Computer graphics processing and selective visual display system – Plural physical display element control system – Display elements arranged in matrix
Reexamination Certificate
2002-12-02
2004-04-13
Vo, Tuyet T. (Department: 2821)
Computer graphics processing and selective visual display system
Plural physical display element control system
Display elements arranged in matrix
C345S060000, C345S079000, C345S077000, C315S169100, C315S169400
Reexamination Certificate
active
06720941
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of driving an AC (Alternating Current) surface-discharge type plasma display panel that enables a scanning period to be shortened.
The present application claims priority of Japanese Patent Application No. 2001-365650 filed on Nov. 30, 2001, which is hereby incorporated by reference.
2. Description of the Related Art
Currently, two types of plasma display panels are available, one being a DC (Direct Current)-discharge type plasma display panel which is operated by exposing electrodes in a discharge space being filled with a discharging gas and by causing a DC discharge to occur between the exposed electrodes, and another being an AC-discharge type plasma display panel which is operated, with electrodes not directly being exposed in the discharging gas by coating electrodes with dielectric layers, in a state in which AC-discharge occurs. There are two types of the AC-discharge type plasma display panels, one having two electrodes in a display cell and another having three electrodes in the display cell. Configurations and driving methods of a conventional three-electrode-surface-discharge AC-type plasma display panel (hereinafter may be referred simply to as a “PDP”) are described below.
FIG. 6
is a perspective view showing configurations of one display cell in the PDP. As shown in
FIG. 6
, in the display cell, an insulating substrate
1
serving as a rear substrate made of a transparent material such as glass and an insulating substrate
2
serving as a front substrate also made of transparent material such as glass are mounted in parallel to each other. On a surface of the insulating substrate
2
facing the insulating substrate
1
are placed a plurality of transparent scanning electrodes
3
and a plurality of common electrodes
4
alternately at specified intervals. On each of the scanning electrodes
3
and on each of the common electrodes
4
are formed a trace electrode
5
and a trace electrode
6
respectively both serving to reduce an electrode resistance value of each of the scanning electrode
3
and of the common electrodes
4
. Moreover, a dielectric film
12
is formed in a manner that it covers the scanning electrodes
3
, common electrodes
4
, and the trace electrode
5
and electrode
6
. On the dielectric film
12
is formed a protective layer
13
made of magnesium oxide or a like which prevents the dielectric film
12
from being affected by discharge.
Moreover, on a surface of the insulating substrate
1
facing the insulating substrate
2
is mounted a plurality of data electrodes
7
each extending in a direction orthogonal to each of the scanning electrodes
3
and the common electrodes
4
. On the data electrodes
7
is formed a dielectric film
14
in a manner so as to cover the data electrodes
7
.
Between the insulating substrate
1
and the insulating substrate
2
are formed ribs
9
(that is, partitioning walls) used to provide space
8
for discharging gas and to partition a display cell (picture cell). The space
8
for discharging gas is filled with an inert gas such as helium, neon, xenon, or a like or mixed gases of these inert gases. Moreover, on a surface of the dielectric film
14
and on a side of each of the ribs
9
are formed phosphors
11
used to absorb ultraviolet rays produced by discharge of the above gas and to emit visible light
10
.
FIG. 7
is a top view schematically showing arrangements of electrodes used in the conventional PDP shown in FIG.
6
. As shown in
FIG. 7
, “n” (n is a natural number) pieces of the scanning electrodes
3
(see
FIG. 6
) (S
1
to Sn); “n” pieces of the common electrodes
4
(see
FIG. 6
) (C
1
to Cn), and “m” (m is a natural number) pieces of the data electrodes
7
(see
FIG. 6
) (D
1
to Dm) are provided in the PDP. Also, as shown in
FIG. 7
, the PDP is provided with “n” pieces of the scanning electrodes S extending in parallel to one another, “n” pieces of the common electrodes C extending in parallel to one another, and “m” pieces of the data electrodes D extending in a direction orthogonal to the scanning electrodes S and common electrodes C. Display cells
15
are formed, each emitting light and each containing one nearest contact of one of the data electrodes D to one of the scanning electrodes S and one nearest contact of one of the data electrodes D to one of the common electrodes C. That is, one of the scanning electrodes S, one of the common electrodes C, and one of the data electrodes D pass through each of the display cells
15
. The display cells
15
are arranged in a matrix form. Therefore, a total number of display cells
15
on an entire screen of the PDP is “(n×m)”.
Next, a method for driving the conventional PDP is described below.
FIG. 8
is a timing chart showing periods contained in one field in the method for driving the conventional PDP. The method shown in
FIG. 8
is called a “sub-field method”. For example, images being switched at a rate of one piece per one sixtieth of a second are displayed in one field
20
which is made up of eight sub-fields SF
1
to SF
8
and a number of times of sustaining discharge occurring in each sub-field is set to be values each being proportional to a power of two so as to be made different from one another. Here, let it be assumed that the number of times of the sustaining discharge in each of the sub-fields SF
1
to SF
8
is given by 27k=128k, 26k=64k, 25k=32k, 24k=16k, 23k=8k, 22k=4k, 21k=2k, and 20k=1k, respectively, where “k” is a constant coefficient. Then, by arbitrarily selecting sub-fields during which the sustaining discharge occurs, out of these sub-fields SF
1
to SF
8
, and by combining the selected sub-fields, 256 shades of gray are made to be displayed in each of the display cells
15
.
FIG. 9
is a diagram showing waveforms of pulses used in the conventional method for driving the PDP for each of the conventional sub-fields (SF
1
to SF
8
).
FIGS. 10A
to
10
C and
FIGS. 11A
to
11
B are diagrams schematically illustrating arrangements of wall charges formed in each of the display cells
15
when the driving method shown in
FIG. 9
is executed.
FIGS. 10A
to
10
B are diagrams illustrating arrangements of wall charges formed during a resetting period
21
.
FIG. 10C
is a diagram illustrating arrangements of wall charges formed during a scanning period
22
,
FIGS. 11A and 11B
are diagrams illustrating arrangements of wall charges formed during a sustaining period
23
. As shown in
FIG. 9
, according to the method employed in the above example, each of the sub-fields SF
1
to SF
8
is divided into the resetting period
21
, the scanning period
22
, and the sustaining period
23
. Hereinafter, operations during each of the above periods the resetting period
21
, the scanning period
22
, and the sustaining
23
making up the sub-field are explained by referring to
FIG. 9
,
FIGS. 10A
to
10
C, and
FIGS. 11A and 11B
. In
FIGS. 10A
to
10
C and
FIGS. 11A and 11B
, a positive wall charge is expressed by a symbol obtained by enclosing “+” with a circle and a negative wall charge is expressed by a symbol obtained by enclosing “−” with a circle.
During the resetting period
21
, wall charges formed in a previous sub-field (not shown) are erased and displayed data is reset. During the resetting period
21
, a priming pulse of a positive polarity Vp+ is applied to each of the scanning electrodes S and, at a same time, a priming pulse of a negative polarity Vp− is applied to each of the common electrodes C. Each of the data electrodes D is set to be at a ground (GND) potential. A total voltage of the priming pulse of the positive polarity Vp+ and the priming pulse of the negative polarity Vp− is set to be more than a surface-discharge firing voltage of the conventional PDP. This causes, as illustrated as a state “A
1
” in
FIG. 10A
, priming discharge (preliminary discharge) to occur between a surface of the dielectric fi
NEC Plasma Display Corporation
Vo Tuyet T.
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