KR20060007520A - Fringe field switching mode lcd - Google Patents

Abstract

The present invention discloses a fringe field switching mode LCD having a pixel structure free of gray trace mura. In the disclosed fringe field switching mode liquid crystal display device, a box-type counter electrode and a slit-type pixel electrode made of ITO are disposed under an insulating film in a unit pixel region defined by a cross-arranged gate bus line and a data bus line. In addition, a lower substrate having a structure in which a sawtooth auxiliary pixel electrode is disposed on both edges of the pixel area at the same time as the data bus line and in contact with both end portions of the slit of the pixel electrode is formed of a black matrix and a color filter. Characterized in that the bonding is formed under the intervening upper substrate and the liquid crystal layer provided.

Description

Fringe field switching mode LCD

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram for explaining occurrence of Gray trace mura. FIG.

2 and 3A illustrate designed electrode patterns and actual formed electrode patterns in a conventional fringe field switching mode liquid crystal display.

3B is a cross-sectional view taken along the line AA ′ of FIG. 3A.

4 and 5A illustrate designed electrode patterns and actual formed electrode patterns in a fringe field switching mode liquid crystal display according to the present invention.

5B is a cross-sectional view taken along line BB ′ of FIG. 5A.

6 is a view for explaining the angle between the liquid crystal and the electric field.

Explanation of symbols on the main parts of the drawings

42,52: counter electrode 44,54: data bus line

46,56 pixel electrode 47,57 auxiliary pixel electrode

50: glass substrate 53: gate insulating film

55 protective film 58 liquid crystal

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fringe field switched mode liquid crystal display, and more particularly, to a fringe field switched mode liquid crystal display having a free pixel structure in a gray trace mura.

A fringe field switching mode LCD (hereinafter referred to as FFS mode LCD) is proposed to improve the low aperture ratio and transmittance of IPS (In Plane Switching) LCD.

In the FFS mode LCD, the counter electrode and the pixel electrode are formed of a transparent metal such as ITO, thereby increasing the aperture ratio and the transmittance compared to the IPS mode LCD, and forming the gap between the counter electrode and the pixel electrode to be smaller than the distance between the 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.

Meanwhile, in the FFS mode LCD, the counter electrode is formed in a box type, the pixel electrode is formed in a slit type, and an electric field is formed between the counter electrode and the pixel electrode in a direction perpendicular to the formed electrode end face. The liquid crystal molecules in the pixel are controlled by this electric field.

However, when a pixel electrode made of ITO is patterned according to a conventional photolithography process in the conventional pixel structure, a phenomenon in which the pattern of the edge portion is not sharply patterned as the designed pattern frequently occurs. Therefore, as the patterning of the ITO for the pixel electrode in the specific region is patterned differently from the initial intention, the liquid crystal molecules cannot all be controlled in the desired direction.

As a result, an undesirably patterned pixel electrode pattern of a particular region creates a reverse rotation liquid crystal molecular region, so that when an electric field is applied, a normal rotation region and a reverse rotation region exist in one pixel, and thus, at the interface A defect that looks black with the disclination line is generated. Normally, a defect caused in response to external pressing due to such disclination is referred to as "gray trace mura".

The gray trace mura is applied when an external force is applied to the surface of the liquid crystal panel, or when a force such as flicking using the acrylic pen 12 is applied as in the touch channel 11 as shown in FIG. 1. A phenomenon in which a certain gray color mark is left along a path of force. Reference numeral 14 denotes a gray trace mura.

In detail, FIGS. 2 and 3A illustrate designed electrode patterns and actual formed electrode patterns in a conventional FFS mode LCD. As shown in FIG. 2, the counter electrode 22 is designed in a box type, and the pixel electrode is illustrated. Although 26 is designed as a slit type, when the counter electrode and the pixel electrode are patterned with ITO according to a conventional photolithography process based on such a design, as shown in FIG. On the other hand, the pixel electrode 36 is patterned roundly without sharply patterning the slit end portion in the shape of the original mask by the characteristics of the photoresist and the exposure of the exposed light upon exposure of the coated photoresist.

Because of this, there is a region in which the liquid crystal molecules 38 are reversely rotated due to the electric field at the roundly patterned end, which not only reduces the panel transmittance but also grays the outer force when the external pressure is applied to the panel. Trace mura occurs.

3B is a cross-sectional view taken along the line AA ′ of FIG. 3A. As illustrated, the counter electrode 32 and the pixel electrode 36 are an insulating film, that is, a gate insulating film 33, in a unit pixel. And a protective film 35 interposed therebetween.

2, 3A, and 3B, reference numerals 24 and 34, which are not described, denote data bus lines, and 30 denote glass substrates, respectively.

Accordingly, an object of the present invention is to provide an FFS mode LCD having a free pixel structure in a gray trace mura, which is devised to solve the conventional problems as described above.

Another object of the present invention is to provide an FFS mode LCD having improved display characteristics by being free of gray trace mura.

In order to achieve the above object, in the present invention, a box-type counter electrode and a slit-type pixel electrode made of ITO are disposed in a unit pixel region defined by a cross-arranged gate bus line and a data bus line. In addition, a lower substrate having a structure in which a sawtooth auxiliary pixel electrode is disposed on both edges of the pixel area at the same time as the data bus line and in contact with both end portions of the slit of the pixel electrode is formed of a black matrix and a color filter. Provided is an FFS mode LCD characterized in that it is bonded to the interposed between the provided upper substrate and the liquid crystal layer.

The auxiliary pixel electrode may be formed in a shape such that an electric field generated between the counter electrode and the pixel electrode including the auxiliary pixel electrode has the same acute angle in all regions with respect to the long axis direction of the liquid crystal.

In addition, the present invention, the lower substrate and the upper substrate disposed opposite; A plurality of gate bus lines formed on the lower substrate; A box type counter electrode formed of ITO formed in each of the pixel predetermined areas on the lower substrate; A gate insulating layer formed on the entire surface of the lower substrate to cover the gate bus line and the counter electrode; A plurality of data bus lines formed to cross gate bus lines on the gate insulating film; A sawtooth auxiliary pixel electrode formed simultaneously with the data bus line at both edge portions of the pixel area defined by the intersecting gate bus line and the data bus line; A thin film transistor formed at an intersection of the gate bus line and the data bus line; A passivation layer formed on the entire surface of the lower substrate to cover the data bus line including the thin film transistor; A slit type pixel electrode made of ITO formed on both sides of the protective film to have both slit end portions disposed on the sawtooth auxiliary pixel electrode; A black matrix and a color filter sequentially formed on the upper substrate; And it provides a FFS mode LCD comprising a liquid crystal layer interposed between the lower substrate and the upper substrate.

(Example)

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

First, the FFS mode LCD according to the present invention, although not shown, a plurality of gate bus lines and data bus lines are arranged to define a unit pixel, the thin film transistor at the intersection of the gate bus line and the data bus line In the pixel region defined by the gate bus line and the data bus line, the lower substrate having a structure in which a counter electrode made of ITO and a pixel electrode are disposed under an insulating film is colored in correspondence with the black matrix and each pixel region. It has a structure bonded to the upper substrate with a filter and the liquid crystal layer interposed.

In such a structure, both the counter electrode and the pixel electrode are made of ITO material, the counter electrode is formed in a box type, and the pixel electrode is formed in a slit type. In the related art, an actual pixel electrode formed through a photolithography process is used. Unlike the pattern shape designed by the edge pattern of the slit pattern, the pattern of the slit is rounded, and thus, the reverse rotation of the liquid crystal occurs in this region, which causes the gray trace mura.

Accordingly, in the present invention, as shown in FIG. 4, the counter electrode 42 is a box type, and the pixel electrode 46 is a slit type while maintaining the design of the data bus line 44 when the pixel is designed. An auxiliary pixel electrode 47 disposed at each of the edge portions of both sides of the slit pattern of the electrode 46 is further designed.

And, through this design, as shown in Figure 5a, according to the photolithography process to form a sawtooth auxiliary pixel electrode 57 disposed in each of the edges on both sides of the slit pattern of the pixel electrode 56, and This is brought into contact with the slit type pixel electrode 56.

FIG. 5B is a cross-sectional view taken along the line BB ′ of FIG. 5A. As illustrated, the counter electrode 52 is formed on the glass substrate 50 and the gate insulating film 53 covers the counter electrode 52. The data bus line 54 and the auxiliary pixel electrode 57 are formed on the gate insulating layer 53, and a passivation layer 55 is formed to cover them, and the auxiliary pixel electrode 57 is formed on the passivation layer 55. It can be seen that the pixel electrode 56 is formed in contact with.

In this way, when the pixel electrode is patterned into the slit structure through the photolithography process, as shown in FIG. 5A, the pixel including the auxiliary pixel electrode 57 is formed, although the edge portion of the slit pattern is patterned round unlike the initial designed shape. The cross section of the electrode 56 has a sharp shape, that is, a desired shape. Therefore, some liquid crystals are caused by an electric field generated between the pixel electrode 56 including the auxiliary pixel electrode 57 and the counter electrode 52. It is possible to control all of the liquid crystals 58, for example, to rotate counterclockwise, without the occurrence of reverse rotation, resulting in a pixel structure in which gray trace mura is not generated.

At this time, it is possible to further prevent the occurrence of the gray trace mura by defining the angle between the long axis direction of the liquid crystal 58 and the electric field. For example, as shown in FIG. 6, the electric field generated between the pixel electrode 56 including the auxiliary pixel electrode 57 and the counter electrode 52 with respect to the major axis direction of the liquid crystal 58 determined by the initial rubbing direction When the angles to be formed have the same acute angle in all areas, there is no reverse rotation area, and thus a pixel structure that is stronger against gray trace mura can be obtained even in external pressing or flicking with an acrylic pen as in a touch panel. Therefore, when the auxiliary pixel electrode 57 is formed, it is preferable that the angle formed by the electric field with respect to the long axis direction of the liquid crystal is formed to have an acute angle.

As described above, the present invention can prevent the gray trace mura from being generated at the edge of the slit pattern by additionally forming a sawtooth auxiliary pixel electrode at the edge of the slit pattern when forming the data bus line. The display characteristics of the display device can be improved.

In addition, the present invention can achieve a panel structure that is pressed to the bar, to improve the brightness and to reduce the parallax (parallax effect) to realize a paper-like display window in a tablet notebook very easily to write the text with a pen You can write or draw a picture.

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.

Claims (4)

A box-type counter electrode and a slit-type pixel electrode made of ITO are disposed in a unit pixel region defined by a cross-arranged gate bus line and a data bus line, and the data bus is formed at each of both edges of the pixel region. A lower substrate having a structure in which a sawtooth auxiliary pixel electrode is disposed to be in contact with both slit ends of the pixel electrode and formed at the same time as the line is bonded to an upper substrate having a black matrix and a color filter and interposed between an upper substrate and a liquid crystal layer. A fringe field switching mode liquid crystal display device, characterized in that. The method of claim 1, wherein the auxiliary pixel electrode is formed in a shape such that the electric field generated between the counter electrode and the pixel electrode including the auxiliary pixel electrode with respect to the long axis direction of the liquid crystal has the same acute angle in all areas. Fringe field switching mode liquid crystal display. A lower substrate and an upper substrate disposed to face each other; A plurality of gate bus lines formed on the lower substrate; A box type counter electrode formed of ITO formed in each of the pixel predetermined areas on the lower substrate; A gate insulating film formed on an entire surface of a lower substrate to cover the gate bus line and a counter electrode; A plurality of data bus lines formed to cross gate bus lines on the gate insulating film; A sawtooth auxiliary pixel electrode formed simultaneously with the data bus line at both edge portions of the pixel area defined by the intersecting gate bus line and the data bus line; A thin film transistor formed at an intersection of the gate bus line and the data bus line; A passivation layer formed on the entire surface of the lower substrate to cover the data bus line including the thin film transistor; A slit type pixel electrode made of ITO formed on both sides of the protective film to have both slit end portions disposed on the sawtooth auxiliary pixel electrode; A black matrix and a color filter sequentially formed on the upper substrate; And And a liquid crystal layer interposed between the lower substrate and the upper substrate. The method of claim 3, wherein the auxiliary pixel electrode is formed in a shape such that the electric field generated between the counter electrode and the pixel electrode including the auxiliary pixel electrode with respect to the long axis direction of the liquid crystal has the same acute angle in all areas. Fringe field switching mode liquid crystal display.

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