Computer graphics processing and selective visual display system – Plural physical display element control system – Display elements arranged in matrix
Reexamination Certificate
2000-09-07
2004-04-27
Shankar, Vijay (Department: 2673)
Computer graphics processing and selective visual display system
Plural physical display element control system
Display elements arranged in matrix
C345S061000, C345S068000
Reexamination Certificate
active
06727870
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a plasma display panel, and more particularly to an electrode structure of a plasma display panel that is capable of improving the brightness. Also, the present invention is directed to a method of driving a sustaining electrode in the plasma display panel.
2. Description of the Related Art
Generally, a plasma display panel (PDP) is a light-emitting device which displays a picture using a gas discharge phenomenon within the cell. This PDP does not require providing an active device for each cell like a liquid crystal display (LCD). Accordingly, the PDP has a simple fabrication process and has the advantage of providing a large-dimension screen.
Such a PDP has a number of discharge cells arranged in a matrix type. The discharge cells are provided at each intersection between sustaining electrode lines for sustaining a discharge and address electrode lines for selecting the cells to be discharged. The PDP is largely classified into a direct current (DC) type panel and an alternating current (AC) type panel depending on whether or not a dielectric layer for accumulating a wall charge exists in the discharge cell.
Referring to FIG.
1
and
FIG. 2
, each cell of the AC-type, three-electrode PDP includes a front substrate
11
provided with a sustaining electrode pair
12
A and
12
B, and a rear substrate
18
provided with an address electrode
20
. The front substrate
10
and the rear substrate
18
are spaced in parallel to each other with having barrier ribs
24
therebetween and sealed with a fritz glass. A mixture gas, such as Ne—Xe or He—Xe, etc., is injected into a discharge space defined by the front substrate
11
, the rear substrate
18
and the barrier ribs
24
. The sustaining electrode pair
12
A and
12
B makes a pair by two within a single of plasma discharge channel. Any one electrode of the sustaining electrode pair
12
A and
12
B is used as a scanning electrode that responds to a scanning pulse applied in an address interval to cause an opposite discharge along with the address electrode
20
while responding to a sustaining pulse applied in a sustaining interval to cause a surface discharge along with the other adjacent sustaining electrode. Also, the sustaining electrode
12
B or
12
A adjacent to the sustaining electrode
12
A or
12
B used as the scanning electrode is used as a common sustaining electrode to which a sustaining pulse is applied commonly.
The sustaining electrode pair
12
A and
12
B includes transparent electrodes
30
A and
30
B and metal electrodes
28
A and
28
B connected electrically to each other, respectively. The transparent electrodes
30
A and
30
B is formed by depositing indium thin oxide (ITO) on the front substrate
10
into an electrode width of about 300 m so as to prevent deterioration of an aperture ratio. The metal electrodes
28
A and
28
B are deposited on the front substrate
10
to have a three-layer structure of Ag or Cr—Cu—Cr. The metal electrodes
28
A and
28
B play a role to reduce a voltage drop caused by the transparent electrodes
30
A and
30
B.
On the front substrate
10
provided with the sustaining electrodes
12
A and
12
B, a dielectric layer
14
and a protective layer
16
are disposed. The dielectric layer
14
is responsible for limiting a plasma discharge current as well as accumulating a wall charge during the discharge. The protective film
16
prevents a damage of the dielectric layer
14
caused by the sputtering generated during the plasma discharge and improves the emission efficiency of secondary electrons. This protective film
16
is usually made from MgO. The rear substrate
18
is provided with a dielectric thick film
26
covering the address electrode
24
. The barrier ribs
24
for dividing the discharge space are extended perpendicularly at the rear substrate
18
. On the surfaces of the rear substrate
18
and the barrier ribs
24
, a fluorescent material
22
excited by a vacuum ultraviolet lay to generate a visible light is provided.
As shown in
FIG. 3
, such cells
1
of the PDP are arranged on a panel
30
in a matrix type. In each cell
1
, scanning/sustaining electrode lines S
1
to Sm, common sustaining electrode lines C
1
to Cm and address electrode lines D
1
to Dn cross each other. The scanning/sustaining electrode lines S
1
to Sm and the common sustaining electrodes C
1
to Cm consists of the sustaining electrode pair
12
A and
12
B in
FIG. 1
, respectively. The address electrode lines D
1
to Dn consist of the address electrodes
20
.
In such an AC-type PDP, one frame consists of a number of sub-fields so as to realize gray levels by a combination of the sub-fields. For instance, when it is intended to realize 256 gray levels, one frame interval is time-divided into 8 sub-fields. Further, each of the 8 sub-fields is again divided into a reset interval, an address interval and a sustaining interval. The entire field is initialized in the reset interval. The cells on which a data is to be displayed are selected by a writing discharge in the address interval. The selected cells sustain the discharge in the sustaining interval. The sustaining interval is lengthened by an interval corresponding to 2
n
depending on a weighting value of each sub-field. In other words, the sustaining interval involved in each of first to eighth sub-fields increases at a ratio of 2
0
, 2
1
, 2
3
, 2
4
, 2
5
, 2
6
and 2
7
. To this end, the number of sustaining pulses generated in the sustaining interval also increases into 2
0
, 2
1
, 2
3
, 2
4
, 2
5
, 2
6
and 2
7
depending on the sub-fields. The brightness and the chrominance of a displayed image are determined in accordance with a combination of the sub-fields.
An emission process of the PDP will be described below. First, a wall charge is uniformly accumulated within the cells of the entire screen by the reset discharge generated in the reset interval. In the address interval, a writing discharge is generated at the cells selected by an address discharge voltage applied to the scanning/sustaining electrode lines S
1
to Sm and the address electrode lines D
1
to Dn. Subsequently, when a sustaining pulse is alternately applied to the scanning/sustaining electrode lines S
1
to Sm and the common sustaining electrode lines C
1
to Cm, a discharge of the cells selected in the address interval is sustained.
When a plasma discharge is generated within the cell, a very small amount of electrons in discharge gases within the cell begin to be accelerated and continuously collide with neutral particles. By such an avalanche effect, the discharge gases within the cell is rapidly ionized into electrons and ions to be in a plasma state and, at the same time, generate a vacuum ultraviolet. This vacuum violet excites the fluorescent material
22
to generate a visible light.
However, the conventional PDP has a limit in improving the brightness into a satisfying level in view of its discharge structure. More specifically, the sustaining discharge of the PDP begins at one opposite surface between the scanning/sustaining electrode lines S
1
to Sm and the common sustaining electrode lines C
1
to Cm and is gradually diffused all over the cells. In such a discharge structure, since the discharge concentrates on only one surface between the scanning/sustaining electrode lines S
1
to Sm and the common sustaining electrodes C
1
to Cm, the brightness becomes low.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide an electrode structure of a plasma display panel and a method of driving a sustaining electrode in the plasma display panel that are adaptive for improving the brightness.
In order to achieve these and other objects of the invention, an electrode structure of a plasma display panel according to one aspect of the present invention includes refractive electrodes connected to a sustaining electrode pair and bent to generate a sustaining discharge at at least two positions within a cell.
A method of driving sustaining electrodes in a
Kim Won Tae
Park Hun Gun
Park Young Chan
Seo Dae Kwan
Dharia Prabodh M.
Fleshner & Kim LLP
LG Electronics Inc.
Shankar Vijay
LandOfFree
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