Plasma display panel

Details Plasma display panel Plasma display panel

2001-12-21

2004-04-13

Wong, Don (Department: 2821)

Electric lamp and discharge devices: systems

Plural power supplies

Plural cathode and/or anode load device

C315S169400

Reexamination Certificate

active

06720736

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a plasma display panel, and more particularly to a plasma display panel that is capable of improving its discharge efficiency and brightness.
2. Description of the Related Art
Generally, a plasma display panel (PDP) radiates a fluorescent body by an ultraviolet ray generated during a gas discharge to thereby display a picture including characters and graphics. Such a PDP is easy to be made into a thin-film and large-dimension type. Moreover, the PDP provides a very improved picture quality owing to a recent technical development.
Referring to
FIG. 1
, a conventional three-electrode, AC surface-discharge PDP includes a scanning electrode Y and a sustaining electrode Z provided on an upper substrate
10
, and a data electrode X provided on a lower substrate
18
.
The scanning electrode Y and the sustaining electrode Z have transparent electrodes
12
Y and
12
Z with a large width and metal bus electrodes
13
Y and
13
Z with a small width, respectively, and are formed on the upper substrate in parallel. An upper dielectric layer
14
and a protective film
16
are disposed on the upper substrate
10
in such a manner to cover the scanning electrode Y and the sustaining electrode Z. Wall charges generated upon plasma discharge are accumulated in the upper dielectric layer
14
. The protective film
16
prevents a damage of the upper dielectric layer
14
caused by a sputtering during the plasma discharge and improves the emission efficiency of secondary electrons. This protective film
16
is usually made from magnesium oxide (MgO). The data electrode X Is perpendicular to the scanning electrode Y and the sustaining electrode Z.
A lower dielectric layer
22
and barrier ribs
24
are formed on the lower substrate
18
. The surfaces of the lower dielectric layer
22
and the barrier ribs
24
are coated with a fluorescent material layer
26
. The barrier ribs
24
separate adjacent discharge spaces in the horizontal direction to thereby prevent optical and electrical crosstalk between adjacent discharge cells. The fluorescent layer
26
is excited by an ultraviolet ray generated during the plasma discharge to generate any one of red, green and blue visible light rays. An inactive mixture gas of He+Xe, Ne+Xe or He+Xe+Ne is injected into a discharge space defined between the upper and lower substrate
10
and
18
and the barrier rib
24
.
Discharge cells of such a PDP are arranged at a panel
30
in a matrix pattern as shown in FIG.
2
. The scanning electrodes Y
1
to Ym and the sustaining electrodes Z
1
to Zm arranged in parallel cross the data electrodes X
1
to Xn at each discharge cell.
Such a PDP drives one frame, which is divided into various sub-fields having a different discharge frequency, so as to realize gray levels of a picture. Each sub-field is again divided into a reset interval for uniformly causing a discharge, an address interval for selecting the discharge cell and a sustaining interval for realizing the gray levels depending on the discharge frequency.
For instance, when it is intended to display a picture of 256 gray levels, a frame interval equal to {fraction (1/60)} second (i.e. 16.67 msec) is divided into 8 sub-fields SF
1
to SF
8
as shown in FIG.
3
. Each of the 8 sub-fields SF
1
to SF
8
is again divided into a reset interval, an address interval and a sustaining interval. The reset interval and the address interval of each sub-field are equal every sub-field. The address discharge for selecting the cell is caused by a voltage difference between the data electrode X and the scanning electrode Y. The sustaining interval is increased at a ration of 2
n
(wherein n=0, 1, 2, 3, 4, 5, 6 and 7) at each sub-field. A sustaining discharge frequency in the sustaining interval is controlled at each sub-field in this manner, to thereby realize a gray scale required for a picture display. The sustaining discharge is generated by a high voltage of pulse signal applied alternately to the scanning electrode Y and a sustaining electrode z.
FIG. 4
illustrates driving waveforms: the three-electrode PDP.
Referring to
FIG. 4
, in the reset interval, signals of square wave or ramp wave type (not shown) are supplied at least once to the sustaining electrode Z or the scanning electrodes Y
1
to Ym to simultaneously discharge the discharge cells of the entire screen. Uniform wall charges are accumulated within the cells of the entire screen by the discharge during the reset interval.
In the address interval, a scanning pulse Sp with a negative polarity is sequentially applied to the scanning electrodes Y
1
to Ym and a data pulse Vd synchronized with the scanning pulse Sp is applied to the data electrode X. An address discharge is generated at the discharge cell supplied with the data pulse Vd.
In the sustaining interval, a sustaining pulse Vs are alternately applied to the scanning electrode Y and the sustaining electrode Z. Then, the discharge calls selected by the address discharge generates a sustaining discharge continuously whenever the sustaining pulse Vs is applied.
Since such a three-electrode FDP has the scanning electrode Y and the sustaining electrode Z positioned at the upper center of the discharge space, it has a low utility of the discharge space. For this reason, in the three-electrode PDP, a voltage for causing a sustaining discharge and a power consumption are high while discharge and light-emission efficiencies daring the sustaining discharge are low. More specifically, the sustaining discharge takes a surface discharge between the scanning electrode Y and the sustaining electrode Z. However, since the scanning electrode Y and the sustaining electrode Z concentrate at the center of the cell to lower a discharge-initiating voltage, a discharge path becomes short to cause low discharge and light-emission efficiencies. When a distance between the scanning electrode Y and the sustaining electrode is enlarged so as to enhance the efficiencies, a discharge-initiating voltage becomes high in proportional to a distance between the two electrodes.
In order to solve the problems of the three-electrode PDP, there has been suggested a five-electrode PDP in which an electrode for causing a sustaining discharge is divided into four electrodes,
Referring to
FIG. 5
, the conventional five-electrode PDP includes a pair of trigger electrodes TY and TZ provided on an upper substrate
34
in such a manner to be positioned at the center of a discharge cell, a pair of sustaining electrodes SY and SZ provided on the upper substrate
34
in such a manner to have the pair of trigger electrodes TY and TZ therebetween and to be positioned at the edge of the discharge cell, and a data electrode X provided at a lower substrate
40
in such a manner to be perpendicular to the trigger electrodes TY and TZ and the sustaining electrodes SY and SZ.
The pair of trigger electrodes TY and TZ and the pair or sustaining electrodes SY and SZ include transparent electrodes having a large width and metal bus electrodes having a small width, respectively, and are formed on the upper substrate
34
in parallel. The pair of trigger electrodes TY and TZ are set to have a small distance Ni between the electrodes.
The pair of sustaining electrodes SY and SZ are set to have a large distance Wi between the electrodes. The pair of sustaining electrodes SY and SZ causes a long-path discharge by utilizing space charges and wall charges formed by a discharge between the pair of trigger electrodes TY and TZ.
An upper dielectric layer
36
and a protective film
38
are disposed on the upper substrate
34
in such a manner to cover the pair of trigger electrodes TY and TZ and the pair of sustaining electrodes SY and SZ, Wall charges generated upon plasma discharge are accumulated in the upper dielectric layer
36
. The protective Film
38
prevents a damage of the upper dielectric layer
36
caused by a sputtering during the plasma discharge and improves the emission efficiency of secondary electron

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