Active solid-state devices (e.g. – transistors – solid-state diode – Non-single crystal – or recrystallized – semiconductor... – Amorphous semiconductor material
Reexamination Certificate
1999-11-24
2001-12-04
Flynn, Nathan (Department: 2826)
Active solid-state devices (e.g., transistors, solid-state diode
Non-single crystal, or recrystallized, semiconductor...
Amorphous semiconductor material
C257S059000, C257S296000, C349S038000, C349S042000, C349S043000
Reexamination Certificate
active
06326641
ABSTRACT:
This application claims the benefit of Korean Patent Application No. 98-51186, filed on Nov. 27, 1998, which is hereby incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a liquid crystal display (LCD) device, and more particularly, to a thin film transistor liquid crystal display device having a high aperture ratio.
2. Discussion of the Related Art
An aperture ratio of a liquid crystal display device is a ratio of an area which a light penetrates with respect to an entire area of the pixel. Such a ratio is important for picture quality of the device.
One of the methods for increasing the aperture ratio is shown in
FIG. 1
, where a pixel electrode is enlarged over data lines and a black matrix is not necessary between the data lines and the pixel electrode.
FIG. 1
is a plan view of a pixel module
100
of a conventional liquid crystal display device. The module
100
is defined by gate lines
2
and
3
adapted for carrying gate drive signals to the pixel modules and data lines
16
and
18
adapted for delivering data signals to the pixel modules. The gate line
3
has a gate electrode
4
, the data line
16
has a source electrode
6
, and a pixel electrode
12
is connected to a drain electrode
8
of a thin film transistor (TFT) denoted by “T” through a contact hole
10
. A storage capacitor for the device is denoted by “S”.
As shown in
FIG. 1
, in order to increase the aperture ratio, the pixel electrode
12
overlaps the data lines
16
and
18
, and there is no interval or space between the data lines and the pixel electrode
12
. Thus, no opaque mask or black matrix for blocking side edges of the pixel module
100
is needed, which increases the aperture ratio of the LCD.
However, there is still an interval “L” between the gate line
3
and the pixel electrode
12
, as shown in
FIG. 2
which is a cross sectional view taken along the line II—II of FIG.
1
. Thus, a black matrix (light shielding layer) for blocking the interval “L” is needed, which decreases the aperture ratio.
Overlapping the gate line
3
with the pixel electrode
12
in order to cover the interval “L”, as shown in
FIG. 3
, causes increased parasitic capacitance (designated by the area “OL”) between the pixel electrode
12
and gate line
3
. Such parasitic capacitance may cause flicker.
FIG. 4
is a corresponding schematic circuit diagram of FIG.
3
. The parasitic capacitance C
gp,i
between the overlapped portion of the pixel electrode
12
and the gate line
3
is connected to the liquid crystal capacitance C
LC,i
. Thus, during the off-time of the TFT “T”, the liquid crystal layer is influenced by the parasitic capacitance C
gp,i
which deteriorates the picture quality.
In
FIG. 4
, the symbols V
g,i
and V
D,i
designate voltages for the gate electrode and the data line, respectively.
SUMMARY OF THE INVENTION
Accordingly, the present invention is directed to a liquid crystal display device having a high aperture ratio that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.
An object of the present invention is to provide an LCD having a high aperture ratio.
Another object of the present invention is to provide an LCD that can minimize reflection by data lines or black matrixes of color filters.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, a liquid crystal display device includes an insulating substrate; first and second gate lines formed on the substrate; first and second data lines crossing the first and second gate lines so as to define a pixel region; an insulating film covering the gate lines; a pixel electrode disposed in the pixel region; a switching element disposed in the pixel region and connected between the second gate line and the pixel electrode; a storage capacitor having a first storage capacitor electrode that includes a portion of the first gate line, a second storage capacitor electrode having a width substantially the same as that of the gate lines, an insulating film between the first and second storage capacitor electrodes, and a protecting film having a contact hole on the second storage capacitor electrode; and wherein the pixel electrode overlaps the first and second gate lines on the protecting film and contacts the second storage capacitor electrode through the contact hole of the protecting film.
According to another aspect of the present invention, a liquid crystal display device comprises an insulating substrate; first and second gate lines on said substrate; first and second data lines crossing said first and second gate lines and defining a pixel region; an insulating film on said gate lines; a pixel electrode in said pixel region; a switching element in said pixel region and connected between one of the first and said second gate lines and said pixel electrode; a storage capacitor including a first storage capacitor electrode made of a portion of said first gate line, a second storage capacitor electrode having a width that is substantially same as that of said first gate line, the insulating film being between the first and second storage capacitor electrodes; and a protecting film having a contact hole on the second storage capacitor electrode; wherein said pixel electrode overlaps said first and second gate lines on the protecting film and contacts the second storage capacitor electrode through the contact hole of the protecting film.
According to a further aspect of the present invention, a method of making a liquid crystal display device having an insulating substrate comprises forming first and second gate lines on said substrate; forming first and second data lines crossing said first and second gate lines and defining a pixel region; forming an insulating film on said gate lines; forming a pixel electrode in said pixel region; forming a switching element in said pixel region and connected between one of the first and said second gate lines and said pixel electrode; forming a storage capacitor including a first storage capacitor electrode made of a portion of said first gate line, a second storage capacitor electrode having a width that is substantially same as that of said first gate line, the insulating film being between the first and second storage capacitor electrodes; and forming a protecting film having a contact hole on the second storage capacitor electrode; wherein said pixel electrode overlaps said first and second gate lines on the protecting film and contacts the second storage capacitor electrode through the contact hole of the protecting film.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.
REFERENCES:
patent: 5757444 (1998-05-01), Takemura
patent: 5923390 (1999-07-01), Jung Mok et al.
patent: 6057896 (2000-05-01), Rho et al.
patent: 6115088 (2000-09-01), Zhang et al.
patent: 6172728 (2001-01-01), Hiraishi
patent: 404044014 (1992-02-01), None
Flynn Nathan
Forde Remmon R.
LG. Philips LCD Co. Ltd.
Long Aldridge & Norman LLP
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