Electric lamp and discharge devices – With gas or vapor – Three or more electrode discharge device
Reexamination Certificate
1999-11-02
2003-08-12
Patel, Vip (Department: 2879)
Electric lamp and discharge devices
With gas or vapor
Three or more electrode discharge device
C313S586000, C313S484000, C315S169300
Reexamination Certificate
active
06605897
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a plasma display device, and more particularly to a plasma display panel that is capable of improving the discharge efficiency using a direct current discharge and a radio frequency discharge. Also, the present invention is directed to a method of driving the same.
2. Description of the Related Art
Recently, a plasma display panel(PDP) feasible to the fabrication of large-scale panel has been available for a flat panel display device. The PDP controls a discharge interval of each pixel to display a picture. Such a PDP is classified into a direct current(DC) type and an alternating current(AC) type in accordance with its electrode structure. An electrode is directly exposed to a discharge gas in the case of a DC-type PDP while an electrode is indirectly exposed through a dielectric material in the case of an AC-type PDP.
Referring to
FIG. 1
, there is shown a discharge cell structure arranged in a matrix pattern in an AC-type PDP with three electrodes. The PDP discharge cell includes an upper plate having a sustaining electrode pair
12
A and
12
B formed on an upper substrate
10
sequentially, an upper dielectric layer
14
and a protective film
16
, and a lower plate having an address electrode
20
formed on a lower substrate
18
sequentially, a lower dielectric layer
22
, a barrier rib
24
and a fluorescent layer
26
. The upper substrate
10
is spaced from the lower substrate
18
by the barrier rib
24
. The sustaining electrode pair
12
consists of a scanning/sustaining electrode and a sustaining electrode. A scanning signal for a panel scanning and a sustaining signal for a discharge sustaining are applied to the scanning/sustaining electrode while a sustaining signal is applied to the sustaining electrode. A charge is accumulated in the upper dielectric layer
14
and the lower dielectric layer
22
. The protective film
16
prevents a damage of the upper dielectric layer
14
caused by the sputtering to prolong a life of the PDP as well as to improve an emission efficiency of secondary electrons. Usually, MgO is used as the protective film
16
. The address electrode
20
is crossed with the sustaining electrode pair
12
. Data signals for selecting cells to be displayed are applied to the address electrode
20
. The barrier rib
24
is formed in parallel to the address electrode
20
. The barrier rib
24
prevents an ultraviolet ray produced by the discharge from being leaked into the adjacent discharge cells. The fluorescent layer
26
is coated on the surface of the lower dielectric layer
22
and the barrier rib
24
to generate any one of red, green and blue visible lights. An inactive gas for a gas discharge is sealed into the inner discharge space.
After the PDP discharge cell with such a structure was selected between the address electrode
20
and the scanning/sustaining electrode, it sustains the discharge by a surface discharge between the sustaining electrode pair
12
. The fluorescent body
26
is luminous by an ultraviolet generated during the sustaining discharge at the PDP discharge cell and hence a visible light is emitted into the exterior of the discharge cell. As a result, the PDP including the discharge cells displays a picture. In this case, the PDP controls a discharge-sustaining interval, that is, a sustaining discharge frequency of the cell to implement a gray scale required for an image display. In this respect, the sustaining discharge frequency becomes an important factor determining the brightness and a discharge efficiency of the PDP. For the sake of such a sustaining discharge, a sustaining pulse having a duty ratio of 1, a frequency of 200 to 300 kHz and a width of about 20 &mgr;s are alternately applied to the sustaining electrode pair
12
A and
12
B. In response to the sustaining pulse, the sustaining discharge generates only one time at an extremely short instant per sustaining pulse. Charge particles generated by the sustaining discharge move a discharge path formed between the sustaining electrode pair
12
A and
12
B depending on the polarity of the sustaining electrode pair
12
A and
12
B to thereby form a wall charge on the surface of the upper dielectric layer
14
. This wall charge cancels a voltage applied between the sustaining electrode pair
12
A and
12
B to reduce a discharge voltage loaded in the discharge space, thereby stopping the sustaining discharge. As described above, the sustaining discharge is generated only once at an extremely shorter instant than a width of the sustaining pulse. Most of the remaining time is wasted for a preparation step for the formation of wall charge and the next sustaining discharge. For this reason, since the conventional PDP has a very short real discharge interval compared with the entire discharge interval, it has low brightness and low discharge efficiency. Referring now to
FIG. 2
, there is shown the structure of a discharge cell arranged in a matrix pattern in a DC-type PDP. The DC-type discharge cell includes a cathode
30
formed on an upper substrate
10
, an anode
32
and an auxiliary anode
34
each formed on a lower substrate
18
, and a barrier rib
24
formed between the upper substrate
10
and the lower substrate
18
to provide a main discharge space
31
and an auxiliary discharge space
33
. The DC-type discharge cell consists of a main discharge cell provided with the main discharge space
31
and an auxiliary discharge cell provided with the auxiliary discharge space
33
. Charged particles produced at the auxiliary discharge cell are introduced into the main discharge cell to cause a display discharge at the main discharge cell. The barrier rib
24
is formed in a lattice structure to prevent a mis-discharge between the adjacent cells caused by a diffusive movement of the charge particles generated by the auxiliary discharge. The anode
32
is formed on the lower substrate
18
provided with the main discharge space
31
while the auxiliary anode
34
is formed on the lower substrate
18
provided with the auxiliary discharge space
33
. A current limiting resistor
36
is provided between the anode
32
and the lower substrate
18
to limit an overshoot of the discharge current. The DC-type discharge cell having the structure as described above generates the discharge between the cathode
30
and the anode
32
and makes use of an auxiliary discharge in the auxiliary discharge cell so as to lower a discharge voltage in the main discharge cell. In other words, by the auxiliary discharge generated from the cathode
30
and the auxiliary anode
34
in the auxiliary discharge cell, charged particles are produced. Then, the charged particles are moved into the main discharge space
31
through a hole defined between the main discharge space
31
and the auxiliary discharge space
33
and used for a display discharge caused by the cathode
30
and the anode
32
.
The DC-type PDP has an advantage in that it has more excellent contrast than the AC-type PDP because a light generated by the auxiliary discharge is shut off by means of a black matrix(not shown) formed on the upper plate. Also, in view of a fact that the AC-type PDP has a time interval at which the discharge is stopped even when a discharge voltage pulse is being applied by a wall charge formed in the dielectric layer while the DC-type PDP generates a continuous discharge when a discharge voltage pulse is being applied, it can be said that the DC-type PDP has a relatively good discharge efficiency. However, the DC-type PDP has a disadvantage in that total discharge efficiency is low due to an energy loss caused by the auxiliary discharge and the resistance.
Further, the AC-type and DC-type PDP rely on only a negative glow discharge having a poor discharge efficiency because the size of the discharge cell is too small, that is, because a distance between the electrodes is very short. In addition, the conventional AC-type and DC-type PDP has a problem in that most of an electric energy applied to the discharge space
21
Fleshner & Kim LLP
LG Electronics Inc.
Patel Vip
Williams Joseph
LandOfFree
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