KR20030053562A - Apparatus for fringe field switching liquid crystal display device - Google Patents

Abstract

PURPOSE: A fringe field switching liquid crystal display device is provided to drive liquid crystal by a fringe field and a cross field between a lower electrode and an upper electrode formed of electrodes receiving common signals and signals of thin film transistors respectively, thereby reducing driving voltage. CONSTITUTION: A gate bus line and a data bus line define unit pixels. A common bus line is arranged in parallel with the gate bus lines. A thin film transistor is arranged at crossing part of the gate bus line and the data bus line. A lower electrode(140) and an upper electrode(180) are opposite to each other for forming an electric field. The lower electrode is formed of a plurality of plate electrodes(140a,140b). One of the plate electrodes is electrically connected with thin film transistor. Another plate electrode is electrically connected with the common bus line. The upper electrode is formed of a plurality of brench electrodes(180a,180b). One of the brench electrodes is electrically connected with the thin film transistor not connected with the plate electrode. Another brench electrode is electrically connected with the common bus line not connected with the plate electrode.

Description

Fringe field switching liquid crystal display {APPARATUS FOR FRINGE FIELD SWITCHING LIQUID CRYSTAL DISPLAY DEVICE}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fringe field switching liquid crystal display, and more particularly, to a fringe field switching liquid crystal display capable of reducing driving voltage and improving image quality by changing an electrode structure.

In general, liquid crystal displays (LCDs) have characteristics such as light weight, thinness, and low power consumption, so that they can be used for terminals or video devices of various information devices in place of cathode ray tubes (CRTs). It is used. 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, the TFT-LCD has a disadvantage in that the viewing angle is narrow since the TN (Twisted Nematic) mode has been adopted. In recent years, an in-plane switching (IPS) liquid crystal display has been proposed. Some narrow viewing angle problems were solved.

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.

In the fringe field switching liquid crystal display according to the related art, as illustrated in FIG. 1, a gate pixel 13 and a data line 12 are arranged in a cross-section to define a unit pixel, and a thin film transistor, which is a switching element, is formed at the intersection. 10 is arranged. The common electrode 15 made of a transparent conductor is disposed in the unit pixel, and the pixel electrode 17 is disposed in the unit pixel so as to overlap the common electrode 15. The pixel electrode 17 is electrically insulated from the common electrode 15. The pixel electrode 17 has a comb tooth shape parallel to the data line 12 and spaced at equal intervals, and one end thereof is connected to a source electrode (unsigned display) of the TFT 100.

In the fringe field switching LCD, when the scan signal is applied to the gate line 13 and the display signal is applied to the data line 12, the thin film transistor 10 is turned on. Then, the display signal is transmitted to the pixel electrode 17 through the thin film transistor 10 and the common signal is continuously applied to the common electrode 15. Thus, an electric field is formed between the common electrode 15 and the pixel electrode 17.

At this time, the electric field formed is a parabolic electric field so that all of the liquid crystal molecules on the electrode are operated so that the long axis of the liquid crystal molecules is twisted according to the electric field. Therefore, the user sees the long axis of the liquid crystal molecules in any direction, thereby improving the viewing angle of the liquid crystal display.

However, the fringe field switching liquid crystal display according to the related art has a better viewing angle than TN and IPS TFT-LCDs, but 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. There was a problem with reliability.

Accordingly, the present invention has been made to solve the problems of the prior art, and an object of the present invention is to change the electrode structure so that the polarity of the charge (dual cross) to reduce the driving voltage and improve the image quality The present invention provides a fringe field switching liquid crystal display device that can be implemented.

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

2 is a plan view of a fringe field switching liquid crystal display device according to the present invention;

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

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

5 is a cross-sectional view of a pixel portion of a fringe field switching liquid crystal display according to an exemplary embodiment of the present invention.

-Explanation of symbols for the main parts of the drawings-

100: substrate 110: thin film transistor

120: gate bus line 130: common bus line

135: gate oxide layer 140: lower electrode

150: active layer 160: data bus line

170: protective film 180: upper electrode

190: insulating film

In order to achieve the above object, a fringe field switching liquid crystal display device includes: a substrate; A gate bus line and a data bus line defining unit pixels; A common bus line arranged in parallel with the gate bus line; A thin film transistor disposed at the gate bus line and the data bus line granting portion; In a fringe field switching liquid crystal display device including a lower electrode and an upper electrode disposed to face each other up and down to form an electric field, the lower electrode is composed of several plate electrodes, and any one of the several plate electrodes is provided. Is electrically connected to the thin film transistor, another one of the plurality of plate electrodes is electrically connected to the common bus line, and the upper electrode is composed of several branch electrodes, one of the several branch electrodes The thin film transistor is not electrically connected to the plate electrode, and the other one of the branch electrodes is electrically connected to a common bus line not electrically connected to the plate electrode.

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.

2 is a plan view of a fringe field switching liquid crystal display according to the present invention, FIG. 3 is a sectional view of the fringe field switching liquid crystal display according to the present invention, and FIG. 4 is a pixel portion of the fringe field switching liquid crystal display according to the present invention. 5 is a cross-sectional view of a pixel portion of a fringe field switching liquid crystal display device according to an exemplary embodiment of the present invention.

As shown in FIG. 2, the fringe field switching liquid crystal display according to the present invention includes a gate bus line 120 and a data bus line 160 intersected with each other so as to define unit pixels on the substrate 100. A common bus line 130 disposed in the unit pixel and arranged in parallel with the gate bus line 120, a thin film transistor 110 as a switching element arranged in the cross-arranged portion, and the gate bus line 120. And an insulating film 190 that insulates the data bus line 160, and a lower electrode 140 and an upper electrode 180 formed to overlap each other with the insulating film 190 interposed therebetween.

Meanwhile, as illustrated in FIG. 3, the fringe field switching liquid crystal display according to the present invention may be classified into a thin film transistor unit, a pixel unit, and a data bus line unit.

The thin film transistor of the fringe field switching liquid crystal display according to the present invention is a gate electrode 120, a gate oxide layer 135, an active layer 150, a passivation layer 170 and a data bus which are part of a gate bus line on the lower substrate 100. It includes the source / drain electrodes 160a and 160b which are part of the line.

In addition, the pixel portion of the fringe field switching liquid crystal display according to the present invention includes a lower electrode composed of plate electrodes 140a and 140b with an insulating layer 190 composed of a gate oxide layer 135 and a passivation layer 170 interposed therebetween. 140, an upper electrode 180 composed of several branch electrodes 180a and 180b, and a common bus line 130 to which a common signal is applied.

In addition, the data bus line portion of the fringe field switching liquid crystal display according to the present invention includes a data bus line 160 and an insulating film 190 on the substrate 100.

Here, the core technical idea of the present invention is to configure the lower electrode 140 as an electrode 140a receiving a common signal and an electrode 140b receiving a signal of a thin film transistor, and the upper electrode 180 likewise applies a common signal. Since the receiving electrode 180b and the electrode 180a receiving the signal of the thin film transistor are configured and arranged to overlap each other under the insulating layer 190, the fringe field and the cross-field are formed to form a fringe field.

As shown in FIG. 4, the pixel portion of the fringe field switching liquid crystal display according to the present invention includes the lower electrode 140, which is composed of several plate electrodes, and any one of the several plate electrodes. The plate electrode 140b is electrically connected to the thin film transistor (not shown) to receive a voltage Vsig applied from the thin film transistor. In this example, the number of plate electrodes was two.

In contrast, the other plate 140a of the several plate electrodes is electrically connected to the common bus line (not shown) to receive the voltage Vcom applied from the common bus line.

Meanwhile, the upper electrode 180 is composed of several branch electrodes, and one of the branch electrodes 180a is electrically connected to the thin film transistor which is not electrically connected to the plate electrode. It is connected to and receives the voltage (Vsig) from the thin film transistor.

In contrast, the other branch electrode 180b of the several branch electrodes is electrically connected to a common bus line that is not electrically connected to the plate electrode to receive a voltage Vcom applied from the common bus line. In this embodiment, the number of branch electrodes is two, and each branch electrode is composed of two sub branches. Therefore, in this embodiment, the branch electrode composed of two sub-branches on one plate electrode is opposed to 1; 1 through the insulating film.

Here, the plate electrode 140b electrically connected to the thin film transistor is disposed to overlap each other under the branch electrode 180b and the insulating layer 190 electrically connected to the common bus line.

Similarly, the plate electrode 140a electrically connected to the common bus line overlaps the branch electrode 180a electrically connected to the thin film transistor and the insulating layer 190.

In the fringe field switching liquid crystal display according to the present invention having the structure as described above, an electric field is formed between the lower electrode 140 and the upper electrode 180, as well as between the branch electrodes 180a and 180b. Since is formed, driving (200a) (200b) of the liquid crystal is made by a cross field (cross field).

Therefore, in the fringe field switching liquid crystal display according to the present invention, the liquid crystals 200a and 200b are deflected in the opposite electric field directions between neighboring regions, so that the viewing angle is extended and high transmittance is obtained.

The operation principle of the fringe field switching liquid crystal display according to the present invention will be described in more detail as follows.

A voltage of Vcom is applied from the common bus line to one of the plate electrodes 140a of the lower electrodes 140 and one of the branch electrodes 180b of the upper electrode 180, and the lower electrode 140 is applied. As the voltage of Vsig from the thin film transistor is applied to the other plate electrode 140b and the other branch electrode 180a of the upper electrode 180, the plate electrodes 140a and 140b and the branch are applied. A fringe field is formed between the electrodes 180a and 180b.

At the same time, a lateral field occurs as voltages of different polarities are applied between the branch electrodes 180a and 18b and between the plate electrodes 140a and 140b. As a result, in the pixel structure of the present invention, a cross field is formed.

In addition, the lower electrode 140 is disposed on the substrate 100, and the upper electrode 180 is disposed on the insulating layer 190. The number of the lower electrodes 140 and the upper electrode The number of 180 may be adjusted to form a more dense electric field.

For example, as shown in FIG. 5, a total of four plate electrodes 240b, 240a, 241b, and 241a are disposed on the substrate 200, and two sub-branches on the insulating film 290, respectively. The plate electrodes 240b, 240a, 241b and 241a of the branch electrodes 280b, 280a, 281b and 281a may be disposed in a 2: 1 ratio to form a double cross field. .

Various embodiments can be easily implemented as well as self-explanatory to those skilled in the art without departing from the principles and spirit of the present invention. Accordingly, the claims appended hereto are not limited to those already described above, and the following claims are intended to cover all of the novel and patented matters inherent in the invention, and are also common in the art to which the invention pertains. Includes all features that are processed evenly by the knowledgeable.

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

In the present invention, the lower electrode and the upper electrode are composed of an electrode receiving a common signal and an electrode receiving a signal of a thin film transistor, respectively, so that a fringe field and a cross field are formed between the electrodes so that the liquid crystal is fringed. The driving voltage can be lowered by being driven by the field and the cross field.

In addition, by forming the polarity arrangement of the charges formed during the operation and stop of the liquid crystal display alternately in the opposite direction, it is possible to suppress the deterioration of image quality such as afterimage and mura and to improve the image quality. .

In addition, by making the pixel form a more dense electric field, the uniformity and transmittance of the electric field applied to the liquid crystal can be improved.

Claims (4)

Board; A gate bus line and a data bus line defining unit pixels; A common bus line arranged in parallel with the gate bus line; A thin film transistor disposed at the gate bus line and the data bus line granting portion; In the fringe field switching liquid crystal display device comprising a lower electrode and an upper electrode disposed to face each other up and down to form an electric field, The lower electrode is composed of several plate electrodes, one of the several plate electrodes is electrically connected to the thin film transistor, the other of the several plate electrodes is electrically connected to the common bus line, The upper electrode includes a plurality of branch electrodes, one of the plurality of branch electrodes is electrically connected to a thin film transistor which is not electrically connected to the plate electrode, and the other of the several branch electrodes is the plate electrode. Fringe field switching liquid crystal display device, characterized in that electrically connected to a common bus line that is not electrically connected to. The method of claim 1, The plate electrode electrically connected to the thin film transistor is arranged to overlap each other under the insulating layer and the branch electrode electrically connected to the common bus line. The method of claim 1, And a plate electrode electrically connected to the common bus line is overlapped with a branch electrode electrically connected to the thin film transistor under an insulating layer. The method according to claim 2 or 3, The plate electrode is disposed on the substrate, the branch electrode is disposed on the insulating film, the branch electrode is composed of several sub-branches fringe field switching liquid crystal display device.