Computer graphics processing and selective visual display system – Plural physical display element control system – Display elements arranged in matrix
Reexamination Certificate
1999-03-03
2002-12-03
Chow, Dennis-Doon (Department: 2775)
Computer graphics processing and selective visual display system
Plural physical display element control system
Display elements arranged in matrix
C345S060000, C345S068000
Reexamination Certificate
active
06489939
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a technology for driving a display panel including a group of cells as display devices having a memory function, and more particularly to a method for driving a plasma display panel and an apparatus for driving the same which are directed to an improvement in the contrast of an alternating current (AC) type plasma display panel. (Generally, the whole plasma display apparatus inclusive of the plasma display panel and peripheral circuits is referred to as a “PDP”.)
The AC type plasma display panel sustains discharge and carries out light emission display by alternately applying voltage waveforms of a plurality of pulses to two electrodes for sustaining this discharge. A discharge (lighting) operation for every discharge period finishes within a few micro-seconds (&mgr;s) after the application of pulses. The ions defined as positive electric charges that are generated by this discharge operation are accumulated over an insulating layer on the electrode to which a negative voltage is applied, and electrons defined as negative electric charges are similarly accumulated over an insulating layer on the electrode to which a positive voltage is applied.
Therefore, if wall charges are first generated by causing the discharge by the pulses (write pulses) each having a relatively high voltage (write voltage) and then the pluses (sustain discharge pulses, that is, sustain pulses) each having a voltage lower than that of each of the write pulses (sustain discharge voltage) and an opposite polarity to each of the write pulses are applied to the electrodes, electric charges generated by the sustain pulses are superimposed on the wall charges previously accumulated by the write pulses so as to enhance the accumulated wall charges. As a result, the potential of the wall charges with respect to a discharge space becomes large and, at least, the above voltage exceeds a discharge threshold voltage at which the discharge starts. In other words, given cells that once effected the write discharge and have formed the wall charges have the characteristics that these cells sustain the discharge when the sustain discharge pulses are alternately applied thereto in opposite polarities. A phenomenon having the above characteristics is referred to as a “memory effect” or “memory drive”. The AC type plasma display panel carries out the display by utilizing this memory effect.
2. Description of the Related Art
The AC type plasma display panels can be classified into a two-electrode type which effects selective discharge (addressing discharge) and the sustain discharge by using two electrodes and a three-electrode type which effects addressing discharge by using a third electrode. In color plasma display panels for carrying out multi-gradation display, a phosphor inside the cells is excited by ultra-violet rays generated due to the discharge between different kinds of electrodes, but this phosphor involves the problem that it is extremely fragile against the impact of the ions defined as the positive charges that are generated simultaneously by the discharge. The former two-electrode type plasma display panel described above employs the construction in which the ions are allowed to collide directly with the phosphor and for this reason, the life of the phosphor is likely to become shortened. To avoid this problem, therefore, the latter three-electrode type plasma display panel utilizing a surface-discharge (that is, surface-discharge type plasma display panels) which is carried out between different electrodes that are located in the same plane, has been generally used in color plasma display panels.
Recently, an interlace system three-electrode type AC plasma display panel which is capable of providing a high definition display screen by reducing the pixel pitch (i.e., a space between adjoining cells) has recently attracted special attention. The method for driving the plasma display panel according to the prior art, etc, will be explained hereby with reference to
FIGS. 1
to
9
that will be mentioned in the later-appearing “BRIEF DESCRIPTION OF THE DRAWINGS” in order to have the plasma display panel and its driving method according to the prior art more easily understood. The conventional method for driving the interlace system plasma display panel, etc, is typically described in Japanese Unexamined Patent Publication No. 9-160525 and No. 10-207417 corresponding to Japanese Patent Application No. 9-12700 filed on Jan. 27, 1997 by the same applicant (Fujitsu) as for the present invention. Such a driving method is referred to as the “Alis” (Alternate Lighting of Surfaces) method.
In a plasma display panel
10
having a schematic construction of a conventional surface-discharge type plasma display panel shown in
FIG. 1
, pixels are represented by dotted lines for only the display line (display row) L
1
. To simplify the explanation, the number of pixels of the plasma display panel
10
is assumed hereby as 6×8=48 in terms of the monochromatic pixels. Incidentally, the present invention can be applied to both color display and monochromatic display, and one pixel of the color display corresponds to three pixels of the monochromatic display.
In order to facilitate the production of the plasma display panel and to provide high definition by reducing the pixel pitch, the plasma display panel
10
employs the construction in which the partitions in the row direction are removed from the conventional plasma display panels. To prevent the occurrence of the erroneous discharge due to influences between the adjacent display lines resulting from the removal of the partition, interlace scanning is carried out so that the voltage waveforms of the sustain pulses have mutually opposite phases between the odd-numbered rows and the even-numbered rows of the electrodes for surface-discharge as will be described later.
In
FIGS. 2 and 3
, a perspective view showing the state in which the opposing gap between the color pixels
10
a
of the plasma display panel shown in
FIG. 1
is expanded and a longitudinal sectional view along a sustain electrode X
1
of the color pixel
10
a
, is illustrated, respectively.
In
FIGS. 2 and 3
, transparent electrodes
121
and
122
of an ITO film, or the like, are disposed in parallel with each other on one of the surfaces of a glass substrate
11
, and metal electrodes
131
and
132
of copper (Cu), or the like, are formed along the center line on the transparent electrodes
121
and
122
in order to reduce the voltage drop in the longitudinal direction of the transparent electrodes
121
and
122
, respectively. The transparent electrode
121
and the metal electrode
131
together constitute the sustain electrode X
1
while the transparent electrode
122
and the metal electrode
132
together constitute the scan electrode Y
1
. A dielectric member
14
for retaining the wall charges is deposited on the glass substrate
11
and the electrodes X
1
and Y
1
, and an MgO protective film
15
is further deposited on the dielectric member
14
.
Address electrodes A
1
, A
2
and A
3
and partitions
171
to
173
for partitioning these address electrodes are formed on the surface of the glass substrate
16
that opposes the MgO protective film
15
in the direction orthogonally crossing the sustain electrode X
1
and the sustain electrode Y
1
. These partitions define discharge cells (which are also referred to merely as the “cells” or “slits”) in the regions where the addressing electrodes cross the sustain electrodes and the scan electrodes. A phosphor
181
emitting red light, a phosphor
182
emitting green light and a phosphor
183
emitting blue light when ultraviolet rays generated by the discharge are incident to them are deposited between the partitions
171
and
172
, between the partitions
172
and
173
and between the partitions
173
and
174
, respectively. A Ne+Xe Penning mixed gas, for example, is sealed into the discharge space between these phosphors
181
to
183
and
Asao Shigeharu
Kanazawa Yoshikazu
Setoguchi Noriaki
Chow Dennis-Doon
Fujitsu Limited
Staas & Halsey , LLP
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