Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
1997-04-10
2001-04-17
Sikes, William L. (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
C349S148000
Reexamination Certificate
active
06219124
ABSTRACT:
FIELD OF THE INVENTION
The present invention generally relates to display devices, and more particularly, to liquid crystal display devices.
BACKGROUND OF THE INVENTION
A liquid crystal display (LCD) typically includes a thin film transistor array panel, a color filter panel, and a liquid crystal layer sandwiched between the thin film transistor array and the color filter panel.
In this design, the thin film transistor array panel will generally include thin film transistors, pixel electrodes, gate lines and data lines. The color filter panel, on the other hand, will generally include color filters and a common electrode.
In operation, a gate electrode of a thin film transistor in the transistor array panel is supplied with a gate driving signal from a gate driver via a gate line which activates the thin film transistor. Therefore, a data signal applied to a source electrode of the thin film transistor from a data driver via a data line is supplied to the pixel electrode in order to switch the LCD pixel of the liquid crystal layer. In addition, the common electrode of the color filter panel is supplied with a common voltage through dummy pads of an out lead bonding (OLB) region and conductive members made of silver paste which are formed in the outer regions of the thin film transistor array panel. It is desirable that the paths through which the gate driving signals and common voltages pass have low resistivity in order to improve low voltage operation and reduced cross-talk. However, the paths of the common voltages encounter numerous resistances such as the contact resistance of the dummy pads, the resistance of the dummy pads themselves, the contact resistance of a common voltage driving circuit, the contact resistance of the conductive members connecting the dummy pads and the common electrode, and the resistance of the common electrode which is typically made of indium-tin-oxide (ITO). Several of these resistances are discussed in more detail below with reference to
FIG. 1
which shows a cross-sectional view of a voltage transfer circuit from an OLB pad region to a short region that is connected to a common electrode.
In
FIG. 1
, a thin film transistor array panel includes a lower substrate
1
on which a gate insulating layer
3
is formed. A metal layer
5
which is connected to a data line is formed on the insulating layer
3
. The metal layer
5
is typically made of chromium (Cr). A passivation layer
7
with two holes is formed on the metal layer
5
, and an ITO layer
9
is formed thereover and connected to the metal layer
5
through the two holes. The thin film transistor array panel includes a dummy pad region B for receiving the external or common voltage and a short region A where a conductive member
11
electrically connects the thin film transistor array panel to the color filter panel. The color filter panel includes an upper substrate
19
covering a black matrix
13
. Adjacent to the black matrix
13
is an overcoat layer
15
. In addition, a common electrode
17
which is typically made of ITO is formed over the common electrode
17
. Accordingly, the conductive member
11
contacts the ITO layer
9
of the thin film transistor array panel at the short region A and the common electrode
17
of the color filter panel, as shown.
When a common voltage supply from the common voltage driving circuit is applied to the dummy pad region B, the resulting voltage at the common electrode
17
is less than the applied common voltage because of the resistance in the pad region B having the structure of insulator/Cr/ITO layers, the resistance in the short region A having the structure of insulator/Cr/ITO layers, the resistance in a central region between the pad region B and the short region A having the structure of insulator/Cr/passivation/ITO layers, and the resistance in the conductive member
11
. In particular, it is noted that the resistivity in the pad region B is relatively large due to its structure of the Cr/ITO layers. Further, the resistance from the center region to the short region A is relatively large due to the large resistivity of the chromium comprising the metal layer
5
. As a result of the resistance to the common voltage, an increase in cross-talk may occur in the liquid crystal display. Thus, it would be desirable to be able to reduce the resistivity to the common voltage applied in order to reduce the presence of cross-talk in the LCD.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a liquid crystal display (LCD) with decreased resistance to a common voltage applied to a common electrode of a color filter panel, and methods of forming same.
Another object of the present invention is to provide an LCD having reduced cross-talk, and methods of forming same.
Another object of the present invention is to provide an LCD having improved electrode and display characteristics, and methods of forming same.
These and other objects are provided in accordance with the present invention by LCD devices having voltage transfer circuits with preferred composite conductive layers. The composite conductive layer comprises a first electrically conductive layer of a first resistance and a second electrically conductive layer of a second resistance, wherein the first resistance is less than the second resistance. Thus, the overall resistance of the composite conductive layer is reduced by the lower resistance of the first layer. Therefore, material having a relatively high resistance but a favorable operational characteristic such as a favorable contact formation with indium-tin-oxide (ITO), can be utilized in the second conductive layer without significantly increasing the resistance of the composite conductive layer.
In a first embodiment of the present invention, a liquid crystal display device comprises a thin film transistor array panel, a color filter panel including a common electrode, and a conductive member that electrically connects the common electrode to the thin film transistor array panel. The thin film transistor array panel comprises a voltage transfer circuit that includes a pad region for receiving a common voltage, a short region for transferring the common voltage, and a center region that connects the pad region to the short region. The center region includes a composite conductive layer comprising a first electrically conductive layer of a first resistance and a second electrically conductive layer of a second resistance, wherein the first resistance is less than the second resistance.
The first conductive layer preferably comprises aluminum or an alloy thereof. As for the second conductive layer, it preferably comprises chromium (Cr), molybdenum (Mo), titanium (Ti), or tantalum (Ta). In addition, a liquid crystal display device may include an anodic oxide layer formed on the first conductive layer in order to reduce hillock formation.
In the first embodiment, the second conductive layer of the composite conductive layer extends from the pad region to the short region of the voltage transfer circuit. Further, an indium-tin-oxide (ITO) layer formed over the composite conductive layer contacts the second conductive layer at the pad region and the short region.
In a second embodiment, the first conductive layer extends from the pad region to the short region and is exposed in either region. Therefore, the conductive member contacts the first conductive layer at the short region in order to form the electrical connection to the common electrode of the color filter panel. At the pad region, the common voltage is applied directly to the first conductive layer. As with the first embodiment, an anodic oxide layer may be formed on the first conductive layer for inhibiting hillock formation.
In a third embodiment, the first conductive layer extends from the center region to the short region and the second conductive layer extends from the pad region to the center region. Further, an ITO layer is formed over the composite conductive layer in the pad region and the center region, and contacts the second conduc
Hong Kweon-Sam
Lee Jung-Hee
Myers Bigel & Sibley & Sajovec
Nguyen Dung
Samsung Electronics Co,. Ltd.
Sikes William L.
LandOfFree
Liquid crystal display device with reduced resistance to... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Liquid crystal display device with reduced resistance to..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Liquid crystal display device with reduced resistance to... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2543700