Computer graphics processing and selective visual display system – Plural physical display element control system – Display elements arranged in matrix
Reexamination Certificate
2001-07-02
2004-09-21
Hjerpe, Richard (Department: 2673)
Computer graphics processing and selective visual display system
Plural physical display element control system
Display elements arranged in matrix
C345S061000, C345S062000, C345S063000, C345S064000, C345S065000, C345S066000, C345S067000, C345S068000, C315S169100, C315S169200, C315S169300, C315S169400, C315S306000, C315S313000, C315S336000
Reexamination Certificate
active
06795044
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a plasma display panel performing an AC discharge type matrix display and a driving method thereof.
2. Description of the Related Art
A first prior art of a conventional plasma display panel and a driving method thereof will be described, referring to the drawings.
FIG. 1
is a partially cross sectional view illustrating the conventional plasma display panel. In the plasma display panel, two isolation substrates
1
a
and
1
b
of a front surface and a rear surface made of glass are provided.
On the isolation substrate
1
a
, transparent scanning electrodes
2
and sustaining electrodes
3
are formed, and trace electrodes
4
are arranged to overlap the scanning electrodes
2
and the sustaining electrodes
3
in order to make the resistance values of the electrodes be lowered. Also, a first dielectric layer
9
is formed to cover the scanning electrode
2
and the sustaining electrode
3
, and a protective layer
10
made of magnesium oxide or the like is formed to protect the dielectric layer
9
from discharge.
On the isolation substrate
1
b
, data electrodes
5
that are extended in perpendicular to the scanning electrodes
2
and the sustaining electrodes
3
are formed. Also, a second dielectric layer
11
is formed to cover the data electrode
5
. On the dielectric layer
11
, a partition wall
7
extended in the same direction as that of the data electrode
5
is formed to partition a display cell that is a unit of display. Moreover, on the side surface of the partition wall
7
and the surface of the dielectric layer
11
on which the partition wall
7
is not formed, a fluorescent layer
8
is formed to transform ultraviolet light generated by discharging of discharge gas into visible light.
A space sandwiched between the isolation substrates
1
a
and
1
b
and partitioned by the partition wall
7
becomes a discharge space
6
filled by discharge gas consisting of helium, neon, xenon, and the like, or mixture of gases thereof.
In the above-configured plasma display panel, surface discharge
100
is generated between the scanning electrode
2
and the sustaining electrode
3
.
FIG. 2
is a schematic diagram illustrating an electrode arrangement of the conventional plasma display panel. One display cell
12
is provided on the intersection of one scanning electrode
2
, one sustaining electrode
3
, and one data electrode
5
, which is in perpendicular to the electrodes. The scanning electrode
2
is connected to a scan driver integrated circuit IC (not shown) so as to individually apply a scan voltage pulse. Since the sustaining electrode
3
applies only a common waveform, it is all electrically commonly connected on the end portion of the panel or driving circuit.
Subsequently, the selective display operation of the display cell will be described.
FIG. 3
is a timing chart illustrating a voltage pulse applied to each electrode. In
FIG. 3
, a period A is a pre-discharge period for easily generating discharge, a period B is a selecting operation period for selecting ON/OFF of display of each display cell, a period C is a sustaining discharge period for performing display discharge in all the selected display cells, and a period D is a sustaining erasing period for stopping display discharge.
First, in the pre-discharge period A, with applying a voltage exceeding a discharge start threshold voltage between the scanning electrode
2
and the sustaining electrode
3
, discharge is generated in all the display cells
12
so that wall charge is formed. After that, with using weak discharge due to a dull pulse, wall charge formed on the scanning electrode
2
and the sustaining electrode
3
is neutralized and erased.
Subsequently, in the selecting operation period B, with sequentially applying a scan pulse to each scanning electrode
2
and simultaneously applying a data pulse to the data electrode
5
in accordance with an image data, wall charge is formed only on the scanning electrode
2
of the display cell
12
to perform display.
After that, in the sustaining discharge period C, sustaining pulses having inverted phases with each other are applied to all the scanning electrodes
2
and all the sustaining electrodes
3
. As a result, discharge for display is generated only in the display cell
12
in which the wall charge is formed during the selecting operation period B.
In the sustaining erasing period D, the wall charge is neutralized and erased by a dull pulse, thereby returning to the initial state.
In the practical plasma display driving, a period from the above-mentioned pre-discharge period A or the selecting operation period B to the sustaining erasing period D has been one sub-field, a combination of a plurality of sub-fields in which the number of pulses is changed in the sustaining discharge period C has been one field, and display brightness has been regulated with selection of ON/OFF of each sub-field. At this time, sub-field selection state for input gradation is determined referring to a lookup table (LUT). In the LUT, the sub-field selection state for all the input gradation is uniquely described.
In addition, as described above, in a manner that the sustaining period when only sustaining discharge is performed is independent of other periods, brightness can be controlled by means of changing a cycle of sustaining pulse applied in the sustaining discharge period C, and high brightness can be achieved by means of supplying high frequency.
Subsequently, a second prior art of a conventional display penal and a driving method thereof will be described.
FIG. 4
is a schematic diagram illustrating an electrode arrangement in a conventional plasma display panel having an electrode structure in which a scanning electrode is shared between upper and lower adjacent display cells. Each discharge space of two display cells
12
sharing the scanning electrode
2
is physically separated by a partition wall (not shown in
FIG. 4
) formed on the scanning electrode
2
. The plasma display panel having such a structure is disclosed, for example, in Japanese Patent No. 2629944.
FIG. 5
is a timing chart illustrating the conventional driving method disclosed in Japanese Patent No. 2629944. In the interval of the sustaining pulse, a pre-discharge pulse and a selective erasing pulse are sequentially applied to a scanning electrode Y, and the pre-discharge pulse is selectively applied to a sustaining electrode X in the upper and lower lines so that the upper and lower display lines are individually selected.
Also, a plasma display panel (a third prior art) having a structure in which display cells are divided into a plurality of blocks and a plurality of scanning electrodes are shared in the blocks is disclosed in Japanese Patent Laid-Open No. 2000-56731. In the conventional plasma display panel, an erasing selection is adapted in the same manner as that of the above-mentioned Japanese Patent No. 2629944.
In the conventional plasma display panel shown in the first prior art, because each scanning electrode
2
is individually selected, the output terminals of scan driver IC are needed as the same number as the scanning electrodes
2
(that is, the number of display lines). On the other hand, because high withstand voltage and high speed of response are needed for the scan driver IC, its price is high so that its using quantity needs to be reduced in order to cut down cost.
Also, in the conventional plasma display panel shown in the second prior art, the number of scanning electrodes
2
is reduced by half with respect to the number of display lines so that the number of scan drivers IC can be reduced by half. However, there are problems in the driving method disclosed in Japanese Patent No. 2629944, as follows.
Firstly, two kinds of pulses of a pulse Vwy for illuminating all the display cells on the display lines and a pulse Vey for selecting the display cells need to be sequentially applied to the scanning electrode. And, in the practical driving, a pulse for stopping discharge
Homma Hajime
Nakamura Tadashi
Tanaka Yoshito
Hjerpe Richard
Lesperance Jean
NEC Corporation
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