Electric lamp and discharge devices – With gas or vapor – Three or more electrode discharge device
Reexamination Certificate
2001-05-10
2004-09-14
O'Shea, Sandra (Department: 2875)
Electric lamp and discharge devices
With gas or vapor
Three or more electrode discharge device
C313S583000, C313S584000, C313S585000
Reexamination Certificate
active
06791263
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electrode structure of a plasma display panel (PDP), and more particularly, to an electrode structure of a PDP with a small discharge gap.
2. Description of the Prior Art
A plasma display panel (POP) is one kind of flat display using gas discharges to create brilliant images. Advantages of the PDP include thin and lightweight design, large display size, and wide viewing angle. The luminescent principle of the PDP involves the production of ultraviolet (UV) rays by plasma first, followed by irradiation of the UV rays to produce visible light. The production efficiency of plasma greatly influences the luminescent efficiency of the PDP. The luminescent efficiency of the PDP can be improved by many methods. For examples increasing UV production can improve the luminescent efficiency of the PDP, but increasing the luminescent efficiency of the fluorescence material is difficult. Nowadays, change of the filling gas and the electrode structure of the PDP will increase, the UV production.
Please refer to FIG.
1
.
FIG. 1
is a cross-sectional view of a PDP
10
in the prior art. The PDP
10
includes a front substrate
12
and a back substrate
14
positioned in parallel, a discharge gas (not shown) filled between the front substrate
12
and the back substrate
14
, and two sustaining electrodes
16
formed on the surface of the front substrate
12
. A discharge gap
17
is defined between the two sustaining electrodes
16
. Two auxiliary electrodes
18
are formed above and parallel to the two sustaining electrodes
16
on the front substrate
12
. A plurality of address electrodes
20
are formed on the surface of the back substrate
14
and perpendicular to the sustaining electrodes
16
.
The PDP
10
further includes a dielectric layer
22
, a protective layer
24
, a plurality of ribs (not shown), and a fluorescent layer
26
. The dielectric layer
22
covers the front substrate
12
, and the protective layer
24
formed above the dielectric layer
22
. The ribs are formed parallel to each other on the back substrate
14
for isolating two neighboring address electrodes
20
. The fluorescent layer
26
are coated above the address electrode
20
and the sidewalls of each rib for producing red, green or blue light.
Generally speaking, the sustaining electrode
16
is transparent and composed of indium tin oxide (ITO). The transparent electrode is able to penetrate visible light but has a large resistance. The auxiliary electrode
18
is opaque and composed of Cr/Cu/Cr metal layers. The opaque electrode has a poor transparency and good conductivity. Thus, the auxiliary electrode
18
is positioned above the sustaining electrode
16
for increasing the conductivity of the sustaining electrode
16
.
Referring to
FIG. 2
, it is a Paschen curve for showing the relationship between the firing voltage (V
f
) of the PDP and the multiplication of the filling gas pressure (P value) with the discharge gap width (D value). When the PD value is equal to a constant C, the firing voltage V
f
will reduce to a minimum value. In the present PDP process, the pressure P of the filling gas is increased in order to heighten the brightness under a constant firing voltage as shown in FIG.
3
. The filling gas is usually a mixture of Xe and Ne gases. However, as shown in
FIG. 2
, an increasing P value leads to an increasing V
f
value. In order to maintain the V
f
value, the D value (discharge gap) must be decreased. The width of the discharge gap
17
, the distance between two sustaining electrodes
16
, is determined by the photoresist patterned by a mask. However, the accuracy of the patterned photoresist is limited by the resolution of the optical exposure tool and the characteristics of the photoresist materials. Therefore, the pattern with a smaller distance between two sustaining electrode is not easily and exactly transfer to the dry film photoresist for forming a smaller discharge gap
17
. Thereby, the large discharge gap will limit the quality of the PDP
10
. In addition, a smaller discharge gap can be formed by the high resolution liquid photoresist, but the material cost will be increased. Moreover, the high standard clean room is needed when using the liquid photoresist, and the fabricating cost of the PDP is also increased.
BRIEF SUMMARY OF THE INVENTION
An objective of the present invention is to provide an electrode structure of a plasma display panel with a reduced discharge gap.
The present invention provides an electrode structure of a plasma display panel (PDP). The electrode structure is formed on a front substrate of the PDP. The electrode structure includes a first and a second sustaining electrode, and a first gap is defined between the first and the second sustaining electrode. The electrode structure further includes an auxiliary electrode electrically connected to the first sustaining electrode. The first sustaining electrode has a first side approaching to the second sustaining electrode and a second side far away from the second sustaining electrode.
In addition, the first auxiliary electrode has a first part and a second part, the first part is formed in the first gap, and the second part is formed above the first sustaining electrode and adjacent to the first side of the first sustaining electrode. A second gap exists between the first part of the first auxiliary electrode and the second sustaining electrode, and the width of the second gap is smaller than that of the first gap. The first auxiliary electrode further includes a third part adjacent to the second side of the first sustaining electrode. The third part of the first auxiliary electrode is formed on the surface of the front substrate or on the first sustaining electrode.
The PDP also includes a back substrate parallel to the front substrate, and a plurality of ribs formed on the back substrate and parallel to each other. The ribs are perpendicular to the axial direction of the first auxiliary electrode. The first auxiliary electrode further includes a fourth part parallel to the ribs. The second sustaining electrode includes a third side distal from the first sustaining electrode. The electrode structure also includes a second auxiliary electrode adjacent to the third side of the second sustaining electrode.
A first lithographic process patterns the first and the second sustaining electrodes, and a second lithographic process patterns the first auxiliary electrode. In the present invention, the misalignment of the auxiliary electrode and the sustaining electrode is obtained from twice lithographic processes for forming a smaller discharge gap. As a result, the discharge gap will not be limited by the resolution of the optical exposure tools and photoresist materials in the present invention. Therefore, the discharge gap is reduced and the image quality of the PDP can be improved.
These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment, which is illustrated in the various figures and drawings.
REFERENCES:
patent: 6031329 (2000-02-01), Nagano
patent: 6465956 (2002-10-01), Koshio et al.
patent: 1269570 (2000-10-01), None
patent: 11297214 (1999-10-01), None
patent: 2000123750 (2000-04-01), None
Lin Yih-Jer
Su Yao-Ching
AU Optronics Corp.
Hsu Winston
Macchiarolo Peter
O'Shea Sandra
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