Gas display panel fabrication method

A gas panel fabrication method includes forming a first set of dielectrically coated parallel conductors on a glass plate, forming a metal spacer layer over the first conductors, oxidizing those areas of the metal spacer layer which are between the first conductors, forming a second set of dielectrically coated parallel conductors over the spacer layer in orthogonal relationship with the first conductors, etching the unoxidized areas of the spacer layer from between the second conductors, and forming a cover plate to hold an ionizable gas adjacent to the orthogonal conductors.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates generally to a method for fabricating a flat 
display panel and more particularly to a method for fabricating a gas 
display panel with a monolithic structure. 2. Description of the Prior Art 
In the prior art, display panels employing gas discharge are well known and 
a variety of such display panels have already been suggested. A typical 
structure of a gas display panel utilizes a pair of glass plates. A 
plurality of parallel conductors are formed on one surface of each of said 
glass plates. Preferably, the conductors are dielectrically coated to 
utilize the memory action by wall charges. The glass plates are placed so 
that the conductors on one glass plate are opposite to and orthogonal to 
the conductors on the other glass plate. Spacer means such as rods is 
placed between the glass plates at their peripheral portions thereby to 
define a distance between the conductors opposite to each other and 
accordingly a discharge gap. The intersections of the orthogonal 
conductors form display cells. The peripheral portions of the glass plates 
are sealed to form a gas discharge chamber including an ionizable gas. An 
example of a method of fabricating a gas display panel with such a 
structure is disclosed in the Japanese laid-open patent application No. 
79972/73. 
However, when the discharge gap is defined by placing such spacer rods at 
the peripheral portions of the panel, it is liable to cause variations in 
the discharge gap between the central portions and the peripheral portions 
of the panel due to the somewhat flexible nature of the glass plates. This 
inclination would be more marked especially in larger panels. Since a 
firing voltage is a function among other things of the discharge gap, such 
variations in the discharge gap with the positions of the cells would be a 
factor of preventing the reliable operation of the panel. If the number of 
the spacer rods were increased so as to be placed also at the central 
portions of the panel, the problem of the variations in the discharge gap 
could be relieved to some extent. However, even if the number of the 
spacer rods were increased, it would practically be impossible to keep the 
discharge gap uniform at all the cells due to the limited flatnesses of 
the glass plates themselves. Further, such incomplete flatnesses of the 
glass plates would not permit them to be placed quite close to each other, 
thereby resulting in preventing the increase of the cell density, 
accordingly the resolution, of the panel. It would be quite difficult and 
quite uneconomical to try to place the spacer rods precisely and to obtain 
completely flat glass plates. 
Therefore, in order to realize a gas display panel which would provide a 
highly reliable operation and a higher cell density, it would be required 
to fabricate a gas display panel such that it would be free from 
restrictions by the flatnesses of the glass plates as much as possible. 
The Japanese laid-open patent application No. 12/72 discloses a gas display 
panel with a structure wherein both sets of conductors orthogonal to each 
other are supported on one glass plate. One set of conductors are formed 
on the glass plate and dielectrically coated. The other set of conductors 
are formed on the dielectric coating so as to extend orthogonally to said 
one set of conductors. Then, a cover plate is attached to hold an 
ionizable gas in the areas adjacent to the sets of conductors orthogonal 
to each other. In ths gas display panel, said problem of the variations in 
the discharge gap due to the incomplete flatnesses of the glass plates may 
be solved since both sets of conductors orthogonal to each other are 
supported on one glass plate. However, in this gas display panel, gas 
discharge is produced along the surface of the dielectric coating near the 
intersections of the orthogonal conductors and cannot be produced 
perpendicularly to the glass plate at the intersections of the orthogonal 
conductors since the areas between the sets of conductors orthogonal to 
each other are completely filled with the dielectric coating. As the 
result, in this gas display panel, it has been impossible to define the 
cells clearly, to increase the cell density, and to obtain a high quality 
in the display. 
The Japanese laid-open patent application No. 56059/73 also discloses a gas 
display panel with a structure wherein the sets of conductors orthogonal 
to each other having a dielectric coating therebetween are supported on 
one glass plate, similar to the gas display panel disclosed in said 
laid-open patent application No. 12/72. In this gas display panel, small 
cavities or blind holes are formed in the dielectric coating adjacent to 
the intersections of the orthogonal conductors, one for each of said 
intersections, thereby to provide a space for gas discharge at each of 
said intersections. However, in this gas display panel, it is still unable 
to increase the cell density since said cavities are not aligned with the 
intersections of the orthogonal conductors. 
Further, the Japanese laid-open patent application No. 37073/73 discloses a 
gas display panel with a structure wherein the sets of conductors 
orthogonal to each other having a dielectric coating therebetween are 
supported on one insulating substrate. This gas display panel is provided 
with holes at the intersections of the orthogonal conductors, one for each 
of said intersections, which pass through the conductors on the dielectric 
coating and the dielectric coating to the surfaces of the conductors on 
the insulating substrate, thereby to provide spaces for gas discharge. 
These holes located at the intersections of the orthogonal conductors may 
accomplish the advantage that the spaces for gas discharge may be aligned 
with the intersections of the orthogonal conductors. However, these 
conductors are liable to be made wider in order to form such holes 
therethrough and this would be a problem in obtaining an increased 
resolution of the panel. Further, in this gas display panel, the memory 
action by wall charges cannot be utilized since both sets of the 
conductors are in direct contact with the gas in the panel. 
OBJECT OF THE INVENTION 
Accordingly, it is a major object of the present invention to provide an 
improved method for fabricating a flat display panel with a monolithic 
structure. 
It is another object of the present invention to provide a method for 
fabricating a gas display panel whereby the discharge gas can be kept 
uniform at all the cells without being restricted by the flatnesses of the 
glass plates and a high resolution display can be realized. 
It is further object of the present invention to provide a method for 
fabricating a gas display panel whereby one set of conductors are 
suspended a given distance from the other set of conductors by spacer 
means so that both sets of conductors orthogonal to each other are 
integrally supported on one substrate and an ionizable gas exists between 
the orthogonal conductors at the intersections of the orthogonal 
conductors. 
SUMMARY OF THE INVENTION 
A method of fabricating a gas display panel in accordance with the present 
invention is started with preparing a substrate having on one surface 
thereof a plurality of elongated first conductors. The first conductors 
may be dielectrically coated. Then, a spacer layer is formed over said 
first conductors which comprises first areas of a material removable by a 
predetermined treatment and second areas of an insulating material 
unremovable by said treatment with said second areas located between said 
first conductors. Next, a plurality of elongated second conductors are 
formed on said spacer layer so as to intersect with said first conductors. 
The second conductors may be dielectrically coated. Then, said first areas 
are removed by subjecting them to said treatment from between said second 
conductors. Finally, a cover plate is attached so as to cover all the 
intersections of said first and second conductors. 
More particularly, in a preferred embodiment of the present invention, a 
plurality of first parallel conductors are formed on a substrate. Then, a 
first dielectric coating is deposited over the first conductors. Next, a 
spacer layer of metal such as aluminium, for example, is deposited over 
the dielectric coating and the areas thereof between the first conductors 
where ultimate spacer means is to be formed are oxidized. A second 
dielectric coating is deposited over the spacer layer comprising the areas 
of a metal and the areas of a metal oxide and a plurality of second 
parallel conductors are formed on the second dielectric coating so as to 
extend orthogonally to the first conductors. A third dielectric coating is 
deposited over the second conductors. Then, the areas of the second and 
third dielectric coatings between the second conductors are removed by 
etching to expose the corresponding areas of the spacer layer. The 
remaining areas of the second and third dielectric coatings completely 
cover the top, bottom and lateral surfaces of the second conductors. 
Thereafter, the exposed areas of the spacer layer between the second 
conductors are subjected to an etching solution thereby to remove the 
metal areas of the spacer layer. Finally, a cover plate is attached so as 
to cover the intersections of the first and second conductors. 
In another embodiment of the present invention, more than one of the step 
of depositing the first dielectric coating, the step of depositing the 
second dielectric coating, and the step of depositing the third dielectric 
coating are eliminated and instead thereof the exposed surfaces of the 
first and/or second conductors are oxidized thereby to form dielectric 
coatings thereon.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring now to the drawings, the present invention will be explained more 
in detail with respect to a preferred embodiment thereof. FIG. 1 
illustrates various steps for fabricating the gas display panel with a 
monolithic structure in accordance with the present invention. As 
illustrated by A in FIG. 1, a plurality of first parallel conductors 2 are 
formed on an insulating substrate such as a glass plate 1, for example. 
Only four conductors are shown in FIG. 1 for illustrative purposes. The 
conductors 2 are formed by vacuum evaporating a metal in a uniform 
thickness on the top surface of the glass plate 1 and then employing the 
well known photolithographic masking and etching techniques. Of course, 
the conductors 2 may be formed also by evaporating a metal with the 
surface of the glass plate 1 masked selectively so as to expose only the 
areas where the conductors 2 are to be formed or may be deposited by any 
other known method. In this embodiment, the conductors 2 are preferably 
made of a transparent conductive material such as SnO.sub.2 or (In.sub.2 
O.sub.3 +SnO.sub.2) since the glass plate 1 is used as a display face. In 
case SnO.sub.2 is used, the conductors 2 are formed by depositing a 
sputtered SnO.sub.2 layer in a thickness of 1.mu., then selectively 
masking the SnO.sub.2 layer with a photoresist layer in the conductor 
pattern, and etching the SnO.sub.2 layer with hydrochloric acid or 
sulfuric acid. The conductors 2 are 130.mu. wide and 40.mu. spaced apart 
from each other. The conductors 2 may be formed also by employing electron 
beam evaporation of SnO.sub.2 or by spraying SnCl.sub.4 onto a glass plate 
heated at 400.degree. to 700.degree. C. The conductors 2 may be made of a 
material such as copper or aluminium bifurcated or provided with small 
holes at the positions where display cells are to be formed in order to 
increase the light outputs. When the conductors 2 are made of a highly 
conductive material such as copper, they may have a thickness of 0.5.mu.. 
As will be described later more in detail, the conductors 2 are preferably 
formed so as to be terminated a given distance from each end of the glass 
plate 1 so that the entire surfaces of the conductors 2 may be 
dielectrically coated to protect them from subsequent metal etching 
processes. 
Then, a dielectric coating 3 is deposited over the conductors 2. The 
materials used for the dielectric coating 3 include SiO.sub.2, Al.sub.2 
O.sub.3, Si.sub.4 N.sub.4 and the like. In case of SiO.sub.2, the glass 
plate 1 is heated at a temperature in the order of room temperature to 
200.degree. C. and SiO.sub.2 is deposited thereon to a thickness of 2.mu. 
by RF sputtering. With an RF power of 500 to 1000 W at 13.56 MHz, the 
deposition rate is about 250 A/min. and the sputtering is performed for 
about 80 minutes to obtain an SiO.sub.2 layer with a thickness of 2.mu.. 
Since the conductors 2 are formed so as to be terminated a given distance 
from each end of the glass plate 1, not only the top surfaces but also the 
lateral and end surfaces of the conductors 2 may be coated with the 
dielectric coating 3. 
Thereafter, as illustrated by A in FIG. 1, a spacer layer 4 of a metal is 
deposited over the dielectric coating 3 in a uniform thickness. The metal 
used therefor may be any of those which would meet the requirements that 
they may be easily deposited, that they may be easily etched, and that 
they form highly insulating oxides when oxidized. For this purpose, 
aluminium is most preferred. Aluminium is deposited by vacuum evaporation 
under a vacuum pressure of 1.times.10.sup.-6 Torr with the glass plate 1 
heated at 300.degree. C. The spacer layer 4 of aluminium has a thickness 
of 10.mu.. As will be clearly understood later, the spacer layer 4 of 
aluminium is not deposited to the edges of the conductors 2 which are 
utilized for external connections to supply driving signals to the 
conductors 2. Other metals such as tantalum, niobium, zirconium and 
hafnium may be also used for the spacer layer 4, but they have extremely 
high melting points and require a sputtering technique to be deposited. 
The sputtering technique demands relatively precise controls and needs 
much time to obtain a relatively thick layer due to its low deposition 
rate. Further, an etching solution of hydrofluoric acid used for etching 
these metals also etches SiO.sub.2 and therefore aluminium is desired to 
be used for the spacer layer 4. However, these metals may be used for the 
spacer layer 4 when other metals such as Al.sub.2 O.sub.3, Si.sub.4 
N.sub.4 and the like which are not etched by hydrofluoric acid are used 
for the dielectric coating. 
Next, as illustrated by B in FIG. 1, the spacer layer 4 of aluminium is 
selectively oxidized so that only the areas 5 between the conductors 2 and 
the areas 5' and 5" at both edges may be oxidized into alumina (Al.sub.2 
O.sub.3). This oxidization is performed by depositing a photoresisit layer 
over the entire surface of the spacer layer 4 of aluminium, selectively 
exposing and developing the photoresist layer so that only the areas 5, 5' 
and 5" of the spacer layer 4 of aluminium are exposed, and then anodizing 
the exposed areas of the spacer layer 4 of aluminium. This anodization of 
aluminium is performed in an aqueous solution of 2% sulfuric acid at a 
temperature below 20.degree. C. with a current density of 0.01 to 0.02 
A/cm.sup.2. Aluminium somewhat increases in its thickness when oxidized 
into alumina. In the figures, the alumina areas 5, 5' and 5" are shown to 
be coplanar with the aluminium areas 6 as the result of an increase in the 
thickness of the alumina areas 5, 5' and 5", but it should be understood 
that for the purpose of clarity they are not always showing precisely the 
actual conditions. It should be understood also that for the purpose of 
clarity the figures are not always showing the dimensions of each element 
to the same scale as its actual structure. 
FIG. 2 is an enlarged fragmentary perspective view illustrating a panel 
having the spacer layer 4 of aluminium which has been selectively anodized 
as described above with the dielectric coating 3 partly broken. Since the 
dielectric coating 3 is transparent, the conductors 2 can be seen 
therethrough. It will be apparent from FIG. 2 that the conductors 2 are 
terminated a given distance from each end of the glass plate 1 to be 
entirely coated with the dielectric coating 3 and that the spacer layer 4 
is formed so as not to cover the edges of the conductors 2. 
In case the end surfaces of the aluminium areas 6 in stripes are exposed, 
they will be also oxidized. However, they may be allowed to be oxidized to 
some extend since they are actually located outside the display area. If 
desired, the photoresist layer may be deposited so as to cover also the 
end surfaces of the aluminium areas 6. Alternatively, the periphery of the 
spacer layer 4 of aluminium located outside the display area may be 
oxidized in a frame pattern. It is only needed to oxidize the areas of the 
spacer layer 4 between the conductors 2 where ultimate spacer means is to 
be formed. 
Next, as illustrated by C in FIG. 1, a second dielectric coating 7 is 
deposited over the spacer layer 4 comprising the alumina areas 5, 5' and 
5" and the aluminium areas 6. The dielectric coating 7 which may be of the 
same material as the dielectric coating 3 is formed in a thickness of 
2.mu. by RF sputtering as in the case of the dielectric coating 3. 
Then, as illustrated by D in FIG. 1, a plurality of second parallel 
conductors 8 are formed on the dielectric coating 7 so as to extend 
orthoganally to the conductors 2. The conductors 8 may be formed in the 
same thickness, the same width and the same spacing with the same material 
as the conductors 2. However, the conductors 8 may be also made of an 
opaque conductive material such as copper since the conductors 8 located 
in the back of the cells formed by the conductors 2 and the conductors 8 
will not affect the light outputs. When copper is used for the conductors 
8, they are formed in a thickness of 0.5.mu.. The conductors 8 are formed 
so as to be terminated a given distance from each end of the spacer layer 
4 as illustrated by D in FIG. 1. 
Thereafter, as illustrated by E in FIG. 1, a third dielectric coating 9 is 
deposited over the conductors 8. The dielectric coating 9 which may be of 
the same material as the dielectric coatings 3 and 7 is formed in a 
thickness of 2.mu. by RF sputtering as in the cases of the dielectric 
coatings 3 and 7. As will be clearly understood later, if the top and 
lateral surfaces of the conductors 8 are not coated with the dielectric 
coating 9, these surfaces would be in direct contact with the gas in a 
completed panel and therefore sputtering would be produced at the exposed 
surfaces of the conductors 8 during the discharging operation, which might 
cause the gas in the panel to be contaminated. Therefore, the conductors 8 
are preferably coated with the dielectric coating 9. Since the conductors 
8 are terminated a given distance form each end of the spacer layer 4, 
their exposed surfaces may be coated completely with the dielectric 
coating 9. 
The next step is to etch selectively the dielectric coatings 7 and 9 so as 
to expose the spacer layer 4 at the areas between the conductors 8. 
Referring now to FIG. 3, the Figure is a sectional view taken along the 
line 3--3 of E in FIG. 1. The areas of the dielectric coatings 7 and 9 to 
be etched are the areas 10 between the conductors 8 as shown in FIG. 3. 
Further, in order to facilitate the etching of the aluminium areas at the 
edges of the spacer layer 4, the dielectric coatings 7 and 9 are 
preferably etched also in the areas 11. This etching operation is 
performed by employing the well known photolithographic masking 
techniques. Namely, a photoresist layer is deposited over the dielectric 
coating 9 and then selectively exposed and developed so that the 
photoresist layer in the areas 10 and 11 may be removed. The dielectric 
coating 9 exposed in the areas 10 and 11 is subjected to an etching 
solution which effectively etches only the dielectric coatings. A solution 
of 10% HF or a solution of (10% HF+NH.sub.4 F) is used as the etching 
solution. 
FIG. 4 is a sectional view, similar to FIG. 3, illustrating the panel when 
the dielectric coatings 7 and 9 have been selectively removed by etching. 
The spacer layer 4 is exposed in the areas 10 and 11. The etching of the 
dielectric coatings 7 and 9 should be performed so that after the etching 
the conductors 8 are still coated completely with the dielectric coatings 
7 and 9. 
Next, the panel is subjected to an etching solution to remove the aluminium 
areas 6 of the spacer layer 4. An etching solution which etches aluminium 
but not alumina nor a dielectric material is used therefor. For this 
purpose, etching solutions based on H.sub.3 PO.sub.4 or NaOH may be 
utilized and an appropriate etching solution is an aqueous solution of 
(H.sub.3 PO.sub.4 +HNO.sub.3). As the result, the aluminium areas 6 of the 
spacer layer 4 are removed by the etching solution which attacks them from 
the areas 10 and 11 and thereby empty spaces 12 are produced as 
illustrated by F in FIG. 1. The empty spaces 12 exist between the first or 
lower conductors 2 and the second or upper conductors 8, and accordingly 
the upper conductors 8 are suspended a given distance from the lower 
conductors 2 by the alumina areas 5, 5' and 5" which act as ultimate 
spacer means. 
In etching the aluminium areas 6 of the spacer layer 4, the dielectrically 
coated upper conductors 8 partly mask the aluminium areas 6 and act to 
prevent the areas masked thereby from being etched. However, since the 
dielectric material and alumina are not substantially etched by the 
aluminium etching solution, the etching operation may be performed for a 
long period of time enough to permit the aluminium areas under the upper 
conductors 8 to be fully undercut thereby. By applying ultrasonic waves, 
the aluminium areas may be removed more rapidly. Since the conductors 2 
and 8 are completely dielectrically coated, they would not be subjected to 
damage by the aluminium etching solution. 
Then, as illustrated by G in FIG. 1 and in FIG. 4, a cover plate 13 is 
placed at an appropriate position to hold an ionizable gas at the areas of 
the cells defined by the intersections of the conductors 2 and the 
conductors 8 and sealed with a sealing material such as a solder glass. 
The cover plate 13 is attached so that one edges of the conductors 2 and 8 
which are utilized for external connections to supply driving signals to 
the gas panel are extended out of the cover plate 13. When the periphery 
of the spacer layer 4 of aluminium is oxidized in a frame pattern as 
described above, the cover plate 13 may be placed on the periphery 
oxidized in a frame pattern. 
Finally, the edges of the dielectric coatings 3, 7 and 9 are removed by 
etching so as to expose one edges of the conductors 2 and 8 which are 
utilized for external connections. This etching operation may be performed 
by immersing the edges of the panel in a solution of 10% HF or a solution 
of (10% HF+NH.sub.4 F). 
FIG. 5 is an enlarged fragmentary perspective view illustrating the gas 
display panel fabricated in accordance with the present invention with the 
cover plate 13 removed. In FIG. 5, for the purpose of clarity, the 
dielectric coatings 7 and 9 remaining between the exposed edges of the 
conductors 2 and the spacer layer 4 are removed. The conductors 2 and 8 
are completely dielectrically coated except for the exposed edges for 
external connections. 
While a preferred embodiment of the present invention has been described 
heretofore, it should be understood that various modifications may be made 
therein. 
For example, while the dielectric coating which covers the lower conductors 
2 has been deposited by RF sputtering a dielectric material such as 
SiO.sub.2 in the preferred embodiment of the present invention, it may be 
provided also by oxidizing the surfaces of the lower conductors to form 
oxide coatings thereon prior to the deposition of the spacer layer. In 
this alternative method, aluminium, tantalum, niobium, zirconium, or 
hafnium may be used as a metal for the lower conductors 2. For example, an 
aluminium layer is deposited on the glass plate 1, the parallel conductors 
2 of aluminium are formed therein by employing the well known 
photolithographic masking and etching techniques as described with 
reference to FIG. 1, and then only the surfaces of the aluminium 
conductors are anodized to be dielectrically coated with alumina. 
Alternatively, instead of forming the parallel conductors of aluminium by 
etching, the aluminium layer on the glass plate 1 may be anodized in 
strips to form parallel aluminium conductors isolated from each other by 
the regions anodized in stripes, and then only the surfaces of the 
aluminium conductors may be anodized. The order of these steps of 
anodizing the aluminium layer for the lower conductors in stripes and 
anodizing the surface of said aluminium layer may be reversed. When the 
step of anodizing the surface of the aluminium layer is performed prior to 
the step of anodizing the aluminium layer in stripes, the aluminium layer 
for the lower conductors and the spacer layer deposited thereon may be 
simultaneously anodized in stripes. The subsequent steps may be performed 
in accordance with the same procedures as described with reference to FIG. 
1. 
Also, in this alternative method, tantalum, zirconium, niobium or hafnium 
may be used for the spacer layer. However, when the steps after the step 
of anodizing the spacer layer are performed as in the case of FIG. 1, the 
dielectric coatings 7 and 9 should be made of Al.sub.2 O.sub.3, Si.sub.4 
N.sub.4, etc. since SiO.sub.4 is etched by hydrofluoric acid as stated 
above. A solution of HF or (HF+HNO.sub.3) is an appropriate etching 
solution for tantalum, zirconium, niobium and hafnium. Since these etching 
solutions do not etch the oxides of these metals, any of these metals may 
be utilized as a metal to be oxidized on its surface and also as a spacer 
layer. Further, since the etching solution for aluminium, namely as 
aqueous solution of (H.sub.3 PO.sub.4 +HNO.sub.3), does not etch the 
oxides of tantalum or the like, tantalum or the like may be used as a 
metal to be oxidized on its surface and aluminium may be used as a spacer 
layer. 
Further, although the step of depositing the dielectric coating 7 and the 
step of depositing the dielectric coating 9 have been used to form 
dielectric coatings on the upper conductors 8 in the preferred embodiment, 
more than one of these steps may be eliminated by anodizing the exposed 
surfaces of the upper conductors 8 to form dielectric coatings on the 
upper conductors after etching the aluminium areas 6 of the spacer layer 
4. In this case, tantalum, niobium, zirconium or hafnium may be used for 
the upper conductors. Since these metals are not substantially etched by 
an etching solution for aluminium, they do not suffer damage by the 
etching solution during the etching of the aluminium areas 6 of the spacer 
layer 4. In this alternative method, the steps from the formation of the 
lower conductors to the selective anodization of the aluminium spacer 
layer may be made in accordance with the procedures stated with reference 
to FIG. 1 or in accordance with the procedures utilizing the above 
mentioned surface oxidization of the lower conductors. When the surface 
oxidization of the lower conductors is employed in this alternative 
method, both of the lower and upper conductors would be opaque. 
Also in this alternative method, the spacer layer may be formed of 
tantalum, niobium, zirconium or hafnium. However, in this case, the upper 
conductors should be formed of aluminium since the upper conductors also 
formed of tantalum, niobium, zirconium or hafnium would be also etched 
during the etching of the spacer layer. The etching solution for tantalum 
or the like such as a solution of (HF+HNO.sub.3) does not substantially 
etch aluminium. However, when tantalum or the like is used for the spacer 
layer, the dielectric materials which would be etched by hydrofluoric acid 
cannot be used for the dielectric coating 3 on the lower conductors. 
Further, it is also possible to eliminate the step of depositing the 
dielectric coating 3 on the lower conductors and more than one of the 
steps of depositing the dielectric coating 7 and depositing the dielectric 
coating 9 and to form dielectric coatings by simultaneously anodizing the 
exposed surfaces of the lower conductors 2 and the upper conductors 8 
after the etching of the aluminium areas 6 of the spacer layer 4. In this 
case, the lower conductors 2 and the upper conductors 8 are formed of 
tantalum, niobium, zirconium or hafnium which are not etched by an etching 
solution for aluminium. Also in this case, both of the lower and upper 
conductors are opaque. As stated before, when the method of forming the 
lower conductors isolated from each other by anodizing the metallic layer 
on the glass plate 1 in stripes is utilized in this alternative method, 
the anodizations in stripes of the metallic layer for the lower conductors 
and the aluminium spacer layer may be performed simultaneously. 
Also in this case, tantalum or the like may be used for the spacer layer. 
However, in this case, aluminium should be used for the lower and upper 
conductors and the dielectric coating 7 or 9, if used, should be formed of 
a material which would not be etched by hydrofluoric acid used for etching 
tantalum or the like. 
Another alternative method may be used wherein a tantalum layer, for 
example, is deposited on the glass plate 1, the aluminium spacer layer is 
deposited thereon, the tantalum layer and the aluminium spacer layer are 
simultaneously anodized in stripes, and the surface of the tantalum layer 
is anodized after the etching of the aluminium areas 6. 
Although the present invention has been described with reference to 
particular embodiments thereof, it would be easily understood that various 
other modifications are possible within the scope of the present 
invention. For example, although all the areas of the metallic spacer 
layer between the lower conductors have been oxidized in stripes to 
provide the ultimate spacer means, it would be easily understood that only 
the discontinuous areas of each area of the metallic spacer layer between 
the lower conductors, which would be necessary for supporting the upper 
conductors so that they may be suspended from the lower conductors, can be 
anodized to remove all the other areas. In this case, however, the 
anodizations of the metallic layer for the lower conductors and the spacer 
layer cannot be performed simultaneously. Further, although the lower and 
upper conductors have been exposed respectively on one side thereof for 
external connections in the preferred embodiment, the alternate edges of 
the conductors may be exposed on opposite sides to facilitate external 
connections of high line densities. The cover plate may be used for the 
display face. 
Further, while the preferred embodiment of the invention has been described 
in terms of a gaseous discharge display, it will be apparent that the 
teaching of the present invention relating to selective removal of a 
spacer layer to form spaces for insertion of a voltage responsive display 
medium between opposing electrodes could also be applied to other flat 
display panels such as liquid crystal displays. Accordingly, it is 
intended that the scope of the invention be limited only as specified in 
the claims.