Active solid-state devices (e.g. – transistors – solid-state diode – Field effect device – Having insulated electrode
Reexamination Certificate
2000-02-07
2003-08-12
Pham, Long (Department: 2814)
Active solid-state devices (e.g., transistors, solid-state diode
Field effect device
Having insulated electrode
C257S080000, C257S082000, C257S088000, C257S089000, C257S093000, C257S103000
Reexamination Certificate
active
06605834
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a plasma display panel (PDP), and more particularly to a dielectric for an upper plate suitable for the PDP and a method of fabricating the same. The present invention also is directed to a dielectric for a lower plate in the PDP and a dielectric composition adaptive for forming a barrier rib in the PDP.
2. Description of the Related Art
Generally, a plasma display panel (PDP) radiates a fluorescent body by an ultraviolet with a wavelength of 147 nm generated during a discharge of He+Xe or Ne+Xe gas to thereby display a picture including characters and graphics. Such a PDP is easy to be made into a thin film and large-dimension type. Moreover, the PDP provides a very improved picture quality owing to a recent technical development. The PDP is largely classified into a direct current (DC) driving system and an alternating current (AC) driving system.
The PDP of AC driving system is expected to be highlighted 30 into a future display device because it has advantages in the low voltage drive and a prolonged life in comparison to the PDP of DC driving system. Also, the PDP of AC driving system allows an alternating voltage signal to be therebetween to generate a discharge every half-period of the signal, thereby displaying a picture. Since such an AC-type PDP uses a dielectric material, the surface of the dielectric material is charged with electricity. The AC-type PDP allows a memory effect to be produced by a wall charge accumulated to the dielectric material due to the discharge.
FIG. 1
is a sectional view showing the structure of a discharge cell in the conventional three-electrode AC-type PDP, in which a lower plate is illustrated in a state of rotating an angle of 90°. In
FIG. 1
, the discharge cell includes an upper plate
10
provided with a sustaining electrode pair
12
and
14
, and a lower substrate
20
provided with an address electrode
20
. The upper substrate
10
and the lower substrate
20
are spaced, in parallel, from each other with having a barrier rib
28
therebetween.
A mixture gas such as Ne—Xe or He—Xe, etc. is injected into a discharge space defined by the upper substrate
10
and the lower substrate
20
and the barrier rib
28
. The sustaining electrode pair
12
and
14
consists of transparent electrodes
12
A and
14
A and metal electrodes
12
B and
14
B. The transparent electrodes
12
A and
14
A are usually made from Indium-Tin-Oxide (ITO) and has an electrode width of about 300 &mgr;m. Usually, the metal electrodes
12
B and
14
B take a three-layer structure of Cr—Cu—Cr and have an electrode width of about 50 to 100 &mgr;m. These metal electrodes
12
A and
14
A play a role to decrease a resistance of the transparent electrodes
12
A and
14
A
6
with a high resistance value to thereby reduce a voltage drop. Any one
12
of the sustaining electrode pair
12
and
14
is used as a scanning/sustaining electrode that responds to a scanning pulse applied in an address interval to cause an opposite discharge along with the address electrode
22
while responding to a sustaining pulse applied in a sustaining interval to cause a surface discharge with the adjacent sustaining electrodes
14
. A sustaining electrode
14
adjacent to the sustaining electrode
12
used as the scanning/sustaining electrode is used as a common sustaining electrode to which a sustaining pulse is applied commonly. A distance between the sustaining electrode pair
12
and
14
is set to be approximately 100 &mgr;m. On the upper substrate
10
provided with the sustaining electrode pair
12
and
14
, an upper dielectric layer
16
and a protective layer
18
are disposed. The dielectric layer
16
is responsible for limiting a plasma discharge current as well as accumulating a wall charge during the discharge. The protective film
18
prevents a damage of the dielectric layer
16
caused by a sputtering generated during the plasma discharge and improves an emission efficiency of secondary electrons. This protective film
18
is usually made from MgO. The address electrode
22
is crossed with the sustaining electrode pair
12
and
14
and is supplied with a data signal for selecting cells to be displayed. On the lower substrate
20
formed with the address electrode
24
, a lower dielectric layer
24
is provided. Barrier ribs
28
for dividing the discharge space are extended perpendicularly on the lower dielectric layer
24
. On the surfaces of the lower dielectric layer
24
and the barrier ribs
28
is coated a fluorescent material
26
excited by a vacuum ultraviolet lay to generate a red, green, or blue visible light.
In such a PDP, the upper dielectric layer
16
has a transmissivity of about 85% at the central wavelength to transmit a visible light. The upper dielectric layer
16
also accumulates a wall charge to thereby sustain the discharge by a discharge sustaining voltage. In this case, since a larger capacitance value is required to lower a discharge voltage, the upper dielectric layer
16
has a relatively high dielectric constant of about 10 to 15. The upper dielectric layer
16
plays a role to protect the sustaining electrodes
12
and
14
from an ion impact during the plasma discharge and serves as an anti-diffusion film. The upper dielectric layer
16
consists of first and second upper dielectric layers
16
A and
16
B that are usually made from a glass having a different softening point. As the first upper dielectric layer
16
A contacted directly with the sustaining electrodes
12
and
14
is used a glass with a relatively higher softening point so as to avoid a chemical reaction between the transparent electrodes
12
A and
14
A and the metal electrodes
12
B and
14
B. The second upper dielectric layer
16
B formed on the first upper dielectric layer
16
A requires a high smoothing coefficient so as to provide the protective film
18
. For this reason, as the second upper dielectric layer
16
B is used a low softening glass having a softening point tens of degrees lower than the first upper dielectric layer
16
A.
FIG. 2
shows a process of forming the upper dielectric layer
16
. At step S
2
, a first glass paste with a relatively high softening point is printed on the upper substrate
10
provided with the sustaining electrodes
12
and
14
using the screen printing technique. In this case, the glass paste is prepared by mixing borosilicate glass powder having a particle diameter of 1 to 2 &mgr;m and containing Pb of about more than 40% with an organic binder. At step S
4
, the printed first glass paste is fired at a temperature of 550 to 580° C. to form the first upper dielectric layer
16
A. Then, at steps S
6
and S
8
, a second glass paste with a relatively low softening point is printed on the first upper dielectric layer
14
A using the screen printing technique and thereafter is fired at a temperature of 550 to 580° C., thereby forming the second upper dielectric layer
16
B.
As described above, the upper dielectric layer
16
is provided by firing a paste, which is a mixture mixed with an organic binder, at a temperature of less than 600° C. so as to prevent a thermal deformation of the upper substrate
10
. Due to this, since the conventional upper dielectric layer
16
fails to become a complete plastic material, a bubble caused by a residual organic material exists in the interior thereof. The bubble existing in the interior of the dielectric layer brings about an insulation destruction to have a serious influence on a characteristic and a life of the device. A bubble generating at a contact portion between the upper dielectric layer
16
and the sustaining electrodes
12
and
14
causes a problem in that it drops a dielectric constant to increase a discharge voltage. Furthermore, the conventional upper dielectric layer
16
has a problem in that a glass component resulting from a diffusion caused by a thermochemical reaction at a portion contacting the sustaining electrodes
12
and
14
upon firing is penetrated into the sustaining electro
Fleshner & Kim LLP
LG Electronics Inc.
Louie Wai-Sing
Pham Long
LandOfFree
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