Electric lamp and discharge devices – With gas or vapor – Three or more electrode discharge device
Reexamination Certificate
1999-01-11
2002-03-12
Wong, Don (Department: 2879)
Electric lamp and discharge devices
With gas or vapor
Three or more electrode discharge device
C315S167000, C315S169400, C345S060000
Reexamination Certificate
active
06356017
ABSTRACT:
BACKGROUND OF THE INVENTION
(a) Field of the Invention
The present invention relates to a plasma display panel and a method for driving the same. More specifically, the present invention relates to a technique for driving an AC discharge plasma display panel.
(b) Description of the Related Art
Generally speaking, a plasma display panel (hereinafter called as “PDP”) has several advantages such as thin configuration, little flicker, large contrast, relatively large display area, high display speed and the like. Thus, plasma display panels will be increasingly used for personal computers, workstations, flat television sets and other applications hereinafter.
There are two different types of PDP with respect to a driving scheme thereof. One is a DC discharge type PDP in which electrode conductors are exposed to the plasma ions, and the other is an AC discharge type PDP in which electrode conductors are covered with a dielectric film for insulation from the plasma ions. The AC discharge type PDP includes a memory PDP in which the display cell itself has a memory function using a charge accumulation effect of the dielectric while discharging through the dielectric, and a refreshing PDP that does not utilize the above memory function. Brightness or intensity of the PDP is generally proportional to the number of discharge times, i.e., the number of repetitive frequency of the drive pulses.
FIG. 1
is a cross section showing a typical AC discharge type color PDP. The PDP includes front and rear glass substrates (panels)
10
and
11
. Scanning electrodes
12
and common electrodes
13
are formed on the front substrate
10
. An insulator layer
15
a
is formed covering the scanning electrodes
12
and the common electrodes
13
on the front substrate
10
. On the insulator layer
15
a
, a protective layer
16
made of MgO etc. is formed so as to protect the insulator layer
15
a
from the plasma discharge. On the other hand, data electrodes
19
are formed on the rear substrate
11
. Covering the data electrodes
19
, an insulator layer
15
b
is formed on the rear substrate
11
. On the insulator layer
15
b
, a fluorescent film
18
is formed by coating to convert the ultraviolet ray generated by the plasma discharge into visual light.
A discharge space
20
is formed between the front substrate
10
and the rear substrate
11
, and discharge gas including a mixture of He, Ne, Ar, Kr, Xe, N
2
, O
2
, CO
2
and other gases is filled in the discharge space
20
. The discharge space
20
is secured by provision of a lattice partition
17
, which separates the front substrate
10
from the rear substrate
11
, and divides the discharge space
20
into a plurality of display cells arranged in a matrix. The fluorescent film
18
is colored in red, green or blue in each display cell, so as to display a multicolor image.
FIG. 2
is a schematic block diagram of the PDP shown in
FIG. 1
for showing the electrode arrangement of the PDP. The electrode arrangement includes pairs of scanning electrode
12
1
-
12
m
and common electrode
13
1
-
13
m
, as well as data electrodes
19
1
-
19
n
. Scanning electrodes
12
1
-
12
m
and common electrodes
13
1
-
13
m
constitute row electrodes, which are disposed in parallel to one another in the row direction on the front substrate
10
. Data electrodes
19
1
-
19
n
constitute column electrodes, which are disposed in the column direction on the rear substrate
11
. Display cells
40
are disposed at respective cross points of the row electrodes and the column electrodes. In
FIG. 2
, display cells
40
are indicated by blocks arranged in a matrix with m x n elements.
A conventional method for driving the PDP of
FIGS. 1
will be described with reference to a timing chart of
FIG. 3
showing pulse waveforms applied to the electrodes of the PDP. A single driving period of the PDP includes a preliminary discharge period, a writing discharge period and a sustaining discharge period, which are iterated in this order so as to display a desired image.
In the preliminary discharge period, an erasing pulse
21
is applied to all the scanning electrodes
12
1
-
12
m
simultaneously, to stop the sustaining discharge, thereby allowing all the display cells
40
to enter an erased state. Thereafter, a preliminary discharging pulse
22
is applied to all the common electrodes
13
1
-
13
m
to force all the display cells to emit light by forced preliminary discharge for facilitating the subsequent writing discharge. Subsequently, a preliminary discharge erasing pulse
23
is applied to the scanning electrodes
12
1
-
12
m
for erasing the preliminary discharge of all the display cells. In this description, “erase or erasing” means an operation of decreasing or deleting wall charge accumulated on the insulator.
In the writing discharge period, a scanning pulse
24
is applied to a corresponding one of the scanning electrodes
12
1
-
12
m
, with a certain timing period disposed between each two of the adjacent scanning pulses. In synchrony with the timing of the scanning pulses
24
, data pulses
27
corresponding to display data are applied to the selected data electrodes
19
1
-
19
n
. Specifically, the data pulses
27
are applied to data electrodes corresponding to the selected display cells, and not applied to data electrodes corresponding to the unselected display cells. In
FIG. 3
, diagonal line in each rectangular data pulse
27
indicates that presence or absence of the data pulse
27
depends on the data to be written.
In the following selected display cell, to which the data pulse
27
was applied at the timing of the scanning pulse
24
, generates writing discharge in the discharge space
20
between the scanning electrode
12
and the data electrode
19
. In the selected display cell that generated the writing discharge, positive wall charge is accumulated on the insulator layer
15
a
adjacent the scanning electrodes
12
. At the same time, negative wall charge is also accumulated on the insulator layer
15
b
adjacent the data electrodes
19
.
In the sustaining discharge period, sustaining pulses
25
and
26
are applied to the common electrodes
13
1
-
13
m
and the scanning electrodes
12
1
-
12
m
so as to perform the sustaining discharge for maintaining a desired intensity in the display cells that performed the writing discharge in the writing discharge period. Specifically, a first sustaining discharge is generated by the potential difference between the positive potential generated by the positive wall charge accumulated on the insulator layer
15
a
and the negative potential of the first negative sustaining pulses
25
applied to the common electrodes
13
. After the first sustaining discharge is generated, the positive wall charge is accumulated on the insulator layer
15
a
at portions adjacent the common electrodes
13
, and the negative wall charge is accumulated on the insulator layer
15
a
at portions adjacent the scanning electrodes
12
. Subsequently, the second sustaining pulses
26
is applied to the scanning electrodes
12
to be superimposed on the potential difference generated by the positive wall charge and the negative wall charge, resulting in generation of a second sustaining discharge.
In the subsequent intervals in the sustaining discharge period, the sustaining discharge is consecutively maintained by superimposing (n+1)th sustaining pulses on the potential difference generated by the positive and negative wall charge accumulated by n-th sustaining discharge. By controlling the number of times for sustaining discharge, the brightness of the display can be controlled for each of the selected display cells. Usually, the sustaining pulses
25
and
26
have repetitive a frequency of approximately 100 KHz at most and each individual pulse has a rectangular waveform.
Since the potentials of the sustaining pulses
25
and
26
are adjusted to a level that does not generate discharge by itself, the wall charge does not exist before the application of the first sustaining pulse
25
in the unselected display cells that did
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