Computer graphics processing and selective visual display system – Plural physical display element control system – Display elements arranged in matrix
Reexamination Certificate
1996-10-16
2001-09-25
Luu, Matthew (Department: 2672)
Computer graphics processing and selective visual display system
Plural physical display element control system
Display elements arranged in matrix
C345S067000
Reexamination Certificate
active
06295040
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to electrode structure of a plasma display panel, referred to hereinafter as a PDP, and its driving method.
2. Description of the Related Arts
PDP is a thin display device of self-luminescent type which allows a high-speed display so as to suit the television.
AC type color A PDPs of a surface discharge type have been popularly employed, resulting in a rapid increase in application od PDP's. Accordingly, there has been required further improvement of the picture quality, such as 256 gradations, so as to achieve large screens of High-Definition TV and computer display, etc.
An electrode matrix of an AC type surface-discharge PDP is composed of plural pairs of first and second sustain electrodes X & Y extending in a first direction of display lines and address electrodes A extending in a second direction of rows orthogonal display lines, respectively, as shown in FIG.
1
.
The sustain electrode pairs are provided on a first substrate of a substrate pair which composes the panel envelope. A space S
1
between the first and second sustain electrodes Xn & Yn, referred to hereinafter as a discharge slit, constitutes respective lines. The suffix n indicates the electrodes are of the n-th line. However, the suffix n may be hereinafter omitted unless the line must be specifically distinguished from the adjacent line, for the explanation.
Both the sustain electrodes are covered with a dielectric layer extending along the entire screen so as to be insulated from a discharge space formed between the first and second substrates.
A single cell C is formed at the intersection of each discharge slit and each address electrode, including the vicinity of the intersection. The cell C is a single unit luminous area.
A memory effect of each cell is utilized to maintain, i.e. to sustain, the lighting state of the cell.
AC type PDPs are constituted so as to possess structurally the memory function by covering the display electrodes with the dielectric layer.
In operating the AG type PDPs, after the wall charges are accumulated only on the above-mentioned dielectric layer of the cell which should light according to the data of the display, voltages of alternating polarity, i.e, sustain voltages, are applied commonly across the cells. This sustain discharge is the surface discharge along the surface of the above-mentioned dielectric layer.
The sustain voltage is lower than the firing voltage between the sustain electrodes. In the cells having the wall charges, a voltage generated by the wall charge is superposed onto the sustain voltage, therefore, an effective voltage, referred to hereinafter a cell voltage, across the cell exceeds the firing voltage so that a discharge is caused therein.
The wall charges having the polarity opposite from the previous state accumulate, after the previous wall charges disappear once in the discharge. Therefore, each time the sustain voltage is alternately applied, the discharge takes place. When the application cycle of the sustain voltages is shortened, a visually continuous lighting state is achieved.
FIG. 2
schematically illustrates an internal structure of a typical prior art PDP of the surface discharge type. In PDP
90
, a plurality of pairs of first and second sustain electrodes
93
&
94
are arranged on the inner surface of a front glass substrate
91
so as to extend along the direction of the lines of the display matrix, that is in the direction vertical (i.e., perpendicular) to the sheet of FIG.
2
.
A space between the electrode pair, that is a discharge slit, forms a single line. These matters will be described later in detail.
There is provided a dielectric layer
96
so as to insulate sustain electrodes
93
&
94
from discharge space
99
. A protection film
97
is deposited on the surface of dielectric layer
96
. Dielectric layer
96
and protection film
97
are both transparent.
On the other hand, in the inner surface of back glass substrate
92
, address electrodes
95
are arranged orthogonal to sustain electrodes
93
&
94
. A fluorescent layer
98
is provided so as to cover back glass substrate
92
and the surface of address electrodes
95
. The fluorescent layer thus located far from the surface discharge can decrease the deterioration of the fluorescent layer caused from ion bombardment thereto.
The address electrodes are arranged generally on the substrate of the side where the fluorescent layer is coated, in order to avoid an increase in the electric power consumption caused from stray capacitance between the sustain electrodes and the address electrodes.
The first sustain electrode
93
is composed of a belt of a metal film
932
narrower than a belt of a transparent conductive film
931
. The second sustain electrode
94
is similarly composed of a belt of a metal film
942
narrower than the belt of a transparent conductive film
941
. Metal films
932
&
942
are supplementary conductors to accomplish good electrical conductivity, and are stacked on an edge of a side apart from the surface discharge slit between transparent conductive films
931
&
941
, respectively.
In a display operation of PDP
90
, addressing operation is usually performed sequentially in the order of the lines. In lighting a certain cell, the address electrodes
95
and the second sustain electrodes
94
associated with respective cells are appropriately biased so as to cause an opposing discharge in the direction of the thickness of the panels so that the wall charges are accumulated on the surface of dielectric layer
96
, where protection film
97
is assumed to be a part of dielectric layer
98
.
When the cell is not to be lit, the voltage of each electrode is set so as to not cause the opposing discharge with address electrodes
95
. After the address period in which lighting
on-lighting of the cell is thus set, the sustain voltages are applied between the first and the second sustain electrodes
94
and
93
so that the polarity of the voltages applied between these sustain electrodes may change alternately, whereby the surface discharge takes place along the dielectric layer ever the discharge slit upon each transition of the applied voltages.
Fluorescent layer
98
is partially excited by ultraviolet rays UV generated by the discharge so as to radiate a visible light of a predetermined color. Among these visible lights the light that has penetrated through front glass substrate
91
becomes a display light.
Lighting efficiency can be improved by expanding the surface discharge area while suppressing the shading of the display light to the minimum, by constituting first and the second sustaining electrode
93
&
94
located on the front side of discharge space
99
with the above-described layered structure.
A part, in the line direction, or discharge slit S
1
is a surface discharge gap. The width or discharge slit S
1
, that is a size in a direction perpendicular from sustain electrode
93
&
94
, is selected so that a surface discharge may be properly caused by an application of a driving voltage of 100 to 200 V.
On the other hand, a slit S
2
between an n-th second sustain electrode
93
and the nest n+1 th first sustain electrode
94
of the adjoining line is called “a reverse slit”; and the width of reverse-slit
62
is selected so wider enough than that of discharge slit
81
that no discharge is generated across reverse-slit S
2
. Each line can be selectively discharged by thus providing discharge slit S
1
and reverse-slit S
2
in the arrangement of the first and second sustaining electrodes
93
&
94
.
The opposing discharge, referred to herein after
95
an address discharge, in the addressing operation is initiated between address electrode
95
and the second metal film
942
of second sustain electrode
94
, and then, as the wall charges accumulate upon the surface or insulating layers
96
and
97
, shifts to a discharge between address electrode
95
and second transparent conductive film
941
.
The address discharge terminates when th
Kondo Nobuyoshi
Nhan Nguyen Thanh
Fujitsu Limited
Luu Matthew
Staas & Halsey , LLP
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