Electric lamp and discharge devices – With gas or vapor – Three or more electrode discharge device
Reexamination Certificate
1998-10-22
2002-08-13
Patel, Ashok (Department: 2879)
Electric lamp and discharge devices
With gas or vapor
Three or more electrode discharge device
C313S584000, C313S585000
Reexamination Certificate
active
06433477
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a plasma display panel(hereafter called as PDP), and more particularly, to a PDP with a varied thickness dielectric film.
2. Discussion of the Related Art
In general, the PDP is the most suitable for a flat display panel because the PDP has a fast data display rate and a large sized panel is available with easy. The PDP is suggested to be an AC type PDP or DC type PDP both with two electrodes, of which, it is known that a surface discharge type AC PDP is the most appropriate for a color display. The PDP is in general one of luminous device which uses gaseous discharge within each discharge cell for displaying an image. Because the PDP is simple to fabricate, easy to fabricate a large sized screen, and fast in response, it is spot lighted as a direct view image display with a large screen, particularly as a display directed to an age of HDTV.
FIG. 1
illustrates an overall perspective view of a related art surface discharge type AC PDP.
Referring to
FIG. 1
, the related art surface discharge type AC PDP is provided with, at large, a front substrate
1
for displaying an image, a rear substrate
2
disposed spaced from, and parallel to the front substrate
1
, a plurality of barriers
3
arranged on the rear substrate
2
opposite to the front substrate
1
at fixed intervals, and a plurality of discharge spaces formed when the front substrate
1
and the rear substrate
2
are bonded. In detail, the PDP is provided with address electrodes
4
each provided between every adjacent barriers
3
, a fluorescent film
5
formed on both walls of each barrier
3
in each of the discharge spaces and on the address electrode
4
on a bottom surface of each of the discharge spaces for emitting a visible light at discharge of the cell, and a display electrode
6
and a bus electrode
7
formed alternatively on the front substrate
1
opposite to the rear substrate
2
. The display electrode
6
and a bus electrode
7
are formed in a direction perpendicular to a direction of the plurality of address electrodes
4
, to have a plurality of cell discharge in an entire screen. There are a dielectric layer
8
formed on the display electrode
6
and a bus electrode
7
for restricting a discharge current, a protection layer
9
formed on the dielectric layer
8
for protecting the display electrode
6
, the bus electrode
7
, and the dielectric layer
8
, and discharge gas in each discharge space for inducing the Penning effect.
FIG. 2
illustrates a cross section of a plurality of discharge cells in a related art surface discharge type AC PDP, wherein one pair of transparent electrodes
13
on a front substrate
11
are shown turned by 90° for convenience of understanding. The display electrode
21
has a pair of a transparent electrode
13
and a metal electrode
22
.
Referring to
FIG. 2
, the related art surface discharge type AC PDP is provided with a top panel having one pair of transparent electrodes
13
formed on a front panel
11
, a first, and a second dielectric layers
14
and
15
on an entire surfaces of the pair the transparent electrodes
13
for restricting a discharge current, and a protection layer
16
formed on the second dielectric layer
15
. And, there is a bottom panel having address electrode
17
formed on a region of a rear substrate
12
to cross the pair of transparent electrodes
13
in the top panel, barriers
19
for providing different colors between adjacent cells each with an address electrode
17
, and a fluorescent material layer
18
formed on the barrier
19
and the address electrodes
17
. There is Frit glass(not shown) bonding the front substrate
11
in the top panel and the rear substrate
12
in the bottom panel together and a mixture gas filled in discharge space
20
and sealed, completely.
In the aforementioned related art surface discharge type AC PDP, upon application of a discharge initiation voltage to one of the display electrodes
21
and an address signal to the address electrode
17
on the same time, a writing discharge is occurred in the discharge cell. That is, an electric field is established in the discharge cell, to accelerate a small amount of electrons present in the discharge gas to collide with neutral particles in the gas, causing ionization of the neutral particles into electrons and ions and another collisions of the ionized electrons with neutral particles, which again causes ionization of the neutral particles into electrons and ions at a faster rate, resulting to turn the discharge gas into a plasma state and cause a surface discharge
20
a
in the discharge space
20
from surfaces of the first, and second dielectric layers
14
and
15
and the protection layer
16
, emitting a vacuum ultra-violet(uv) ray. This vacuum ray excites the fluorescent material layer
18
, to cause the fluorescent material layer to emit a visible light, which is directed to outside of the panel through the front substrate
11
, to display R, G, B color. That is, spatial charges present in the discharge space
20
are accelerated by a sustain voltage applied to each display electrode
21
, and make collision with the inert gas filled in the discharge space
20
at 400~500 Torr, emitting the vacuum UV ray. The inert mixture gas has helium He as a major gas, and added with xenon Xe and neon Ne. The vacuum UV ray hits on the fluorescent material layer
18
on the address electrode
17
and the barrier
19
, emitting a visible light. In other words, a color display is made by a combination of R, G, B, defined at least 3 luminescent regions.
It is required in the aforementioned PDP to reduce a discharge current for improving a luminous efficiency. This discharge current is substantially influenced by thicknesses of the first, and second dielectric layers
14
and
15
on the display electrode
21
; if the first, and second dielectric layers
14
and
15
are thin, the discharge initiation voltage is in general low and the discharge current is increased, but if the first and second dielectric layers
14
and
15
are the more thicker, the discharge initiation voltage becomes the more lower and the discharge current becomes reduced the more. Therefore, if the dielectric layer is simply formed thicker, the discharge current may be reduced, but the discharge initiation voltage rises, making actual PDP driving difficult. Charges in the space after initiation of a discharge moves from {circle around (1)} to {circle around (2)} to cut off an external voltage and attached to surfaces of the first, and second dielectric layers
14
and
15
to drop a voltage in the discharge space. According to this, a waveform of the discharge current is formed in a form the discharge stops once the discharge is occurred. Since a tail portion of the discharge current serves nothing in the light emission but waste power, it is required to shorten the tail portion of the discharge current. The luminous efficiency can be defined by an equation (1), below.
Luminous
Efficiency
(
lm
/
W
)
=
luminance
(
cd
/
m
2
)
×
area
(
m
2
)
×
π
power
consumption
(
W
=
voltage
×
current
)
(
1
)
When the discharge initiated from a gap of the display electrodes in the surface type AC PDP propagates in a width direction step by step, the tail portion of the discharge current corresponds to an end portion in the width direction of the display electrode. In this instance, it is possible that the discharge current can be dropped without raising the discharge voltage by providing a dielectric layer having a thickness formed gradually thicker in the width direction of the display electrode.
The blind reduction of the dielectric layer thickness in the related art surface type AC PDP for lowering the discharge initiation voltage to cause a surface discharge in each cell results in an increased capacitance, that causes problems of an increased power consumption and a breakage
Ha Hong Ju
Kim Jae Sung
Fleshner & Kim LLP
Guharay Karabi
LG Electronics Inc.
Patel Ashok
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