Electric lamp and discharge devices – With gas or vapor – Three or more electrode discharge device
Reexamination Certificate
2000-03-20
2004-08-03
Patel, Nimeshkumar D. (Department: 2879)
Electric lamp and discharge devices
With gas or vapor
Three or more electrode discharge device
C313S586000, C313S587000, C430S312000, C430S321000
Reexamination Certificate
active
06771022
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a backplate for a Plasma Display Panel (PDP) and a method for fabricating thereof, and in particular to a backplate for a PDP and a fabrication method thereof which are capable of uniformly coating a phosphor material on an inner portion (a region of a backplate and a region surrounded by the barrier ribs) of a discharge cell of a PDP based on the height of a barrier rib.
2. Description of the Background Art
Recently, since the structure of a Plasma display Panel (PDP) is simple as a flat type display unit and there is not limit in the size of the display, the PDP will receive a big attention as a key display unit in the flat display market. In the PDP, ultraviolet rays generated during a plasma discharge by He—Ne or Ne—Xe gas in discharge cells separated by the barrier ribs excite Red, Green and Blue phosphor materials formed on the barrier ribs, so that a visual ray is generated when the excited phosphor material is transited to a base state. Therefore, a certain character or graphic is displayed by the thusly emitted visual rays using the above-described visual ray discharge principle.
FIG. 1
is a view illustrating the structure of an AC-PDP and one cell in a conventional AC-PDP which includes a front glass substrate
1
for displaying an age, a backplate
23
installed parallel with the front glass substrate
1
and distanced from the front glass substrate
1
by a certain distance, and a plurality of barrier ribs
13
formed between the front glass substrate
10
and the backplate
12
a certain distance therebetween for forming a discharge region in the interior of a discharge cell for preventing an electrical/optical interference between the cells.
Here, the front glass substrate
1
includes an upper dielectric layer
3
for cumulating a barrier wall electric charge, sustaining a discharge sustaining voltage, protecting electrodes from an ion impact during a gas discharge and preventing diffusion of ions, and a protection film layer
9
formed on the surface of the upper dielectric layer
3
, protecting the upper dielectric layer
3
from a sputtered plasma particle, extending the life span of the same, increasing the efficiency of the discharge of a relatively high secondary electron when a relatively low ion energy collides with the surface during the plasma discharge and decreasing the changes of a discharge characteristic of a fireproof metal. At this time, the protection film layer
9
is formed of MgO.
In the interior of the upper dielectric layer
3
, there are a sustain electrode
5
using Indium tin Oxide (ITO) as a transparent electrode, and a bus electrode
7
formed of a metal engaged with the sustain electrode
5
.
The backplate
23
includes an address electrode
19
for generating a discharge with respect to the sustain electrode
5
and the bus electrode
7
, an under layer
21
for adhering the address electrode
19
and the backplate, a lower dielectric layer
17
for covering the address electrode
19
, and a phosphor material
15
for covering the lower dielectric layer
17
and the barrier ribs
13
formed thereon and generating a visual ray.
A black top
11
is engaged at an upper end of the barrier rib
13
for absorbing light externally inputted through the front glass substrate
1
.
In the thusly constituted PDP, in a state that a mixed gas of He—Ne and Ne—Xe is filled, a discharge is generated between the address electrode
19
and the sustain electrode
5
, and when a discharge is continuously generated between the sustain electrodes
5
, a vacuum ultraviolet (VUV) of 147 nm wavelength is outputted. Thereafter, the vacuum ultraviolet ray excites the phosphor material
15
. When the phosphor material is transited from the excited state to the base state, a visual ray of Red, Green and Blue is discharged, so that a certain image is displayed on the front glass substrate
1
.
Therefore, since the phosphor material
15
outputs light for displaying a certain image on the front glass substrate, the phosphor material
15
must be uniformly coated at the discharge cell based on a material characteristic of the phosphor material.
As a method for coating the phosphor material, there are a screen printing method, a sand blast method, a photolithography method, an electric melting method, etc. Among the above-described methods, the screen printing and sand blast methods are widely used.
FIG. 2
is a flow chart of a fabrication method of a backplate of a conventional PDP using a screen printing method. As shown therein, a screen mask is arranged on the backplate having barrier ribs. The above-described fabrication method includes a step ST
11
for arranging a screen mask on the backplate for coating a red phosphor material, and a step ST
12
for printing/drying the red phosphor material for thereby coating a red phosphor material. Identically to the step for coating the red phosphor, material on the backplate, the screen mask is arranged on the backplate with respect to the green and blue phosphor materials in Steps ST
13
and ST
15
. Thereafter, the green phosphor material and blue phosphor material are printed and dried in Step ST
14
and ST
16
. The green and blue phosphor materials are sequentially coated on each discharge cell after coating the red phosphor material.
FIGS. 3A through 3C
are cross-sectional views for coating a phosphor material on the discharge cell of the conventional PDP using the screen printing method.
As shown in
FIG. 3A
, the screen mask
33
is positioned on the backplate
23
on which the under layer
21
, the address electrode
19
, the lower dielectric layer
17
and the barrier ribs
13
are sequentially formed, and the red, green or blue phosphor material
15
of the paste state is printed on the backplate
23
. After printing the phosphor material, the screen mask
33
is removed, and as shown in
FIG. 3B
, the phosphor material
15
is coated a height similar to the height of the barrier rib
13
. At this time, when drying the backplate including the coated phosphor material, as shown in
FIG. 3C
, an organic solvent is evaporated, and the volume of the same is decreased. Therefore, the phosphor material
15
is coated only on the surfaces of the lower dielectric layer
17
and the barrier ribs
13
.
FIG. 4
is a flow chart of a backplate fabrication method of a conventional PDP using the sand blast method. As shown therein, the method includes Steps ST
21
, ST
23
and ST
25
for printing and drying the red, green and blue phosphor materials on the front surface of the backplate
23
having the barrier ribs, Steps ST
22
, ST
24
and ST
26
for light-exposing and developing the red, green and blue phosphor materials using a desired screen mask, so that the red, green and blue phosphor materials are coated on a corresponding discharge cell at the height of the barrier ribs. Next, glass bids are sprayed for thereby partially removing the red, green and blue phosphor materials, so that the red, green and blue phosphor materials are coated on the surfaces of the lower dielectric layer
17
and the barrier ribs
13
in Step ST
27
. Next, the backplate coated with the phosphor materials is molded for thereby forming the red, green and blue phosphor materials in Step ST
28
.
In the conventional screen printing method or sand blast method, in the case that the height of the barrier rib
13
is 100~200 &mgr;m, it is possible to coat the phosphor material at the height of the entire barrier ribs.
However, in order to increase the discharge efficiency, the PDP using the high frequency discharge must have an enough distance between two electrodes which generate a high frequency discharge. Therefore, the height of the barrier ribs is generally 500~2000 &mgr;m. In the case that the height of the barrier rib is high, it is impossible to uniformly coat the phosphor material by the conventional screen printing method and sand blast method. Namely, since the barrier ribs having the coated phosphor materials is formed of a glass having a high frictio
Fleshner & Kim LLP
LG Electronics Inc.
Patel Nimeshkumar D.
Santiago Mariceli
LandOfFree
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