KR100668137B1 - Fringe field switching mode lcd - Google Patents

Abstract

The present invention discloses a fringe field switching mode LCD device which can prevent deterioration of image quality caused by an unwanted electric field generated between a signal line and a counter electrode. The fringe field switching liquid crystal display device of the present invention disclosed is a transparent insulating substrate; Several gate lines arranged in one direction on the transparent insulating substrate; Several data lines arranged to be orthogonal to the gate lines; A thin film transistor disposed at an intersection of the gate line and the data line; A counter electrode disposed in the pixel region defined by the gate line and the data line; And a pixel electrode disposed on the counter electrode under the first insulating layer, wherein the counter electrode overlaps the adjacent gate line or data line and the second insulating layer.

Description

Fringe field switching mode liquid crystal display {FRINGE FIELD SWITCHING MODE LCD}

1 is a cross-sectional view showing an array substrate of a fringe field switched mode liquid crystal display device according to the prior art.

2 is a plan view for explaining a problem in the fringe field switching mode liquid crystal display device according to the prior art.

3A is a schematic plan view of an array substrate of a fringe field switched mode liquid crystal display device according to a first embodiment of the present invention;

3B is a cross-sectional view taken along the line Y-Y 'of FIG. 3A;

4A is a plan view schematically illustrating an array substrate of a fringe field switched mode liquid crystal display according to a second exemplary embodiment of the present invention.

4B is a cross-sectional view taken along the line X-X 'of FIG. 4A.

5A is a plan view schematically illustrating an array substrate of a fringe field switched mode liquid crystal display according to a third exemplary embodiment of the present invention.

FIG. 5B is a cross-sectional view taken along the line Z-Z 'of FIG. 5A;

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

30: glass substrate 33: gate line

34A, 34B, 34C: counter electrode 35: gate insulating film

36 pixel electrode 37 insulating film

39: data line 39a: source electrode

40: protective film

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fringe field switching mode liquid crystal display, and more particularly, to a fringe field switching mode liquid crystal display capable of suppressing generation of an unwanted electric field between a signal line and a counter electrode.

As is well known, liquid crystal display devices are used in terminals, video devices, and the like of various information devices in place of the CRT (Cathod-ray tube) because they have characteristics such as light weight, thinness, and low power consumption. In particular, an active matrix liquid crystal display device in which a thin film transistor is provided as a switching element for each pixel arranged in a matrix form, that is, a thin film transistor liquid crystal display device has excellent response characteristics and has an advantage suitable for high pixel number. High quality and large size can be achieved.

On the other hand, the thin film transistor liquid crystal display device has adopted a TN (Twist Nematic) mode as its driving mode, the TN mode has a disadvantage that the viewing angle is narrow, it is limited in its use. Thus, an In-Plain Switching (IPS) mode has been proposed, and a liquid crystal display device having a wide viewing angle has been implemented by the IPS mode.

On the other hand, the IPS mode liquid crystal display (hereinafter referred to as IPS-LCD) has realized a wide viewing angle, but as is well known, the counter electrode has a low aperture ratio and transmittance characteristics due to the opaque metal material. Accordingly, a fringe field switching (FFS) mode has been proposed that maintains the characteristics of the wide viewing angle of the IPS-LCD while improving the aperture ratio and transmittance. Such an FFS mode liquid crystal display device (hereinafter referred to as FFS) is proposed. -LCD) was filed in Korean Patent Application No. 98-9243.

In such FFS-LCDs, in brief, the counter electrode and the pixel electrode are formed of a transparent metal, that is, ITO, and the spacing between the electrodes is formed to be smaller than the spacing between the substrates, whereby a fringe field is formed between the electrodes. By forming the fringe field, all of the liquid crystal molecules present on the electrodes are operated, and by using a liquid crystal having negative dielectric anisotropy, the structure is made to realize high brightness and wide viewing angle.

1 is a cross-sectional view showing a portion of an array substrate of an FFS-LCD according to the prior art, which will be described below.

On the glass substrate 1 corresponding to the pixel region, a counter electrode 2 is formed of a transparent metal, for example, ITO, and has a box shape or a shape having several slits. Further, a gate line (not shown) and a common line 4 are formed on a predetermined portion of the glass substrate 1 including the gate electrode 3a which is coplanar with the counter electrode 2 and made of an opaque metal. At this time, the common line 4 is formed such that a part thereof contacts the counter electrode 2. The gate insulating film 5 is formed on the entire surface of the glass substrate 1 so as to cover the counter electrode 2, the gate line including the gate electrode 3a, and the common line 4. A pixel electrode 6 having a comb shape is formed while forming ITO on the gate insulating film portion corresponding to the pixel region, that is, the gate insulating film portion on the counter electrode 2.

A thin film transistor (TFT) having a reverse staggered structure having an etch stopper 8 is formed on a portion of the gate insulating layer above the gate electrode 3a, and the passivation layer 10 is formed on a resultant product including the thin film transistor TFT. Is formed. Here, the thin film transistor TFT, as is well known, is formed on the gate electrode 3a, the gate insulating film 5 covering it, and the semiconductor layer 8 made of an a-Si layer while being formed on the gate insulating film 5. ), The source electrode 9a and the source formed together with the etch stopper 8 and the data line (not shown) formed on the semiconductor layer 8 to be in contact with the pixel electrode 6. It consists of the drain electrode 9b which opposes and arrange | positions the electrode 9a.

The thin film transistor TFT may be formed in a back-channel etch structure in which an etch stopper is omitted.

However, conventional FFS-LCDs have improved aperture and transmittance characteristics compared to IPS-LCDs, but as shown in FIG. 2, signal lines and counter electrodes 2, i.e., gate lines 3 and The arrangement of liquid crystals is caused by the generation of an unwanted electric field between the counter electrode 2 and the data line 9 and the counter electrode 2, that is, an electric field independent of the driving control of the thin film transistor TFT or the drive IC. The light leakage phenomenon due to the change is generated, and in addition, disclination of the liquid crystal occurs, which adversely affects the liquid crystal array in the pixel region, and thus does not have good image quality.

On the other hand, not only FFS-LCDs, but also most active matrix LCDs properly adjust the width of the black matrix on the color filter substrate, thereby preventing light leakage and declining due to unwanted electric field generation, and thereby, the display screen. To prevent deterioration of the image quality. However, the expansion of the black matrix leads to a reduction of the opening area, which is not in line with the basic intention of realizing a high opening ratio.

Therefore, the present invention devised to solve the above problems is to provide an FFS-LCD which can suppress the generation of an unwanted electric field between the signal lines and the counter electrode, and thus can prevent the deterioration of image quality. There is this.

FFS-LCD of the present invention for achieving the above object, the transparent insulating substrate; Several gate lines arranged in one direction on the transparent insulating substrate; Several data lines arranged to be orthogonal to the gate lines; A thin film transistor disposed at an intersection of the gate line and the data line; A counter electrode disposed in the pixel region defined by the gate line and the data line; And a pixel electrode disposed on the counter electrode under the first insulating layer, wherein the counter electrode overlaps the adjacent gate line or data line and the second insulating layer.

According to the present invention, since the counter electrode is formed to overlap with the signal line, the phenomenon in which an unwanted electric field is generated between the counter electrode and the signal line is suppressed as much as possible, and thus, due to the light leakage and the declining phenomenon Image degradation is prevented.

(Example)

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

3A is a plan view schematically illustrating an array substrate of an FFS-LCD according to a first embodiment of the present invention. As shown, the gate lines 33 are arranged in the row direction, and the data lines 39 are arranged in the column direction perpendicular to the gate lines 33. In addition, a thin film transistor (TFT) having a reversed staggered structure, which functions as a switching element, is disposed at the intersection of the gate line 33 and the data line 39, and the gate line 33 and the data line ( In the pixel region defined by 39, a counter electrode 34A made of a transparent metal such as ITO is disposed.

Here, the counter electrode 34A has a box shape, and the upper and lower edge portions of the counter electrode 34A are overlapped with the gate line 33, and a predetermined portion thereof is a source of the thin film transistor TFT. It contacts with the electrode 39a.

In detail, FIG. 3B is a cross-sectional view taken along the line YY 'of FIG. 3A. As shown in the drawing, the counter electrode 34A has a gate line 33 in which both edge portions thereof are interposed between the gate insulating films 35. It is arranged to overlap with. In addition, the pixel electrode 36 is disposed on the counter electrode 34A with the insulating film 37 interposed therebetween. In this case, the insulating film 37 is a protective film formed to protect the thin film transistor TFT or an added insulating film. Unexplained reference numeral 30 denotes a glass substrate.

In the FFS-LCD according to the present invention having such a structure, since the gate line and the counter electrode only overlap, and there is no space between them, an unwanted electric field is generated between the gate line and the counter electrode. Therefore, the generation of light leakage or disclination due to unwanted electric field generation is also suppressed, so that no deterioration in image quality of the display screen is caused.

4A is a plan view schematically illustrating an array substrate of an FFS-LCD according to a second embodiment of the present invention. As shown, the counter electrode 34B in this embodiment is disposed such that each of the opposing one side and the other edge portion overlaps with the data line 39, and a portion of the lower edge portion of the thin film transistor TFT. It contacts with the electrode 39a. That is, the counter electrode 34B is formed to extend to a size such that a portion thereof can overlap with the data line 39 at the time of its formation, and then the counter electrode (B) is formed by forming the data line 39. 34B and the source electrode 39a of the data line 39 are contacted.

FIG. 4B is a cross-sectional view taken along the line XX ′ of FIG. 4A. As shown in the drawing, the counter electrode 34B overlaps the data line 39 at both edge portions thereof with the gate insulating layer 13 interposed therebetween. do. In addition, the pixel electrode 36 is disposed above the counter electrode 34A with the insulating film 37 interposed therebetween. The insulating film 37 is a protective film formed to protect the thin film transistor TFT as in the previous embodiment, or an added insulating film. Unexplained reference numeral 30 denotes a glass substrate.

5A is a plan view schematically illustrating an array substrate of an FFS-LCD according to a third embodiment of the present invention. As shown, the counter electrode 34C in this embodiment is arranged such that each of the opposing upper and lower edge portions adjacent to the gate line 33 overlaps the gate line 33, as well as the data line 39. Each of the opposing one side and the other edge portion adjacent to each other) is overlapped with the data line 39, and a predetermined portion is in contact with the source electrode 39a of the thin film transistor TFT.

In other words, the counter electrode 34C is coupled with both the gate line 33 and the data line 39 to prevent any unwanted electric field that may be generated between the gate line 33 and the data line 39. It is arranged to be extended to overlap the size.

5B is a cross-sectional view taken along the line Z-Z ′ of FIG. 5A. As shown, the counter electrode 34C is disposed such that the upper and lower sides thereof, as well as the one side and the other edge thereof overlap the gate line 33 and the data line 39. In this case, the gate line 33 and the counter electrode 34C are insulated by the gate insulating layer 35, and the counter electrode 34C and the data line 39 are insulated by the added insulating layer 37. In addition, the pixel electrode 36 is disposed on the counter electrode 34C with the protective film 40 interposed therebetween. The pixel electrode 36 and the data line 39 are also insulated by the passivation layer 40. Unexplained reference numeral 30 denotes a glass substrate.

In the FFS-LCD according to the embodiments of the present invention as described above, since the space between the gate line and the counter electrode and the space between the data line and the counter electrode are minimized or eliminated, the gate line and the counter electrode and the data are eliminated. Light leakage, disclination and the like caused by the generation of an unwanted electric field between the line and the counter electrode can be suppressed, so that the image quality deterioration of the FFS-LCD of the present invention is prevented.

In addition, a signal delay phenomenon may occur in the gate line and the data line by arranging the counter electrode to overlap with the gate line and the data line, and thus may cause a deterioration in image quality due to a decrease in response speed. .

Therefore, in order to prevent such a defect from occurring, the present invention uses an organic insulating film having a dielectric constant? Of 4 or less as the insulating film, and the thickness thereof is about 2 to 3 m.

Meanwhile, although the above-described embodiments are illustrated and described with respect to the inverse staggered thin film transistor structure, the present invention is also applicable to the staggered thin film transistor structure. In addition, although the present invention has been shown and described with respect to a transmissive LCD, the present invention can be applied to a transflective LCD as well as a reflective type.

Here, the overall structure when the counter electrode structure according to the present invention is applied to an FFS-LCD having a staggered thin film transistor structure, and when the counter electrode structure according to the present invention is applied to a reflective and semi-transmissive LCD, and its It is believed that the manufacturing method can be easily inferred by those skilled in the art.

Therefore, the drawings and descriptions of these examples will be omitted here.

As described above, the present invention can be arranged so that the counter electrode overlaps the gate line and the data line, so that the space between them is minimized or eliminated, thereby suppressing elements that adversely affect image quality, such as light leakage or distraction. Therefore, it is possible to provide an FFS-LCD having good image quality while achieving high opening ratio and high transmittance.

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

Claims (5)

A transparent insulating substrate, several gate lines arranged in one direction on the transparent insulating substrate, several data lines arranged orthogonally to the gate lines, and formed at intersections of the gate lines and the data lines. A fringe field switching mode liquid crystal display device comprising a thin film transistor, a counter electrode disposed in a pixel region defined by the gate line and a data line, and a pixel electrode disposed on the counter electrode. The counter electrode is a fringe field switching mode liquid crystal display device, characterized in that overlapping disposed between the adjacent gate line or data line and the insulating film. The method of claim 1, wherein the counter electrode A fringe field switching mode liquid crystal display device, wherein the fringe field switching mode is disposed to overlap any one of an adjacent gate line or an adjacent data line. The method of claim 1, wherein the counter electrode A fringe field switching mode liquid crystal display device, wherein the fringe field switching mode overlaps with both the adjacent gate line and the adjacent data line. delete delete

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