Electric lamp and discharge devices: systems – Plural power supplies – Plural cathode and/or anode load device
Reexamination Certificate
1999-02-04
2002-01-22
Wong, Don (Department: 2821)
Electric lamp and discharge devices: systems
Plural power supplies
Plural cathode and/or anode load device
C313S484000, C313S505000
Reexamination Certificate
active
06340866
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a display device, and more particularly to an improved plasma display pane (PDP) for displaying a picture with the aid of a discharge caused by a radio frequency voltage signal. Also, this invention is directed to an improved driving method for the PDP.
2. Description of a Related Art
A conventional PDP brightens a fluorescent material by ultraviolet rays generated upon the gaseous discharge to display a picture including a character and graphic information. Then, the picture is displayed by visible rays emitted from the fluorescent material. The ultraviolet rays are emitted from gaseous particles when electrons included in the gaseous particles are excites and then transited, and are impacted to the fluorescent material. The gaseous discharge for generating such a glow discharge will be described.
A voltage signal is applied between a cathode
4
and an anode
6
installed into a discharge tube
2
as shown in FIG.
2
. Then, an electrical field is formed in a discharging space between the cathode
4
and the anode
6
, and electrons move from the cathode
4
toward the anode
6
in such a manner to be accelerated by the electrical field. The accelerated electron impacts into the gaseous particles, such as neutral atoms and molecules, injected in the discharging space to cause the ionization and excitation of gases. A variety pattern of luminescence appears at the glow discharge. Among the variety pattern of the luminescence, a negative glow generated in the vicinity of the cathode
4
and a positive column caused in the long region proceeding from the middle portion of the discharging space to the anode
6
affect to a brightness characteristics. Particularly, the positive column has a discharging efficiency of about 60-70 percents for the voltage that is applied between the cathode
4
and the anode
6
. The positive column appears only in the case that the cathode
4
stands apart from the anode
6
above 1 mm. In other words, the electron must be moveable the long distance of above 1 mm. However, in the conventional PDP, a distance between two electrodes for receiving a discharge voltage is set below 150 &mgr;m. Due to this, the conventional PDP must have used only the negative glow having the discharging efficiency of below 6 percents.
As PDP using such a negative glow, it is an alternative current type of PDP having plasma display cells as shown in
FIGS. 2A and 2B
. The plasma display cells are arranged in a matrix pattern. Referring to
FIGS. 2A and 2B
, the plasma display cell includes an upper substrate
10
and a lower substrate
12
installed apart from each other by compartment walls
14
in parallel. These upper and lower substrates and compartment walls
14
are formed a discharging space
26
. The compartment walls
14
are formed by a material reasonable for preventing an optical interference and an electrical interference between the plasma display cells, and support the upper substrate
10
. First and second sustain electrodes
16
A and
16
B, each called as a scan/sustain electrode and a sustain electrode, are installed on the upper substrate
10
in parallel with the compartment walls
14
. On the upper substrate
10
with the first and second sustain electrodes
16
A and
16
B, a dielectric material layer
18
is formed to have an even surface. The dielectric material layer
18
stores up an electric charge. Also, a protective film
20
can be disposed on the first dielectric material layer
18
. The protective film
20
protects the first dielectric material layer
18
from a spattering of gaseous particles to extend the lifetime of the PDP and to enhance an emitting rate or second electrons. The protective film
20
frees the discharge characteristics of a fireproof metal from a variation. As the protective film
20
, it is mainly used a Magnesium Oxide (MgO) film. The upper substrate
10
with the above structure is disposed on the compartment walls
14
in such a manner that the sustain electrodes
16
A and
16
B are opposite to the lower substrate
12
. Meanwhile, the lower substrate
12
has an address electrode
22
installed in such a manner to cross with the sustain electrodes
16
A and
16
B. On the lower substrate
12
with the address electrode
22
, there is disposed a fluorescent material layer
24
. The fluorescent material saver
24
excites and then transits by vacuum ultraviolet rays generated upon a gaseous discharge. The fluorescent material layer
24
emits visible rays having a primary color such as a red, a green or a blue color at a transition. The lower substrate
12
is positioned under the compartment walls
14
in such a manner that the address electrode
22
is opposite to the sustain electrodes
16
A and
16
B. These upper and lower substrates
10
and
12
and compartment walls
14
provide the discharging space
26
to be filled with discharge gases such as He, Ne, Xe and so on.
In the plasma display cell with such a structure, the sustain electrodes
16
A and
16
B stand apart from each other about 60-80 &mgr;m. The compartment walls
14
are formed to be below 200 &mgr;m in the height. In other words, all the distances between the electrodes
16
A,
16
B and
22
included in the plasma display cell is below 200 &mgr;m. Due to this, the alternative current type of the PDP can not use the positive column. Consequently, the discharging efficiency of the PDP drops off. Also, the alternative current type of the PDP causes a address discharge between any one of the sustain electrode
16
A and
16
B and the address electrode
22
before a display discharge (or a sustained discharge) is generated between the first and second sustain electrodes
16
A and
16
B, thereby displaying a desired picture.
In the next, the PDP having the above structure will be described. The address discharge is generated by any one of the sustain electrodes
16
A and
16
B and the address electrode
22
and then the sustain discharge is continuously caused by the sustain electrodes
16
A and
16
B. The vacuum ultraviolet rays generating by the sustain discharge excite and transit the fluorescent material layer
24
to emit visible rays, thereby displaying a desired picture. The visible rays are generated when the fluorescent material layer
24
is transited. In other words, the alternative current type of the PDP displays a desired picture by the sustain discharge. In order to generate the sustain discharge, a sustain pulse is applied between the sustain electrodes
16
A and
16
B. The sustain pulse has a frequency of about 200-300 kHz and a width of about 2-3 &mgr;m, as shown in FIG.
3
. Responding to the sustain pulse, the sustain discharge causes only once at the shorter moment of the period of the sustain pulse. In other words, the greater part of the period of the sustain pulse is consumed regardless of real discharge.
For example, if the sustain pulse is applied to the first sustain electrode
16
A, a charged particle moves from the second sustain electrode
16
B having an opposing polarity toward the first sustain electrode
16
A along a discharge path, as shown in FIG.
4
. Then, the gaseous particles are excited and transited by the charged particle. As a result, the sustain discharge is generated in vicinity or the second sustain electrode
16
B when a predetermined time have passed since the raising edge or the sustain pulse. Also, the charged particles from the electrode
16
B opposite to the first electrode
16
A are stored on the dielectric material layer
18
surrounding the surfaces of the sustain electrodes
16
A and
16
B. In other words, a wall charge is formed on the dielectric material layer
18
when the predetermined time have passed since the sustain discharge have been started. The wall charge offsets the voltage applied between the sustain electrodes
16
A and
16
B to drop down a voltage input to the discharging space, thereby reducing the sustain discharge. Consequently, the sustain discharge is generated only once during the shorter moment rel
Fleshner & Kim LLP
LG Electronics Inc.
Tran Thuy Vinh
Wong Don
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