Computer graphics processing and selective visual display system – Plural physical display element control system – Display elements arranged in matrix
Reexamination Certificate
2000-12-22
2003-11-04
Hjerpe, Richard (Department: 2674)
Computer graphics processing and selective visual display system
Plural physical display element control system
Display elements arranged in matrix
C345S063000, C345S066000
Reexamination Certificate
active
06642912
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a plasma display panel (PDP) and more particularly, to a method of driving a PDP of the ac discharge type having a preliminary discharge period for applying a preliminary discharge pulse or pulses to the scan electrodes and/or the sustain electrodes, a scan period for applying successively scan pulses to the individual scan electrodes, and a sustain period for applying sustain pulses to the scan and/or sustain electrodes.
2. Description of the Related Art
PDPs, which display images by utilizing light emission due to gas discharge, have ever been known as a display device that can be easily fabricated to have a large-sized flat screen. PDPs are divided into two types (i.e., the dc type and the ac type) according to the difference in the panel structure and operation principle. The dc-type PDPs have electrodes exposed to the discharge spaces while the ac-type PDPs have electrodes covered with dielectric.
The PDP according to the invention is of the ac-type and thus, only the ac-type PDPs will be explained below.
The ac-type PDPs have a typical configuration as shown in
FIGS. 45
,
46
, and
47
.
FIG. 45
is a partially cutaway, perspective view showing the main elements or parts of the typical ac-type PDP,
FIG. 46
is a cross-sectional view along the line XXXXVI—XXXXVI in
FIG. 45
, and
FIG. 47
is a cross-sectional view along the line XXXXVII-XXXXVXI in FIG.
45
.
As seen from
FIGS. 45
to
47
, the typical ac-type color PDP comprises two opposing dielectric substrates, i.e., a front substrate
51
and a rear substrate
52
, that form a gap between them. The substrates
51
and
52
are typically made of glass. The following structure is provided in the gap.
Specifically, on the inner surface of the front substrate
51
, scan electrodes
53
and sustain electrodes
54
are formed to be parallel to each other. The scan electrodes
53
and the sustain electrodes
54
constitute row electrodes. The electrodes
53
and
54
are covered with a dielectric layer
55
a
such as MgO. The dielectric layer
55
a
is covered with a protection layer
56
.
On the inner surface of the rear substrate
52
, data electrodes
57
are formed to be parallel to each other. The electrodes
57
are perpendicular to the row electrodes (i.e., the scan and sustain electrodes
53
and
54
). The data electrodes
57
are covered with a dielectric layer
55
b
such as MgO. To convert the ultraviolet (UV) rays emitted by discharge to visible light, a phosphor layer
58
is formed on the layer
55
b
. The layer
58
includes three types of phosphor sublayers for three primary colors of red (R), green (G), and blue (B) arranged in the respective discharge cells, making it possible to display color images.
Partition walls
60
are provided in the gap between the front and rear substrates
51
and
52
to form the discharge cells, defining discharge spaces
59
for the respective cells. A gaseous mixture of at least two ones of He, Ne, Ar, Kr, Xe, N
2
, O
2
and CO
2
is filled in the respective spaces
59
as the discharge gas.
FIG. 48
is a plan view showing the electrode structure of the color PDP shown in
FIGS. 45
to
47
.
As shown in
FIG. 48
, the count of the scan electrodes
53
extending along the rows of the PDP is m, where m is a natural number greater than unity. The scan electrodes
53
are referred as S
i
(i=1, 2, . . . , m). The count of the data electrodes
57
extending along the columns of the PDP is n, where n is a natural number greater than unity. The data electrodes
57
are referred as D
j
(j=1, 2, . . . , n). The discharge cells
61
are located at the respective intersections of the scan and data electrodes
53
and
57
. Thus, the cells
61
are arranged in a matrix array.
The count of the sustain
54
extending along the rows of the PDP is m. Each of the sustain electrodes
54
and a corresponding, adjoining one of the scan electrodes
53
, which are parallel to and apart from each other at a specific interval, forms an electrode pair. The sustain electrodes
54
are referred as C
i
(i=1, 2, . . . , m).
With the above-described ac-type color PDP, electric charge caused by discharge in the discharge spaces
59
is temporarily stored in the dielectric layers
55
a
and/or
55
b
and is eliminated therefrom. The electric charge (which may be termed simply “charge” hereinafter) stored in the layers
55
a
and
55
b
is termed the “wall charge”. Generation and elimination of the discharge is controlled by adjusting or controlling the amount and/or distribution state of the “wall charge”.
Next, an example of the conventional methods of driving the above-described ac-type PDP is explained below with reference to
FIGS. 1 and 2
.
FIG. 1
shows schematically the waveforms of the driving voltage applied to the respective electrodes.
FIGS. 2A
to
2
F show schematically the distribution of the wall charge in the respective electrodes.
In
FIG. 1
, the period of time T
2
in which the elimination pulse
105
and the preliminary discharge pulses
106
and
107
are applied is termed the “preliminary discharge period”. The period of time T
3
in which the scan pulse
108
and the data pulse
109
are applied is termed the “scan period”. The period of time T
4
in which the sustain pulse
110
is applied is termed the “sustain period”. The combination of the “preliminary discharge period T
2
”, the “scan period T
3
”, and the “sustain period T
4
” is termed the “sub-field T
1
”. In other words, the “sub-field T
1
” is formed by the preliminary discharge period T
2
, the scan period T
3
, and the sustain period T
4
.
The sub-field T
1
corresponds to each cycle of the conventional driving method of the PDP explained here. Thus, the waveform diagram during one of the sub-fields T
1
is shown in FIG.
1
and the change of the wall charge distribution during the same is shown in FIG.
2
.
In the subsequent explanation in this specification, the rise of a positive pulse means the positive change of the voltage (i.e., the increase of the absolute value or amplitude of the voltage), and the fall of a positive pulse means the negative change of the voltage (i.e., the decrease of the absolute value or amplitude of the voltage). Also, the rise of a negative pulse means the negative change of the voltage (i.e., the increase of the absolute value or amplitude of the voltage), and the fall of a negative pulse means the negative change of the voltage (i.e., the decrease of the absolute value or amplitude of the voltage).
(1. Elimination of Sustain Discharge)
The rectangular elimination pulse
105
is applied to all the sustain electrodes
54
(C
1
to C
m
). Thus, the ac discharge occurring in the light-emitting cells
61
due to the application of the rectangular sustain pulses
110
is stopped and at the same time, the wall charge stored in the dielectric layers
55
a
and
55
b
decreases or disappear. This operation to apply the elimination pulse
105
is termed the “sustain discharge elimination”.
FIG. 2A
shows the state where the wall charge stored in the dielectric layers
55
a
and
55
b
has disappeared.
Several methods for the “sustain discharge elimination” have been known. In the method shown in
FIG. 1
, a narrow rectangular pulse is used as the elimination pulse
105
. However, as the elimination pulse
105
, a rectangular pulse
105
a
with a less amplitude and a greater width shown in
FIG. 3
than the pulse
105
shown in
FIG. 1
may be used. Also, a sawtooth-shaped pulse
105
b
with a linearly-increasing amplitude shown in
FIG. 4
may be used as the elimination pulse
105
.
(2. Preliminary Discharge)
After eliminating the sustain discharge by the pulse
105
, a preliminary discharge pulse
106
is commonly applied to all the sustain electrodes
54
(C
1
to C
m
) while a preliminary discharge pulse
107
is commonly applied to all the scan electrodes
53
(S
1
to S
m
). At the rise time (i.e., at the leading edges) of the pulses
106
and
107
, all the cells
61
are comp
Dinh Duc Q
Hjerpe Richard
NEC Corporation
Scully Scott Murphy & Presser
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