Liquid crystal cells – elements and systems – Particular excitation of liquid crystal – Electrical excitation of liquid crystal
Reexamination Certificate
2001-06-28
2003-11-04
Dudek, James (Department: 2871)
Liquid crystal cells, elements and systems
Particular excitation of liquid crystal
Electrical excitation of liquid crystal
Reexamination Certificate
active
06642972
ABSTRACT:
This application claims the benefit of Korean Patent Application No. 2000-40117, filed on Jul. 13, 2000 in Korea, which is hereby incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a liquid crystal display device, and more particularly, to an array substrate for a liquid crystal display device.
2. Description of Related Art
In general, liquid crystal display (LCD) devices make use of optical anisotropy and polarization properties of liquid crystal molecules to control arrangement orientation. The arrangement direction of the liquid crystal molecules can be controlled by an applied electric field. Accordingly, when an electric field is applied to liquid crystal molecules, the arrangement of the liquid crystal molecules changes. Since refraction of incident light is determined by the arrangement of the liquid crystal molecules, display of image data can be controlled by changing the electric field applied to the liquid crystal molecules.
Of the different types of known LCDs, active matrix LCDs (AM-LCDs), which have thin film transistors and pixel electrodes arranged in a matrix form, are the subject of significant research and development because of their high resolution and superiority in displaying moving images.
LCD devices have wide application in office automation (OA) equipment and video units because of their light, thin, low power consumption characteristics. The typical liquid crystal display (LCD) panel has an upper substrate, a lower substrate and a liquid crystal layer interposed therebetween. The upper substrate, commonly referred to as a color filter substrate, usually includes a common electrode and color filters. The lower substrate, commonly referred to as an array substrate, includes switching elements, such as thin film transistors (TFTs), and pixel electrodes.
As previously described, LCD device operation is based on the principle that the alignment direction of the liquid crystal molecules is dependent upon an electric field applied between the common electrode and the pixel electrode. Moreover, because the liquid crystal molecules have a spontaneous polarization characteristic, the liquid crystal layer is considered an optical anisotropy material. As a result of this spontaneous polarization characteristic, the liquid crystal molecules possess dipole moments when a voltage is applied to the liquid crystal layer between the common electrode and pixel electrode. Thus, the alignment direction of the liquid crystal molecules is controlled by the application of an electric field to the liquid crystal layer. When the alignment direction of the liquid crystal molecules is properly adjusted, incident light is refracted along the alignment direction to display image data. The liquid crystal molecules function as an optical modulation element having variable optical characteristics that depend upon polarity of the applied voltage.
FIG. 1
shows a typical LCD device. The LCD device
11
includes an upper substrate
5
and a lower substrate
22
with a liquid crystal layer
14
interposed therebetween. The upper substrate
5
and the lower substrate
22
are commonly referred to as a color filter substrate and an array substrate, respectively.
In the upper substrate
5
and upon the surface opposing the lower substrate
22
, a black matrix
6
and a color filter layer
7
are formed in the shape of an array matrix and includes a plurality of red (R), green (G), and blue (B) color filters so that each color filter is surrounded by corresponding portions of the black matrix
6
. Additionally, a common electrode
18
is formed on the upper substrate
5
that covers the color filter layer
7
and the black matrix
6
. In the lower substrate
22
and upon the surface opposing the upper substrate
5
, a thin film transistor (TFT) “T”, is formed in the shape of an array matrix corresponding to the color filter layer
7
. A plurality of crossing gate lines
13
and data lines
15
are positioned such that each TFT “T” is located near each crossover point of the gate lines
13
and the data lines
15
.
Furthermore, a plurality of pixel electrodes
17
are formed on a pixel region “P” that is defined by the gate lines
13
and the data lines
15
of the lower substrate
22
. The pixel electrode
17
includes a transparent conductive material having good transmissivity such as indium-tin-oxide (ITO) or indium-zinc-oxide (IZO), for example.
According to the LCD device
11
of
FIG. 1
, a scanning signal is applied to a gate electrode of the TFT “T” through the gate line
13
, while a data signal is applied to a source electrode of the TFT “T” through the data line
15
. As a result, the liquid crystal molecules of the liquid crystal layer
14
are aligned and arranged by operation of the TFT “T”, and incident light passing through the liquid crystal layer
14
is controlled to display an image.
FIG. 2
is a plan view showing several pixels of an array substrate fabricated using a four-mask fabrication process for use in a conventional liquid crystal display device.
FIG. 3
is an enlarged plan view of a thin film transistor “T” of FIG.
2
.
In
FIGS. 2 and 3
, an array substrate
22
includes a plurality of pixel regions “P” each having a corresponding thin film transistor (TFT) “T”, a pixel electrode
17
and a storage capacitor “C”. Gate lines
13
are arranged in a transverse direction and data lines
15
are arranged in a longitudinal direction such that each pair of the gate lines
13
and the data lines
15
define a pixel region “P”. Each TFT “T” includes a gate electrode
26
, a source electrode
28
and an active layer
33
. The gate electrode
26
of each TFT “T” extends from the gate line
13
, while the source electrode
28
of each TFT “T” extends from the data line
15
. Furthermore, gate pads
18
are respectively positioned at ends of each gate line
13
, while data pads
19
are respectively arranged at one end of each data line
15
.
In general, both data lines
15
and gate lines
13
are classified into even numbered data lines and odd numbered data lines. The gate pads
18
and the data pads
19
are also correspondingly classified into even numbered gate and data pads and odd numbered gate and data pads. Among the gate lines
13
and the data lines
15
, the even numbered lines and the odd numbered lines are respectively connected to different shorting bars to prevent discharge of static electricity from occurring in the gate lines
13
and the data lines
15
.
In other words, because transparent glass substrates are conventionally used for substrates of LCD devices, any static electricity generated during manufacturing processes will flow into array pattern portions of the array substrate. Accordingly, the TFT, the gate lines and the data lines are all susceptible to significant damage as a result of any discharge of the static electricity. To prevent any damage due to any static electrical discharge, shorting bars are connected with the gate lines and the data lines.
For conventional array substrates fabricated using four-mask processes, one gate shorting bar is usually located at one end of the gate lines
13
and another gate shorting bar is usually located at another end of the gate lines
13
. Each gate-shorting bar is connected with either the corresponding even or odd numbered gate line via the even or odd numbered gate pads. However, both gate shorting bars can be located at one end of the gate lines
13
and respectively be connected with either the even or odd numbered gate lines via the even or odd numbered gate pads. Furthermore, in the array substrate fabricated using a four-mask process as shown in
FIG. 2
, data shorting bars
29
and
32
, which are formed in the same plane as the gate lines
13
, are arranged at one end of the data lines
15
and respectively connected with either the even or odd numbered data lines via the corresponding even or odd numbered data pads.
In
FIG. 2
, odd numbered data pads are connected with first data pad connectors
42
(“first connectors
42
”
Jung Yu-Ho
Kim Hu-Sung
Kim Yong-Wan
Kwak Dong-Yeung
Lee Woo-Chae
Dudek James
LG. Philips LCD Co. Ltd.
Morgan & Lewis & Bockius, LLP
Rude Timothy
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