Computer graphics processing and selective visual display system – Plural physical display element control system – Display elements arranged in matrix
Reexamination Certificate
2000-08-29
2003-09-02
Mengistu, Amare (Department: 2673)
Computer graphics processing and selective visual display system
Plural physical display element control system
Display elements arranged in matrix
C313S484000
Reexamination Certificate
active
06614412
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field of the Invention
The present invention relates to a plasma display panel (PDP), and in particular to a panel structure, its manufacturing method, its drive method, and its drive device which makes possible low voltage drive and fast writing, and which can achieve high luminance, a high efficiency, and a longer life.
2. Description of the Prior Art
In PDP, electrons accelerated by an electric field collide with gas atoms or molecules and ultraviolet light generated by the collision is converted to visible light by fluorescent materials to display color images. PDP is one of the flat panel display apparatuses with large area and large capacity. Conventional PDP is explained, referring to
FIGS. 15
to
18
. In these figures, the portions relating to various electrodes are mainly illustrated.
In a structure shown in
FIG. 15
, data electrode
2
is formed in a column direction on back glass substrate
1
. On data electrode
2
, dielectric layer
3
is formed. On the dielectric layer
3
, scan electrode
4
is formed in a row direction. On scan electrode
4
, dielectric layer
5
is formed. In a portion where the electrodes cross with each other, a unit cell for pixel is formed. In a PDP having such a structure, write discharge
21
(planar discharge) for selecting a cell for the display occurs at the intersection of data electrode
2
and scan electrode
4
formed on substrate
1
, and thereafter sustaining discharge
22
(planar discharge) for emitting visible light occurs. Such a structure is called cross planar discharge type, and has a feature that the electrodes are formed only on a substrate, unlike a cross vertical discharge type shown in FIG.
16
.
In this structure, however, write discharge
21
and sustaining discharge
22
are generated at the same place. Therefore, the high energy ions attack a not-shown protection layer at the time of the discharges. Therefore, ion impact due to write discharge
21
is superposed on that of sustaining discharge
22
at the same place. This results in a problem of a short operation life, due to degradation of the protection layer. Unlike the case of the vertical discharge described later, especially in the case of the planar discharge, the distortion of the electric field (concentration of electric lines of force
17
) at the electrode edge portion is great, high energy ions concentrate in the protection layer located near the electrode edge portion, and ions are incident obliquely on the protection layer. In the case of the planar discharge, therefore, damage of the protection layer caused by the ion impact becomes more severe. Furthermore, there is also a problem of a low luminance and a low conversion efficiency from the electric power to the luminance, because the discharge region is narrow. Furthermore, there is also a problem of complicated driving sequence and a complicated drive circuit, because the electrode pair causing write discharge
21
and sustaining discharge
22
lies at the same place. Further, in general, PDP is a distributed parameter circuit, due to the resistances and capacitances of the electrodes. Therefore, the peak values of sustaining pulse
20
vary, depending upon the location of the display panel. Concretely, the luminance at the connection portion with an external drive circuit is different from that at the position remote from the connection portion. This variation of the peak values destroys the uniformity in luminance in the displayed pictures. The luck of uniformity in the pictures becomes serious, as the display area becomes larger, particularly in case of the AC discharge—PDP, wherein pulse discharge current is high.
On the other hand, in the structure shown in
FIG. 16
, data electrode
2
is formed along a column direction on a back glass substrate
1
. On the data electrode
2
, dielectric layer
3
is formed. On front glass substrate
10
, scan electrode
4
is formed along the row direction. On scan electrode
4
, dielectric layer
13
is formed. In the PDP having such a structure, write discharge
21
(vertical discharge) occurs in between data electrode
2
and scan electrode
4
, and thereafter sustaining discharge
22
(vertical discharge) occurs. In this case, both write discharge
21
and sustaining discharge
22
are of the vertical discharge type. As compared with the structure shown in
FIG. 15
, there is an advantage that the damage of the not shown protection layer, caused by the ion impact is reduced. Furthermore, since the discharge region can be expanded by widening the distance between electrodes, there is a possibility that the luminance and the conversion efficiency from the electric power to the luminance can be improved. In this case, however, the voltage for driving the PDP becomes very high.
The structure as shown in
FIG. 16
as well as the structure as shown in
FIG. 15
has a problem of a shortened life caused by superposition of ion impact at the same place. The life is dependent upon the type of PDP, because each electrode is covered with a dielectric layer in the AC discharge system, while each electrode is exposed in a direct current (DC) discharge system. Furthermore, there is a problem of complicated driving sequence and a drive circuit caused by the fact that an electrode pair generates the write discharge
21
and the sustaining discharge
22
. Furthermore, there is a problem that the luminance varies, depending upon the location on the display panel.
On the other hand, in the structure shown in
FIG. 17
, data electrode
2
is formed along a column direction on back glass substrate
1
. On data electrode
2
, dielectric layer
3
is formed. On dielectric layer
3
, scan electrode
4
and common electrode
11
are formed in the row direction. On scan electrode
4
and common electrode
11
, dielectric layer
13
is formed. In a portion where the electrodes cross with each other, a unit cell is formed. In PDP having such a structure, write discharge
21
(planar discharge) is generated in the intersection of data electrode
2
and scan electrode
4
formed on substrate
1
, and thereafter sustaining discharge
22
(planar discharge) is generated between scan electrode
4
and common electrode
11
. In this case, there is an advantage that the drive method and circuit are simplified, because different electrode pairs cause write discharge
21
and sustaining discharge
22
. Furthermore, there is also an advantage that the life of the non-shown protection layer becomes longer than that of the structure as shown in
FIGS. 15 and 16
.
In the structure shown in
FIG. 17
, there is an advantage in the manufacturing process that all electrodes are formed on one substrate. However, there is a disadvantage that the capacitance between data electrode
2
, scan electrode
4
and common electrode
11
become large and hence the driving load increases. This poses a serious problem especially in large area display panels. Furthermore, since each discharge is of the planar discharge, the problem of the shortened life caused by degradation of a protection layer not easily solved.
On the other hand, in the structure shown in
FIG. 18
, data electrode
2
is formed in a column direction on back glass substrate
1
. On data electrode
2
, dielectric layer
3
is formed. On front glass substrate
10
, scan electrode
4
and common electrode
11
are formed in the row direction. On scan electrode
4
and common electrode
11
, dielectric layer
13
is formed. In PDP having such a structure, write discharge
21
(vertical discharge) is generated between data electrode
2
and scan electrode
4
formed on different substrates via discharge space, and thereafter sustaining discharge
22
(planar discharge) is generated between scan electrode
4
and common electrode
11
. In this case, there is an advantage that the driving method and circuit become simple, because different electrode pairs cause write discharge
21
and sustaining discharge
22
. Furthermore, since data electrode
2
is formed on the back glass substrate
1
side, there i
Hirano Naoto
Nunomura Keiji
Hayes & Soloway P.C.
Mengistu Amare
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