KR100968561B1 - Liquid crystal display - Google Patents

Abstract

Gate wirings, data wirings, thin film transistors, and pixel electrodes are formed on the thin film transistor substrate, and the pixel electrodes have cutouts. A color filter, a black matrix, and a common electrode are formed on the color filter substrate facing the thin film transistor substrate, and the common electrode has cutouts and protrusions. The pixel region of the liquid crystal display device has a liquid crystal director of four domains by the cutout of the pixel electrode and the cutout of the common electrode, and at the same time, has a liquid crystal director facing the projection by the projection of the common electrode. In this case, different liquid crystal modes may be applied to one pixel area to improve front and side visibility of the liquid crystal display.

LCD, Aperture, Projection, Dual Mode, Visibility

Description

Liquid crystal display

1 is a layout view of a thin film transistor substrate for a liquid crystal display according to an exemplary embodiment of the present invention.

2 is a layout view of a color filter substrate for a liquid crystal display according to an exemplary embodiment of the present invention.

3 is a layout view of a liquid crystal display according to an exemplary embodiment of the present invention.

4 is a cross-sectional view taken along line IV-IV 'of FIG. 3,

5 is a cross-sectional view taken along the line VV of FIG.

6 is a graph illustrating gamma (γ) gamma curves in front and side surfaces of a liquid crystal display device to which a vertical alignment mode is applied.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device, and more particularly, to a liquid crystal display device for securing a wide viewing angle.

In general, a liquid crystal display device injects a liquid crystal material between an upper substrate on which a common electrode and a color filter are formed, and a lower substrate on which a thin film transistor and a pixel electrode are formed. By applying a different potential to form an electric field to change the arrangement of the liquid crystal molecules, and through this to control the light transmittance is a device that represents the image.

However, it is an important disadvantage that the liquid crystal display device has a narrow viewing angle. To overcome these shortcomings, various methods for widening the viewing angle have been developed. Among them, the long axis of the liquid crystal molecules is oriented vertically with respect to the upper and lower substrates without an electric field applied thereto, and a constant incision is made between the pixel electrode and the common electrode. A method of forming wealth or forming projections is influential.

As a method of forming the cutout, a cutout is formed in each of the pixel electrode and the common electrode, and the viewing angle is widened by adjusting the direction in which the liquid crystal molecules lie down using a fringe field formed by the cutout.

The method of forming the protrusions is a method of controlling the lying direction of the liquid crystal molecules by using the electric field distorted by the protrusions by forming the protrusions on the pixel electrode and the common electrode formed on the upper and lower substrates, respectively.

In another method, a cutout is formed in the pixel electrode formed on the lower substrate, and a protrusion is formed on the common electrode formed on the upper substrate, so that the direction of the liquid crystal lies down using a fringe field formed by the cutout and the protrusion. Regulating to form a domain.

In the multi-domain liquid crystal display, a gray scale inversion reference viewing angle defined as a contrast ratio non-reference viewing angle based on a contrast ratio of 1:10 or a limit angle of luminance inversion between gray levels is very excellent, more than 80 ° in all directions. However, the gamma curve of the front side and the gamma curve of the side do not coincide with each other, resulting in inferior visibility in the left and right sides compared to the twisted nematic (TN) mode liquid crystal display. For example, in the patterned vertically aligned (PVA) mode in which openings are formed by domain dividing means, the screen looks brighter toward the side and the color tends to shift toward white. Occasionally, the picture appears clumped and disappears. However, visibility is becoming more and more important as monitors are being used for multimedia in recent years.

The technical problem to be achieved by the present invention is to implement a liquid crystal display device having excellent side visibility.

In order to solve this problem, two or more different VA modes are simultaneously applied to one pixel area.

Specifically, the first insulating substrate, the first wiring formed on the first insulating substrate, the second wiring formed on the first insulating substrate and insulated from and intersecting the first wiring, the first wiring and the first wiring; A pixel electrode formed in each pixel region defined by the crossing of the second wiring, the thin film transistor connected to the first wiring, the second wiring and the pixel electrode, and a second insulating substrate facing the first insulating substrate. And a common electrode formed on the second insulating substrate, first and second domain dividing means formed on the first insulating substrate, and third and fourth domain dividing means formed on the second insulating substrate. The first and second domain dividing means are formed with cutouts in the pixel electrode, and the third domain dividing means is formed with cutouts in the common electrode. The domain dividing means provides a liquid crystal display device formed with projections on the common electrode.

In this case, the first domain dividing means is formed to face the third domain dividing means, and the second domain dividing means is formed to face the fourth domain dividing means.

The first domain dividing means and the third domain dividing means are preferably formed by diagonal cutouts.

The liquid crystal layer may further include a liquid crystal layer interposed between the first insulating substrate and the second insulating substrate and in which liquid crystal molecules contained therein are oriented perpendicular to the first insulating substrate without an electric field applied thereto. .

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.

Next, a liquid crystal display according to an exemplary embodiment of the present invention will be described with reference to the drawings.

1 is a layout view of a thin film transistor substrate for a liquid crystal display according to an embodiment of the present invention, FIG. 2 is a layout view of a color filter substrate for a liquid crystal display according to an embodiment of the present invention, and FIG. 3 is an embodiment of the present invention. 4 is a cross-sectional view of the liquid crystal display according to the present invention, FIG. 4 is a cross-sectional view taken along line IV-IV ′ of FIG. 3, and FIG. 5 is a cross-sectional view taken along line V-V of FIG. 3.

First, a structure of a thin film transistor substrate of a liquid crystal display according to an exemplary embodiment of the present invention will be described with reference to FIGS. 1, 4, and 5.

The gate line 121 is formed on the insulating substrate 110. The gate line 121 is elongated in the horizontal direction and includes a gate electrode 124 that is a part of the gate line 121. At this time, one end portion 129 of the gate line 121 is extended in width for connection with an external circuit.

The gate line 121 may be formed in a single layer, but may also be formed in a double layer or a triple layer. In the case of forming a single layer, it may be made of aluminum (Al) or aluminum (Al) -neodymium (Nd) alloy, and in the case of forming a double layer, physicochemical such as chromium (Cr), molybdenum (Mo), or molybdenum alloy film A lower layer made of a material having excellent properties may be formed, and an upper layer made of a material having low specific resistance such as aluminum (Al) or an aluminum alloy may be formed.

A gate insulating layer 140 made of silicon nitride (SiNX) is formed on the entire surface of the substrate including the gate line 121.

A semiconductor layer 150 made of amorphous silicon or the like is formed on the gate insulating layer 140. The semiconductor layer 150 includes a linear semiconductor 151 that is elongated in the longitudinal direction, and an island-type semiconductor 154 that protrudes from the linear semiconductor 151 and is formed at a portion corresponding to the gate electrode 124.

An ohmic contact layer 160 formed by doping a high concentration of n-type impurities to a semiconductor material such as amorphous silicon is formed on the semiconductor layer 150. The ohmic contact layer 160 is formed on the linear semiconductor 151 in such a pattern and has two island-type ohmic contact members facing each other with respect to the gate electrode 124 and the linear ohmic contact member 161. 163, 165).

The data line 171 is formed on the ohmic contact layer 160 and the gate insulating layer 140.

The data line 171 vertically intersects the gate line 121 to define a pixel region, is a branch of the data line 171, and is connected to the ohmic contact layer 163 and the source electrode 173 and the source electrode 173. And a drain electrode 175 formed on the island-like ohmic contact layer 165 opposite to the source electrode 173 with respect to the gate electrode 123. At this time, one end portion 179 of the data line 171 is extended in width for connection with an external circuit.

The data line 171 may be formed of a single layer like the gate line 121, but may also be formed of a double layer or a triple layer. In the case of forming a single layer, it may be made of aluminum (Al) or aluminum (Al) -neodymium (Nd) alloy, and in the case of forming a double layer, physical and chemical such as chromium (Cr), molybdenum (Mo), or molybdenum alloy film A lower layer made of a material having excellent properties may be formed, and an upper layer made of a material having low specific resistance such as aluminum (Al) or an aluminum alloy may be formed.

A passivation layer 180 made of a nitride material is formed on the data line 171 and the gate insulating layer 140. In this case, the passivation layer 180 has a first contact hole 181 exposing one end portion 129 of the gate line 121 and a second contact hole 182 exposing one end portion 179 of the data line 171. The third contact hole 185 exposing the drain electrode 175 is formed.

On the passivation layer 180, one end portion 129 of the pixel line 190 connected to the drain electrode 175 through the third contact hole 185 and the gate line 121 through the first contact hole 181. And a data contact assistant member 82 connected to one end portion 179 of the data line 171 through a gate contact assistant member 81 and a second contact hole 182 connected to each other. The pixel electrode 190 and the contact auxiliary members 81 and 82 are made of a transparent conductive material such as indium tin oxide (ITO) or indium zinc oxide (IZO).                     

In this case, the pixel electrode 190 is largely divided into a first pixel region having a first domain dividing unit and a second pixel region having a second domain dividing unit. The first domain dividing means includes diagonal cutouts 91 and 93 and horizontal cutouts extending from and in the upper and lower portions of the first pixel region, respectively, and extending from the diagonal cutouts 91 and 93. It consists of a central incision 92 having a branch incision each side by side. At this time, the two diagonal cut portions 91 and 93 are perpendicular to each other. This is to evenly distribute the direction of the fringe field in four directions. In addition, the second domain dividing means includes a cutout portion 94, 95, 96, which allows the pixel electrode 190 of the second pixel region to have a shape in which a plurality of quadrangles having curved vertices are arranged in rows and connected to each other. 97, 98, 99). In FIG. 1, the first domain dividing means and the second domain dividing means are shown as three and six, respectively, but the number of these domain dividing means can be changed as necessary.

Next, a color filter substrate for a liquid crystal display according to an exemplary embodiment of the present invention will be described with reference to FIGS. 2, 4, and 5.

On the transparent insulating substrate 210 made of glass or the like, a black matrix 220 made of a single layer of chromium for preventing light leakage, a double layer of chromium and chromium oxide, or an organic material to which black pigment is added is formed. The red, green, and blue color filters 230 are formed on the black matrix 220. At this time, one red, green, and blue color filter 230 is formed for each pixel area partitioned by the black matrix 220. A common electrode 240 made of a transparent conductive material is formed on the color filter 230, and the common electrode 270 is formed of a first common region having a third domain division means and a fourth domain division means having a fourth domain division means. It is divided into two common areas. Here, the third dividing means has two branch cutouts parallel to the diagonal cutouts 271 and 274 and diagonal cutouts 271 and 274 respectively formed in upper and lower portions of the first common area. It consists of a central incision 272, 273 in the form. At this time, the two diagonal cutouts 271 and 274 are perpendicular to each other. This is to evenly distribute the direction of the fringe field in four directions. In this case, the overcoat layer 250 may be formed between the color filter 230 and the common electrode 270 to prevent the color filter 230 from being exposed through the cutouts 271, 272, 273, and 274. . The fourth domain dividing means is a projection 281, 282, 283, 284, 285, 286, 287, 288, 289 made of an organic material on the common electrode 270 of the second common region. The organic materials constituting the projections 281, 282, 283, 284, 285, 286, 287, 288, and 289 have a dielectric constant different from that of the liquid crystal layer 3 injected between the color filter substrate and the thin film transistor substrate.

Finally, a liquid crystal display according to an exemplary embodiment of the present invention will be described with reference to FIGS. 3 to 6.

The liquid crystal display device is formed by aligning and combining the thin film transistor substrate of FIG. 1 and the color filter substrate of FIG. 2, and injecting the liquid crystal layer 3 therebetween. The liquid crystal molecules included in the liquid crystal layer 3 have directors with respect to the thin film transistor substrate 100 and the color filter substrate 200 without an electric field applied between the pixel electrode 190 and the common electrode 270. Are oriented vertically. The thin film transistor substrate and the color filter substrate are aligned such that the pixel electrode 150 overlaps with the color filter 220 precisely. In this case, the pixel region is common to the first pixel region where the first domain dividing means of the pixel electrode 190 and the third domain dividing means of the common electrode 270 and the second domain dividing means of the pixel electrode 190 face each other. The fourth domain dividing means of the electrode 270 is divided into a second pixel area facing each other.

First, a first pixel region in which the first domain dividing unit and the third domain dividing unit of the common electrode 270 face each other will be described with reference to FIGS. 3, 4, and 6.

The first pixel region includes diagonal cutouts 91 and 93 as first domain dividing means and diagonal cutouts 271 and 274 and third cutouts as third domain dividing means of the central cutout 92 and the common electrode 270. By the units 272 and 273, the first pixel region is divided into a plurality of small domains, and these small domains are classified into four types according to the average long axis direction of the liquid crystal molecules located therein.

In this case, when a driving voltage is applied between the common electrode 270 and the pixel electrode 190, the fringe field is formed by the first domain dividing means of the pixel electrode 190 and the third domain dividing means of the common electrode 270. As a result, the liquid crystal molecules are inclined in a direction perpendicular to the long side of the small domain. As such, the direction in which the liquid crystal is inclined is evenly distributed in four directions, thereby improving not only the front visibility but also the side visibility. However, simply dividing the domain in four directions using only the cutout as a domain dividing means does not sufficiently improve the side visibility. Therefore, the screen tends to appear brighter and the color shifts toward white toward the side, and in severe cases, the picture may appear clumped because the gap between bright grays disappears.

In more detail, it can be seen that the gamma curve when viewed from the side (60 °) is higher than the gamma curve when the LCD is viewed from the front. In particular, at low gray scales, the width between the front gamma curve and the side gamma curve is very large, so that a luminance difference of 2 to 10 times or more occurs depending on whether the same gray scale is viewed from the front or the side.

When the gamma curve is distorted in the form as shown in FIG. 6, the color having a lower ratio in the front is higher in the side, whereas the color having a higher ratio in the front is lower in the side, so the ratio of red, green, and blue is similar. Will be displayed. As a result, when viewed from the front, the different colors appear to be similar colors because the color difference is reduced on the side, and the overall color becomes thin and becomes white-shifted. This phenomenon results in poor color reproducibility and blurry picture. The biggest cause of white-shift is the large distortion of the gamma curve at low grayscale. Although gamma distortion occurs at high gradation, it is not a big change in terms of ratio, but at low gradation (below 32 gradations), the luminance varies by 2 to 10 times due to gamma distortion, so that the front visibility is excellent, but the side visibility is deteriorated.

In order to solve the above problems, the present invention forms a domain having a liquid crystal director different from the first pixel region by applying domain dividing means different from the first pixel region to the second pixel region.                     

3 and 5, a second pixel region in which the second domain dividing means of the pixel electrode 190 and the third domain dividing means of the common electrode 270 face each other will be described.

In the second pixel region, the pixel electrodes 190 are formed in a shape in which a plurality of quadrangles having curved vertices by the second domain dividing unit are arranged in a row, and sides are connected to each other, and a plurality of curved vertices are formed. Projections 281, 282, 283, 284, 285, 286, 287, 288, and 289 as fourth domain dividing means are formed on the common electrode 270 so as to face the center portions of the quadrangles. Accordingly, in the second pixel region, the fringe fields formed by the second and fourth domain dividing means are arranged radially around the liquid crystal molecules toward the fourth domain dividing means, which is a projection.

In this way, the light emitted through the second pixel region exhibits a gamma curve different from the light emitted through the first pixel region. When the light emitted from these two regions is mixed, the light of the gamma curve at the side becomes less distortion. .

That is, the present invention may improve visibility of the side surface by dividing one pixel area into several regions and applying different liquid crystal driving modes to each region to compensate for light emitted from the two driving modes.

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. In particular, the arrangement of the cutouts formed in the pixel electrode and the common electrode may have various variations.

Through the above configuration, the front and side visibility of the vertical alignment mode liquid crystal display device can be improved.

Claims (6)

First insulating substrate, First wiring formed on the first insulating substrate, A second wiring formed on the first insulating substrate and insulated from and intersecting the first wiring; A pixel electrode formed for each pixel region defined by crossing the first wiring and the second wiring, and divided into a first pixel region and a second pixel region; A thin film transistor connected to the first wiring, the second wiring and the pixel electrode; A second insulating substrate facing the first insulating substrate, A common electrode formed on the second insulating substrate and divided into a first common region facing the first pixel region and a second common region facing the second pixel region; First domain dividing means including an oblique cutout extending in an oblique direction with the second wiring in the first pixel region; Second domain dividing means formed by rectangular cutouts in which a plurality of quadrangles having curved vertices in the second pixel region are arranged in a row; Third domain dividing means formed in the cutout in parallel with the first domain dividing means in the first common region; And a fourth domain dividing means formed in the second common region by projections spaced apart from the second domain dividing means. In claim 1, The first domain dividing means is symmetrical up and down, And a horizontal cutout extending in a horizontal direction at a central portion of the first pixel area, and a branch cutout extending in an oblique direction from the horizontal cutout. delete In claim 1, The liquid crystal display further includes a liquid crystal layer interposed between the first insulating substrate and the second insulating substrate, wherein the liquid crystal molecules contained therein are oriented perpendicular to the first insulating substrate without an electric field applied thereto. Device. In claim 4, And a director of the liquid crystal corresponding to the first pixel region and a director of the liquid crystal corresponding to the second pixel region. First insulating substrate, First wiring formed on the first insulating substrate, A second wiring formed on the first insulating substrate and insulated from and intersecting the first wiring; A pixel electrode formed for each pixel region defined by crossing the first wiring and the second wiring, and divided into a first pixel region and a second pixel region; A thin film transistor connected to the first wiring, the second wiring and the pixel electrode; A second insulating substrate facing the first insulating substrate, A common electrode formed on the second insulating substrate and divided into a first common region facing the first pixel region and a second common region facing the second pixel region; First domain dividing means formed in the first pixel region in an oblique direction to the second wiring; Second domain dividing means formed by arranging a plurality of quadrangles having curved vertices in the second pixel area in a matrix; Third domain dividing means formed in the first common region in parallel with the first domain dividing means spaced apart from each other; A fourth domain dividing means formed in the second common region and spaced apart from the second domain dividing means, The first and third domain dividing means are formed as cutouts, and the second and fourth domain dividing means are formed as protrusions, And the first and third domain division means are formed as protrusions, and the second and fourth domain division means are formed as cutouts.

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