KR100569266B1 - Lower substrate structure in lcd - Google Patents

Abstract

The present invention discloses a lower substrate structure of a liquid crystal display device capable of improving rubbing defects in a portion of the thin film transistor, thereby improving image quality characteristics of the liquid crystal display device. The present invention discloses a lower substrate; A gate bus line extending in a predetermined direction on the lower substrate; A data bus line extending in a direction substantially perpendicular to the gate bus line to define a unit pixel together with the gate bus line; A thin film transistor disposed over the gate bus line near an intersection point with the data bus line; A pixel electrode in contact with a predetermined portion of the thin film transistor and disposed in the unit pixel space; An alignment layer disposed on the lower substrate resultant and rubbed in a predetermined direction, wherein the thin film transistor includes: a gate electrode extending in a direction parallel to the rubbing direction of the alignment layer by a predetermined length from the gate bus line toward the unit pixel; An active layer overlapping the gate electrode, a source electrode extending from the data bus line while being in contact with one side of the active layer and being perpendicular to the gate electrode, and being in contact with the other side of the active layer and being perpendicular to the gate electrode. And a drain electrode formed to be formed and contacting the pixel electrode.

Description

Lower substrate structure of liquid crystal display device {LOWER SUBSTRATE STRUCTURE IN LCD}

1 is a plan view showing unit pixels of a conventional active matrix liquid crystal display device.

2 is a plan view showing a thin film transistor structure of the liquid crystal display according to the present invention.

(Explanation of symbols for the main parts of the drawing)

20-Bottom Board 21-Gate Bus Line

21a-gate electrode 22-data bus line

22a-source electrode 22b-drain electrode

25-Thin Film Transistor 25a-Active Layer

27-pixel electrode

The present invention relates to a lower substrate structure of a liquid crystal display device, and more particularly, to a thin film transistor structure of a liquid crystal display device capable of improving rubbing uniformity.

Generally, in the liquid crystal display element, the active matrix liquid crystal display element has a high speed response and has a large number of pixels. As a result, the display screen has high characteristics such as high image quality, large size, and color screen, and is used in portable TVs, notebook PCs, automobile navigation systems, and the like.

In such an active matrix liquid crystal display device, switching elements such as diodes or thin film transistors are arranged and designed at intersections of gate lines and data lines to selectively turn on / off the pixel electrodes.

1 is a plan view illustrating a unit pixel of a conventional active matrix liquid crystal display device.

Referring to FIG. 1, a gate bus line 11 in the drawing extends on the lower substrate 10 made of glass, and the data bus lines 12 are arranged to intersect with the gate bus line 11 to form a unit pixel space. This is limited. At this time, a gate insulating film (not shown) is interposed between the gate bus line 11 and the data bus line 12 to insulate the two lines.

The thin film transistor 15 is disposed above the gate bus line 11 near the intersection point of the gate bus line 11 and the data bus line 12. At this time, the thin film transistor 15 extends from the gate bus line 11 toward the unit pixel by a predetermined length in parallel with the data bus line, and the active layer 15a overlapping the gate electrode 11a. ) And a source electrode 12a extending from the data bus line 12 while being in contact with one side of the active layer 15a and a drain electrode 12b being in contact with the other side of the active layer 15a. The pixel electrode 17 is disposed in the unit pixel space to be in contact with the drain electrode 12b of the thin film transistor 15. At this time, the pixel electrode 17 is formed of a transparent conductor as is known.

Although not shown in the drawing, an upper substrate including a common electrode is disposed on the lower substrate 10 at a predetermined distance, and a liquid crystal layer is interposed between the upper substrate and the lower substrate 10.

An alignment film (not shown) is formed on the resulting product of the lower substrate to control the initial arrangement of the liquid crystal molecules. The alignment film is rubbed by rubbing the rubbing cloth 18 to form a predetermined direction, for example, about ± 45 ° with the gate bus line 11. Herein, reference numeral 19 denotes a rubbing direction.

However, during the process of rubbing the alignment layer with the rubbing cloth 18, the region in which the pixel electrode without the lower structure is formed is rubbed uniformly in a desired shape, while having a height of about 1 to 2 μm from the substrate 1. Due to the height of the thin film transistor portion, rubbing failure occurs. For this reason, the liquid crystal molecules are misaligned due to the nonuniform rubbing process of the alignment layer in the portion where the thin film transistor is formed.

Light leakage occurs due to misalignment of the liquid crystal molecules in the portion where the thin film transistor is formed, thereby degrading an image quality characteristic of the liquid crystal display.

Accordingly, an object of the present invention is to provide a lower substrate structure of a liquid crystal display device capable of improving the image quality characteristics of a liquid crystal display device by improving rubbing defects in a thin film transistor part. .

The lower substrate structure of the liquid crystal display according to the present invention for achieving the above object is a lower substrate; A gate bus line extending in a first direction on the lower substrate; A data bus line extending in a second direction perpendicular to the gate bus line to define a unit pixel together with the gate bus line; A thin film transistor configured to be disposed near an intersection point of the gate bus line and the data bus line; A pixel electrode electrically connected to the thin film transistor and disposed in the unit pixel space; An alignment layer disposed on the lower substrate resultant and rubbed in the same direction, wherein the thin film transistor includes: a gate electrode extending from the gate bus line toward the unit pixel in a direction parallel to the direction in which the alignment layer is rubbed; An active layer overlapping the upper electrode, a source electrode formed to be in contact with one side of the active layer and extending from the data bus line and perpendicular to the gate electrode, and in contact with the other side of the active layer and perpendicular to the gate electrode. And a drain electrode formed to be in contact with the pixel electrode and electrically connected to the pixel electrode. Preferably, the alignment layer is rubbed at an angle of ± 45 ° with the gate bus line.

According to the present invention, by arranging the thin film transistors to match the rubbing direction of the orientation of the lower substrate, the rubbing defect of the thin film transistor portion is minimized. Accordingly, the liquid crystal molecules are not misaligned in the thin film transistor portion, so that no light leakage occurs. Therefore, the image quality characteristic of the liquid crystal display device is improved.

(Example)

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

2 is a plan view illustrating a thin film transistor structure of a liquid crystal display according to the present invention.

First, referring to FIG. 2, a gate bus line 21 extends and is disposed in a predetermined direction on a lower substrate 20 made of glass, and the data bus line 22 is substantially perpendicular to the gate bus line 21. It is arranged to extend in the direction to form a matrix form with the gate bus line 21. Accordingly, the unit pixel space is limited.

  The thin film transistor 25 serving as the switching element is disposed near the intersection point of the gate bus line 21 and the data bus line 22. In this case, the thin film transistor 25 may include the gate electrode 21a extending from the gate bus line 21 toward the unit pixel, the active layer 25a overlapping the gate electrode 21a, and the active layer 25a. A source electrode 22a which is in contact with one side and extends from the data bus line 22 and a drain electrode 22b which is in contact with the other side of the active layer 25a are included. Here, the gate electrode 21a of the thin film transistor 25 is later extended in a direction parallel to the rubbing direction of the alignment layer (not shown), that is, ± 45 ° with the gate bus line 21, and the source electrode 22a. ) And the drain electrode 22b are arranged to be perpendicular to the extending direction of the gate electrode 21a. Accordingly, the thin film transistor 25 is formed at one corner portion of the unit pixel space.

The pixel electrode 27 is disposed in each unit pixel to contact the drain electrode 22b of the thin film transistor 25. In this case, the pixel electrode 27 is formed of a transparent conductor, for example, indium tin oxide (ITO) as is known, and includes a gate bus line 21, a data bus line 22, and a thin film forming the unit pixel. The gate electrode 21a and the source electrode 22a of the transistor are spaced apart from each other by a predetermined distance.

An alignment layer (not shown) is formed on the resultant of the lower substrate 20, and the rubbing layer is rubbed with the rubbing cloth 28 to form ± 45 ° with the gate bus line 21 or the data bus line 22. .

In addition, the upper substrate (not shown) and the liquid crystal layer (not shown) are disposed in the same manner as in the prior art.

In the liquid crystal display device of the present invention having such a configuration, the portion of the thin film transistor 25 having the highest step in the unit pixel, in particular, the gate electrode 21a extends in the same direction as the rubbing axis, and has a source and drain electrode 22a. Since 22b) is formed to be orthogonal to the rubbing axis, when rubbing the thin film transistor portion, it comes into contact with the rubbing cloth at 90 °, and the rubbing uniformity is greatly improved.

As described in detail above, according to the present invention, the thin film transistors are arranged to match the rubbing direction of the orientation of the lower substrate, thereby minimizing rubbing defects of the thin film transistor portions. Accordingly, the liquid crystal molecules are not misaligned in the thin film transistor portion, so that no light leakage occurs. Therefore, the image quality characteristic of the liquid crystal display device is improved.                     

In addition, this invention can be implemented in various changes within the range which does not deviate from the summary.

Claims (2)

Lower substrate; A gate bus line extending in a first direction on the lower substrate; A data bus line extending in a second direction perpendicular to the gate bus line to define a unit pixel together with the gate bus line; A thin film transistor configured to be disposed near an intersection point of the gate bus line and the data bus line; A pixel electrode electrically connected to the thin film transistor and disposed in the unit pixel space; An alignment layer disposed on the lower substrate resultant and rubbed in the same direction, The thin film transistor may include a gate electrode extending in a direction parallel to a direction in which the alignment layer is rubbed from the gate bus line toward the unit pixel, an active layer overlapping the gate electrode, and one side of the active layer. A source electrode extending from a data bus line and formed to be perpendicular to the gate electrode, and a drain electrode contacting the other side of the active layer and perpendicular to the gate electrode and electrically connected to the pixel electrode. The lower substrate structure of the liquid crystal display device. The lower substrate structure of claim 1, wherein the alignment layer is rubbed at an angle of ± 45 ° with the gate bus line.

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