KR20050067735A - Fringe field switching mode lcd - Google Patents

Abstract

The present invention discloses a fringe field switching mode LCD. In the fringe field switching mode liquid crystal display device of the present invention, a plurality of gate bus lines and data bus lines are arranged to be intersected to define unit pixels, and a thin film transistor is disposed near an intersection point of the gate bus lines and the data bus lines. In a fringe field switching mode liquid crystal display in which a counter electrode made of ITO and a pixel electrode are disposed under an insulating film in a pixel area defined by the gate bus line and the data bus line, the counter electrode is formed between gate bus lines. It is disposed in an integral stripe shape and is in direct contact with a common electrode formed simultaneously with the gate bus line outside the display area.

Description

Fringe field switching mode LCD

The present invention relates to a liquid crystal display device, and more particularly, to a fringe field switching mode liquid crystal display device having an improved aperture ratio.

Fringe Field Switching mode LCD (hereinafter referred to as FFS-LCD) has been proposed to improve the low aperture ratio and transmittance of IPS (In-Plane Switching) LCD. 98-9243.

In the FFS-LCD, the counter electrode and the pixel electrode are formed of a transparent conductor to increase the aperture ratio and the transmittance compared to the IPS-LCD, and the gap between the counter electrode and the pixel electrode is narrower than the gap between the upper and lower substrates. By forming a fringe field between the counter electrode and the pixel electrode, even the liquid crystal molecules existing on the electrodes are operated to obtain more improved transmittance.

In detail, FIG. 1 is a schematic diagram of a conventional FFS-LCD previously applied, and as shown, a counter electrode 2 and a pixel electrode 9 made of ITO are interposed between the insulating film 4 on the lower glass substrate 1. The lower glass substrate 1 is bonded to the upper glass substrate 11 having a color filter (not shown) under the interposition of the liquid crystal layer composed of the plurality of liquid crystal molecules 12. Here, the counter electrode 2 is formed in a plate shape, and the pixel electrode 9 is formed in a comb shape including a plurality of combs.

Although not shown, the counter electrode 2 is in contact with the common bus line formed together with the gate bus line to have a reference voltage with respect to the pixel electrode 9.

The FFS-LCD having such a configuration operates as follows.

When an electric field is formed between the counter electrode 2 and the pixel electrode 9, the distance between the upper and lower glass substrates 1 and 11 is greater than the distance between the counter electrode 2 and the pixel electrode 9. A fringe field is formed between the two electrodes and over each of the electrodes. This fringe field extends across the top of the counter electrode 2 and the pixel electrode 9 to operate all of the liquid crystal molecules 12 on the top of the electrode, so that the FFS-LCD realizes high opening ratio and high transmittance. do.

However, according to the above-described FFS-LCD, as shown in Figs. 2A and 2B, the opacity of the common bus line 4 passing through the center of the pixel region inevitably leads to a decrease in aperture ratio.

Meanwhile, as shown in FIGS. 3A and 3B, the common bus line 4 may be formed so as to pass through the edge of the pixel region. In this case, the common bus line 4 may be somewhat reduced than the case where the common bus line 4 passes through the center of the pixel. However, the reduction of the aperture ratio is inevitable, and in this case, in particular, the possibility that an electrical short between the two lines 3 and 4 will occur due to the common bus line 4 being adjacent to the gate bus line 3 This is high.

In addition, as shown in Figs. 4A and 4B, conventionally, the counter electrode 2 is formed in an integral plate shape over the entire lower glass substrate while omitting the formation of the common bus line, and thus the aperture ratio due to the common bus line. In this case, although the reduction is advantageous in this case, the insulating film 13 must be interposed between the counter electrode 2 and the gate bus line 3 including the gate electrode 3a. In addition, a process of electrically connecting the counter electrode 2 and the common electrode 3b by using the ITO 14 for the pixel electrode outside the display area has to be added. .

2A, 2B, 3A, 3B, 4A, and 4B, reference numeral 1 denotes a lower glass substrate, 3a a gate electrode, 5 a gate insulating film, 7 a data bus line, and 7a a source electrode. 7b represents a drain electrode, 8 represents a protective film, and 10 represents a thin film transistor.

Accordingly, an object of the present invention is to provide an FFS-LCD which is designed to solve the conventional problems as described above, so that the aperture ratio is improved without increasing the process.

In order to achieve the above object, according to the present invention, a plurality of gate bus lines and data bus lines are arranged in an intersecting manner to limit unit pixels, and a thin film transistor is disposed near an intersection point of the gate bus lines and the data bus lines. In a FFS-LCD in which a pixel electrode defined by ITO and a pixel electrode are disposed under an insulating film in a pixel area defined by the gate bus line and the data bus line, the counter electrode is formed as an integral stripe between gate bus lines. And a direct contact with a common electrode formed simultaneously with the gate bus line outside the display area.

(Example)

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

5 is a plan view illustrating a pixel structure of an FFS-LCD according to an embodiment of the present invention. Here, the same parts as in Fig. 2A are designated by the same reference numerals.

As shown in the figure, the FFS-LCD of the present invention has a plurality of gate bus lines 3 and data bus lines 7 intersected to define unit pixels, and the gate bus lines 3 and data bus lines ( A thin film transistor 10 serving as a switching element is arranged near the intersection point of 7), and a counter electrode made of ITO is formed in the pixel region defined by the gate bus line 3 and the data bus line 7. 2) is arranged.

In particular, the counter electrode 2 is disposed in the form of an integrated stripe between the gate bus lines 3, unlike the conventional one in which only the unit pixel region is individually disposed.

Although not shown in detail, a gate insulating film and a protective film are interposed between the counter electrode 2 and the data bus line 7, and the storage capacitor Cst is disposed between the counter electrode 2 and the data bus line 7. ) Is obtained.

Although not shown, a comb-shaped pixel electrode is separately disposed for each pixel on the counter electrode 2 in the pixel region, and the source electrode of the thin film transistor 10 is disposed. Contact with 7a). In addition, the counter electrode 2 is integrated and connected to the common electrode outside the display area.

The lower substrate having the pixel structure as described above is bonded to the upper substrate including the color filter and the liquid crystal layer to form the FFS-LCD.

In such a pixel structure, since the counter electrode 2 is not disposed below the gate bus line 3, there is no need to interpose an insulating film therebetween, and therefore, an insulating film deposition process is not necessary as compared with the prior art. Further, since no common bus line is formed, the reduction of the aperture ratio due to the common bus line is fundamentally prevented.

As a result, according to the FFS-LCD according to the present invention, the aperture ratio can be improved by omitting the formation of the common bus line by changing the shape of the counter electrode, and the counter electrode and the common electrode outside the display region as well as the insulating film forming process. By directly contacting the liver, it is not necessary to add a process for electrical connection between the electrodes, thereby preventing an increase in the number of processes.

As described above, in the present invention, the counter electrode is designed in a stripe shape disposed between the gate bus lines, and the common electrodes disposed in the pixel region are directly contacted by directly contacting the counter electrode and the common electrode formed when the gate bus lines are formed. By eliminating the bus lines, the aperture ratio can be improved, and the process margin can be improved by eliminating the insulating film deposition process for the electrical separation between the counter electrode and the gate bus line and the additional process for the electrical connection between the counter electrode and the common electrode. Can be.

As mentioned above, although specific embodiments of the present invention have been described and illustrated, modifications and variations can be made by those skilled in the art. Accordingly, the following claims are to be understood as including all modifications and variations as long as they fall within the true spirit and scope of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a driving schematic diagram of a conventional fringe field switching mode liquid crystal display device.

2A and 2B are plan views and cross-sectional views illustrating a pixel structure in a conventional fringe field switching mode liquid crystal display device.

3A and 3B are a plan view and a sectional view for explaining a pixel structure in another conventional fringe field switching mode liquid crystal display device.

4A and 4B are a plan view and a sectional view for explaining a pixel structure in another conventional fringe field switching mode liquid crystal display device.

5 is a plan view illustrating a pixel structure of a fringe field switching mode liquid crystal display device according to an exemplary embodiment of the present invention.

Explanation of symbols on the main parts of the drawings

2: counter electrode 3: gate bus line

7: data bus line 7a: source electrode

7b: drain electrode 10: thin film transistor

Cst: Auxiliary Capacity

Claims (2)

A plurality of gate bus lines and data bus lines intersect to define unit pixels. A thin film transistor is disposed near an intersection point of the gate bus lines and the data bus lines, and a pixel area defined by the gate bus lines and the data bus lines. In a fringe field switching mode liquid crystal display device in which a counter electrode and a pixel electrode made of ITO are disposed under an insulating film, The counter electrode is disposed in the form of an integral stripe between the gate bus lines, the fringe field switching mode liquid crystal display device, characterized in that the direct contact with the common electrode formed at the same time as the gate bus line outside the display area. 2. The fringe field switching mode liquid crystal display of claim 1, wherein a storage capacitor Cst is formed between the counter electrode and the data bus line.