KR100658074B1 - Cross field switching mode lcd improved transmittance and residual image - Google Patents

Abstract

The present invention discloses a cross-field switching mode liquid crystal display device having improved transmittance and afterimage to improve screen quality. The disclosed liquid crystal display device includes: a transparent insulating substrate; A plurality of gate bus lines and data bus lines cross-arranged to define unit pixels on the substrate; A common bus line arranged in parallel in the unit pixel while being spaced apart from the gate bus line as much as possible; A thin film transistor disposed at each intersection of the gate bus line and the data bus line; A counter electrode disposed in the unit pixel and composed of several first branches formed of a transparent conductive film; And a pixel electrode disposed in the unit pixel so as to overlap the counter electrode with an insulating layer interposed therebetween, the pixel electrode having the same number of second branches as the counter electrode made of a transparent conductive film. The first branches of the pixel electrode and the second branches of the pixel electrode are arranged on a vertical line, and the odd and even branches are interconnected to each other, and the odd or even branches are on the common bus line, and the remaining branches are thin film transistors. Is electrically contacted with each other so that the first branch of the counter electrode and the second branch of the pixel electrode arranged on the vertical line are applied with a voltage of the same polarity, and a cross between the branch of the neighboring counter electrode and the branch of the pixel electrode. Characterized in that the field occurs.

Description

CROSS FIELD SWITCHING MODE LCD IMPROVED TRANSMITTANCE AND RESIDUAL IMAGE

1 is a plan view showing an array substrate of a conventional fringe field switching mode liquid crystal display device.

2 and 3 are plan and cross-sectional views of a cross-field switching mode liquid crystal display according to an exemplary embodiment of the present invention.

4 is a view for explaining the operation principle of the cross-field switching mode liquid crystal display according to an embodiment of the present invention.

Explanation of symbols on the main parts of the drawings

11: glass substrate 12: gate bus line

13 common bus line 14 counter electrode

14a and 14b: first branch 15: gate insulating film

16: data bus line 17: protective film

18: pixel electrode 18a, 18b: second branch

20: insulating film TFT: thin film transistor

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device, and more particularly, to a cross field switching mode liquid crystal display device capable of suppressing afterimage generation in a fringe field switching mode liquid crystal display device.

As is well known, liquid crystal displays have been developed in place of the cathode-ray tube (CRT). In particular, the thin film transistor liquid crystal display device has been in the spotlight in the information display of a portable terminal device, the screen display of a notebook PC, the monitor of a laptop computer, etc., and thus, the utilization of the thin film transistor as a display device that can replace the CRT has been very high. .

On the other hand, the thin film transistor liquid crystal display device has typically adopted the TN (Twist Nematic) mode as the driving mode, the TN mode liquid crystal display device has a disadvantage that the viewing angle is narrow, it has been limited to use. Accordingly, in-plane switching (IPS) mode has been proposed as a driving mode capable of realizing a wide viewing angle. Although the IPS mode liquid crystal display implements a wide viewing angle, it has limitations in terms of aperture ratio and transmittance. Indicated.

Accordingly, a fringe field switching mode liquid crystal display (hereinafter referred to as FFS-LCD) capable of improving the aperture ratio and transmittance while maintaining the characteristics of the wide viewing angle of the IPS mode liquid crystal display has been proposed by the present applicant. And Korean Patent Application No. 98-9243.

The FFS-LCD has a structure in which a counter electrode and a pixel electrode are formed of a transparent metal such as ITO and the gap between the electrodes is smaller than a cell gap, and the FFS-LCD has a fringe field generated between the electrodes. As a result, all of the liquid crystal molecules present on the electrodes are operated to realize high opening ratio and high transmittance, as well as high brightness and wide viewing angle.

FIG. 1 is a plan view showing an array substrate of a conventional FFS-LCD. As shown in FIG. 1, a gate bus line 2 and a data bus line 6 are alternately arranged so that a unit pixel is defined. Near the intersection between 2 and 6, a thin film transistor (TFT) is arranged as a switching element.

A counter electrode 4 having a plate shape and made of a transparent conductive film such as ITO is disposed in the unit pixel, and the common bus line 3 is located at a position in the unit pixel spaced apart from the gate bus line 2 as far as possible. It is arranged in parallel with the gate bus line (2). The common bus line 3 is formed to continuously supply a common signal to the counter electrode 4, and is formed at the same time as the gate bus line 2 and extends in parallel with the data bus line 6. And light blocking means disposed at both edges of the counter electrode 4.

A pixel electrode 8 having a slit shape and made of a transparent conductive film such as ITO is arranged to overlap the counter electrode 4 in the unit pixel with an insulating film (not shown) interposed therebetween, and a part of the thin film transistor It is in contact with (TFT).

Although not shown, the array substrate having the above-described structure is bonded to the color filter substrate having the black matrix and the color filter and interposed between the liquid crystal layer composed of negative liquid crystal molecules. In this case, the array substrate and the color filter substrate are bonded to have a larger gap than the gap between the counter electrode and the pixel electrode provided in the array substrate.

In the FFS-LCD, negative liquid crystal molecules are rotated by causing the pixel electrode 8 to cause a potential difference between the liquid crystal molecules on the counter electrode 4 that serves as storage and the common electrode Vcom. As a result, the light that has advanced through the polarizing plate proceeds toward the color filter substrate to display a predetermined image.

However, the FFS-LCD has a superior viewing angle compared to the IPS and TN mode liquid crystal display devices, but due to unwanted parasitic capacitance due to overlapping of the counter electrode and the pixel electrode, the residual image is long when the same image is implemented for a long time. Problems in terms of the screen quality, such as the) remains badly. In particular, in order to improve such a problem, it is necessary to supplement the system, but above all, the structural improvement of the panel is necessary.

Accordingly, an object of the present invention is to provide a liquid crystal display device capable of suppressing the generation of an afterimage in an FFS-LCD, which is devised to solve the above problems.

In addition, another object of the present invention is to provide a liquid crystal display device which can improve screen quality by suppressing afterimages and improving transmittance.

Liquid crystal display device of the present invention for achieving the above object, a transparent insulating substrate; A plurality of gate bus lines and data bus lines cross-arranged to define unit pixels on the substrate; A common bus line arranged in parallel in the unit pixel while being spaced apart from the gate bus line as much as possible; A thin film transistor disposed at each intersection of the gate bus line and the data bus line; A counter electrode disposed in the unit pixel and composed of several first branches formed of a transparent conductive film; And a pixel electrode disposed in the unit pixel so as to overlap the counter electrode with an insulating layer interposed therebetween, the pixel electrode having the same number of second branches as the counter electrode made of a transparent conductive film. The first branches of and the second branches of the pixel electrode are arranged on a vertical line, and the odd and even branches are interconnected with each other, and the odd or even branches are on the common bus line, and the remaining branches are electrically connected to the thin film transistor. The first branch of the counter electrode disposed on the vertical line and the second branch of the pixel electrode are applied with a voltage of the same polarity, and a cross field is generated between the branch of the neighboring counter electrode and the branch of the pixel electrode. It is characterized by.

In the liquid crystal display of the present invention, the branches electrically contacted with the common bus line are Vcom, and the branches electrically contacted with the thin film transistor are applied with Vsig, so that the branches to which the Vcom and Vsig are applied are alternately arranged. It is characterized by.

In addition, the liquid crystal display of the present invention is characterized in that the width W1 of the branch of the counter electrode is greater than or equal to 1 μm than the branch width W2 of the pixel electrode.

In addition, the liquid crystal display of the present invention is characterized in that the interval between the first branches of the counter electrode and the second branches of the pixel electrode arranged in a vertical line is different for each region.

In addition, the liquid crystal display of the present invention is characterized in that the first branch of the counter electrode and the pixel electrode have any one shape in which the second branch is selected from the group consisting of |, ∨, <,>, and ∧.

According to the present invention, the counter electrode and the pixel electrode arranged in a vertical line not only have the same polarity, but also have opposite polarities between adjacent branches, so that the generation of an afterimage due to deterioration of the insulating film can be suppressed as much as possible. As a result, the deterioration of the screen quality of the liquid crystal display device can be prevented.

(Example)

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

2 and 3 are a plan view and a cross-sectional view of a cross-field switching mode liquid crystal display according to an exemplary embodiment of the present invention.

2 and 3, the gate bus line 12 and the data bus line 16 are arranged to cross each other so that unit pixels are limited, and the common bus line 13 is connected to the gate bus line 12. The gate bus line 12 may be disposed in parallel with each other at a position within the unit pixel spaced apart from each other. The thin film transistor TFT is disposed near the intersection point between the lines 12 and 16.

A counter electrode 14 made of a transparent conductive film such as ITO and composed of several first branches 14a and 14b is disposed in a unit pixel, and made of a transparent conductive film such as ITO, The pixel electrodes 18 composed of the same number of second branches 18a and 18b as the first branches 14a and 14b are disposed to overlap the upper portion of the counter electrode 14 under an insulating film (not shown). have. Here, the first branches 14a and 14b of the counter electrode 14 and the second branches 18a and 18b of the pixel electrode 18 are disposed on a vertical line, respectively, in particular odd and even numbers. Interconnected, for example, the odd first and second branches 14a, 18b are in electrical contact with the common bus line 13, and the even first and second branches 14b, 18b are The thin film transistor TFT is electrically contacted with the source electrode of the thin film transistor TFT more accurately.

2 and 3, reference numeral 11 denotes a glass substrate, 15 a gate insulating film, 17 a protective film, Vcom denotes a voltage applied from a common bus line, and Vsig denotes a voltage applied from a thin film transistor.

In the structure of the present invention as described above, since the first branch of the counter electrode and the second branch of the pixel electrode arranged in a vertical line have the same polarity, the field applied to the liquid crystal is improved than that in the fringe field switching mode. In particular, since a high cross field is formed in parallel, the response speed is also improved. In particular, by having opposite polarities between adjacent branches on a horizontal line, generation of an afterimage due to deterioration of the insulating film can be suppressed as much as possible.

In detail, FIG. 4 is a view for explaining the principle of operation of the cross-field switching mode liquid crystal display according to an exemplary embodiment of the present invention. Here, reference numeral 11 denotes a glass substrate, 14a and 14b denote a first branch, 20 an insulating film, and 18a and 18b denote a second branch, respectively.

The first branches 14a and 14b of the counter electrode and the second branches 18a and 18b of the pixel electrode are arranged in a vertical line, respectively, through the insulating film 20, and in particular, a pair of first lines arranged in the vertical line. And the second branches 14a, 18a, 14b, 18b have the same polarity. For example, Vcom is applied or Vsig is applied to both of the pair of first and second branches 14a, 18a, 14b, and 18b arranged in a vertical line. Vsig is applied to the other first and second branches 14b and 18b adjacent to the two branches 14a and 18a.

In this case, not only a field occurs between the first branches 14a and 14b of the adjacent counter electrode, but also a field occurs between the second branches 18b and 18a of the adjacent pixel electrode. Will happen. Therefore, since the field applied to the liquid crystal is strong, the response speed of the liquid crystal is improved.

In addition, since electrodes having the same polarity are arranged in a vertical line, a phenomenon such as insulation film deterioration due to excessive charge accumulation to the insulation film during the on / off operation can be suppressed, whereby an afterimage can be suppressed as much as possible.

In addition, when the horizontal electric fields cross each other, the liquid crystal polarization rate is increased to improve the transmittance.

On the other hand, in the liquid crystal display device of the present invention, the branch width W1 of the counter electrode is designed to be 1 μm or more larger than the branch width W2 of the pixel electrode in order to make the cross field dense.

Further, in the liquid crystal display of the present invention, the distance between the first branch of the counter electrode and the second branch of the pixel electrode arranged in a vertical line may be designed to be different for each region.

In addition, in the liquid crystal display device of the present invention, in order to have 2 to 4 domains in the unit pixel, the first branch and the pixel electrode of the counter electrode are formed from a group consisting of |, ∨, <,>, and ∧. It can be designed to have any shape selected.

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

As described above, the present invention arranges the counter electrode and the pixel electrode composed of the same number of branches in a vertical line, and at the same time the same polarity is applied to the branches arranged on the vertical line, By applying the opposite polarity between the branches, the afterimage problem in the fringe field switching mode liquid crystal display device can be solved, and the response speed and transmission path of the liquid crystal caused by the strong field can be improved, thereby providing a liquid crystal display. The screen quality of the device can be improved.

Claims (5)

Transparent insulating substrates; A plurality of gate bus lines and data bus lines cross-arranged to define unit pixels on the substrate; A common bus line arranged in parallel in the unit pixel while being spaced apart from the gate bus line as much as possible; A thin film transistor disposed at each intersection of the gate bus line and the data bus line; A counter electrode disposed in the unit pixel and composed of several first branches formed of a transparent conductive film; And a pixel electrode disposed in the unit pixel so as to overlap the counter electrode with an insulating film interposed therebetween, the pixel electrode having the same number of second branches as the counter electrode made of a transparent conductive film. The first branches of the counter electrode and the second branches of the pixel electrode are disposed on a perpendicular line, and the odd and even branches are connected to each other on the common bus line, while the odd and even branches are interconnected with each other. They are electrically contacted with the thin film transistor so that a voltage of the same polarity is applied to the first branch of the counter electrode and the second branch of the pixel electrode arranged on a vertical line, and the branches of the neighboring counter electrode and the pixel electrode are applied. And a cross field between the liquid crystal display device. The branch of claim 1, wherein the branches electrically contacted with the common bus line are Vcom, and the branches electrically contacted with the thin film transistor are applied with Vsig, so that the branches to which the Vcom and Vsig are applied are alternately applied. Liquid crystal display, characterized in that arranged. The liquid crystal display device according to claim 1, wherein the branch width (W1) of the counter electrode is greater than or equal to 1 µm than the branch width (W2) of the pixel electrode. The liquid crystal display of claim 1, wherein an interval between the first branches of the counter electrode and the second branches of the pixel electrode arranged in the vertical line is different for each region. The method of claim 1, wherein the first branch of the counter electrode and the pixel electrode have a second branch. A liquid crystal display device having any one shape selected from the group consisting of, ∨, <,>, and ∧.

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