KR101201324B1 - In-plane switching mode liquid crystal display device - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an IPS mode liquid crystal display device for improving charging characteristics of a device by adding a storage capacitance by extending a common wiring under a contact hole where a drain electrode and a pixel electrode contact each other. A plurality of gate lines and data lines that vertically cross and define a unit pixel; A thin film transistor formed at an intersection point of the gate line and the data line; A protective film formed on the entire surface including the thin film transistor; A plurality of pixel electrodes contacting the drain electrode of the thin film transistor through a contact hole on the passivation layer; A common wiring including upper and lower wirings parallel to the gate wiring at the edge of the unit pixel and first and second connecting portions parallel to the data wiring at the edge of the unit pixel and connecting the upper and lower wirings; And a plurality of common electrodes contacting the first connection portion of the common wiring on the passivation layer and formed in parallel between the pixel electrodes, wherein the lower wiring overlaps the drain electrode or the pixel electrode around the contact hole. The upper wiring and the second connection portion overlap the pixel electrode.

IPS, storage capacitance

Description

IPS mode liquid crystal display device {IN-PLANE SWITCHING MODE LIQUID CRYSTAL DISPLAY DEVICE}

1 is a plan view of a conventional IPS mode liquid crystal display device.

2 is a plan view of an IPS mode liquid crystal display device according to the present invention;

3 is a cross-sectional view taken along the line II ′ of FIG. 2.

* Explanation of symbols on the main parts of the drawings

112: gate wiring 112a: gate electrode

114: semiconductor layer 115: data wiring

115a: source electrode 115b: drain electrode

117: pixel electrode 118: first contact hole

119: second contact hole 124: common electrode

125: common wiring

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

In recent years, active matrix liquid crystal display devices have been widely used in flat panel TVs, portable computers, monitors, and the like, as their performance is rapidly developed.

Among the active matrix liquid crystal display devices, twisted nematic (TN) type liquid crystal display devices are mainly used. In the twisted nematic method, electrodes are installed on two substrates and the liquid crystal directors are arranged to be twisted by 90 °. It is a technique of driving a liquid crystal director by applying a voltage to an electrode.

Twisted nematic liquid crystal display devices are spotlighted for providing excellent contrast and color reproducibility, but suffer from the chronic problem of narrow viewing angles.

In order to solve the viewing angle problem of the TN method, an IPS mode in which two electrodes are formed on a single substrate and a transverse electric field generated between the two electrodes is controlled.

Hereinafter, described in detail with reference to the accompanying drawings as follows.

1 is a plan view of a conventional IPS mode liquid crystal display device.

First, as shown in FIG. 1, the IPS mode liquid crystal display device includes a gate line 12 and a data line 15 that vertically intersect to define a unit pixel, and are formed at intersections of the gate line and the data line. A thin film transistor TFT and a common electrode 25 and a pixel electrode 17 are formed to cross each other in parallel to each other to generate a transverse electric field.

In this case, the common electrode 25 is integrally formed with the common wiring 25 parallel to the gate wiring 12 to receive a voltage outside the active region.

As described above, the IPS mode liquid crystal display device forms liquid crystal molecules by forming a common electrode 24 and a pixel electrode 17 on the same substrate and applying a voltage between the two electrodes to generate a horizontal electric field in the horizontal direction with respect to the substrate. It is characterized in that the rotating to the horizontal state with respect to the substrate.

Such an IPS mode liquid crystal display device has an S-IPS (Super-IPS) and an H-IPS (Horizental) depending on whether the pixel electrode 24 and the common electrode 17 are arranged in the data wiring direction or the gate wiring direction. -IPS), as shown in FIG. 1, the pixel electrode 24 and the common electrode 17 are disposed in the direction of the data line 15, and are referred to as S-IPS. And H-IPS in which the common electrode is arranged in the gate wiring direction. The H-IPS is proposed to improve luminance and response speed which are disadvantages of the S-IPS mode.

On the other hand, the pixel electrode and the common electrode may have a structure to be bent, as shown in FIG. 1, the data wiring is formed in a structure that is bent in parallel with the pixel electrode and the common electrode is called AS-IPS (Advanced Super-IPS).

The liquid crystal display device according to the prior art as described above had the following problems.

That is, when the luminance, response speed, aperture ratio, and the like of the devices were compared with each other, the H-IPS mode in which the electrodes were disposed in the transverse direction was superior to the S-IPS mode and the AS-IPS mode in which the electrodes were disposed in the vertical direction. Therefore, research on H-IPS mode has been actively conducted in recent years.

However, the S-IPS and AS-IPS as well as the H-IPS mode liquid crystal display device have a structural weakness of low Cst (storage capacitance).

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and extends a common wiring under a contact hole in which a drain electrode and a pixel electrode are contacted to add storage capacitance to improve charging characteristics of the device. An object of the present invention is to provide an IPS mode liquid crystal display device.

The IPS mode liquid crystal display device of the present invention for achieving the above object is a plurality of gate wiring and data wiring to define a unit pixel vertically crossing on the substrate, and a thin film transistor formed at the intersection of the gate wiring and the data wiring And a passivation layer formed on the entire surface including the thin film transistor, a plurality of pixel electrodes contacting the drain electrode of the thin film transistor through a contact hole on the passivation layer, parallel to the gate wiring, and extended to the bottom of the contact hole. And a common wiring overlapping the drain electrode or the pixel electrode around the contact hole, and a plurality of common electrodes contacting the common wiring on the passivation layer and formed in parallel between the pixel electrodes.

That is, the present invention is to increase the storage capacitance by extending the common wiring parallel to the gate wiring to the bottom of the contact hole to overlap the drain electrode or the pixel electrode around the contact hole.

Hereinafter, an IPS mode liquid crystal display device according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 2 is a plan view of an IPS mode liquid crystal display device according to the present invention, and FIG. 3 is a sectional view taken along the line II ′ of FIG. 2.

As shown in FIGS. 2 and 3, a thin film transistor array substrate of an IPS mode liquid crystal display device according to the present invention includes a gate having a plurality of gate lines 112 arranged in a line and a gate insulating layer 113 interposed therebetween. A plurality of data lines 115 defining a unit pixel perpendicularly to the wiring, a thin film transistor (TFT) serving as a switching role, a passivation layer 116 formed on the entire surface including the thin film transistor, A plurality of pixel electrodes 117 contacting the drain electrode 115b of the thin film transistor through the first contact hole 118, and a common wiring parallel to the gate wiring 112 and extending to the periphery of the first contact hole ( 125 and a common electrode 124 contacted to the common wiring through the second contact hole 119 and formed in parallel between the pixel electrodes 117 to generate a transverse electric field.

In this case, the thin film transistor TFT may include a gate electrode 112a branched from the gate line 112, a gate insulating layer 113 formed on the entire surface including the gate electrode 112a, and the gate electrode 112a. A stack of a semiconductor layer 114 formed on the upper gate insulating layer 113 and a source electrode 115a and a drain electrode 115b branched from the data line 115 and formed at both ends of the semiconductor layer 114, respectively. Is made of membrane.

In addition, since the common wiring 125 is provided on the same layer as the gate wiring 112, the common electrode 124 is formed by removing the gate insulating layer 113 and the protective layer 116 from the second contact hole 119. And the pixel electrode 117 are contacted to the drain electrode 115b of the thin film transistor through the first contact hole 118 formed by removing the passivation layer.

 The pixel electrode 117 and the common electrode 124 are formed on the same layer on the passivation layer 116. When the pixel electrode 117 and the common electrode 124 are formed on the same layer, indium tin oxide (ITO) or It is formed of a transparent conductive material such as indium zinc oxide (IZO). As such, the structure in which both the pixel electrode and the common electrode are made of a transparent conductive material such as ITO is called an ITO-ITO electrode structure.

The horizontal field type liquid crystal display device configured as described above applies a Vcom voltage to the common electrode 124 and a pixel voltage to the pixel electrode 117 to generate a horizontal electric field E between the two electrodes.

On the other hand, the common wiring formed parallel to the gate wiring overlaps the pixel electrode at the pixel edge to form a storage capacitance Cst. The common wiring 125 to which the Vcom voltage is applied and the pixel electrode to which the pixel voltage is applied are formed. 117 and a gate insulating film and a protective film provided between the common wiring and the pixel electrode constitute a storage capacitor.

However, the thickness of the gate insulating film and the protective film laminated film provided between the common wiring and the pixel electrode is so thick that there is a limit to sufficiently secure the storage capacitance.

Therefore, according to the present invention, the drain electrode and the pixel electrode are provided around the first contact hole 118, and the common wiring 125 is extended to the periphery of the first contact hole, so that the drain electrode and the common wiring overlap each other. Alternatively, the storage capacitor Cst 'may be further formed between the pixel electrode and the common wiring.

As a result, the storage capacitance of the IPS mode liquid crystal display device can be increased.

The present invention described above is not limited to the above-described embodiment and the accompanying drawings, and it is common in the art that various substitutions, modifications, and changes can be made without departing from the technical spirit of the present invention. It will be evident to those who have knowledge of.

The IPS mode liquid crystal display device according to the present invention as described above has the following effects.

In other words, the common wiring is extended below the contact hole where the drain electrode and the pixel electrode are contacted, and the storage capacitance is further formed between the drain electrode and the common wiring around the contact hole or between the pixel electrode and the common wiring. charging characteristics can be improved.

Claims (7)

A plurality of gate lines and data lines defining unit pixels at vertical crossings on the substrate; A thin film transistor formed at an intersection point of the gate line and the data line; A protective film formed on the entire surface including the thin film transistor; A plurality of pixel electrodes contacting the drain electrode of the thin film transistor through a contact hole on the passivation layer; A common wiring including upper and lower wirings parallel to the gate wiring at the edge of the unit pixel and first and second connecting portions parallel to the data wiring at the edge of the unit pixel and connecting the upper and lower wirings; And A plurality of common electrodes contacted to the first connection portion of the common wiring on the passivation layer and formed in parallel between the pixel electrodes; And the lower interconnection overlaps the drain electrode or the pixel electrode around the contact hole, and the upper interconnection and the second connection part overlap the pixel electrode. The method of claim 1, The common electrode and the pixel electrode are in the same layer, characterized in that the IPS mode liquid crystal display device. The method of claim 2, And the common electrode and the pixel electrode are formed of ITO. The method of claim 1, And wherein the common wiring is on the same layer as the gate wiring. The method of claim 1, The common electrode and the pixel electrode are formed in the gate wiring direction. The method of claim 1, And the common electrode and the pixel electrode are formed in the data line direction. delete

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