Computer graphics processing and selective visual display system – Plural physical display element control system – Display elements arranged in matrix
Reexamination Certificate
1998-07-15
2003-01-28
Hjerpe, Richard (Department: 2774)
Computer graphics processing and selective visual display system
Plural physical display element control system
Display elements arranged in matrix
Reexamination Certificate
active
06512501
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method and device for driving a plasma display.
Recently, in display devices, there has been activity in increasing the screen size up the display density and improvements in the capability of displaying a variety of information and the flexibility of placement conditions. Examples of such display devices are a plasma display panel (PDP), a cathode-ray tube (CRT), a liquid crystal display (LCD), an electro-luminescence (EL), a fluorescent display tube and a light-emitting diode. The key factor in the above activity in the development of display devices is to increase the display quality.
Particularly, there has been considerable activity in the development of the plasma display panel because it has various advantages such as no flicker noise, easy implementation of a large-size screen, high luminance and long lifetime. The plasma display panel is categorized in a dual-electrode type and a triple-electrode type. The dual-electrode type realizes a selective discharge (address discharge) and a sustain discharge by means of two electrodes. The triple-electrode type realizes the address discharge by using the third electrode. A color plasma display panel capable of realizing gradation display has a mechanism such that a fluorescent substance formed in a discharge cell is excited by a ultraviolet ray created by the discharge. However, there is a disadvantage in that the fluorescent substrate is susceptible to impact of ions of positive charges simultaneously generated by the discharge. The dual-electrode type has an arrangement in which the fluorescent substance is directly hit by the ions, and the lifetime thereof may thus be shortened.
The triple-electrode type utilizing a surface discharge can realize the color plasma display panel in which the above disadvantage is avoided. The triple-electrode type is categorized in a first arrangement and a second arrangement. In the first arrangement, the third electrodes is formed on a substrate on which the first and second electrodes for the sustain discharge are arranged. In the second arrangement, the third electrode is formed on another substrate opposite the substrate on which the first and second electrodes are arranged. The first arrangement is categorized in two types. The first type has the third electrode arranged above the two electrodes for the sustain discharge. The second type has the third electrode arranged under the two electrodes. There are also a transparent type and a reflection type. In the transparent type, visible light emitted from the fluorescent substance is viewed through the fluorescent substance. In the reflection type, visible light is viewed after it is reflected by the fluorescent substance. The cells in which a discharge takes place are spatially isolated from adjacent cells by means of a rib or barrier. The barrier is provided in a first or second arrangement. In the first arrangement, the barrier is provided on the four sides of each discharge cell and completely seals the discharge cell. In the second arrangement, the barrier is arranged only in one direction, spatial couplings in the other directions are implemented by an appropriate distance between the electrodes, in other words, an appropriate gap therebetween.
The present invention is concerned with the plasma display panels.
2. Description of the Related Art
The present specification is exemplarily directed to a plasma display panel having the following arrangement. The first and second electrodes for the sustain electrode are formed on a first substrate, and the third electrode is formed on a second subatrate opposite the first substrate. The barrier is formed only in the vertical direction, which is orthogonal to the first and second electrodes and is parallel to the third electrode. The sustain electrodes partially have a transparent electrode.
FIG. 1
is a schematic plan view of a plasma display panel having the above arrangement (which can be called a triple-electrode surface-discharge AC type plasma display panel).
FIG. 2
schematically shows a vertical section of the plasma display panel, and
FIG. 3
schematically shows a horizontal section thereof.
FIGS. 2 and 3
show only one discharge cell.
The plasma display panel is generally formed of two glass plates. A front glass plate
18
is equipped with X electrodes
13
and Y electrodes
14
, which function as sustain electrodes
19
extending in parallel. Each of the X electrodes
13
and the Y electrodes
14
is made up of a transparent electrode
19
a
and a bus electrode
19
b.
The transparent electrode
19
a
has a role of allowing reflected light coming from a fluorescent substance
17
to pass therethrough. In this regard, the transparent electrode
19
a
is formed of ITO (which a transparent conductive film having a main component of indium oxide). The bus electrode
19
b
is required to have a relatively low resistance in order to prevent occurrence of a voltage drop, and is thus made of, for example, Cr or Cu. The sustain electrodes
19
are covered by a dielectric layer (glass layer)
20
. A MgO film
21
serving as a protection film is formed on a discharge surface of the dielectric layer
20
.
A back glass plate
16
is opposite the front glass plate
18
. Address (opposing) electrodes
15
are provided oan the back glass plate
16
so that the address electrodes
15
are orthogonal to the sustain electrodes
19
. Barriers
11
are respectively provided between the address electrodes
15
. The fluorescent substances
17
each having the red, green and blue light emitting performance are respectively provided between the barriers
11
so that the fluorescent substances
17
cover the respective address electrodes
15
. The glass plates
16
and
18
are assembled into a unit so that the tops of the barriers
11
tightly contact the MgO film
21
.
FIG. 4
is a waveform diagram of a conventional electrode driving operation on the plasma display panel shown in
FIGS. 1 through 3
. More particularly,
FIG. 4
shows one subfield period in a conventional “address period/sustain discharge period separation type write address system”.
In the example shown in
FIG. 4
, one subfield is segmented into a reset period, an address period and a sustain discharge period. During the reset period, all the Y electrodes Y
1
−Y
N
are reset to 0 V, and simultaneously a whole screen write pulse of a voltage Vs+Vw (approximately equal to 330 V) is applied to the X electrodes. Hence, irrespective of the previous display state, all cells of all display lines are discharged. The potentials of the address electrodes at that time are approximately equal to 100 V (Vaw). Next. the potentials of the X electrodes and the address electrodes are changed to 0 V, a discharge is started in all the cells in such a way that the voltage of the wall charge itself exceeds a discharge starting voltage. In the above discharge, the wall charge is not formed because there is no potential difference between the electrodes. Hence, the space charge is self-neutralized and the discharge is ceased. That is, the self-erase discharge occurs. By the self-erase discharge, all the cells in the panel are changed to an even state having no wall charge. The reset period functions to set all the cells to the even state irrespective of the lighting states of the calls during the previous subfield. Hence, the next address (write) discharge can stably be caused.
In the address period subsequent to the reset period, the address discharge is caused in line-sequential formation in order to turn ON or OFF of the cells in accordance with display data. First, a scan pulse of a −Vy level (approximately equal to −150 V) is serially applied to the Y electrodes, and an address pulse of a voltage Va (approximately equal to 50 V) is selectively applied to address electrodes required to cause the sustain discharge, that is, the address electrodes corresponding to cells to be lighted. Hence, a discharge occurs between the address electrode and
Hirose Tadatsugu
Kameyama Shigeki
Kaneko Keiichi
Kishi Tomokatsu
Nagaoka Keishin
Fujitsu Limited
Hjerpe Richard
Laneau Ronald
Staas & Halsey , LLP
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