KR100737633B1 - Thin film transistor lcd - Google Patents

Abstract

The present invention discloses a thin film transistor liquid crystal display device capable of removing flicker and residual images generated on a screen of a liquid crystal display device. The present invention disclosed is a substrate; A plurality of gate bus lines arranged to extend in one direction on the substrate; A plurality of data bus lines arranged perpendicular to the gate bus lines to define a unit pixel area; A thin film transistor disposed at an intersection of the gate bus line and the data bus line; A common bus line disposed in the center of the unit pixel areas in parallel with the gate bus line; And a pixel electrode disposed on the unit pixel region, wherein the pixel electrode overlaps with a predetermined portion of the common bus line, respectively, and includes a first pixel electrode disposed on both sides of the common bus line in the unit pixel region. The thin film transistor includes two drain electrodes drawn from the data bus line to an upper portion of the gate bus line, and one source electrode disposed between the drain electrodes. The electrodes are in contact with adjacent first and second pixel electrodes, respectively.

Description

Thin Film Transistor Liquid Crystal Display {THIN FILM TRANSISTOR LCD}

1 is a plan view showing a thin film transistor in a thin film transistor liquid crystal display device according to the prior art.

FIG. 2 is a cross-sectional view taken along the line AA ′ of FIG. 1.

3 is a plan view showing a thin film transistor liquid crystal display device according to the present invention;

4A is a plan view showing a thin film transistor in a thin film transistor liquid crystal display device according to the present invention;

4B is a cross-sectional view taken along the line BB ′ in FIG. 4A;

* Description of the symbols for the main parts of the drawings *

21: data bus line 22: thin film transistor (TFT)

23: gate bus line 29a: first pixel electrode

29b: second pixel electrode 31: common bus line

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device, and more particularly, to a thin film transistor liquid crystal display device having improved flicker and afterimage during display to improve screen quality.

In general, a thin film transistor liquid crystal display device is a device that displays a graphic signal applied along a data bus line to a pixel electrode using a TFT as a driving element.

FIG. 1 is a plan view showing a thin film transistor in a thin film transistor liquid crystal display according to the related art. As shown, the gate bus line 3 where the gate bus line 3 and the data bus line 1 intersect each other is shown. The channel layer 5 is formed on it. Source electrodes 7a in contact with the data bus line 1 are disposed on both sides of the edge of the channel layer 5, and although not shown in the figure, drain electrodes 7b in contact with the pixel electrodes are disposed.

FIG. 2 is a cross-sectional view taken along the line AA ′ of FIG. 1, as shown in FIG. 1, wherein a gate electrode 3 is formed on the transparent insulating substrate 10, and a gate is formed on the gate electrode 3. The insulating film 11 and the channel layer 5 are formed. The source / drain electrodes 7a and 7b are formed with an ohmic contact layer 13 made of a doped amorphous silicon film therebetween.

However, as the liquid crystal display becomes larger and higher in quality, a thin film transistor driven with a large current is required. In order for the thin film transistor to operate with a large current, the distance between the source / drain electrodes and the width of the channel layer must be large. Since the width of the source / drain electrodes must be large to increase the width, in this case, there is a problem that aperture ratio and luminance decrease.                         

In addition, a large screen thin film transistor liquid crystal display device is usually manufactured through a split exposure process, and overlapping lengths L ₁ and L ₂ between the gate electrode and the source and drain electrodes shown in FIG. 2 are exposed during the manufacturing process. As a result, the voltage drop of the pixel voltage (ΔV _p) is caused by the difference in parasitic capacitance of the overlapping portion between the gate, the source, and the drain electrode when the thin film transistor drives the liquid crystal display. ) Will cause a difference. However, this phenomenon appears as flicker and afterimages when the liquid crystal display is displayed, which seriously degrades the screen quality.

Accordingly, an object of the present invention is to solve the above problems and to provide a thin film transistor liquid crystal display device having a thin film transistor capable of driving with a large current.

In addition, another object of the present invention is to provide a thin film transistor liquid crystal display device which can improve screen quality through flicker and afterimage prevention.

To achieve the above object, the present invention is a substrate; A plurality of gate bus lines arranged to extend in one direction on the substrate; A plurality of data bus lines arranged perpendicular to the gate bus lines to define a unit pixel area; A thin film transistor disposed at an intersection of the gate bus line and the data bus line; A common bus line disposed in the center of the unit pixel areas in parallel with the gate bus line; And a pixel electrode disposed on the unit pixel region, wherein the pixel electrode overlaps with a predetermined portion of the common bus line, respectively, and includes a first pixel electrode disposed on both sides of the common bus line in the unit pixel region. The thin film transistor includes two drain electrodes drawn from the data bus line to an upper portion of the gate bus line, and one source electrode disposed between the drain electrodes. The electrodes are in contact with adjacent first and second pixel electrodes, respectively.

According to the present invention, by forming two drain electrodes of the thin film transistor, it is possible to supply a large amount of current necessary for high resolution of the liquid crystal display device.

(Example)

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

3 is a plan view illustrating a thin film transistor liquid crystal display device according to an exemplary embodiment of the present invention. As illustrated, a plurality of data bus lines 21 and gate bus lines 23 are vertically disposed to define a unit pixel area. The common bus line 31 parallel to the gate bus line 23 is disposed at the center of the unit pixel areas. The first pixel electrode 29a and the second pixel electrode 29b are disposed in the unit pixel area so as to overlap the predetermined portions of the common bus line 31, respectively. The thin film transistor 22 serving as a switching is disposed on the gate bus line 23 on the region where the data bus line 21 and the gate bus line 23 cross each other.                     

The thin film transistor 22 has two drain electrodes, each drain electrode being in contact with a pixel electrode in a unit pixel region adjacent to a divided pixel electrode in a unit pixel.

4A is a plan view illustrating a thin film transistor in a thin film transistor liquid crystal display according to an exemplary embodiment of the present invention, wherein a channel layer 25 is formed on the gate bus line 23, and both edges of the channel layer 25 are formed on the gate bus line 23. Drain electrodes 28a and 28b are disposed, respectively. The source electrode 27 in contact with the data bus line 21 is disposed at the center of the channel layer 25.

FIG. 4B is a cross-sectional view of a portion BB ′ of FIG. 4A being vertically cut. As illustrated, a gate bus line 23 serving as a gate electrode is formed on the transparent insulating substrate 30, and the gate bus line ( The gate insulating film 21 is formed on the 23. The channel layer 25, the source electrode 27, and the two drain electrodes 28a and 28b are disposed on the gate insulating layer 21 with the ohmic contact layer 23 interposed therebetween.

The thin film transistor having such a structure operates as follows. First, since it has two drain electrodes 28a and 28b, two channel regions are formed like the source electrode 27 disposed in the center, thereby obtaining twice as much current as the conventional thin film transistor. In addition, the lengths L ₃ and L ₄ of the two drain electrodes overlapping the gate electrode 23 may be different from each other, but the overlapping lengths, that is, L ₃ + L _4, are constant so that the drop of the pixel voltage (ΔV _P ) is constant. No difference The constant drop of the pixel voltage ΔV _P is controlled by adjusting the common voltage applied from the common bus line so that the sum of the AC voltages of the pixels applied as positive (+) and negative (−) AC voltages becomes zero (0). Direct current can be prevented from being applied. Therefore, the flicker and the afterimage can be prevented by preventing the DC voltage from being applied.

As described in detail above, according to the present invention, by forming two drain electrodes, the thin film transistor can be driven by twice the current used in the conventional thin film transistor, thereby enabling a high resolution display of the liquid crystal display device. There is an advantage.

In addition, since the overlapping lengths of the two drain electrodes and the gate electrode are generally constant, the pixel voltage drop is constant so that flicker and afterimages can be removed, thereby improving screen quality.

Various embodiments are obvious to those skilled in the art without departing from the spirit and spirit of the invention and can be easily invented. Thus, the claims appended hereto are not limited to those described above, and the claims are intended to cover all of the patented novelties inherent in this invention, and furthermore, having ordinary skill in the art to which this invention pertains. It includes all features processed evenly by the ruler.

Claims (1)

Board; A plurality of gate bus lines arranged to extend in one direction on the substrate; A plurality of data bus lines arranged perpendicular to the gate bus lines to define a unit pixel area; A thin film transistor disposed at an intersection of the gate bus line and the data bus line; A common bus line disposed in the center of the unit pixel areas in parallel with the gate bus line; And A pixel electrode disposed on the unit pixel region, wherein the pixel electrode overlaps a predetermined portion of the common bus line and is disposed on both sides of the common bus line in the unit pixel region, respectively; Composed of pixel electrodes, The thin film transistor includes two drain electrodes drawn from the data bus line to an upper portion of the gate bus line, and one source electrode disposed between the drain electrodes, wherein each of the drain electrodes is adjacent to each other. A thin film transistor liquid crystal display device, which is in contact with each of the two pixel electrodes.

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