KR100801152B1 - In-Plane Switching Mode Liquid Crystal Display Device - Google Patents

Abstract

In the present invention, the substrate; A plurality of gate lines formed on the substrate in a first direction; A plurality of data lines formed in a second direction crossing the first direction; A thin film transistor formed at a point where the gate and the data line cross each other; A common wiring formed in the first direction at a position spaced apart from the gate wiring by a predetermined distance; A plurality of common electrodes connected to the common wire and positioned in the second direction; A plurality of pixel electrodes connected to the thin film transistors and alternately disposed with the plurality of common electrodes; A substrate for a transverse electric field type liquid crystal display device including a plurality of pixel electrodes connected to each other and a pixel electrode connection part formed to completely cover the gate wiring in the second direction is provided.

Description

In-Plane Switching Mode Liquid Crystal Display Device             

1 is a cross-sectional view showing a cross section of a general transverse electric field type liquid crystal display device.

2A and 2B are cross-sectional views showing operation characteristics in off and on states of a general transverse electric field type liquid crystal display device.

3 is a plan view of a conventional transverse electric field type liquid crystal display device.

4 is a cross-sectional view taken along the line IV-IV of FIG. 3.

5 is a plan view of a lower substrate for a transverse electric field type liquid crystal display device according to a first embodiment of the present invention.

6 is a cross-sectional view taken along the line VI-VI of FIG. 5.

7 is a plan view of a lower substrate for a transverse electric field type liquid crystal display device according to a second exemplary embodiment of the present invention.

FIG. 8 is an enlarged view of region “VIII” of FIG. 7;

9 is a cross-sectional view of a transverse electric field type liquid crystal display device according to the present invention;

<Description of the symbols for the main parts of the drawings>

202: gate wiring 206: common wiring

208: first common electrode 210: second common electrode

220: data wiring 222: third common electrode

230: pixel electrode

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device, and more particularly to an in-plane switching mode (IPS) liquid crystal display device.

In general, the driving principle of the liquid crystal display device uses the optical anisotropy and polarization of the liquid crystal. Since the liquid crystal is thin and long in structure, the liquid crystal has directivity in the arrangement of molecules, and the direction of the molecular arrangement can be controlled by artificially applying an electric field to the liquid crystal.

Accordingly, when the molecular arrangement of the liquid crystal is adjusted by the optical anisotropy of the liquid crystal, light may be refracted to express image information.

Currently, a thin film transistor (TFT), which is a switching element that opens and closes each pixel, is positioned for each pixel, and the first electrode connected to the thin film transistor is a pixel electrode that is turned on and off in units of pixels. In the second electrode, an active matrix liquid crystal display (AM-LCD) used as a common electrode has been attracting the most attention because of its excellent resolution and ability to implement video.

That is, the liquid crystal display includes a color filter substrate (upper substrate) having a liquid crystal layer interposed therebetween and an array substrate (lower substrate) having pixel electrodes formed thereon, and in the liquid crystal display device, common electrodes disposed to face each other. As the liquid crystal is driven by the vertical electric field applied between the and the pixel electrodes, the characteristics such as transmittance and aperture ratio are excellent. However, when the liquid crystal is driven by the vertical electric field, the long axis of the substrate and the liquid crystal are perpendicular to each other, so that the viewing angle range is narrow.

Recently, in order to improve the viewing angle characteristic of a liquid crystal display, a horizontal electric field type (horizontal electric field type) liquid crystal display has been proposed.

1 is a cross-sectional view showing a cross section of a general transverse electric field type liquid crystal display device, and FIGS. 2A and 2B are cross-sectional views showing operation characteristics in voltage off and on states of a general transverse electric field type liquid crystal display device.

As shown in FIG. 1, in a transverse electric field type liquid crystal display device, an upper substrate 10, which is a color filter substrate, and a lower substrate 20, which is an array substrate, are disposed to face each other, and between the upper and lower substrates 10 and 20. In the structure in which the liquid crystal layer 30 is interposed, both the common electrode 22 and the pixel electrode 24 are provided on the lower substrate 20, thereby generating between the common electrode 22 and the pixel electrode 24. The liquid crystal layer 30 is driven in the horizontal direction by the horizontal electric field 26.

2A and 2B show the operating characteristics of the liquid crystal molecules 32 in the voltage off / on states, respectively. As shown in FIG. 2A, the upper side of the liquid crystal molecules 32 when the voltage is off. This does not happen. In FIG. 2B, as the voltage is applied, there is no phase change of the liquid crystal molecules 32a at positions corresponding to the common electrode 22 and the pixel electrode 24, but the common electrode 22 and the pixel electrode 24 are not changed. The liquid crystal molecules 32b positioned in the intervals between the liquid crystal molecules 32b have an operating characteristic arranged in parallel with the substrate by a horizontal electric field 26 generated between the common electrode 22 and the pixel electrode 24.

That is, in the transverse electric field type liquid crystal display device, the liquid crystal moves by the horizontal electric field, so that when the display screen is viewed from the front, it can be seen from about 80 ° to 85 ° in the up / down / left / right directions. It is possible to widen the viewing angle range than the vertical field type liquid crystal display device.

Hereinafter, the conventional transverse electric field type liquid crystal display device will be described in more detail with reference to FIG. 3, and the center of the lower substrate structure for the liquid crystal display device is illustrated.

As shown, the thin film transistor T, the gate wiring 40 for turning on the thin film transistor T, the data wiring 52 crossing the gate wiring 40, and the thin film transistor T In the pixel electrode 56 connected to the common electrode 42 and the common electrode 42 to which the common voltage is applied, an area where the gates and the data lines 40 and 52 cross each other is defined as the pixel area P. Referring to FIG.

In the common electrode 42 for each pixel region P, the common wiring 44 including three patterns including the pattern disposed in close proximity to the data wiring 52 is branched, and the common electrode ( The capacitor electrode 54 is overlapped with the capacitor 42, and the capacitor electrode 54 is integrally connected to the common electrode 44 and the pixel electrodes 56 that are alternately arranged.

In this case, the common electrode 42 and the gate wiring 40 are made of the same material in the same process, preferably, an opaque metal material having a low specific resistance, and the pixel electrode 56 is made of a transparent conductive material. .

The region where the common electrode 42 and the capacitor electrode 54 overlap with each other forms a storage capacitor C _ST with an insulator interposed therebetween.

In the transverse electric field type liquid crystal display device, it is important for the image quality characteristic that the common wiring 44 is positioned between the data wiring 52 and the pixel electrode 56. When the data line 52 and the pixel electrode 56 are adjacent to each other, cross talk, which is a deterioration of image quality, is caused by an electric field generated from the data line 52 affecting the pixel electrode 56. Because it occurs.

The thin film transistor T may include an “i” type semiconductor layer 46 positioned on the gate line 40, a drain electrode 50 positioned on the semiconductor layer 46, and connected to the pixel electrode 56. And a source electrode 48 spaced apart from the drain electrode 50 at a predetermined interval and branched from the data line 52. In this case, the semiconductor layer 46 is formed inside the gate wiring 40 to prevent light from being irradiated. Further, in the transverse type liquid crystal display device, as the thin film transistor T is connected between up and down adjacent pixels, the source electrode 48 drawn from the data line 52 is led out in the up and down directions.                         

The semiconductor pattern 47 formed at the intersections of the pixel regions P has a purpose of preventing a short circuit between the gate wiring 40 and the data wiring 52 and the common wiring 44 and the data wiring 52. .

4 is a cross-sectional view taken along the cutting line IV-IV of FIG. 3, and illustrates a laminated structure of upper and lower substrates.

As illustrated, the upper and lower substrates having the liquid crystal layer 90 interposed therebetween and defining the pixel area P and the opening PP may be defined as a region that substantially realizes a screen in the pixel area P. In the structure in which the 70 and 60 are disposed to face each other, a plurality of common electrodes 44 spaced apart from each other by pixel regions P are formed on the transparent substrate 1 of the lower substrate 60. The gate insulating layer 45 is formed on the electrode 44, and the data line 52 is positioned between the two common electrodes 44 on the left side, and the common electrode 44 and the pixel electrode in the pixel region P. 56 are alternately arranged, and a protective layer 57 is formed on the common wiring 44, the data wiring 52, the pixel electrode 56, and the gate insulating film 45.

The black matrix 72 is formed under the transparent substrate 1 of the upper substrate 70 at a position corresponding to the data line 52 and the common electrode 44 adjacent to the data line 52. The color filter 74 for each color is repeatedly formed in connection with the black matrix 72, and an overcoat layer 76 is formed under the color filter 74.

The overcoat layer 76 is formed for the purpose of preventing the dye or pigment component constituting the color filter 74 from penetrating into the liquid crystal layer 90 and for planarization. In addition, the alignment of the liquid crystal layer 90 may be easily performed on the contact surface between the overcoat layer 76 and the liquid crystal layer 90 and the contact surface between the protective layer 57 and the liquid crystal layer 90 of the lower substrate 60. Upper and lower alignment layers 77 and 58 for induction are formed, respectively. In addition, upper and lower polarizers 78 and 59 are attached to respective outer surfaces of the upper and lower substrates 70 and 60 to realize perfect black or white image quality in a voltage-off state.

However, such a conventional transverse field type liquid crystal display device has an aperture ratio and a storage capacitor capacitance due to the fact that the common electrode positioned at the center of the pixel region is made of an opaque metal, and the storage capacitor depends on the overlapping area between the common wiring and the pixel electrode. This has a low disadvantage.

In order to solve this problem, it is an object of the present invention to provide a transverse electric field type liquid crystal display device having an aperture ratio and a storage capacitor enhancement structure.

Hereinafter, embodiments proposed by the present invention will be described with reference to the drawings to achieve the above object.

FIG. 5 is a plan view of a lower substrate for a transverse electric field type liquid crystal display device according to Embodiment 1 of the present invention, and is illustrated based on one pixel unit.

As shown, the gate wiring 102 is formed in the first direction, the data wiring 120 is formed in the second direction crossing the first direction, and the gate and data wirings 102 and 120 are formed. The thin film transistor T is formed at the intersection point.

The thin film transistor T may include a gate electrode 104 branched from the gate wiring 102, a semiconductor layer 112 formed to overlap the gate electrode 104 and the data wiring 120, and on the semiconductor layer 112. The source electrode 114 and the drain electrode 116 are spaced apart from each other by a predetermined distance.

In the present invention, the gate material 104 is formed by extending the semiconductor layer 112 in a pattern corresponding to the data line 120 and turning on the thin film transistor T.

In this case, an area of the semiconductor layer 112 positioned to correspond to the data line 120 serves as a buffer layer of the data line 120. In addition, unlike the related art, as the thin film transistor T is configured in the gate electrode 104, light flowing into the semiconductor layer 112 constituting the thin film transistor T may be blocked by a black matrix (not shown).

In addition, a common wiring 106 is applied to receive a common voltage in a parallel direction at a position spaced apart from the gate wiring 102 by a predetermined distance, and the common wiring 106 has a direction parallel to the data wiring 120. The first and second common electrodes 108 and 110 branch off.

The gate wiring 102 is made of an opaque metal having a low specific resistance value, and preferably, a double layer metal including molybdenum (Mo) and aluminum neodymium (AlNd) as upper and lower layers, respectively.

In addition, a section made of a transparent conductive material (preferably indium tin oxide (ITO)) in a direction parallel to the first and second common electrodes 108 and 110 may be formed in the section between the first and second common electrodes 108 and 110. Three common electrodes 122 are formed. Here, the first and second common electrodes 108 and 110 may be formed of the first and second common electrodes 108a and 108b and the second and second common electrodes 110a and 110b, respectively. 108a and 110a are made of the same material as the gate wiring 102, and the first and second common electrodes 108b and 110b are made of the same material as the third common electrode 122. In particular, the 2b common electrode 110b and the third common electrode 122 are integrally connected through the common electrode connecting portion 124 at a position corresponding to the common wire 106, and the first and second common electrodes 108a and 108b are integrated. , 108b and the second and second common electrodes 110a and 110b are connected to each other through the common electrode contact hole 111, respectively.

The pixel electrode 130 is disposed in the second direction in a section in which the pixel electrode first connection part 126 connected to the thin film transistor T and the pixel electrode second connection part 128 overlapping the gate wiring 102 face each other. The pixel electrode 130 is divided into a plurality of branches, and the pixel electrode 130 has a section between the first common electrode 108 and the third common electrode 122 and a section between the third common electrode 122 and the second common electrode 110. Are located on each. The material forming the pixel electrode first connector 126, the pixel electrode second connector 128, and the pixel electrode 130 is selected from the same material as the third common electrode 122.

Further, in the transverse electric field type liquid crystal display device, a capacitor electrode 118 extending from the drain electrode 116 and formed in a pattern corresponding to the common wiring 106 is formed, and the capacitor electrode 118 and the common wiring 106 are formed. ) Overlapping regions form a common first storage capacitor C _ST1 with an insulator interposed therebetween, and an area of the pixel electrode second connection portion 128 overlapping the gate wiring 102 with an insulator interposed therebetween. A second storage capacitor C _ST2 of a front gate type is formed.

In particular, the first storage capacitor C _ST1 includes the storage capacitor and the common wiring 106 and the capacitor electrode 118 and the pixel electrode 130 or the common electrode in the region where the common wiring 106 and the capacitor electrode 118 overlap. In the region in which the wiring 106, the capacitor electrode 118, and the common electrode connection unit 124 overlap each other, the sum of the storage capacitors in series is formed.

As described above, according to the present exemplary embodiment, the aperture ratio may be improved by forming the third common electrode 122 positioned at the center portion of the transparent conductive material without additional processing, and employing the front gate method and the common method, and thus the storage capacitor. The capacity of (C _ST ) can be improved.

However, in the transverse electric field type liquid crystal display device having such a structure, a defect in which the pixel electrode 130 is disconnected at a position corresponding to the stepped portion of the gate wiring 102 easily occurs. To describe in more detail, a cross-sectional view of the stepped portion of the gate wiring 102 is presented as follows.

6 is a cross-sectional view taken along the line VI-VI of FIG. 5.

As shown, a gate insulating film 107 covering the gate wiring 102 and the entire surface of the substrate is formed on the substrate 101 on which the gate wiring 102 is formed, and the pixel electrode second is formed on the gate insulating film 107. The connecting portion 128 and the pixel electrode 130 are integrally formed.

The material constituting the gate insulating film 107 may be a low temperature process, and a silicon nitride film (SiN _X ) or a silicon oxide film (SiO _X ), which is a kind of inorganic insulating material having excellent adhesion characteristics, is mainly used.

However, since the inorganic insulating material has a weak bonding force between the silicon atoms, the step coverage characteristic indicating the film formation degree on the stepped portion formed by the substrate and the gate wiring 102 is inferior, resulting in a step difference in the gate insulating film 107. The pixel electrode 130 in the region corresponding to the negative portion is likely to be shorted or disconnected from the gate wiring 102 during the process, so that a pattern failure occurs.

In order to improve this problem, another embodiment of the present invention is to provide a transverse electric field type liquid crystal display device to secure the process margin (margin) by changing the pixel electrode structure overlapping the gate wiring, and improved production yield.

In order to achieve the above object, in one aspect of the present invention; A plurality of gate lines formed on the substrate in a first direction; A plurality of data lines formed in a second direction crossing the first direction; A thin film transistor formed at a point where the gate and the data line cross each other; A common wiring formed in the first direction at a position spaced apart from the gate wiring by a predetermined distance; A plurality of common electrodes connected to the common wire and positioned in the second direction; A plurality of pixel electrodes connected to the thin film transistors and alternately disposed with the plurality of common electrodes; A substrate for a transverse electric field type liquid crystal display device including a plurality of pixel electrodes connected to each other and a pixel electrode connection part formed to completely cover the gate wiring in the second direction.

The plurality of common electrodes includes first and second common electrodes configured to be adjacent to the data line, and a third common electrode made of a transparent conductive material positioned in a section between the first and second common electrodes. The common electrode is composed of two layers including a lower layer made of the same material as the gate wiring and an upper layer made of the same material as the third common electrode, and one of the first and second common electrodes and the third common electrode Characterized in that it is integrally configured through the common electrode connection.

The thin film transistor includes a gate electrode branched from the gate line, a semiconductor layer covering the gate electrode, a drain electrode connected to a source electrode and a pixel electrode branched from a data line spaced apart from each other on the semiconductor layer by a predetermined distance. And a capacitor electrode in a region extending from the drain electrode to correspond to the common wiring, and a region in which the capacitor electrode and the common wiring correspond to form a first storage capacitor with an insulator interposed therebetween. The overlapping pixel electrode connectors form a second storage capacitor with an insulator interposed therebetween, and the pixel electrode connectors have an area covering a stepped portion of the overlapping gate line.

In still another aspect of the present invention, there is provided a transverse electric field liquid crystal display device including the substrate for the transverse electric field liquid crystal display device.

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

FIG. 7 is a plan view of a lower substrate for a transverse electric field type liquid crystal display device according to a second exemplary embodiment of the present invention, and descriptions of parts overlapping with those of FIG. 6 will be omitted.

As shown, the gate wiring 202 is formed in a first direction, the data wiring 220 is formed in a second direction crossing the first direction, and in a direction parallel to the gate wiring 202. The common line 206 is disposed to be spaced apart from each other and includes a plurality of first, second, and third common electrodes 208, 210, and 222 spaced apart from each other in a direction parallel to the data line 220. The thin film transistor T is formed at a point where the gate and the data lines 202 and 220 intersect with each other, the pixel electrode first connection part 226 connecting the thin film transistor T and the pixel electrode 230; The pixel electrode second connecting portion 228 is formed to overlap with the gate wiring 202, and the first, second and third common electrodes 208, 210, and the second connecting portion 228 are formed between the two connecting portions in a direction parallel to the data wiring 220. 222 and a plurality of pixel electrodes 230 positioned to cross each other are formed It is.

In particular, as shown in FIG. 8, which is an enlarged view of the region “Ⅷ” of FIG. 7, in this embodiment, the area of the pixel electrode second connecting portion 228 overlapping the gate wiring 202 is widened, and thus the existing gate wiring is expanded. Addressing the problem of disconnection of the pixel electrode 230 at an overlapping portion between the 202 and the pixel electrode 230, and a second storage capacitor in an area where the gate wiring 202 and the pixel electrode second connection part 228 correspond to each other. It is characterized by increasing the capacity of (C _ST2 ).

In the present embodiment, the overlapping width IX of the gate wiring 202 and the pixel electrode second connecting portion 228 is increased by using the portion overlapping the stepped portion of the gate wiring 202 as the pixel electrode second connecting portion 228. I was. As an example, the overlap width corresponding to the “IX” is approximately 4 μm corresponding to the line width of the pixel electrode 230, but in this embodiment, the disconnection of the pixel electrode 230 is bad due to the extension to approximately 25 μm. The incidence rate can be significantly reduced.

However, in the transverse field type liquid crystal display device according to the present invention, the number of common electrodes and pixel electrodes positioned in the pixel region may be variously changed, and in forming the semiconductor layer pattern, the thin film transistor may have an island shape. The example can be applied.

FIG. 9 is a cross-sectional view of a transverse electric field type liquid crystal display device according to an exemplary embodiment of the present invention. The stacked structure of the upper and lower substrates is shown centering on one pixel area, and a description of the overlapping part with FIG. 4 will be briefly described.

As shown, the upper substrate has a structure in which the liquid crystal layer 350 is interposed and the upper and lower substrates 330 and 310 in which the opening P is defined in the pixel region P and the pixel region P are opposed to each other. A color filter 334 and a color filter 334 that are partially overlapped with the black matrix 332 and the black matrix 332 positioned in a region other than the opening PP and formed for each pixel region P under the 330. Lower overcoat layer 336 is located.

In addition, the common electrode 316 and the pixel electrode 318 are alternately disposed in the pixel region P on the lower substrate 310, and are disposed on one side of the pixel region P. The data line 320 is disposed at a position adjacent to the 312.

The first common electrode 312 is made of an opaque metal material having a low specific resistance, and is positioned on the first common electrode 312a and the first common electrode 312a that form a lower layer, and the pixel electrode 318. As described above, the first b common electrode 312 b made of a transparent conductive material is connected to the common electrode contact hole 311. Since the second common electrode 314 positioned in the opening PP is made of a transparent conductive material such as the first b common electrode 312b and the pixel electrode 318, the second common electrode 314 may be formed of an opening ( It is possible to provide a transverse electric field type liquid crystal display device having an improved aperture ratio by widening the light transmission region in PP).

In addition, upper and lower alignment layers 338 and 322 are formed on inner surfaces of the upper and lower substrates 330 and 310 that contact the liquid crystal layer 350, respectively. It further includes upper and lower polarizers 354 and 352 located on the surface.

However, it is not limited to the said embodiment of this invention, It can implement in various changes within the range which does not deviate from the meaning of this invention.

As described above, according to the transverse electric field type liquid crystal display device according to the present invention, not only can the aperture ratio and the storage capacitor be improved, but also the pixel electrode formation area overlapping with the gate wiring can be increased, so that the process margin is sufficiently secured. According to the present invention, it is possible to provide a transverse electric field type liquid crystal display device having improved production yield by effectively reducing disconnection defects.

Claims (8)

A substrate; A plurality of gate lines formed on the substrate in a first direction; A plurality of data lines formed in a second direction crossing the first direction; A thin film transistor formed at a point where the gate and the data line cross each other; A common wiring formed in the first direction at a position spaced apart from the gate wiring by a predetermined distance; A plurality of common electrodes connected to the common wire and positioned in the second direction; A plurality of pixel electrodes connected to the thin film transistors and alternately disposed with the plurality of common electrodes; A pixel electrode connection part which connects the plurality of pixel electrodes to each other and completely covers the gate wiring in the second direction A substrate for a transverse electric field type liquid crystal display device comprising a. The method of claim 1, The plurality of common electrodes may include first and second common electrodes configured to be adjacent to the data line, and a third common electrode made of a transparent conductive material positioned in a section between the first and second common electrodes. Board. The method of claim 2,  The first and second common electrodes may be formed of two layers including a lower layer made of the same material as the gate wiring and an upper layer made of the same material as the third common electrode. The method of claim 3, wherein 1. The substrate of claim 1, wherein the common electrode and the third common electrode are integrally formed through a common electrode connection unit. The method of claim 1, The thin film transistor includes a gate electrode branched from the gate wiring, a semiconductor layer covering the gate electrode, and a source electrode and a drain electrode spaced apart from each other on the semiconductor layer by a horizontal. The method of claim 5, wherein A capacitor electrode is positioned in a region extending from the drain electrode to correspond to the common wiring, and a region corresponding to the capacitor electrode and the common wiring is a transverse electric field liquid crystal display device that forms a first storage capacitor with an insulator interposed therebetween. Board. The method of claim 1, And a pixel electrode connection portion overlapping the gate line to form a second storage capacitor in an insulator interposed therebetween. delete

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