Computer graphics processing and selective visual display system – Plural physical display element control system – Display elements arranged in matrix
Reexamination Certificate
1999-08-13
2001-04-17
Mengistu, Amare (Department: 2778)
Computer graphics processing and selective visual display system
Plural physical display element control system
Display elements arranged in matrix
C315S169400, C345S068000
Reexamination Certificate
active
06219013
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a driving method for an AC type discharge display device.
BACKGROUND ART
Discharge display devices {plasma display panels (PDPs)} using a scheme for performing a light emission by using gas discharging are roughly classified into an AC type discharge display device (AC type PDP) having one pair of discharge electrodes which are opposite to each other to cross through a discharge gas, each of which is constituted by a plurality of line-shaped electrodes, and both of the pair of discharge electrodes are covered by a dielectric layer, and a DC type discharge display device (DC type PDP) in which a pair of discharge electrodes both have metals on the electrode surfaces exposed to a discharge space. As an intermediate type discharge display device therebetween, a semi-AC type or semi-DC type display discharge device (semi-AC type or semi-DC type PDP) in which one discharge electrode of one pair of discharge electrodes is covered with a dielectric layer, and a metal on the electrode surface of the other discharge electrode is exposed to a discharge space is known.
There is also provided a color discharge display device (color PDP) in which infrared rays generated from gas discharging are irradiated on phosphor layers for emitting red, green, and blue lights to perform a color display. In this color discharge display device, the phosphor layer directly receives ion impact in a gas, or materials spattered by ion impact to the discharge electrode are accumulated on the surface of the phosphor, so that the phosphor must be prevented from being degraded.
Therefore, in a color discharge display device, first, the discharge electrodes must be strong against the ion impact. With respect to this point, an AC type discharge display device is advantageous. More specifically, in the AC type discharge display device, the discharge electrodes are covered with a dielectric layer such as low-melting-point glass or the like, and the surfaces of the discharge electrodes are covered with an electrode protecting layer which also serves as a secondary electron discharging material such as a magnesium oxide (MgO) or the like for protecting the electrodes from the ion impact. For this reason, it is not likely that materials spattered by the ion impact received by the discharge electrodes are accumulated on the phosphor layers, and high reliability can be obtained.
By the way, since in the AC type discharge display device, one pair of electrodes opposite to each other through a discharge space is not classified into anode and cathode electrodes, either of discharge electrodes may receive the ion impact. For this reason, an AC type discharge display device of an opposite-two-electrode type which has the simplest structure and can be easily manufactured is not easily used as a color discharge display device. Therefore, an AC type discharge display device of a surface-discharge three-electrode type in which a discharge electrode for a display is separated from an address electrode to assure an area on which a phosphor is coated has been practically used. However, the price of this AC type discharge display device is high because of a large number of electrodes. The high price hinders achievement of high resolution.
The problems of the opposite-two-electrode type discharge display device with respect to a conventional driving method will be described below with reference to
FIG. 5
showing an example of the semi-AC type discharge display device serving as an opposite-two-electrode type discharge display device. The semi-AC type discharge display device shown in
FIG. 5
is constituted by an AC type Y electrode
1
serving as one discharge electrode constituted by a plurality of line-shaped electrodes and a DC type X electrode
3
serving as the other discharge electrode constituted by a plurality of line-shaped electrodes, and the AC type Y electrode
1
and the DC type X electrode
3
are opposite to each other to cross through a discharge gas, i.e., are arranged in the form of a matrix.
The Y electrode
1
is constituted by line-shaped electrodes (transparent electrodes) covered with a dielectric layer
2
, each having a predetermined width, and arranged at a predetermined interval, and is formed on a front-surface glass plate (not shown). The X electrode
3
is constituted by metal wires (stripe electrodes may also be used) each having a predetermined diameter, arranged at a predetermined interval, and consisting of stainless steel, nickel or the like each having a predetermined diameter and arranged at a predetermined interval, and the electrode surfaces of the electrodes are exposed to a gas space. The X electrode
3
is opposite to the inner walls of a large number of trenches
4
formed on a rear-surface glass plate
6
by an etching method, a sand blast method or the like to be close to or be in contact with the inner walls, and phosphor layers
5
for emitting red, green, and blue lights are formed to be sequentially and cyclically covered on the inner walls of the trenches
4
.
FIGS. 1A
to D show timing charts for explaining sustain discharging for memory discharging which is a prior art of a driving method for a discharge display device (the above mentioned semi-AC discharge display device in FIG.
5
). The timing charts will be described below. Reference symbol Tad denotes an address period, and Tst denotes a sustain period.
FIG. 1C
shows a waveform of a voltage Vxy between the X electrode
3
and the Y electrode
1
. This waveform is an AC pulse waveform which is symmetrical with respect to positive and negative sides. In order to apply the voltage Vxy having the waveform shown in
FIG. 1C
across the X electrode
3
and the Y electrode
1
, as shown in
FIGS. 1A and B
, two pulse voltages Vy and Vx which are negative pulses having the same waveform and have a predetermined phase difference are applied to the Y electrode
1
and the X electrode
3
, or the voltage having the waveform shown in
FIG. 1C
may be applied to any one of the Y electrode
1
and the X electrode
3
, and the voltage of the other electrode may be set to be zero.
FIG. 1D
shows a discharge keeping pulse applied to one pair of display electrodes, i.e., the Y electrode
1
and the X electrode
3
and only a change in electrode surface potential caused by wall charges generated by the discharge keeping pulse. A description of the process in which wall charges depending on a picture screen are formed on a selected cell by an address operation performed prior to the change in electrode surface potential will be omitted. More specifically, the explanation is made on the sustain period Tst where the wall charges have been formed on the Y electrode
1
and the X electrode
3
or both the electrodes in an address period Tad, and the memory discharging is performed by applying the discharge keeping pulse.
A state that negative wall charges are formed in the address period Tad on the Y electrode
1
serving as an AC type electrode is assumed, and the pulse voltage Vy having a waveform shown in
FIG. 1A
is applied to the Y electrode
1
in the sustain period Tst. Since the other electrode X
3
is a DC type electrode, no wall charges are formed on the X electrode
3
. However, a pulse voltage Vx shown in FIG.
1
B and having a phase difference of 180° with respect to the pulse voltage shown in
FIG. 1A
is applied to the X electrode
3
.
In this manner, since positive and negative charges generated by wall charges when respective pulse voltages are applied are alternately reversed and superposed one another, the voltage Vxy applied across the X electrode
3
and the Y electrode
1
becomes the an AC pulse voltage having a waveform shown in FIG.
1
C. More specifically, as shown in
FIG. 1D
, since it is assumed that negative charges are accumulated on the Y electrode
1
first, the voltage superposed with the voltage Vy having the waveform shown in
FIG. 1A
exceeds a discharge start voltage Vb1. For this reason, a first discharging occurs. Then, the negative charges on the
Bauer & Schaffer, LLP
Mengistu Amare
Nguyen Jimmy H.
Technology Trade and Transfer Corp.
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