Electric lamp or space discharge component or device manufacturi – Process – With assembly or disassembly
Reexamination Certificate
1998-10-01
2001-07-17
Ramsey, Kenneth J. (Department: 2879)
Electric lamp or space discharge component or device manufacturi
Process
With assembly or disassembly
C445S046000, C216S023000, C216S102000, C438S754000
Reexamination Certificate
active
06261144
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a wiring substrate comprising a wiring substrate with a wiring pattern formed thereon, a gas discharge display device using the same , and a method therefor.
Gas discharge display devices such as plasma display and the like make display through a self-luminescence, and therefore are characterized in that the field angle is large, the display is easy to see, the thickness can be lessened, and a large picture plane can be realized. Thus, such gas discharge display devices have become applied to display devices of information terminal equipment and high-quality picture tubes of television. Plasma displays are roughly classified into direct current driving type and alternate current driving type. Among them, the alternate current type of plasma display shows a high luminance owing to the memory action of dielectric layer covering electrodes, and its lifetime has reached a practical level through formation of protective layer. This results in practical application of plasma displays to video monitors for many uses.
FIG. 9
is a perspective view illustrating the structure of a practical plasma display panel, wherein the front side substrate
100
is shown apart from the back side substrate
200
for the purpose of facilitating understanding.
The front side substrate
100
comprises a display electrode
600
made of a transparent conductive material such as ITO (indium tin oxide), tin oxide (SnO
2
) or the like, a bus electrode
700
made of a low-resistance material, a dielectric layer
800
made of a transparent insulating material and a protecting layer
900
made of magnesium oxide (MgO) or the like, all being formed on a front side glass substrate
400
.
The back side substrate
200
comprises an address electrode
1000
, a barrier rib
1100
and a fluorescent material layer
1200
, all formed on a back side glass substrate
500
. Although not shown in
FIG. 9
, a dielectric layer
1300
is formed on the address electrode
1000
, too.
By affixing the front side substrate
100
to the back side substrate
200
so that the display electrode
600
makes an approximately right angle with the address electrode
1000
, a discharge space region
300
is formed between the front side substrate
100
and the back glass side substrate
500
.
In this gas discharge display device, an alternate current voltage is applied between one pair of display electrodes
600
provided on the front side substrate
100
, and a voltage is applied between the address electrode
1000
provided on the back side substrate
200
and the display electrode
600
, whereby an address discharge is made to occur and a main discharge is generated in a prescribed discharging cell. The main discharge generates an ultraviolet ray, which induces emission of lights from the red- green- and blue-color fluorescent materials
1200
separately coated on respective discharging cells. A display is made by emission of these lights.
Examples of such prior gas discharge display devices are described in, for instance, FLAT PANEL DISPLAY 1996 (Edited by Nikkei Microdevice, 1995), pages 208-215.
Here, the method for forming the bus electrode
700
carried on the front side substrate
100
and the address electrode
1000
carried on the back side substrate
200
will be mentioned below in more detail.
FIG. 5
,
8
A-
8
O illustrate an exemplary process for forming address electrode
1000
on back side glass substrate
500
. Explanation of the process for forming bus electrode
700
carried on front side substrate
100
is omitted, because it can be formed by a similar process.
First, a Cr/Cu/Cr layer (
1000
a-c
) for forming address electrode
1000
on the back side glass substrate
500
and a resist
2500
for forming the pattern of address electrode
1000
are successively piled lamination-wise by a film-forming technique such as sputtering, evaporation, spin coating, dry filling, etc. (Step (a), FIG.
8
A: Film forming step). Next, the resist
2500
is exposed to light and developed so as to form a desired pattern of address electrode
1000
(Steps (b) and (c), FIGS.
8
B and
8
C: Photolithographic step). Next, using an etching solution for Cr, the Cr layer
1000
a
is etched to form the desired pattern (Step (d), FIG.
8
D: Etching step). Next, the exposed and developed resist
2500
is peeled off, and a resist
2500
is again formed (Steps (e) and (f), FIGS.
8
E and
8
F). The above-mentioned treatments are repeated for each of Cu layer
1000
b
and Cr layer
1000
c
(Steps (g) to (o), FIGS.
8
G-
8
O). Thus, address electrode
1000
is formed on the back side glass substrate
500
.
The above-mentioned process using an etching solution is generally called “wet etching”. In the conventional wet etching processes, the resist
2500
is formed from an organic material.
Further, in the conventional formation of electrodes by wet etching, a photolithographic step for forming a resist is indispensable.
SUMMARY OF THE INVENTION
In order to reduce the number of repetition of the photolithographic steps, the present inventors have studied on a technique for forming a multi-layered wiring such as those having a structure of Cr layer
1000
a
/Cu layer
1000
b
/Cr layer
1000
c
, etc. by using only the resist
2500
formed by Steps (a)-(c). This technique may be realizable if an etching solution capable of selectively etching Cr layer or Cu layer is used. Actually, however, it has experimentally been revealed that Cr layers
1000
a
and
1000
c
are quite readily side-etched and accuracy of fabrication of the Cr/Cu/Cr layer is quite unstable, so far as an etching solution giving no damage to alkali-developable releasable resists is used. If a Cr layer is side-etched, the side-etched portions form gaps, which incurs inclusion of voids and contaminants such as etching solution. The contaminants cause corrosion and breakage of wiring in the step of firing the dielectric. Occurrence of breakage in the wiring means existence of wire portions not contributing to display in a gas discharge display panel, which is a fatal problem to a display panel. Since Cr/Cu/Cr layer constitutes a wiring of lower resistance as compared with other electrode materials, it is quite useful for large-sized display devices such as gas discharge display panel and the like. But, the same problem as mentioned above arises also in case of forming a multi-layer wiring such as Cr/Al/Cr by the method of wet etching.
Further, if the resist is formed of an organic material, the adhesion between resist and electrode is insufficient, which causes corrosion by etching solution at the resist interface. It has further been revealed that, in such a resist, extraneous materials and air bubbles are included to cause defects in resist, due to which corrosion and thereby caused breakage of wiring can occur. Further, since conventional resists have been formed by a photolithographic process, they are apt to have defects due to extraneous matter. If electrode is formed by wet etching from a resist including defects, the regions corresponding to the defects are similarly etched, which causes breakage of wiring. These problems arise not only in Cr/Cu/Cr type multi-layer wiring, but also in case of forming a wiring of Al, Ag, Ni, Au, etc. by wet etching.
As above, in the gas discharge display panels and wiring substrates in which electrodes are formed by the conventional wet etching technique, breakage of wiring has readily occurred due to side-etching of electrode and unexpected corrosion. Further, breakage of wiring due to defects of resist has also been apt to occur.
It is an object of this invention to suppress the breakage of wiring in the electrodes formed in wiring substrates and gas discharge display panels. In particular, the object of this invention consists in suppressing the breakage of wiring in the case of forming electrodes by wet etching process.
In order to achieve the object mentioned above, this invention forms a resist from an inorganic material in a wet etching process.
Thus, this invention forms a gas discharge disp
Fukushima Makoto
Ijuin Masahito
Kawai Michifumi
Murase Tomohiko
Nishiki Masashi
Antonelli Terry Stout & Kraus LLP
Haynes Mack
Hitachi Ltd
Ramsey Kenneth J.
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