Electric lamp and discharge devices – With gas or vapor – Three or more electrode discharge device
Reexamination Certificate
2000-06-02
2004-09-21
Patel, Ashok (Department: 2879)
Electric lamp and discharge devices
With gas or vapor
Three or more electrode discharge device
C313S336000, C313S583000, C313S584000, C313S585000, C313S586000, C313S587000, C313S590000
Reexamination Certificate
active
06794820
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 driven with a radio frequency that is adapted to reducing a discharge voltage as well as a leakage current between electrodes. Also, the present invention is directed to a method of fabricating the same.
2. Description of the Related Art
Generally, a plasma display panel (PDP) radiates a fluorescent body by an ultraviolet with a wavelength of 147 nm generated during a discharge of He+Xe or Ne+Xe gas 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. The PDP is largely classified into a direct current (DC) driving system and an alternating current (AC) driving system. Since the AC-type PDP has an advantage of a low voltage driving and a long life in comparison to the DC-type PDP, it will be highlighted as the future display device. The AC-type PDP allows an alternating voltage signal to be applied between electrodes having dielectric layer therebetween to generate a discharge every half-period of the signal, thereby displaying a picture. Such an AC-type PDP uses a dielectric material that allows a wall charge to be accumulated on the surface thereof upon discharge.
Referring to
FIG. 1
, the AC-type PDP includes a front substrate
1
provided with a sustaining electrode pair
10
, and a rear substrate
2
provided with address electrodes
4
. The front substrate
1
and the rear substrate
2
are spaced in parallel to each other with having a barrier rib
3
therebetween. A mixture gas, such as Ne−Xe or He−Xe, etc., is injected into a discharge space defined by the front substrate
1
, the rear substrate
2
and a barrier rib
3
. The sustaining electrode pair
10
makes a pair by two within a single of plasma discharge channel. Any one of the sustaining electrode pair
10
is used as a scanning/sustaining electrode that responds to a scanning pulse applied in an address interval to cause an opposite discharge along with the address electrode
4
while responding to a sustaining pulse applied in a sustaining interval to cause a surface discharge with the adjacent sustaining electrodes
10
. Also, the sustaining electrode
10
adjacent to the sustaining electrode used as the scanning/sustaining electrode is used as a common sustaining electrode to which a sustaining pulse is applied commonly. On the front substrate
1
provided with the sustaining electrodes
10
, a dielectric layer
8
and a protective layer
9
are disposed. The dielectric layer a is responsible for limiting a plasma discharge current as well as accumulating a wall charge during the discharge. The protective film
9
prevents a damage of the dielectric layer
8
caused by the sputtering generated during the plasma discharge and improves the emission efficiency of secondary electrons. This protective film
9
is usually made from MgO. At the rear substrate
2
, a dielectric thick film
6
covering the address electrodes
4
is formed and barrier ribs
3
for dividing the discharge space are extended perpendicularly. On the surfaces of the rear substrate
2
and the barrier ribs
3
, a fluorescent material excited by a vacuum ultraviolet lay to generate a visible light is provided.
In such an AC-type PDP, one frame consists of a number of sub-fields so as to realize gray levels by a combination of the sub-fields. For instance, when it is intended to realize 256 gray levels, one frame interval is time-divided into 8 sub-fields Further, each of the 8 sub-fields is again divided into a reset interval, an address interval and a sustaining interval. The entire field is initialized in the reset interval. Cells on which a data is to be displayed are selected by the address discharge in the address interval. The selected cells sustain the discharge in the sustaining interval. The sustaining interval is lengthened by an interval corresponding to 2
n
depending on a weighting value of each sub-field. In other words, the sustaining interval involved in each of the first to eighth sub-fields increases at a ratio of 2
0
, 2
1
, 2
3
, 2
4
, 2
5
, 2
6
and 2
7
. To this end, the number of sustaining pulses generated in the sustaining interval also increases into 2
0
, 2
1
, 2
3
, 2
4
, 2
5
, 2
6
and 2
7
depending on the sub-fields. The brightness and the chrominance of a displayed image are determined in accordance with a combination of the sub-fields.
In the AC-type PDP, a sustaining pulse having a duty ratio of 1, a frequency of 200 to 30 kHz and a pulse width of 10 to 20 &mgr;s is alternately applied to the sustaining electrode pair
10
. The sustaining discharge occurring between the sustaining electrode pair
10
in response to the sustaining pulse is generated only once at an extremely short instance. Charged particles produced by the sustaining discharge moves through a discharge path between the sustaining electrode pair
10
in accordance with the polarity of the sustaining electrode pair
10
to be accumulated on an upper dielectric layer
14
and thus be left into a wall charge. This wall charge lowers a driving voltage during the next sustaining discharge, but it reduces an electric field at a discharge space during the present sustaining discharge. Thus, if a wall charge is formed during the sustaining discharge, then a discharge is stopped. As mentioned above, the sustaining discharge is generated only once at a much shorter instance than a width of the sustaining pulse, and the majority of sustaining discharge time is wasted for a preparation step for the wall charge formation and the next sustaining discharge. For this reason, since the conventional AC-type PDP has a much shorter real discharge interval than the entire discharge interval, it has a low brightness and low discharge efficiency.
In order to solve the above-mentioned low brightness and discharge efficiency problem in the AC-type PDP, there has been suggested a radio frequency PDP, hereinafter referred to as “RFPDP”, for exploiting a radio frequency signal of tens of to hundreds of MHz to cause the sustaining discharge. In the RFPDP, electrons make a vibrating motion within the cell by the radio frequency discharge.
Referring to
FIG. 2
, the RFPDP includes a rear substrate
12
formed in such a manner that an address electrode
14
is perpendicular to the scanning electrode
18
, and a rear substrate
30
formed in such a manner that a radio frequency electrode
28
is parallel to the scanning electrode
18
. Between the address electrode
14
and the scanning electrode
18
, a first lower dielectric layer
16
for insulation between these electrodes is provided. A second lower dielectric layer
20
and a protective film
22
are disposed on the scanning electrode
18
. An upper dielectric layer
29
is formed evenly on the rear substrate provided with the radio frequency electrode
28
, and a rectangular barrier rib
24
is formed thereon. The surface of the rectangular barrier rib
24
is coated with a fluorescent material
26
.
The RFPDP displays a picture by a combination of a number of sub-fields each of which includes a reset interval, an address interval and a sustaining interval. In the reset interval, the entire field is initialized. Next, in the address interval, cells are selected by a discharge between the address electrode
14
and the scanning electrode
18
. The selected cells displays a picture by the vibration motion of electrons in the sustaining interval. At this time, a radio frequency signal of several to tens of MHz is applied to the radio frequency electrode
28
, and a desired level of direct current bias voltage is applied to the scanning electrode. By this radio frequency signal, electrons within the cells make a vibration motion within the discharge space in accordance with the polarity of the radio frequency signal. The vibration motion of electrons successively ion
Kang Jung Won
Kim Oe Dong
Fleshner & Kim LLP
Hodges Matt
LG Electronics Inc.
Patel Ashok
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