KR100466390B1 - Apparatus for fringe field switching liquid crystal display - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fringe field switching liquid crystal display device, wherein a common electrode and a pixel electrode are disposed to form a parabolic electric field in a liquid crystal cell between a lower substrate and an upper substrate. The common electrode and the pixel electrode are formed in a slit shape where the common electrode and the pixel electrode overlap each other in the region, and the common electrode and the pixel electrode are disposed so that the polarity arrangement of the electric field formed between the common electrode and the pixel electrode is opposite to the adjacent polarity arrangement. The polarization of the electric field applied to the pixel is different from the conventional one, and the afterimage property can be improved, the response speed of the liquid crystal can be prevented, and the mura phenomenon can be prevented by minimizing the insulating film under the pixel electrode which is a stress factor. It is.

Description

Fringe field switching liquid crystal display {Apparatus for fringe field switching liquid crystal display}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fringe field switching liquid crystal display device, and more particularly, alters the structure and driving charge flow of a common electrode and a pixel electrode, thereby altering the polarity arrangement of the charges, thereby reducing driving voltage and remaining afterimage. The present invention relates to a fringe field switching liquid crystal display device capable of achieving an improvement and improving the response speed of the liquid crystal by removing the insulating film between the electrodes.

Liquid crystal displays (hereinafter, LCDs) are used for terminals or video devices of various information devices in place of cathode ray tubes (CRTs) because they have characteristics such as light weight, thinness, and low power consumption. In particular, a TFT-LCD equipped with a thin film transistor (hereinafter referred to as TFT) has excellent response characteristics and is suitable for high pixel numbers, thereby realizing high quality and large display devices.

On the other hand, since the TFT-LCD has adopted a twisted nematic (TN) driving mode, the TFT-LCD has a disadvantage in that the viewing angle is narrow. In recent years, an in-plane switching (IPS) liquid crystal display has been proposed. The narrow viewing angle problem was solved to some extent.

However, the IPS-LCD has a low aperture ratio and a low transmittance due to the counter electrode and the pixel electrode being made of an opaque metal, despite the wide viewing angle.

Accordingly, in order to improve the low aperture ratio and transmittance of the IPS-LCD, Fringe Field Switching (FFS) liquid crystal display has been proposed.

1 is a plan view schematically illustrating a lower array substrate of a fringe field switching liquid crystal display according to the related art.

As shown in FIG. 1, the gate bus line 13 and the data bus line 12 are arranged in a cross-section to define a unit pixel, and a thin film transistor 100, which is a switching element, is disposed at the intersection.

The common electrode 15 made of a transparent conductor is disposed in the unit pixel, and the pixel electrode 21 is disposed in the unit pixel so as to overlap the common electrode 15. The pixel electrode 21 is electrically insulated from the common electrode 15.

The pixel electrode 21 is in the form of a comb tooth parallel to the data bus line 12 and spaced at equal intervals, and one end thereof is connected to a source electrode (not shown) of the TFT 100.

2 is a cross-sectional view schematically illustrating a lower array substrate of a fringe field switching liquid crystal display device according to the related art.

As shown in FIG. 2, the fringe field switching liquid crystal display has a common electrode 15 contacting the common electrode 13a on a transparent insulating substrate, for example, a glass substrate 11, and has a comb-tooth shaped pixel electrode. 21 is disposed so as to overlap the common electrode 15 with the gate insulating film 17 and the passivation film 19 interposed therebetween. In addition, a TFT 100 including a source and a drain electrode (not shown) is disposed as the switching element.

Here, the lower glass substrate 11 and the upper glass substrate 23 are arranged to face each other at a predetermined distance under the interposition of the liquid crystal layer (not shown). In this case, the gap between the lower glass substrate 11 and the upper glass substrate 23 is referred to as a cell gap. This is larger than the distance between the common electrode 15 and the pixel electrode 21, so that a parabolic fringe field (shown by two curved dotted lines) is formed between the electrodes.

In the conventional fringe field switching liquid crystal display device as described above, a fringe field is formed between the common electrode 15 and the pixel electrode 21 so as to form a fringe field between the upper and lower glass substrates 11 and 23. The liquid crystal molecules (not shown) having negative dielectric anisotropy intervening are all operated so that the whole light passes through the polarizer (not shown) to realize high brightness and wide viewing angle.

However, the fringe field switching liquid crystal display device has a better viewing angle than TN and IPS driving TFT-LCDs, but there is a problem that afterimages remain severe when the same shape is formed for a long time due to the overlapping area between the common electrode and the pixel electrode and the insulating film. have.

The fringe field switching liquid crystal display device according to the present invention is designed to solve the problems of the prior art, and an object of the present invention is to change the structure of the common electrode and the pixel electrode and the driving charge flow. SUMMARY OF THE INVENTION An object of the present invention is to provide a fringe field switching liquid crystal display device capable of staggering the polarity arrangement of charges) to achieve a reduction in driving voltage and to improve image retention.

In addition, another object of the present invention is to provide a fringe field switching liquid crystal display device capable of improving the response speed of the liquid crystal by removing the insulating film between the electrodes.

1 is a plan view showing a fringe field switching liquid crystal display according to the prior art.

Figure 2 is a cross-sectional view showing a fringe field switching liquid crystal display device according to the prior art.

3 is a cross-sectional view of a pixel portion of a fringe field switching liquid crystal display device according to a first embodiment of the present invention;

4A and 4B are plan views illustrating a method of manufacturing a fringe field switching liquid crystal display device according to a first embodiment of the present invention;

5 is a cross-sectional view showing a fringe field switching liquid crystal display device according to a first embodiment of the present invention;

6 is a view showing the direction of the charge flow according to the first embodiment of the present invention.

7 is a cross-sectional view of a pixel portion of a fringe field switching liquid crystal display device according to a second embodiment of the present invention.

8A and 8B are plan views illustrating a method of manufacturing a fringe field switching liquid crystal display device according to a second embodiment of the present invention;

* Description of the symbols for the main parts of the drawings *

111; Substrate 112; Data line

112a; Source 112b; drain

113; Gate 115; Common electrode

115a; Lower common electrode 115b; Upper common electrode

117; A gate insulating film 118; Active layer

119; Protective film 120; Insulating film

121; The pixel electrode 121a; Lower pixel electrode

121b; An upper pixel electrode 130; LCD

In the fringe field switching liquid crystal display device according to Embodiment 1 of the present invention for achieving the object of the present invention, a fringe field in which a common electrode and a pixel electrode are arranged such that a parabolic electric field is formed in the liquid crystal cell between the lower substrate and the upper substrate. In a switching liquid crystal display device, a common electrode and a pixel electrode are formed in a slit shape in which the common electrode and the pixel electrode overlap vertically in the pixel region on the lower substrate, and the polarity array of the electric field formed between the common electrode and the pixel electrode is adjacent to each other. The common electrode and the pixel electrode cross each other so as to be opposite to the polarity arrangement.

In addition, in the fringe field switching liquid crystal display according to Embodiment 2 of the present invention, a common electrode and a pixel electrode are disposed to form a parabolic electric field in a liquid crystal cell between a lower substrate and an upper substrate. In the fringe field switching liquid crystal display device, a common electrode and a pixel electrode are formed in a slit shape in which the common electrode and the pixel electrode overlap vertically in the pixel region on the lower substrate, and the pixel electrode is formed in a slit shape under the insulating film member. The common electrode and the pixel electrode are intersected so that the polarity arrangement of the electric field formed between the common electrode and the pixel electrode is opposite to the adjacent polarity arrangement.

Hereinafter, a fringe field switching liquid crystal display device according to the present invention will be described in detail with reference to the accompanying drawings.

3 is a cross-sectional view illustrating a pixel portion of a fringe field switching liquid crystal display device according to a first embodiment of the present invention, and FIGS. 4A and 4B illustrate a method of manufacturing a fringe field switching liquid crystal display device according to a first embodiment of the present invention. 5 is a cross-sectional view illustrating a fringe field switching liquid crystal display device according to a first embodiment of the present invention, and FIG. 6 illustrates a direction of a charge flow according to the first embodiment of the present invention.

7 is a cross-sectional view illustrating a pixel portion of a fringe field switching liquid crystal display device according to a second embodiment of the present invention, and FIGS. 8A and 8B illustrate a method of manufacturing a fringe field switching liquid crystal display device according to a second embodiment of the present invention. It is a top view shown.

In the fringe field switching liquid crystal display device according to the first embodiment of the present invention, the electrode structure in the pixel portion, which is a characteristic element of the present invention, has a gate insulating film 117 and a protective film on the substrate 111 as shown in FIG. The lower common electrode 115a and the upper pixel electrode 121b are formed to overlap each other under the interlayer of the insulating layer 120 formed of (119), and the lower pixel electrode 121a is disposed with the portion where the insulating layer 120 is removed therebetween. ) And the upper common electrode 115b are formed to overlap each other under the insulating film 120, so that the common electrodes 115a and 115b and the pixel electrodes 121a and 121b intersect with each other.

In addition, since the liquid crystal 130 exists not only on the upper electrodes 121b and 115b but also at a portion where the insulating layer 120 is removed, mismatch between horizontal and vertical dielectric constants of the liquid crystal is improved.

Meanwhile, the forming of the common electrode and the pixel electrode which overlap and intersect with each other as described above is as follows.

First, as shown in FIG. 4A, the lower common electrode 115a is formed in a unit pixel in which the gate 113 is formed, and in parallel thereto, the lower pixel electrode 121a is formed. In this case, the lower common electrode 115a and the lower pixel electrode 121a are formed to be spaced apart from each other so as not to overlap each other.

Next, although not shown in FIG. 4A, an insulating film, that is, a gate insulating film and a protective film is formed on the substrate including the electrodes 115a and 121a, and then the insulating film between the electrodes 115a and 121a is removed. .

Next, as shown in FIG. 4B, an upper pixel electrode 121b is formed on the lower common electrode 115a, and an upper common electrode 115b is formed on the lower pixel electrode 121a. That is, the common electrode 115 and the pixel electrode 121 are configured to have a slit shape that overlaps and intersects.

In this case, the lower common electrode 115a and the upper common electrode 115b are contacted by the reference numeral h3, and the lower pixel electrode 121a and the upper pixel electrode 121b are contacted by the reference numeral h2 and the upper common electrode 115b is contacted. The pixel electrode 121b is contacted by the data line 112 and reference numeral h1.

In this case, the width of the upper electrodes 115a and 121a is formed so as not to be larger than the width of the lower electrodes 115b and 121b overlapping with each other, so that the flow and orientation of the liquid crystal when the liquid crystal is not injected. Make it even smoother.

5 is a cross-sectional view of a fringe field liquid crystal display including the common electrode and the pixel electrode which are overlapped and overlapped with each other.

For convenience, cross sections of the thin film transistor unit, the pixel unit, and the data line unit are shown in one drawing.

As illustrated in FIG. 5, the thin film transistor unit may include a gate 113, a gate insulating layer 117, an active layer 118, a source / drain 112a and 112b, a passivation layer 119, and the like on the substrate 111. The pixel electrode 121 is formed, and the data line portion is formed of a gate insulating film 117, an active layer 118, a data line 112, and a protective film 119 on the substrate 111.

Meanwhile, the pixel portion, which is a characteristic element of the present invention, overlaps each other on the substrate 111 with the common electrode 115 and the pixel electrode 121 interposed between the insulating film 120 including the gate insulating film 117 and the protective film 119. And the insulating layer 120 is removed between the electrodes formed to overlap each other.

The depth of the portion where the insulating film is removed is 3,000 to 20,000 angstroms, and is at least 5,000 to 10,000 angstroms. Liquid crystals may exist in parallel with the thickness of the removed insulating layer 120. In addition, since the insulating layer is removed, the gap of the liquid crystal cell can be reduced to realize a maximum of 6,000 angstroms or less.

In the fringe field switching liquid crystal display device according to the first embodiment of the present invention having the above configuration, the polarity arrangement of the charges formed in the pixel portion when the thin film transistor is turned on / off is described above. Since the common electrode 115 and the pixel electrode 121 cross each other in the vertical direction, as shown in FIG. 6, the common electrode 115 and the pixel electrode 121 are formed to be opposite to the adjacent polarity array.

Meanwhile, luminance may be adjusted by adjusting the distance between the common electrode 115 and the pixel electrode 121 and the number of branches of each electrode.

In the fringe field switching liquid crystal display device according to the second embodiment of the present invention, the electrode structure in the pixel portion, which is a characteristic element of the present invention, has a gate insulating film 217 and a protective film on the substrate 211 as shown in FIG. The common electrode 215 and the upper pixel electrode 221b are formed to overlap each other under the insulating film 220 formed of 219, and the lower pixel electrode 221a is formed at the portion where the insulating film 220 is removed. have.

In addition, since the liquid crystal 230 is present not only on the upper portion of the electrode 221b but also at a portion where the insulating layer 220 is removed, mismatch between the horizontal and vertical dielectric constants of the liquid crystal is improved.

Meanwhile, the forming steps of the common electrode 215 and the pixel electrode 221 in the pixel portion are as follows.

First, as shown in FIG. 8A, the common electrode 215 is formed in the unit pixel in which the gate 213 is formed, and in parallel thereto, the lower pixel electrode 221a is formed. In this case, the common electrode 115 and the lower pixel electrode 221a are formed to be spaced apart from each other so as not to overlap each other.

Next, although not shown in FIG. 8A, an insulating film, that is, a gate insulating film and a protective film, is formed on the substrate including the electrodes 215 and 221a, and then the insulating film between the electrodes 215 and 221a is removed. .

Then, as shown in FIG. 8B, the upper pixel electrode 121b is formed only on the common electrode 215, and only the lower pixel electrode 221a is formed in the portion where the insulating film 2200 is removed, and the insulating film ( The portion where the 220 is formed is configured such that the common electrode 215 and the upper pixel electrode 221b vertically overlap with each other through the insulating layer 220.

In this case, the lower pixel electrode 221a and the upper pixel electrode 221b are contacted by the reference numeral h5, and the upper pixel electrode 221b is contacted by the data line 212 and the reference numeral h4.

As described above, the second embodiment of the present invention is the same as the first embodiment of the present invention except that only the lower pixel electrode 221a is formed at the portion where the insulating film 220 is removed, and the rest is the same. .

The embodiments disclosed herein are intended to express the technical spirit of the present invention in detail and are not intended to limit the present invention thereto. In addition, it can implement in various changes within the range which does not deviate from the summary of this invention.

As described above, the fringe field switching liquid crystal display according to the present invention has the following effects.

In the present invention, the afterimage characteristic can be improved by minimizing the insulating layer under the pixel electrode, which is a stress factor, unlike the conventional arrangement of the polarity of the electric field applied to the pixel.

In addition, the response speed of the liquid crystal can be improved by canceling the directions of the electric fields applied to the electrodes and placing the liquid crystals between the electrodes and the lower portion where the insulating film is removed.

On the other hand, since the liquid crystals are parallel to the thickness of the insulating film by partially removing the insulating film, the afterimage can be improved by improving the horizontal and vertical dielectric constant mismatch of the liquid crystal, and also reducing the cell gap by reducing the liquid crystal cell gap. The mura phenomenon caused by uniformity can be prevented.

Claims (12)

In a fringe field switching liquid crystal display device having a common electrode and a pixel electrode arranged to form a parabolic electric field in a liquid crystal cell between a lower substrate and an upper substrate, The common electrode and the pixel electrode are formed in a slit shape in which the common electrode and the pixel electrode are overlapped up and down in the pixel region on the lower substrate, so that the polarity arrangement of the electric field formed between the common electrode and the pixel electrode is opposite to the adjacent polarity arrangement. A fringe field switching liquid crystal display device, wherein an electrode and a pixel electrode cross each other. The method of claim 1, And the width of the overlapping lower electrode is not smaller than the width of the overlapping upper electrode. The method of claim 1, And the pixel region is configured such that the common electrode and the pixel electrode are overlapped under the insulating film, and divided into a portion in which the common electrode and the pixel electrode are arranged in a slit shape, and a portion in which the insulating film is removed. The method of claim 3, wherein The portion at which the insulating film is removed has a depth within a range of 3,000 to 20,000 Å. The method of claim 1, Fringe field switching liquid crystal display device characterized in that the interval of the liquid crystal cell is less than 6,000 Å. delete In a fringe field switching liquid crystal display device having a common electrode and a pixel electrode arranged to form a parabolic electric field in a liquid crystal cell between a lower substrate and an upper substrate, The common electrode and the pixel electrode are formed in a slit shape in which the common electrode and the pixel electrode are overlapped up and down in the pixel region on the lower substrate, and the pixel electrode is formed in the slit type under the insulating film member, and is formed between the common electrode and the pixel electrode. A fringe field switching liquid crystal display device, characterized in that the common electrode and the pixel electrode are formed so that the polarity array of the electric field is opposite to the adjacent polarity array. The method of claim 7, wherein And the width of the overlapping lower electrode is not smaller than the width of the overlapping upper electrode. The method of claim 7, wherein And the pixel region is configured such that the common electrode and the pixel electrode are overlapped under the insulating film, and divided into a portion in which the common electrode and the pixel electrode are arranged in a slit shape, and a portion in which the insulating film is removed. The method of claim 9, The portion of the insulating film is removed, the depth of the fringe field switching liquid crystal display device, characterized in that in the range of 3,000 to 20,000 Å. The method of claim 7, wherein Fringe field switching liquid crystal display device characterized in that the interval of the liquid crystal cell is less than 6,000 Å. delete