Electric lamp and discharge devices – With gas or vapor – Three or more electrode discharge device
Reexamination Certificate
2002-10-22
2004-10-19
Patel, Vip (Department: 2879)
Electric lamp and discharge devices
With gas or vapor
Three or more electrode discharge device
C313S584000
Reexamination Certificate
active
06806645
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a plasma display panel, and more particularly, to a plasma display panel to require a low power consumption and improve discharge efficiency.
2. Background of the Prior Art
In recent years, there are being actively developed flat panel displays such as Liquid Crystal Display (LCD), Field Emission Display (FED) and Plasma Display Panel (PDP).
PDP displays letter or image including graphic while phosphors emit light by means of ultraviolet rays having wavelength of 147 nm generated during discharge of inert mixture gas such as He+Xe or Ne+Xe. These PDPs have advantages in that they are easily made in a thin and large-sized structure. In addition, since the PDPs have a simplified structure, it is easy to fabricate them. Further, the PDPs have advantages in that they are higher in brightness and light emission efficiency than other flat panel displays. Owing to the above advantages, researches for the PDP are being actively carried out.
Especially, in the three-electrode AC surface discharge type PDP, wall charges are accumulated on the surfaces of the electrodes during discharge and the electrodes are protected from the sputtering that is generated by discharge. So, the three-electrode AC surface discharge type PDP has low voltage driving and long life characteristics.
FIGS. 1 and 2
illustrate the structures of the barrier ribs in the conventional PDPs. Specifically,
FIG. 1
shows a stripe type barrier rib structure and
FIG. 2
shows a wall type barrier rib structure.
Referring to
FIGS. 1 and 2
, the PDP has a pair of electrodes, e.g., scan electrodes
12
Y and sustain electrodes
12
Z, formed on a front substrate
10
, and an address electrode formed on a rear substrate
18
.
Each of the scan electrodes
12
Y and the sustain electrodes
12
Z is made of transparent electrode material (Indium Tin Oxide: hereinafter referred to as ITO) to transmit visible light, and includes a transparent electrode
12
a
and a bus electrode
12
b
. The transparent electrode
12
a
is larger in area than the bus electrode
12
b
. The bus electrode
12
b
compensates for the resistance of the transparent electrode
12
a
. A scan signal for scanning a panel and a sustain signal for sustaining discharge are mainly applied to the scan electrodes
12
Y, and sustain signal is applied to the sustain electrodes
12
Z.
A front dielectric layer
14
and a protective layer
16
are successively laminated on the electrodes
12
Y and
12
Z formed on the front substrate
10
. On the front dielectric layer
14
is accumulated the wall charge generated during plasma discharge. The protective layer
16
protects the front dielectric layer
14
from damages caused by sputtering during plasma discharge and also enhances the emission efficiency of the secondary electrons. The protective layer
16
is usually made of magnesium oxide (MgO).
The address electrodes
12
X are formed to cross over the electrodes
12
Y and
12
Z and are provided with data signals to select discharge cells for display images. A rear dielectric layer
22
is formed on the address electrodes
12
X. Barrier ribs
24
a
and
24
b
are formed on the rear dielectric layer
22
in parallel with the address electrodes
12
X.
A phosphor layer
26
is coated on the surfaces of the rear dielectric layer
22
and the barrier ribs
24
a
and
24
b
. The phosphor layer
26
is excited by the ultraviolet rays generated during the plasma discharge to generate one of visible rays of red, green and blue colors. The inert gas for discharge is injected into discharge spaces prepared between the front substrate
10
/the rear substrate
18
and the barrier ribs
24
a
and
24
b
. The barrier ribs
24
a
and
24
b
are formed in parallel with the address electrodes
12
X to prevent the ultraviolet rays and the visible rays generated by discharge from leaking into the neighboring discharge cells.
In general, a PDP has an efficiency of 11 m/W, brightness of 400 cd/m
2
and power consumption of 300 W. Usually, the PDP for home television (TV) needs to improve the brightness and reduce the power consumption. To meet these requirements, the light emission efficiency of panel should be improved.
The light emission efficiency of a PDP is expressed as the following equation 1:
η
=
π
BS
P
,
Equation
1
where B is brightness, S is the area of light emission and P is power consumption.
As expressed in the equation 1, the light emission efficiency is proportional to the brightness B and the area of light emission S but inversely proportional to the power consumption P. Accordingly, to improve the light emission efficiency of the PDP, it is required to elevate the brightness B and reduce the power consumption P.
Until now, the stripe type barrier rib (depicted in
FIG. 1
) and the wall type barrier rib (depicted in
FIG. 2
) were described.
The stripe type barrier rib
24
a
separates the discharge cells in a stripe fashion. The phosphors formed in the discharge cells separated in this manner are arranged in a successive configuration of red, blue and green. Each of the discharge cells separated by the stripe type barrier ribs
24
a
has a ratio of horizontal length to vertical length of 1:3. Since the horizontal length is shorter than the vertical length, the discharge space is reduced and so the discharge efficiency is lowered. In other words, the stripe type barrier rib
24
a
is useful to gas evacuation but its light emission efficiency is low due to the small covering area of the phosphors. Also, in the stripe type barrier rib
24
a
, the visible light is not effectively emitted to the outside of the discharge cell since the occupying area of the phosphors
26
formed on the lower portions of the discharge cells is small.
To overcome the above-described problem, there is proposed a wall type barrier rib
24
b
in which the shape of discharge cells substantially approaches the square. While this wall type barrier rib
24
b
enlarges the coated area of the phosphors
26
to elevate the brightness, it has a problem in that the gas evacuation is not easy. To overcome this problem, there is suggested is the PDP having delta type barrier ribs illustrated in
FIGS. 3 and 4
.
Referring to
FIGS. 3 and 4
, a discharge cell of the PDP having delta type barrier ribs
24
c
includes electrodes
12
Y and
12
Z formed on a front substrate
10
and an address electrode
12
X formed on a rear substrate
18
. The delta type barrier rib
24
c
is formed on the rear substrate
18
on which the address electrode
12
X is formed, and has discharge cells each surrounded by six faces to form a connection structure of narrow channels
34
. The channel
34
makes gas evacuation and gas injection easy.
Each of the electrodes
12
Y and
12
Z have a transparent electrode
12
a
made of ITO that has good transparency and a metal electrode
12
b
to lower the high resistance of the transparent electrode
12
a
. These electrodes
12
Z and
12
Y are arranged symmetrically at all discharge cells, and so the metal electrode
12
b
is located at the center of the transparent electrode
12
a
unlike the discharge cells of the stripe type barrier ribs and the wall type barrier ribs. Since the metal electrode
12
b
shields the light that is incident into the discharge cell, the brightness is reduced depending on the shielded light amount. In addition, the delta type barrier rib
24
c
makes it difficult to secure the discharge space due to a tendency toward the high definition of the PDP, so that the discharge efficiency is reduced. Also, since the discharge area of the transport electrode
12
a
relates to discharge voltage, the increase of the discharge area causes the discharge voltage necessary for discharge to be increased. As a result, the power consumption is increased and thus the light emission efficiency is lowered. To this end, it is strongly required to reduce the discharge area and maximize the discharge efficiency.
SUMMARY OF THE INVENTION
An object of th
Fleshner & Kim LLP
LG Electronics Inc.
Patel Vip
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