Compositions: ceramic – Ceramic compositions – Glass compositions – compositions containing glass other than...
Reexamination Certificate
2000-05-17
2002-05-07
Marcheschi, Michael (Department: 1755)
Compositions: ceramic
Ceramic compositions
Glass compositions, compositions containing glass other than...
C501S017000, C501S018000, C501S022000, C501S024000, C501S026000, C501S045000, C501S048000
Reexamination Certificate
active
06383961
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a composition of a dielectric for a plasma display panel, and more particularly, to a composition of a dielectric applied to a dielectric thick film coated at the upper surface of a transparent electrode of a front substrate (a substrate on which characters or picture is displayed) of a plasma display panel.
2. Description of the Background Art
Recently, a research and development for flat panel display apparatuses such as a liquid crystal display (LCD), a field emission display(FED) or a plasma display panel(PDP) is actively being conducted. Especially, the PDP is the most remarkable owing to its advantages in that it is easily produced due to its simple structure, a memory function, and a wide view angle more than 160° is attained, and a large screen more than 40 inches can be implemented.
FIG. 1
is a schematic view showing a structure of a plasma display panel in accordance with a conventional art.
As shown in the drawing, the conventional plasma display panel includes a rear substrate
10
on which address electrodes
11
are mounted, a rear dielectric thick film
12
coated with a predetermined thickness on the upper portion of the rear substrate
10
for charging a wall charge, barrier ribs
13
formed on the upper portion of the rear dielectric thick film
12
, separating discharge cells
30
; a fluorescent material
14
excited by a light generated in plasma discharging, a front substrate
20
, a counterpart of the rear substrate, for displaying a picture or characters, a transparent electrode
21
formed at the lower surface of the front substrate
20
, a front dielectric thick film
22
coated with a predetermined thickness, for charging the wall charge; and a protective film
23
coated at the upper portion of the front dielectric thick film
22
, for protecting the front dielectric thick film
22
from sputtering caused by discharging.
When a predetermined driving voltage (i.e., 200 V) is applied to the address electrode
11
and to the transparent electrode
21
, a plasma discharge is generated due to the electrons discharged from the address electrode
11
in the discharge cells.
In detail, as the electrons discharged from the electrode collides with atom of a mixture of gases of He and Xe or of a mixture of gases of Ne and Xe sealed in the discharge cells, the atoms of the mixture of gases are ionized, so that the second electrons are discharged. At this time, the second electrons collide repeatedly with the atoms of the mixture of gases, sequentially ionizing the atoms of the mixture of gases. That is, it goes to avalanche process in which the electrons and ions are increased double. The light generated in the avalanche process emits fluorescent material of a red color (referred to as ‘R’ hereinafter), a green color (referred to as ‘G’ hereinafter) and a blue color (referred to as ‘B’ hereinafter). The light of R, G and B emitted from the fluorescent material proceeds by way of the protective film, the front dielectric thick film and the transparent electrode to the front substrate
20
, thereby displaying characters or graphics.
In this respect, the front dielectric thick film
22
coated on the front substrate
20
needs to transmit the light generated from the fluorescent material. Thus, it requires a property of a high transmissivity. In addition, in order to lower the discharge voltage, it requires a property of a high dielectric constant. Besides, the front dielectric thick film
22
necessarily has characteristics of a low thermal expensive coefficient, thermal stability, a low sintering temperature and a fine organization, and an excellent matching between the electrode material and the protective film.
In order to meet the requirement, the principle ingredient of the composition for fabricating the front dielectric thick film of the conventional art is a PbO—B
2
O
3
—SiO
2
glass, and its specific composition ratio is as follows. That is, on the assumption that the weight of the PbO—B
2
O
3
—SiO
2
glass is 100 wt %, its composition ratios are 50-85 wt % of PbO, 10-20 wt % of SiO
2
, 10-20 wt % of B
2
O
3
, 0-10 wt % of K
2
O, 0-10 wt % of Na
2
O.
A method for fabricating a dielectric thick film comprised of the composition of a dielectric having the above composition ratio will now be described.
First, the PbO—B
2
O
3
—SiO
2
glass mixed with the above-described composition ratio is made to a fine powder below 10 &mgr;m. Subsequently, the fine powder is mixed with a organic solvent to make a paste or a slurry, which is then coated on the glass substrate (front substrate of the PDP) with a thickness of 20~30 &mgr;m. Finally, after the paste or the slurry coated on the glass substrate is dried for 15~20 minutes at the temperature of 300~350° C., it is sintered at the temperature of 580~590° C., thereby obtaining a transparent dielectric thick film. Such dielectric thick film having the above composition ratio in accordance with the conventional art has the following characteristics.
Namely, the light transmissivity (%), the most critical characteristic of the dielectric thick film for the front substrate, is approximately 75-85% on the basis of a 400~800 nm visible ray, its dielectric constant is 12~14, its thermal expensive coefficient is 65~90×10
−7
/° C., and its withstand voltage is more than 1.5V
In detail, since the dielectric constant is relatively low, the plasma discharge voltage is increased. And, since radio of the PbO is so high that the plasma display device weighs heavy. Also, due to the high content of PbO, its light transmissivity is low, and thus, the light emitting efficiency of the plasma display panel is low. Moreover, its fabricating process causes a problem of an environmental pollution. In addition, due to the high sintering temperature, the glass substrate (the front substrate of the plasma display panel) is easily deformed and damaged during a certain process.
Generally, the material for the dielectric thick film to be formed on the upper surface of the rear substrate should have characteristics of a low dielectric constant, a high reflectivity, a low sintering temperature, while the material for the dielectric thick film to be formed on the front substrate should have characteristics of a high dielectric constant, a high light transmissivity and a low sintering temperature.
Accordingly, it is required to develop a material that would satisfy the characteristics of the dielectric thick film for the front substrate of the plasma display panel.
SUMMARY OF THE INVENTION
Therefore, an object of the present invention is to provide a composition of a dielectric for a plasma display panel in user for fabricating a dielectric thick film for a front substrate having a low sintering temperature, a low thermal expensive coefficient, a high dielectric constant and a high withstand voltage.
To achieve these and other advantages and in accordance with the purposed of the present invention, as embodied and broadly described herein, there is provided a composition of a dielectric for a plasma display panel using a P
2
O
5
—ZnO—PbO glass.
In order to achieve the above objects, there is also provided a composition of a dielectric for a plasma display panel using the P
2
O
5
—ZnO—PbO glass that has the composition radios of 30~60 wt % of P
2
O
5
, 5~40 wt % of PbO, 0~5 wt % of MgO, 0~5 wt % of CaO, 0~10 wt % of La
2
O
3
, 0~5 wt % of SrO, 1~5 wt % of Al
2
O
3
0~2 wt % of Sb
2
O
3
, 0~2 wt % of As
2
O
3
, 5~25 wt % of BaO, and 0~5 wt % of TeO
2
.
In order to achieve the above objects, there is also provided a composition of a dielectric for a plasma display panel using the P
2
O
5
—ZnO-PbO glass mixed with an oxide filler.
In order to achieve the above objects, there is also provided a composition of a dielectric for a plasma display panel using the P
2
O
5
—ZnO—PbO glass mixed with the oxide filler, of which the oxide filler refers to at least one of PbTiO
3
, Bi
2
O
3
, BaTiO
3
CaTiO
3
, CaSnO
3
, PbZrO
3
and CaSiTiO.
REFERENCES:
patent: 38859
Fleshner & Kim LLP
LG Electronics Inc.
Marcheschi Michael
LandOfFree
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