Electric lamp and discharge devices – With gas or vapor – Three or more electrode discharge device
Reexamination Certificate
2001-11-27
2004-10-12
Patel, Ashok (Department: 2879)
Electric lamp and discharge devices
With gas or vapor
Three or more electrode discharge device
C313S584000, C313S631000
Reexamination Certificate
active
06803722
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Filed of the Invention
The present invention relates to an AC memory type plasma display panel. More specifically it relates to a plasma display panel for stably generating a writing discharge.
2. Description of the Related Art
A plasma display panel generally contains the following characteristics. A plasma display panel has a thin structure. It hardly generates flickers. It provides a high display contrast. It may have a relatively large screen. It provides a high response speed. It is a self-light-emitting type, and may provide multiple color light emission by means of the phosphor. The uses of plasma display panels have been increasing in the fields of large public display apparatuses and color television sets and the like recently.
The operation type of plasma display panel is classified into two categories: AC discharge type (AC type), which has electrodes covered by a dielectric material, and operates in an indirect AC discharge state; and DC discharge type (DC type), which has electrodes exposed to a discharge space, and operates in a DC discharge state. The AC discharge type is further classified into memory operation type, which uses a memory of a discharge cell, and refresh operation type, which does not use a discharge cell. The luminance of a plasma display panel is approximately proportional to the number of discharges, namely, the number of repetitions of a pulse, whether it is the memory operation type or the refresh operation type. Because the refresh type presents a decrease in luminosity as display capacity increases, it is mainly used for small display capacity applications.
FIG. 1
is an exploded oblique perspective view of a display cell constitution in a standard AC discharge memory operation type plasma display panel.
The plasma display panel is provided with front and rear insulation substrates
1
and
2
made of glass. A transparent scanning electrode
3
and a transparent sustaining electrode
4
are formed on the insulation substrate
2
and are placed in parallel with each other. Bus electrodes
5
and
6
are placed so as to overlap the scanning electrode
3
and the sustaining electrode
4
for reducing electrode resistances. Data electrodes
7
crossing the scanning electrode
3
and the sustaining electrode
4
are formed on the insulation substrate
1
. A discharge gas space
8
is formed between the insulation substrates
1
and
2
where discharge gas containing helium, neon, xenon or the like, or mixed gas thereof is filled. Phosphor layers
9
are formed to convert ultraviolet ray generated by a discharge of the discharge gas into visible light
14
. A dielectric material layer
10
covering the scanning electrode
3
and the sustaining electrode
4
are formed on the insulation substrate
1
. A protection layer
11
made of magnesium oxide or the like and protecting the dielectric material layer
10
from the discharge is formed on the dielectric material layer
10
. A dielectric material layer
12
covering the data electrode
7
is formed on the insulation substrate
2
. Partition walls
13
separating neighboring display cells are formed on the dielectric material layer
12
. The surface of data electrode
7
is covered with the dielectric layer
12
. The partition wall
13
for separating the display cells is provided between the neighboring data electrodes
7
on the dielectric layer
12
. The phosphor layer
9
is applied to the dielectric material layer
12
between the partition walls
13
, and on the side faces of partition walls
13
. The phosphor layer
9
is painted in three primary colors including red, green and blue, and is arranged to display different colors.
FIG. 2
is a vertical section view showing the display cell in the AC discharge memory operation type plasma display panel shown in FIG.
1
.
The following section describes a discharge operation of a selected display cell while referring to FIG.
2
.
When a pulse voltage exceeding a discharge threshold is applied between the scanning electrode
3
and the data electrode
7
of individual display cells to start a discharge, negative and positive electric charges are attracted on the surfaces of dielectric material layers
10
and
12
according to the polarity of pulse voltage, thereby generating electric charge accumulations. An equivalent internal voltage caused by these electric charge accumulations, namely, a wall voltage, has a polarity reverse to the pulse voltage. Thus, because an effective voltage in the cell decreases as the discharge grows, maintaining the pulse voltage to a constant value does not keep the discharge, and the discharge finally stops.
When a discharge starts between the scanning electrode
3
and the data electrode
7
, this discharge triggers a discharge between the scanning electrode
3
and the sustaining electrode
4
if a voltage more than a certain level is applied between the scanning electrode
3
and the sustaining electrode
4
. As the result, electric charge accumulations are generated in the dielectric layer
10
so as to cancel the voltage applied at this moment as the discharge between the scanning electrode
3
and the data electrode
7
.
Then, a sustaining discharge pulse, which has a pulse voltage with a polarity same as the wall voltage, is applied between the scanning electrode
3
and the sustaining electrode
4
, a voltage corresponding to the wall voltage is superimposed as an effective voltage, and the discharge occurs exceeding the discharge threshold when a voltage amplitude of the sustaining discharge pulse is low. Thus, keeping the sustaining discharge pulse applied alternately between the scanning electrode
3
and the sustaining electrode
4
maintains the discharge. This function is the memory function described before.
FIG. 3
is a block diagram showing a constitution of a display apparatus using a plasma display panel where the display cells shown in
FIG. 2
are formed as a matrix arrangement.
A plasma display panel
15
is a panel for dot matrix display where the display cells
16
are arranged as m×n of rows and columns. As row electrodes, scanning electrodes X
1
, X
2
, . . . , Xm and sustaining electrodes Y
1
, Y
2
, . . . , Ym are provided in parallel with one another. As column electrodes, data electrodes D
1
, D
2
, . . . , Dn are arranged in crossing the scanning electrodes and the sustaining electrodes.
A scanning driver
17
applies a scanning electrode drive wave on the scanning electrodes X
1
, X
2
, . . . , Xm. A sustaining driver
18
applies a sustaining electrode drive wave on the sustaining electrodes Y
1
, Y
2
, . . . , Ym. A data driver
19
applies a data electrode drive wave on the data electrodes D
1
, D
2
, . . . , Dn.
A control circuit
20
generates control signals for the individual drivers based on base signals (Vsync, Hsync, Clock, and DATA). The control circuit
20
is provided with a signal processing and memory controller
20
a
for generating control signals for a frame memory and a driver-controller from the base signals, a frame memory
20
b
for storing the DATA signal, which is image data, and a driver-controller
20
c
for generating the control signals for the individual electrode drivers.
FIG. 4
is a timing chart showing driving signal waveforms provided from the scanning driver
17
, the sustaining driver
18
, and the data driver
19
.
Wu indicates a sustaining electrode driving pulse applied commonly on the sustaining electrodes Y, Y
2
, . . . , Ym, Ws
1
, Ws
2
, . . . , Ws
3
indicate scanning electrode driving pulses applied respectively on the scanning electrodes X
1
, X
2
, . . . , Xm, and Wd indicates a data electrode driving pulse applied on a data electrode Di (1≦i≦n) in FIG.
4
.
One cycle of the driving (1 Sub-Field: SF) is composed of a preliminary discharge period, a writing discharge period, a sustaining discharge period, and an erasing discharge period, and repeating them provides a desired video image display.
The preliminary discharge period is a period for generating active particles in the discharge gas sp
Aibara Nobumitsu
Araki Kouta
Hasegawa Hiroshi
Hirano Naoto
Homma Hajime
Hayes & Soloway P.C.
NEC Corporation
Patel Ashok
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