Computer graphics processing and selective visual display system – Plural physical display element control system – Display elements arranged in matrix
Reexamination Certificate
1998-05-22
2002-07-30
Shalwala, Bipin (Department: 2673)
Computer graphics processing and selective visual display system
Plural physical display element control system
Display elements arranged in matrix
C315S169400
Reexamination Certificate
active
06426732
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of energizing an AC discharge plasma display panel for use as a large-area flat display panel with a personal computer, a workstation, or a wall television set.
2. Description of the Relates Art
Plasma display panels (also referred to as “PDP”) are classified according to operating principles into DC discharge PDPs in which electrodes are exposed to a discharge gas and cause a discharge only when a voltage is applied, and AC discharge PDPs in which electrodes are covered with a dielectric layer and cause a discharge while being not exposed to a discharge gas. Discharge cells of the AC discharge PDPs have a memory function because of a charge storage action of the dielectric layer.
One general AC discharge color PDP will be described below with reference to
FIG. 1
of the accompanying drawings.
FIG. 1
shows a fragmentary cross section of the AC discharge color PDP. As shown in
FIG. 1
, the AC discharge color PDP comprises a front substrate
10
of glass and a back substrate
11
of glass which are spaced from each other with a space defined therebetween.
Scanning electrodes
12
and common electrodes
13
which are spaced from each other by given distances are disposed on the front substrate
10
. The scanning electrodes
12
and the common electrodes
13
are covered with an insulating layer
15
a
which is covered with a protective layer
16
of MgO or the like that protects the insulating layer
15
a
from electric discharges.
Data electrodes
19
which extend perpendicularly to the scanning electrodes
12
and the common electrodes
13
are disposed on the back substrate
11
. The data electrodes
19
are covered with an insulating layer
15
b
which is coated with a phosphor layer
18
that converts an ultraviolet radiation generated by electric discharges into visible light for display.
Partitions
17
extend between the insulating layers
15
a
and
15
b,
providing a discharge space
20
therebetween. The partitions
17
define pixels for displaying images on the PDP. The discharge space
20
is filled with a discharge gas which comprises a mixture of He, Ne, Xe, etc.
FIG. 2
of the accompanying drawings shows the layout of the electrodes in the color PDP shown in FIG.
1
.
In
FIG. 2
, the color PDP has m scanning electrodes S
i
(i=1, 2, . . . , m)
12
extending as rows, n data electrodes D
j
(j=1, 2, . . . , n)
19
extending as columns, the scanning electrodes S
i
and the data electrodes D
j
intersect with each other at the pixels, and m common electrodes C
i
(i=1, 2, . . . , m)
13
extending as rows parallel to the scanning electrodes S
i
and paired with the scanning electrodes S
i
. The phosphor layer
18
has a plurality of areas aligned respectively with the pixels
14
and coated with different colors of R, G, B for enabling the PDP to display color images.
A process of energizing the conventional color PDP shown in
FIGS. 1 and 2
will be described below with reference to
FIG. 3
of the accompanying drawings.
FIG. 3
is a timing chart of drive voltages which are applied to the electrodes of the conventional color PDP.
First, erasing pulses
21
are applied to all the scanning electrodes
12
to turn off all the pixels which have previously emitted visible light.
Then, preliminary discharge pulses
22
are applied to the common electrodes
13
for forcibly discharging all the pixels to emit visible light. Thereafter, preliminary discharge erasing pulses
23
are applied to all the scanning electrodes
12
to turn off a preliminary discharge at all the pixels. The preliminary discharge allows a subsequent writing discharge to be effected with ease.
After the preliminary discharge is turned off, scanning pulses
24
are applied at different times to the scanning electrodes (S
1
−S
m
)
12
, and data pulses
27
representative of data to be displayed are applied to the data electrodes (D
1
−D
n
)
19
in timed relation to the scanning pulses
24
. Diagonal lines indicated in the data pulses
27
show that the presence or absence of data pulses
27
is determined according to whether there is data to be displayed or not. If a data pulse
27
is applied to a pixel when a scanning pulse
24
is applied thereto, then a writing discharge occurs at the pixel in the discharge space
20
between the scanning electrode
12
and the data electrode
19
. If no data pulse
27
is applied to a pixel when a scanning pulse
24
is applied thereto, then no writing discharge occurs at the pixel.
At a pixel where a writing discharge occurs, a positive charge called a wall charge is collected in the insulating layer
15
a
on the scanning electrodes
12
. At this time, a negative wall charge is collected in the dielectric layer
15
b
on the data electrodes
19
. The positive wall charge in the insulating layer
15
a
and first negative sustaining pulses
25
applied to the common electrodes
13
are superposed thereby to generate a first sustained discharge. When the first sustained discharge is generated, a positive wall charge is collected in the insulating layer
15
a
on the common electrodes
13
, and a negative wall charge is collected in the insulating layer
15
a
on the scanning electrodes
12
. Second sustaining pulses
26
applied to the scanning electrodes
12
are superposed on the potential difference between these wall charges thereby to generate a second sustained discharge. In this manner, the potential difference between wall charges developed by an xth sustained discharge and (x+1)th sustaining pulses are superposed thereby to continue sustained discharges. The number of times that a sustained discharge is continued controls the amount of visible light emitted from the pixels.
The voltage of the sustaining pulses
25
,
26
is adjusted such that the voltage of these pulses alone will not develop a discharge. At a pixel where no writing discharge has been developed, there is no potential due to a wall charge before the first sustaining pulses
25
are applied. At such a pixel, therefore, no first sustained discharge is produced even when the first sustaining pulses
25
are applied, and no subsequent sustained discharge will be produced.
Each of the erasing pulses
21
, the preliminary discharge pulses
22
, the preliminary discharge erasing pulses
23
, the scanning pulses
24
, the sustaining pulses
25
,
26
, and the data pulses
27
described above has heretofore been a rectangular pulse whose rise and fall times are 1 microsecond or less each as shown in FIG.
4
A.
When the color PDP develops a discharge with the rectangular pulse shown in
FIG. 4A
, a discharging current shown in
FIG. 4B
flows in an electrode to which the rectangular pulse is applied. The discharging current starts to flow several hundreds nanoseconds after the application of the rectangular pulse, reaches a peak level another several hundreds nanoseconds thereafter, subsequently sustains for several hundreds of nanoseconds, and is then terminated.
The time from the application of the pulse to the start of the discharging current, the time to the peak level, and the subsequent time for which the discharging current is sustained depend on the composition of the discharge gas, the composition of the dielectric layer, the thickness of the dielectric layer, the composition of the electrodes, the sizes of the electrodes, and the size of the discharge space.
For example, a phosphor material has a discharge emission efficiency of about 80 lm/W, and a PDP which is energized by the above conventional process has a much lower discharge emission efficiency of about 1 lm/W. Therefore, the PDP needs to consume a large amount of electric energy in order to increase the emission luminance.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a method of energizing a plasma display panel to increase emission efficiency with sustained discharges for thereby reducing electric energy consumption.
To achieve the above object, the
Frenel Vanel
Shalwala Bipin
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