Electric lamp and discharge devices – With gas or vapor – Three or more electrode discharge device
Reexamination Certificate
1999-07-15
2002-04-30
Patel, Ashok (Department: 2879)
Electric lamp and discharge devices
With gas or vapor
Three or more electrode discharge device
C313S587000
Reexamination Certificate
active
06380677
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a PDP(Plasma Display Panel), and in particular to a structure for a discharge sustaining electrode which makes it possible to form an image display for a certain time by generating a surface discharge in a certain discharge space when a discharge voltage is supplied in a form of multiple pairs in a display apparatus using a plasma.
2. Description of the Background Art
Generally, a PDP(Plasma Display Panel) is a plane display apparatus which is capable of displaying a motion picture or a still picture using a gas discharge phenomenon and is classified into a 2-electrode type, a 3-electrode type and a 4-electrode type. The 2-electrode type is directed to applying a voltage for an addressing and sustaining operation using
2
electrodes, and the 3-electrode type is directed to a surface discharge type and is switched or sustained based on a voltage applied to an electrode installed at a lateral surface of a discharge cell.
FIGS. 1 through 4
illustrate a conventional 3-electrode surface discharge type PDP as a representative example.
FIG. 1
is a perspective view illustrating separated upper and lower substrates,
FIG. 2
is a view illustrating an installation of each electrode, and
FIG. 3
is a cross-sectional view illustrating a pixel.
FIG. 3
illustrates an upper substrate which is rotated at
90
for explaining a discharge principle.
As shown therein, the conventional 3-electrode surface discharge type PDP includes a front substrate
1
which is a display surface of an image and a back substrate
2
parallely spaced apart from the front substrate
1
.
The front substrate
1
includes a pair of discharge sustaining electrodes C and S installed at each pixel in a pair form for sustaining a light emitting operation of cells based on a discharge, a dielectric layer
8
for limiting a discharge current of the sustaining electrodes C and S and insulating the electrodes, and a protection layer
9
formed on the dielectric layer
8
for protecting the sustaining electrodes C and S.
The back substrate
2
includes a partition wall
3
for separating a plurality of discharge spaces, namely, the cells, a plurality of address electrodes A formed in parallel with the partition wall
3
for forming discharge pixels at each portion where the discharge sustaining electrodes C and S are crossed on the front substrate
1
, and a phosphorus layer
5
formed on the partition wall
3
and the back substrate
2
in the inner surfaces of each discharge pixel for emitting a visual light for displaying an image.
In addition, the sustaining electrodes C and S formed in pairs are formed of a scan electrode S and a common electrode C. As shown in
FIGS. 3 and 4
, each electrode includes an ITO electrode
6
formed of a transparent conductive material and a metallic BUS electrode
7
for enhancing a transmissivity and forms a certain distance “a” therebetween. In particular, the ITO electrode
6
forms a surface discharge in a corresponding discharge space when a voltage is supplied, and the BUS electrode
7
which is formed of a low resistance metallic material and is formed on the ITO electrode
6
for preventing a voltage drop due to the resistance of the transparent conductive material when a current is applied.
The light emitting process of a certain pixel in the conventional PDP will be explained as follows.
First, in a certain cell, a discharge start voltage of 150~300V is supplied to the scan electrode S, a discharge is formed between the scan electrode S and the address electrode A for thereby forming a wall electric potential on the inner surface of a corresponding discharge space.
Thereafter, when an address discharge voltage is supplied to the scan electrode S and a corresponding address electrode A, an address discharge is formed between the scan electrode S and the address electrode A.
Namely, an electric field is formed in the interior of the cell, and a small amount of electrons in the discharge gas is accelerated. The thusly accelerated electrons collide with a neutral particle in the gas and are separated into electrons and ions, and the neutral particles are more fast separated into electrons and ions due to another collision between the separated electrons and neutral particles, so that the discharge gas becomes a plasma state and a vacuum ultraviolet rays are generated.
The thusly generated ultraviolet rays excite the phosphorus layer
5
for thereby generating a visual ray, and the thusly generated visual ray is radiated to the outside via the front substrate, so that it is possible to recognize a certain cell light emitting operation, namely, an image display.
When a sustaining discharge voltage of more than 150V is supplied to the common electrode C of the light emitting cell, a sustaining discharge is generated between the scan electrode S and the common electrode C for thereby sustaining a light emitting operation of the cell.
The conventional PDP electrode structure has the following problems.
First, since the scan electrode S is formed of a transparent ITO electrode
6
for preventing a decrease of the transmissivity due to the metallic BUS electrode
7
, the entire area is increased for thereby increasing the capacitance of the electrode.
Namely, when the capacitance is increased, more energy is needed compared to the same voltage for activating all cells for thereby decreasing the discharging speed during an initial address discharge and increasing the entire power consumption, so that one time discharge amount is increased, and a contrast is decreased as the dark portion luminance is increased.
Second, since the BUS electrode
7
is positioned at an outer portion of the ITO electrode
6
in the scan electrode S and the common electrode C for minimizing the decrease of the transmissivity of the discharge cells, the distance between the BUS electrodes
7
is increased at each discharge cell, so that the transition time for the sustaining discharge is extended for the address discharge.
Namely, when the transition time for the sustaining discharge is extended, the address discharge time is extended thereby, so that the image display on the display screen takes long time.
In addition, when the discharge speed is decreased during the address discharge, and the discharge time is extended, a small amount of the charged particles generated during the address discharge is used for the sustaining discharge, so that the charged particles are spread into the neighboring cells for thereby causing an erroneous discharge and a color blurring problem on the display screen.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention minimize the area of a scan electrode in a state that a discharge characteristic is not decreased, decrease the capacitance which is required for a discharge, decrease the entire power consumption and increase a contrast based on one time discharge amount.
It is another object of the present invention to implement a short time sustaining discharge by making a metallic BUS electrode close to the scan electrode and the common electrode.
It is still another object of the present invention to prevent an erroneous discharge with other neighboring electrodes when a discharge voltage is applied to the scan electrode and the common electrode.
To achieve the above objects, there is provided an electrode structure for a PDP according to a first embodiment of the present invention which includes a discharge pair formed of three electrodes at each pixel in the discharge sustaining electrode, and a scan electrode installed at a center portion of three electrodes, and a common electrode installed at both side of the same, respectively, wherein the PDP includes two engaged substrates having a discharge space therebetween, a discharge sustaining electrode arranged on one side of the substrates for forming a plurality of discharge pairs, and an address electrode arranged on the other side of the substrates for forming a discharge pixel at a portion in which the discharge
Ha Hong-Ju
Park Hun-Gun
Fleshner & Kim LLP
LG Electronics Inc.
Patel Ashok
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