Computer graphics processing and selective visual display system – Plural physical display element control system – Display elements arranged in matrix
Reexamination Certificate
1998-08-19
2003-07-22
Shalwala, Bipin (Department: 2778)
Computer graphics processing and selective visual display system
Plural physical display element control system
Display elements arranged in matrix
C345S060000, C345S063000
Reexamination Certificate
active
06597334
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a driving method of a plasma display panel and, particularly, to a driving method of a plasma display panel, which performs a matrix display of an A.C. discharge type.
2. Description of Related Art
In general, the plasma display panel (referred to as “PDP”, hereinafter) has several advantageous features. That is, for example, the PDP has a thin structure and a large contrast ratio of display without flicker. Further, the PDP allows a screen size to be made relatively large and its response speed is high. In addition, the PDP emits light spontaneously and is capable of emitting multi-color light by utilizing suitable fluorescent materials. Therefore, the PDP has been becoming more popular in the fields of display related to computers and color picture displays, etc.
Depending upon the operating system of the PDP, the driving method of such PDP is roughly classified to an A.C. discharge type and a D.C. discharge type. In the A.C. discharge type PDP, a dielectric member covers electrodes and the PDP is operated indirectly in an A.C. discharge state. In the D.C. discharge type PDP, electrodes are exposed to a discharge space and the PDP is operated in a D.C. discharge state. The A.C. discharge type PDP is further classified to those of a memory operating type, which utilizes memories of discharge cells as its driving system, and a refresh operating type, in which discharge cell memories are not utilized. Incidentally, luminance of the PDP is proportional to the number of discharges, that is, the repetitive number of pulse voltage. In the case of the above mentioned refresh type PDP, the larger the display capacity provides the lower the luminance. Therefore, PDP of the refresh operation type is mainly used for those having small display capacity.
FIG. 1
is a perspective view of an example of a construction of one of display cells
16
of the A.C. discharge, memory operation type PDP in a disassembled state. The display cell
16
is composed of a front and rear insulating substrates
1
and
2
both formed of glass material, a transparent scan electrode
3
formed on a lower surface of the insulating substrate
2
, a transparent sustaining electrode
4
also formed on the lower surface of the insulating substrate
2
, trace electrodes
5
and
6
arranged on the scan electrode
3
and the sustaining electrode
4
, respectively, in order to reduce electrode resistance thereof, a data electrode
7
formed on an upper surface of the insulating substrate
1
and extending perpendicularly to both the scan electrode
3
and the sustaining electrode
4
, a discharge gas space
8
defined by the insulating substrates
1
and
2
and partition walls
9
, which define the display cell, and filled with discharge gas such as helium, neon or xenon or a mixture thereof, a fluorescent material
11
for converting ultra-violet ray generated by discharge of the discharge gas into a visible light
10
, a dielectric member
12
covering the scan electrode
3
and the sustaining electrode
4
, a protective layer
13
of such as magnesium oxide for protecting the dielectric member
12
against discharge and a dielectric member
14
covering the data electrode
7
.
Describing a discharge operation of the selected one of the display cells
16
shown in
FIG. 1
, when discharge of gas in the discharge gas space
8
is started by applying a pulse voltage exceeding a discharge threshold value of discharge gas between the scan electrode
3
and the data electrode
7
, positive and negative charges are attracted to surfaces of the oppositely arranged dielectric members
12
and
14
, respectively, correspondingly to the polarity of the pulse voltage and accumulated thereon. An equivalent internal voltage caused by the accumulated electric charges, that is, a wall voltage, is opposite in polarity to the applied pulse voltage. Therefore, an effective voltage inside the display cell is lowered with growth of the discharge, so that it becomes impossible to sustain the discharge and the discharge is terminated even if the applied pulse voltage is held at a constant value. When a sustaining pulse voltage, which is the same in polarity as the wall voltage, is applied between the scan electrode
3
and the sustaining electrode
4
, a portion of the sustaining pulse voltage, which corresponds to the wall voltage, is overlapped as an effective voltage. Therefore, it is possible to provide discharge with a discharge voltage exceeding the discharge threshold value even if a voltage level of the sustaining pulse is low. As a consequence of this fact, it becomes possible to sustain the discharge by continuously applying the sustaining pulse voltage across the scan electrode
3
and the sustaining electrode
4
. This function is the memory operation of the A.C. discharge type PDP mentioned previously. Applying a wide and low voltage pulse or an erase pulse, which can neutralize the wall voltage, to the scan electrode
3
or the sustaining electrode
4
, can terminate the above sustaining discharge. The erase pulse may be a narrow pulse having a voltage amplitude as small as that of the sustaining pulse.
FIG. 2
is a plan view schematically showing a PDP
15
formed by arranging the display cells
16
each shown in
FIG. 1
in matrix. In
FIG. 2
, the PDP
15
takes in the form of a panel constituted by arranging the display cells
16
in a matrix of n rows and m columns. The PDP
15
includes scan electrodes Sw
1
, Sw
2
, . . . , Swn and sustaining electrodes Su
1
, Su
2
, . . . , Sun, which are arranged in parallel to each other, as the row electrodes and data electrodes D
1
, D
2
, . . . , Dm, which are orthogonal to the scan electrodes and the sustaining electrodes, as the column electrodes.
FIG. 3
shows driving pulse waveforms for illustrating a conventional drive method of the PDP shown in
FIGS. 1 and 2
. This driving method is equivalent to that proposed in “Society for Information Display International Symposium Digest of Technical Papers”, Vol. XXVI (pp. 807-810) and this driving method will be referred to as “first prior art example”, hereinafter.
In
FIG. 3
, Wu depicts a waveform of a sustaining electrode driving pulse, which is commonly applied to the sustaining electrodes Su
1
, Su
2
, . . . , Sun, Ws
1
, Ws
2
, . . . , Wsn depict waveforms of scan electrode driving pulses applied to the respective scan electrodes Sw
1
, Sw
2
, . . . , Swn, respectively, and Wd depicts a waveform of a data electrode driving pulse selectively applied to one of the data electrode Di (1≦i≦m). One driving period (1 frame) is constituted with a pre-discharge period A, a write discharge period B and a sustaining discharge period C and a desired image display is obtained by repeating this driving period.
The pre-discharge period A is provided in order to produce active charges particles and wall charges in the discharge gas space to thereby obtain a stable write discharge characteristics in the write discharge period B. In the pre-discharge period A, a pre-discharge pulse Pp for preliminarily discharging all display cells of the PDP
15
is applied to all of the sustaining electrodes and then a pre-discharge erase pulse Ppe for extinguishing electric charges among the wall charges produced in the pre-discharge period A, which block the write discharge and the sustaining discharge, is applied to all of the respective scan electrodes, simultaneously. That is, the discharge is produced in all of the display cells by applying the pre-discharge pulse Pp to the sustaining electrodes Su
1
, Su
2
, . . . , Sun, first, and, thereafter, the erase discharge is produced by applying the erase pulse Ppe to the scan electrodes Sw
1
, Sw
2
, . . . , Swn to erase the wall charges accumulated by the pre-discharge pulse Pp.
A scan base pulse Pbw is commonly applied to the respective scan electrodes Sw
1
, Sw
2
, . . . , Swn throughout the write discharge period B. Further, in the write discharge period B, a sequentially scan pulse Pw is sequentially supplied
Lewis David L.
McGinn & Gibb PLLC
NEC Corporation
Shalwala Bipin
LandOfFree
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