Electric lamp and discharge devices – With luminescent solid or liquid material – Solid-state type
Reexamination Certificate
2000-07-07
2003-01-21
Patel, Vip (Department: 2879)
Electric lamp and discharge devices
With luminescent solid or liquid material
Solid-state type
C313S506000, C313S509000, C315S169300
Reexamination Certificate
active
06509688
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an electro-luminescence display (ELD), and more particularly to an electro-luminescence display that is capable of widening an effective display area. Also, the present invention is directed to an ELD that is capable of assuring a sufficient storage capacitance of a capacitor.
2. Description of the Related Art
The ELD is a display device in which electrons and holes are injected from the exterior thereof to re-combine the electrons with the holes and thus produce excited molecules so as to exploit the luminescence of these excited molecules. Since the ELD does not require a backlight, a thin panel can be used and there is a relatively low power consumption. Accordingly, there is a growing interest in a display of this type for use in the future.
FIG. 1
is an equivalent circuit diagram of a unit cell in the conventional ELD. In
FIG. 1
, a gate line G crosses a data line D to define a pixel cell area. At the pixel cell area, a power supply line L is arranged in parallel to the data line D. The power supply line L may be arranged in parallel to the gate line G. The pixel cell area includes a switching device T
1
, a driving device T
2
, a storage capacitor C and an electro-luminescent (EL) diode EL. The switching device T
1
has a gate connected to the gate line G, a source connected to the data line and a drain connected to the driving device T
2
. The drain of the driving device T
2
is connected to an anode(+) of the EL diode EL while the source thereof is connected to the power supply line L. The storage capacitor C is connected between the gate of the driving device T
2
and the power supply line L. A cathode(−) of the EL diode EL is connected to a common electrode terminal
10
.
An operation of the ELD having the structure as described above will be described. If the gate line G connected to the switching device TI is selected by a gate driver (not shown) to be turned on, then a data signal from the data line D connected to the switching device T
1
is stored in the storage capacitor C. When the switching device T
1
is turned off, a voltage of the storage capacitor C is maintained until the gate line G is selected again. At this time, the storage capacitor C has a voltage applied to the gate of the driving device T
2
. Thus, a source current determined in accordance with a gate voltage of the driving device T
2
arrives at the common electrode
10
, via the driving device T
2
and the EL diode EL, from the power supply line L. In this operational process, the EL diode EL becomes luminous. In this manner, the driving device T
2
responds to a selecting signal applied to the gate line G and the data line D selectively to control a current flowing through the driving T
2
from the power supply line L. The EL diode EL controls a magnitude of current with the aid of the driving device T
2
and is luminous into a desired magnitude of brightness corresponding to the magnitude of current. For example, if a certain gate voltage is applied to the gate of the driving device T
2
, then the magnitude of a current passing through the driving device T
2
is determined. Accordingly, the magnitude of a current flowing through the diode EL also is determined.
FIG. 2
is a plane view showing the structure of a conventional ELD. Referring to
FIG. 2
, a gate line
22
crosses a data line
21
to define one pixel cell area. A power supply line
25
is arranged in parallel to the data line
21
. A switching device T
1
is electrically connected to the data Line
21
and the gate line
22
. The switching device T
1
consists of an active layer
23
, a gate electrode
22
G superposed on the active layer
23
, a source electrode
21
S protruded from the data line
21
and a drain electrode
24
opposed to the source electrode
21
S. A driving deviceT
2
for driving an EL emitting part
28
is connected to the drain electrode
24
of the switching device T
1
. A driving device T
2
consists of an active layer
27
, a gate electrode
26
G connected to the drain electrode
24
of the switching device T
1
, and a source electrode
25
S protruded from the power supply line
25
. A drain electrode
26
D of the driving device T
2
is electrically connected to the EL emitting part
28
.
A storage capacitor Cap is provided within a pixel cell corresponding to a space between the driving device T
2
and the power supply line
25
. The storage capacitor Cap uses a portion of a wire connecting the source
25
S of the driving device T
2
to the power supply line
25
as an upper electrode
25
C and uses a wire extended from the gate electrode
26
G of the driving device T
2
to be superposedwith the upper electrode
25
C as a lower electrode
26
C.
FIG.
3
and
FIG. 4
are section views taken along “A—A” and “B—B” lines in
FIG. 2
, respectively. Referring to FIG.
3
and
FIG. 4
, the switching device T
1
consists of a semiconductor layer
32
, a gate insulating film
30
, the gate electrode
22
G, a film
36
for insulation between layers, the source electrode
21
S and the drain electrode
24
which are formed on a substrate
40
. The driving device T
2
consists of a semiconductor layer
44
, a gate insulating film
42
, the gate electrode
26
G, the film
36
for insulation between layers, the source electrode
25
S and the drain electrode
26
D which are formed on the substrate
40
. The storage capacitor Cap consists of the lower electrode
26
C extended from the gate electrode
26
G of the driving device T
2
, and the upper electrode
25
C extended from the source electrode
25
S of the driving device T
2
. After the switching device T
1
, the driving device T
2
and the storage capacitor Cap is formed, a protective film
60
is formed in such a manner to cover them. The protective film is provided with contact holes to electrically connect a transparent pixel electrode
70
to the drain electrode
26
D of the driving device T
2
. The pixel electrode
70
is connected to the EL emitting part
28
. In other words, the drain electrode
26
D of the driving device T
2
is electrically connected to the EL emitting part
28
. The source electrodes
21
S and
25
S and the drain electrodes
24
and
26
D are coupled with the semiconductor layers
32
and
44
through the contact holes provided within the film
36
for insulation between layers.
The conventional ELD configured as described above uses a wire protruded from the power supply line into the interior of the pixel cell with having a desired area. In such an LCD, an effective display area of the pixel cell is reduced in proportion to an area protruded from the power supply line. Particularly, since an area of the upper electrode must be enlarged so as to increase an accumulated capacitance of the storage capacitor, the effective display area of the pixel cell becomes smaller. Also, a thickness of the film for insulation between layers formed between the lower electrode and the upper electrode of the storage capacitor must be thinned in order to increase a capacitance of the storage capacitor. However, as a thickness of the film for insulation between layers becomes thinner, locations of the source and drain electrodes formed at the same layer as the upper electrode becomes closer to the substrate. In other words, a distance between the source and drain electrodes and the gate electrode is decreased in order to each other to increase a parasitic capacitance. To the contrary, if a thickness of the film for insulation between layers becomes larger to reduce a parasitic capacitance, then an accumulated capacitance of the storage capacitor is decreased so that it is impossible to accumulate the level of voltage required for a driving of the pixel cell.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide an electro-luminescence display that is capable of widening an effective display area of a pixel.
A further object of the present invention is to provide an electro-luminescence display that is capable of assuring a sufficient
Bae Sung Joon
Lee Jae Yoon
Park Jae Yong
Birch & Stewart Kolasch & Birch, LLP
LG. Philips LCD Co. Ltd.
Patel Vip
Quarterman Kevin
LandOfFree
Electro-luminescent display with storage capacitor formed in... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Electro-luminescent display with storage capacitor formed in..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Electro-luminescent display with storage capacitor formed in... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3048192