallel to each other, and the liquid crystal molecules of the liquid crystal layer 3 have a positive or negative dielectric anisotropy.

As illustrated in FIG. 1, a first common electrode 131 is formed on an insulating substrate 110 made of transparent glass or plastic in the lower panel 100 of the main pixel region. An insulating layer 140 made of silicon nitride (SiNx) or silicon oxide (SiOx) is formed on the first common electrode 131.

A plurality of first pixel electrode lines 191a are formed on the insulating layer 140. They may be made of a transparent conductive material such as indium tin oxide (ITO) or indium zinc oxide (IZO).

The first pixel electrode 191a to which the data voltage is applied generates a electric field together with the first common electrode 131 to which the first common voltage is applied, thereby liquid crystal of the liquid crystal layer 3 positioned on the two electrodes 191a and 131. Determine the orientation of the molecule. The polarization of light passing through the liquid crystal layer varies according to the direction of the liquid crystal molecules determined as described above.

The first pixel electrode 191a and the first common electrode 131 form a liquid crystal capacitor Clc (not shown) using the liquid crystal layer 3 as a dielectric to maintain an applied voltage even after the thin film transistor is turned off. 191a and 131 also form a holding capacitor Cst (not shown) with the insulating film 140 as a dielectric to enhance the voltage holding capability of the liquid crystal capacitor.

An insulating substrate 210 made of transparent glass or the like is formed on the upper panel 200 of the main pixel region.

Next, the sub-pixel area includes the lower panel 100, the upper panel 200, and the liquid crystal layer 30 formed between them. The lower panel 100 and the upper panel 200 face substantially parallel to each other, and the liquid crystal molecules of the liquid crystal layer 30 have positive or negative dielectric anisotropy.

The lower panel 100 of the sub-pixel region may be formed of an insulating film made of a first common electrode and silicon nitride (SiNx) or silicon oxide (SiOx) of a main pixel on an insulating substrate 110 made of transparent glass or plastic. insulating layer 140 is formed.

A second pixel electrode line 191b is formed on the insulating layer 140. They may be made of a transparent conductive material such as indium tin oxide (ITO) or indium zinc oxide (IZO).

Next, referring to the upper panel 200 of the sub-pixel region, the second common electrode 270 is formed on the insulating substrate 210 made of transparent glass or the like. Herein, the second common electrode 270 to which the second common voltage is applied generates an electric field together with the second pixel electrode 191b, so that the direction of the liquid crystal molecules of the liquid crystal layer 30 positioned between the two electrodes 270 and 191b. Determine. The polarization of light passing through the liquid crystal layer varies according to the direction of the liquid crystal molecules determined as described above.

Alignment layers (not shown) are formed on inner surfaces of the two display panels 100 and 200, respectively. Since this alignment film is formed at one time, it has the same rubbing direction in the main pixel region and the sub pixel region. Polarizers (not shown) are provided on the outer surfaces of the display panels 100 and 200, respectively.

When the voltage is applied to the liquid crystal display by changing the modes of the main pixel A and the sub pixel B as described above, the long-axis direction of the liquid crystal molecules in the main pixel A region is parallel to the display panels 100 and 200. The liquid crystal molecules of the subpixel B region are arranged such that their major axes are perpendicular to the display panels 100 and 200.

That is, when the PLS mode and the ECB mode are implemented in one pixel, when the narrow viewing angle is required, the side viewing angle can be reduced by applying a voltage to the subpixel in the ECB mode.

As described above, the principle of the narrow viewing angle using the dual mode will be described with reference to FIG. 3.

3A is a graph showing the transmittance of the liquid crystal display of the PLS mode, and FIG. 3B is a graph showing the transmittance of the liquid crystal display of the ECB mode.

As shown in FIG. 3A, it can be seen that the transmittance of the liquid crystal display of the PLS mode decreases as the viewing angle increases in the state where a voltage is applied. However, as shown in FIG. 3B, it can be seen that the transmittance of the liquid crystal display of the ECB mode increases as the viewing angle increases in the state where a voltage is applied.

Therefore, when a narrow viewing angle is required, when a voltage is applied to the subpixel portion of the ECB mode, the image is not distorted in the front side, but the image is distorted due to the subpixel in the ECB mode.

4 is a view illustrating a driving principle for driving a subpixel of an ECB mode in order to implement a narrow viewing angle in the liquid crystal display of the present invention.

Referring to FIG. 4, the liquid crystal display according to the exemplary embodiment of the present invention includes a liquid crystal panel assembly 300 and a signal controller 600 connected thereto.

The liquid crystal panel assembly 300 includes a plurality of pixels arranged in a matrix. The pixels are represented by R, G, B, and W according to the color filters facing each other.

In this case, the signal controller 600 separately drives the main pixel including the R, G, and B color filters and the subpixel including the W color filter, as necessary. That is, when a wide viewing angle is required, a voltage is not applied to the subpixel so that the liquid crystal layer 30 of the subpixel region is aligned with the liquid crystal layer of the main pixel region. As a result, the liquid crystal layer 30 in the sub pixel region is vertically aligned with the liquid crystal layer in the main pixel region. Alternatively, a pattern memory for driving by applying a voltage to the sub-pixel formed in the ECB mode may be provided separately.

As described above, when the narrow viewing angle is required, the liquid crystal display according to the present invention may implement the narrow viewing angle by reducing the side viewing angle by applying a voltage to the subpixel of the ECB mode.

Accordingly, the liquid crystal display according to the present invention can switch between narrow viewing angle and wide viewing angle mode, and can exhibit flexible viewing angle characteristics as necessary.

5 is a schematic diagram illustrating one pixel of a liquid crystal display according to another exemplary embodiment of the present invention.

As shown in FIG. 5, the main pixels C are formed in the PLS mode by dividing pixels displaying primary colors such as three primary colors of red, green, and blue, and the sub-pixel D that is a part of each pixel. Is formed in the ECB mode.

The subpixel D may have a smaller size than the main pixel C.

Therefore, when a wide viewing angle is required, no voltage is applied to the subpixel so that the liquid crystal layer 30 of the subpixel region is aligned with the liquid crystal layer of the main pixel region, and when a narrow viewing angle is required, a voltage is applied to the subpixel. As a result, the liquid crystal layer 30 in the sub pixel region is vertically aligned with the liquid crystal layer in the main pixel region. Alternatively, a pattern memory for driving a subpixel formed in the ECB mode may be separately provided.

Although the preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concepts of the present invention defined in the following claims are also provided. It belongs to the scope of rights.

As described above, the liquid crystal display according to the present invention can switch between the narrow viewing angle and the wide viewing angle mode, and thus can be used in the narrow viewing angle mode when the privacy protection function is required. In addition, since the liquid crystal display device of the dual mode is formed using the same liquid crystal in the same rubbing direction, only one process of forming a common electrode on the upper display panel is required to form the subpixel of the ECB mode. Therefore, it does not require any additional process, so the production cost and development cost is low and there is no need for a separate production line, which has advantages in terms of cost.

Claims (6)

First substrate, A first common electrode formed on the first substrate and made of a transparent conductor, An insulating film formed on the first common electrode, A plurality of first pixel electrodes formed on the insulating layer and overlapping the first common electrode; A second pixel electrode formed on the insulating layer and spaced apart from the first pixel electrode; A second substrate facing the first substrate, A second common electrode formed on a portion of the second substrate so as to face the second pixel electrode; A first liquid crystal layer interposed between the second substrate on which the second common electrode is not formed and the first substrate, and A second liquid crystal layer interposed between the second substrate on which the second common electrode is formed and the first substrate, A white color filter is formed on a second substrate on which the second common electrode is formed, and a red, blue, and green color filter is formed on a second substrate on which the second common electrode is not formed. In claim 1, The dielectric constant of the first and second liquid crystal layers has a positive anisotropy. In claim 1, The dielectric constants of the first and second liquid crystal layers have negative anisotropy. In claim 1, When voltage is applied to the first and second pixel electrodes and the first and second common electrodes, the long axis direction of the liquid crystal molecules of the first liquid crystal layer is perpendicular to the long axis direction of the liquid crystal molecules of the second liquid crystal layer. Liquid crystal display. In claim 1, When a voltage is applied to the second pixel electrode and the second common electrode, the major axis direction of the liquid crystal molecules of the second liquid crystal layer is perpendicular to the first and second substrates. In claim 1, An alignment layer is further formed on inner surfaces of the first substrate and the second substrate.

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