U.S. patent number 3,837,724 [Application Number 05/405,205] was granted by the patent office on 1974-09-24 for gas panel fabrication.
This patent grant is currently assigned to International Business Machines Corporation. Invention is credited to Peter H. Haberland, Frank M. Lay, Thomas J. Murphy, Marvin B. Skolnik, Oliver S. Spencer, Peter R. Wagner, Howard L. Whitaker, Donald M. Wilson.
United States Patent |
3,837,724 |
Haberland , et al. |
September 24, 1974 |
GAS PANEL FABRICATION
Abstract
A method is disclosed for the fabrication of a gas panel which
includes depositing parallel lines as electrical conductors on a
pair of glass plates, providing a protective coating of glass over
the parallel lines, placing a sealing material between the glass
plates around the periphery thereof, spacing the glass plates a
given distance apart, firing the assembly in an oven to seal the
glass plates together with a chamber therebetween, evacuating the
chamber, filling it with an illuminable gas, and exposing each
parallel lines at one end of each glass plate as an electrical
contact.
Inventors: |
Haberland; Peter H. (Woodstock,
NY), Lay; Frank M. (Woodstock, NY), Murphy; Thomas J.
(Rhinebeck, NY), Skolnik; Marvin B. (Woodstock, NY),
Spencer; Oliver S. (Woodstock, NY), Wagner; Peter R.
(Lake Katrine, NY), Whitaker; Howard L. (Kingston, NY),
Wilson; Donald M. (Kingston, NY) |
Assignee: |
International Business Machines
Corporation (Armonk, NY)
|
Family
ID: |
26908900 |
Appl.
No.: |
05/405,205 |
Filed: |
October 10, 1973 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
|
214348 |
Dec 30, 1971 |
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Current U.S.
Class: |
445/25; 313/584;
315/169.1; 315/169.4; 445/58 |
Current CPC
Class: |
C03C
17/3671 (20130101); H01J 9/20 (20130101); C03C
17/3615 (20130101); C03C 17/3649 (20130101); H01J
9/261 (20130101); C03C 17/3655 (20130101); C03C
17/36 (20130101); C03C 17/3652 (20130101) |
Current International
Class: |
H01J
9/26 (20060101); H01J 9/20 (20060101); C03C
17/36 (20060101); H01j 009/38 (); H01j 009/18 ();
H01j 009/26 () |
Field of
Search: |
;313/220,221
;29/251,25.11,25.13,25.16,25.19,472.5,472.9,625,631 ;316/17,19,20
;65/36,59,154,147,138,139,23 ;117/201 ;315/169,169TV,165 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Lanham; C. W.
Assistant Examiner: Walkowski; Joseph A.
Parent Case Text
CROSS-REFERENCES TO RELATED APPLICATIONS
This is a continuation, of application Ser. No. 214,348 filed Dec.
30, 1971 and now abandoned.
Application Ser. No. 214,151 filed on Dec. 30, 1971 for Improved
Method of Gas Panel Construction by Thomas J. Murphy et al., now
U.S. Pat. No. 3,804,609.
Application Ser. No. 214,150 filed on Dec. 30, 1971 for Method of
Protecting Electrical Conductor Terminations during Gas Panel
Fabrication by Peter R. Wagner et al., now U.S. Pat. No. 3,778,901.
Claims
What is claimed is:
1. A method of fabricating a gas panel, said method including the
steps of:
1. cutting a pair of glass plates to appropriate dimensions to
provide an overlap area of a desired size for the gas panel,
2. disposing parallel lines as electrical conductors on each glass
plate with the electrical conductors terminating a given distance
from each end of each glass plate,
3. heating each glass plate in an atmosphere which oxidizes the
exposed surface of each parallel line thereby to render each
parallel line passive during a subsequent protective coating
operation,
4. spraying a mixture of glass frit in a suspension vehicle over
the parallel lines of each glass plate with precision spray
equipment thereby to deposit the mixture with a uniform depth on
each glass plate,
5. firing each glass plate on a level surface in an oven to reflow
the glass frit whereby a protective glass coating completely covers
the parallel lines,
6. placing on one of the glass plates a sealing material composed
of glass frit in a binder prefabricated in the form of a rectangle,
and placing spacers at selected locations near the sealing material
on said one glass plate,
7. heating one said glass plate to bake the binder out of the
sealing material,
8. placing the other glass plate on said one glass plate with the
parallel lines on said one glass plate extending orthogonally to
the parallel lines on the other glass plate,
9. heating the assembly in an oven on a level surface to reflow the
glass frit that was in a binder and seal the two glass plates
together spaced apart a given distance thereby to form a chamber
therebetween,
10. heating the assembly in an oven and simultaneously evacuating
the chamber, thereafter backfilling the chamber with an illuminable
gas, and sealing the illuminable gas in said chamber under less
than atmospheric pressure, and
11. exposing each parallel line at one end of each glass plate as
an electrical contact.
2. The method of claim 1 wherein the spraying of step 4 is
performed by using a regulated constant blower pressure and a
regulated constant speed of relative movement between the spray
equipment and the glass plates.
3. The method of claim 2 including the further step of using freon
vapor as a propellent in the spray equipment.
4. The method of claim 1 wherein the sprayed mixture of step 4 is a
slurry prepared by adding finely ground glass frit to a suspension
vehicle composed of a solution of nitrocellulose polymer binder in
amyl acetate, and mixing thoroughly to disperse the finely ground
glass frit uniformly throughout the solution to form the
slurry.
5. The method of claim 1 wherein each of the parallel lines in step
2 is a laminate made by depositing a first layer composed of
chromium on each glass plate, depositing a second layer composed of
copper on the first layer, depositing a third layer composed of
chromium on the second layer, applying a coating of photoresist on
the third layer, exposing the photoresist with art work having a
light pattern of alternate light and dark lines, developing the
exposed photoresist material, etching the laminate between the
remaining regions of photoresist material, exposing the remaining
photoresist material and developing again to remove the remainder
of the exposed photoresist material.
6. The method of claim 5 wherein the heating operation of step 3 is
performed in an atmosphere composed of 90 percent nitrogen, 10
percent hydrogen, and water vapor thereby to form a layer of
chromium oxide on the outer surface of the third layer composed of
chromium whereby the outer layer of chromium oxide renders the
laminated parallel lines passive or non-reactive to subsequent high
temperature operations.
7. A method of fabricating a gas panel, said method comprising the
steps of:
1. cutting two glass plates to appropriate dimensions for the
desired size of a gas panel,
2. depositing parallel lines as electrical conductors on each glass
plate with the electrical conductors terminating a given distance
from each end of each glass plate, each parallel line being a
laminate composed of a first layer composed of chromium deposit on
each glass plate, a second layer composed of copper deposited on
the first layer, and a third layer composed of chromium, deposited
on the second layer,
3. heating each glass plate in an atmosphere composed of 90 percent
nitrogen, 10 percent hydrogen, and water vapor to form a layer of
chromium oxide on the outer surface of the third layer composed of
chromium whereby the outer layer of chromium oxide renders the
laminated parallel lines passive or non-reactive to subsequent
firing operations,
4. spraying a slurry composed of a finely ground glass frit,
uniformly dispersed in a suspension vehicle, on each glass plate to
cover the laminated parallel lines on each glass plate with a
uniform depth of such slurry.
5. firing each glass plate on a level surface in an oven to reflow
the glass frit whereby a protective glass coating completely covers
the laminated parallel lines,
6. placing on one of the glass plates a sealing material composed
of glass frit in a cellulose binder prefabricated in the form of a
frame or rectangle, placing spacers at selected locations near the
sealing material on said one glass plate, and heating said one
glass plate to bake the cellulose binder out of the sealing
material,
7. placing the other glass plate on said one glass plate with the
parallel lines of one plate extending orthogonally to the parallel
lines of the other glass plate,
8. heating the assembly in an oven thereby to seal the two glass
plates together spaced a given distance apart and forming a chamber
therebetween,
9. evacuating the chamber and simultaneously baking the assembly in
an oven, thereafter backfilling the chamber with an illuminable gas
under less than atmospheric pressure, and sealing the illuminable
gas in said chamber, and
10. removing the protective glass coating and the upper layer of
chromium from the end regions of the laminated parallel lines at
one end of each glass plate, thereby exposing the copper layer of
each parallel line as an electrical contact.
8. The method of claim 7 wherein step 4 is performed using spray
gun equipment with regulated constant blower pressure and regulated
constant speed of relative movement between the spray gun and the
surface of the glass plates thereby to provide accurate control of
the thickness of the slurry sprayed over the laminated parallel
lines, and using freon vapor as a propellent for the spray gun.
9. A method of fabricating a gas panel, said method including the
steps of:
1. cutting first and second glass plates to appropriate dimensions
to provide an overlap area of a desired size for the gas panel, and
making a hole in the first glass plate,
2. disposing parallel lines as electrical conductors on each glass
plate with the electrical conductors terminating a given distance
from each end of each glass plate,
3. heating each glass plate in an atmosphere which oxidizes the
exposed surface of each parallel line thereby to render each
parallel line passive during a subsequent protective coating
operation,
4. spraying a mixture composed of glass frit in a suspension
vehicle, over the parallel lines of each glass plate with precision
spray equipment thereby to deposit the mixture with a uniform depth
on each glass plate,
5. firing each glass plate on a level surface in an oven to reflow
the glass frit whereby a protective glass coating completely covers
the parallel lines,
6. placing on the second glass plates a sealing material composed
of a glass frit in a cellulose binder prefabricated in the form of
a frame or rectangle, and placing spacers at selected locations
near the sealing material on the second glass plate,
7. heating the second glass plate to bake the cellulose binder out
of the sealing material,
8. applying a bead of a mixture of glass frit and suspension
vehicle on one end of a tubulation and placing such end in the hole
on the first glass plate,
9. placing the first glass plate on the second glass plate with the
parallel lines on the first glass plate extending orthogonally to
the parallel lines on the second glass plate,
10. heating the assembly in an oven on a level surface to seal the
two glass plates together spaced apart a given distance thereby to
form a chamber therebetween.
11. heating the assembly in an oven and simultaneously evacuating
the chamber through the tubulation, thereafter backfilling the
chamber through the tubulation with an illuminable gas, and tipping
off the tubulation thereby sealing the illuminable gas in said
chamber under less than atmospheric pressure, and
12. exposing each parallel line at one end of each glass plate as
an electrical contact.
10. The method of claim 9 wherein the spraying of step 4 is
performed by using a regulated constant blower pressure and a
regulated constant speed of relative movement between the spray
equipment and the glass plates.
11. The method of claim 10 including the further step of using
freon vapor as a propellent in the spray equipment.
12. The method of claim 10 wherein the sprayed mixture of step 4 is
a slurry prepared by adding finely ground glass frit to a
suspension vehicle composed of a solution of nitrocellulose polymer
binder in amyl acetate, and mixing thoroughly to disperse the
finely ground glass frit uniformly throughout the solution to form
the slurry.
13. The method of claim 10 wherein each of the parallel lines in
step 2 is a laminate made by depositing a first layer composed of
chromium on the first and second glass plates, depositing a second
layer composed of copper on the first layer, depositing a third
layer composed of chromium on the second layer, applying a coating
of photoresist on the third layer, exposing the photoresist with
art work having a light pattern of alternate light and dark lines,
developing the exposed photoresist material, etching the laminate
between the remaining regions of photoresist material, exposing the
remaining photoresist material and developing again to remove the
remainder of the exposed photoresist material.
14. The method of claim 13 wherein the heating operation of step 3
is performed in an atmosphere composed of 90 percent nitrogen, 10
percent hydrogen, and water vapor thereby to form a layer of
chromium oxide on the outer surface of the third layer composed of
chromium whereby the outer layer of chromium oxide renders the
laminated parallel lines passive or non-reactive to subsequent high
temperature operations.
15. A method of fabricating a gas panel, said method comprising the
steps of:
1. cutting first and second glass plates to appropriate dimensions
to provide an overlap area of a desired size for the gas panel, and
providing a hole in the first glass plate,
2. depositing a first layer composed of chromium on the first and
second glass plates with said first layer terminating a given
distance from each end of the first and second glass plates,
depositing a second layer composed of copper on the first layer,
depositing a third layer composed of chromium on the second layer,
thereby to form a laminate, applying a coating of photoresist on
the third layer, exposing the photoresist with art work having a
light pattern of alternate light and dark lines, developing the
exposed photoresist, etching the laminate between the remaining
regions of photoresist, exposing the remaining photoresist, and
developing again to remove the remainder of the exposed
photoresist, whereby laminated parallel lines which serve as
electrical conductors are formed on the first and second glass
plates,
3. heating the first and second glass plates in an atmosphere
composed of 90 percent nitrogen, 10 percent hydrogen, and water
vapor thereby to form a layer of chromium oxide on the outer
surface of the third layer composed of chromium whereby the outer
layer of chromium oxide renders the laminated parallel lines
passive or non-reactive to subsequent high temperature
operations,
4. spraying on the first and second glass plates with a precision
spray gun a slurry prepared by adding finely ground glass frit
mixed thoroughly to disperse the finely ground glass frit uniformly
throughout a suspension vehicle composed of a solution of
nitrocellulose polymer binder in amyl acetate, thereby to deposit
the mixture with a uniform depth on the first and second glass
plates,
5. firing the first and second glass plates on a level surface in
an oven to reflow the glass frit thereby to form a protective glass
coating which covers completely the ends, sides and top of the
parallel lines,
6. placing on the second glass plate a sealing material composed of
a glass frit in a cellulose binder prefabricated in the form of a
frame or rectangle the inner periphery of which represents the
desired dimensions of a chamber to be formed between the first and
second glass plates,
7. heating the second glass plate to bake the cellulose binder out
of the sealing material,
8. applying a bead of a mixture of glass frit and suspension
vehicle on one end of a tubulation and placing such end in the hole
on the first glass plate,
9. placing the first glass plate on the second glass plate with the
parallel lines on the first glass plate extending orthogonally to
the parallel lines on the second glass plate,
10. heating the assembled first and second glass plates in an oven
on a level surface to seal the first and second glass plates
together spaced apart a given distance as determined by said
spacers thereby to form a chamber therebetween, and cooling the
assembly,
11. heating the assembly again in an oven and simultaneously
evacuating the chamber through the tubulation, thereafter
back-filling the chamber through the tubulation with an illuminable
gas, and tipping off the tubulation thereby sealing the illuminable
gas in said chamber under less than atmospheric pressure, and
12. removing the protective glass coating and the third layer of
chromium from the end regions of each parallel line at one end of
the first and second glass plates, thereby to expose the second
layer composed of copper as an electrical contact for each parallel
line.
16. The method of claim 15 wherein the spraying in step 4 is done
by regulating the blower pressure of the spray gun to be constant,
regulating the speed of relative movement between the spray gun and
the surface of the first and second glass plates to be constant
thereby to provide accurate control of the thickness of the slurry
sprayed over the laminated parallel lines of the first and second
glass plates, and using freon vapor as a propellent for the spray
gun thereby to minimize the presence of contaminants.
17. The method of claim 16 wherein the finely ground glass frit for
the slurry is milled in a ball mill to form a powder, sifting the
powder to obtain a particle size equal to or less than 0.0015 of an
inch in diameter, and using a jet in the spray head which has a
diameter of 0.030 of an inch, baking the finely ground glass frit
to remove all moisture thereby to prevent cohesion of the glass
frit particles before adding them to the suspension vehicle,
whereby the small glass frit particles are prevented from
collecting together in the suspension vehicle and forming group
particle sizes which might clog the jet of the spray head.
18. A method of fabricating a gas panel, said method including the
steps of:
1. depositing parallel lines as electrical conductors on a pair of
glass plates with the parallel lines terminating a given distance
from each end of each glass plate,
2. providing a protective cover over each one of the parallel lines
on each glass plate,
3. providing a protective coating of glass over the ends, sides,
and top of each parallel line on the glass plates,
4. placing on one of the glass plates a sealing material composed
of glass frit in a cellulose binder prefabricated in the form of a
frame or rectangle, placing spacers at selected locations near the
sealing material on said one glass plate, and heating said one
glass plate to bake the cellulose binder out of the sealing
material,
5. placing the other glass plate on said one glass plate with the
parallel lines of one glass plate extending orthogonally to the
parallel lines of the other glass plate,
6. heating the assembly in an oven thereby to seal the two plates
together spaced apart a given distance to form a chamber
therebetween,
7. evacuating the chamber and filling it with an illuminable gas,
and
8. exposing each parallel line at one end of each glass plate as an
electrical contact.
19. The method of claim 18 wherein the protective coating of step 3
is added by spraying a slurry composed of finely ground lead glass
powder thoroughly mixed with a suspension vehicle composed of a
solution of nitrocellulose polymer binder in amyl acetate,
regulating the spray equipment to have a constant blower pressure,
and regulating the spray equipment to have a constant speed of
relative movement between the spray equipment and the glass
plates.
20. The method of claim 19 including the further step of using
freon vapor as a propellent in the spray equipment.
21. The method of claim 19 wherein the finely ground lead glass
powder is prepared by milling lead glass granules in a ball mill to
produce a fine powder, sifting the powder to limit the maximum
particle size to a given diameter, baking the sifted powder to
remove all moisture until the sifted powder is mixed in the
suspension vehicle.
22. The method of claim 18 including the further step of cutting
off one side of each glass plate flush with the ends of the
parallel lines.
23. The method of claim 18 wherein each one of the parallel lines
in step 1 is a laminate made by depositing a first layer composed
of chromium on each glass plate, depositing a second layer composed
of copper on the first layer, depositing a third layer composed of
chromium on the second layer, applying a coating of photoresist on
the third layer, exposing the photoresist with art work having a
light pattern of alternate light and dark lines, developing the
exposed photoresist, etching the laminate between the remaining
regions of photoresist, exposing the remaining photoresist, and
developing again to remove the remainder of the exposed
photoresist.
24. The method of claim 23 including the further step of heating
each glass plate in an atmosphere composed of 90 percent nitrogen,
10 percent hydrogen, and water vapor thereby to form a layer of
chromium oxide on the outer surface of the third layer composed of
chromium whereby the outer layer of chromium oxide renders the
laminated parallel lines passive or non-reactive to subsequent high
temperature operations.
25. A method of fabricating a gas panel, said method including the
steps of:
1. cutting a pair of glass plates to appropriate dimensions to
provide an overlap area of a desired size for the gas panel,
2. disposing parallel lines as electrical conductors on each glass
plate with the electrical conductors terminating a given distance
from each end of each glass plate.
3. heating each glass plate in an atmosphere which oxidizes the
exposed surface of each parallel line and thereby to render each
parallel line passive during a subsequent protective coating
operation,
4. spraying a mixture of glass frit in a suspension vehicle over
the parallel lines of each glass plate with precision spray
equipment thereby to deposit the mixture with a uniform depth on
each glass plate,
5. firing each glass plate on a level surface in an oven to reflow
the glass frit whereby a protective glass coating completely covers
the parallel lines,
6. placing on one of the glass plates, a glass sealing material
around the periphery thereof, and placing spacers at selected
locations near the glass sealing material on said one glass
plate,
7. placing the other glass plate on said one glass plate with the
parallel lines on said one glass plate extending orthogonally to
the parallel lines on the other glass plate,
8. heating the assembly in an oven on a level surface to reflow the
glass sealing material and thus seal the two glass plates together
spaced apart a given distance thereby to form a chamber
therebetween,
9. heating the assembly in an oven and simultaneously evacuating
the chamber, thereafter backfilling the chamber with an illuminable
gas, and sealing the illuminable gas in said chamber under less
than atmospheric pressure, and
10. exposing each parallel line at one end of each glass plate as
an electrical contact.
26. A method of fabricating a gas panel, said method including the
steps of:
1. cutting first and second glass plates to appropriate dimensions
to provide an overlap area of a desired size for the gas panel, and
making a hole in the first glass plate,
2. disposing parallel lines as electrical conductors on each glass
plate with the electrical conductors terminating a given distance
from each end of each glass plate,
3. heating each glass plate in an atmosphere which oxidizes the
exposed surface of each parallel line thereby to render each
parallel line passive during a subsequent protective coating
operation,
4. spraying a mixture composed of glass frit in a suspension
vehicle over the parallel lines of each glass plate with precision
spray equipment thereby to deposit the mixture with a uniform depth
on each glass plate,
5. firing each glass plate on a level surface in an oven to reflow
the glass frit whereby a protective glass coating completely covers
the parallel lines,
6. placing on the second glass plate a glass sealing material
around the periphery thereof, and placing spacers at selected
locations near the glass sealing material on the second glass
plate,
7. applying a bead of a mixture of glass frit and suspension
vehicle on one end of a tubulation and placing such end in the hole
on the first glass plate,
8. placing the first glass plate on the second glass plate with the
parallel lines on the first glass plate extending orthogonally to
the parallel lines on the second glass plate,
9. heating the assembly in an oven on a level surface to seal the
two glass plates together spaced apart a given distance by the
spacers thereby to form a chamber therebetween,
10. heating the assembly in an oven and simultaneously evacuating
the chamber through the tubulation, thereafter backfilling the
chamber through the tubulation with an illuminable gas, and tipping
off the tubulation thereby sealing the illuminable gas in said
chamber under less than atmospheric pressure, and
11. exposing each parallel line at one end of each glass plate as
an electrical contact.
27. A method of fabricating a gas panel, said method including the
steps of:
1. depositing parallel lines as electrical conductors on a pair of
glass plates with the parallel lines terminating a given distance
from one end of each glass plate,
2. providing a protective cover over each one of the parallel lines
on each glass plate,
3. providing a protective coating of glass over the ends, sides,
and top of each parallel line on the glass plates,
4. placing on one of the glass plates a glass sealing material
around the periphery thereof, and placing spacers at selected
locations near the glass sealing material on said one glass
plate,
5. placing the other glass plate on said one glass plate with the
parallel lines of one glass plate extending orthogonally to the
parallel lines of the other glass plate,
6. heating the assembly in an oven thereby to seal the two plates
together spaced apart a given distance to form a chamber
therebetween,
7. evacuating the chamber and filling it with an illuminable gas,
and
8. exposing each parallel line at one end of each gas plate as an
electrical contact.
Description
BACKGROUND OF THE INVENTION
1. This invention relates to gas panels and more particularly to a
method of constructing gas panels.
2. The introduction of gas panels for use as display devices or
storage devices has lead to an increased demand for them
particularly where they are reliable in operation and reasonable in
cost and upkeep. It is highly desirable for both display and
storage purposes to have a large number of cells per unit area of
the gas panel. When used in conjunction with other devices, display
panels must be uniform in their optical and electrical
characteristics whereby they readily may be interchanged. For
example, if the characteristics of the gas vary widely from one
panel to another, then standard electrical signals from other
devices may operate one panel but not another. Such inconsistency
or lack of uniformity may result in unreliable operation in some
instances. If the electrical conductors are pitted, eroded, or
broken in the fabrication process, an unreliable gas panel results.
Defective gas panels must be discarded, and as the number of such
defective gas panels increases in a production operation, the cost
of producing acceptable gas panels increases accordingly. A method
of fabrication is needed, therefore, for the production of gas
panels having uniformity in their mechanical, electrical and
optical characteristics. Such method of construction preferably
should provide gas panels which are relatively less expensive to
manufacture, maintain, and operate.
It is to this end that the present invention is directed.
SUMMARY OF THE INVENTION
It is a feature of this invention to provide an improved method of
mass producing reliable gas panels thereby to reduce the per unit
cost of manufacture.
It is a feature of this invention to provide an improved
fabrication technique for the reproduction of gas panels each of
which has substantially the same mechanical, electrical, and
optical characteristics whereby such gas panels may be employed
interchangeably.
It is a feature of this invention to provide an improved technique
for constructing gas panels wherein the parts thereof are not
pitted, eroded, broken, or defaced in the fabrication process.
In a preferred embodiment of the method according to this invention
two glass plates are cut to appropriate dimensions, and a laminate
preferably of chromium-copper-chromium is disposed on one side of
each glass plate. The laminate is terminated back a given distance
from the ends of each glass plate. A coating of photoresist
material is disposed on the laminate and dried. The photoresist
material is exposed to a light pattern of artwork having alternate
light and dark parallel lines. The two glass plates are immersed in
a developer until the exposed photoresist is removed. The remaining
photoresist is in the form of parallel lines. Each plate is cleaned
and then immersed in a solution which etches away the laminate from
regions not protected by the parallel lines of photoresist
material. This etching process leaves a plurality of laminated
parallel lines having an outer coating of unexposed photoresist.
This photoresist is exposed and placed in a developer until it is
removed. The resulting laminated parallel lines terminate a given
distance from the edges at both ends of each glass plate. The two
glass plates are heated in a forming gas atmosphere and water vapor
to oxidize the exposed surface of the outer chromium layer thereby
to render the laminated parallel lines passive during a subsequent
dielectric coating operation. A glass frit is sprayed over the
conductive parallel lines of each glass plate. The glass frit
preferably is a lead glass which is applied to a uniform depth by
precision spraying. The glass plates then are fired in an oven to
reflow the glass frit whereby a glass coating covers the laminated
parallel lines. The two glass plates are spaced apart a given
distance and sealed around the periphery thereby to form a chamber
therebetween for holding an illuminable gas. Thereafter the chamber
between the two glass plates is evacuated and refilled with an
illuminable gas under less than atmospheric pressure. The
dielectric coating and the outer chromium layer are removed from
the end regions of the parallel lines at one end of each glass
plate so that electrical connections can be made to the exposed
copper lands. The dielectric coating may be removed by immersion in
an etching solution such as hydrochloric acid, and the outer
chromium layer may be removed by immersion in an etching solution
such as potassium ferricyanide. The fabrication of the panel is
complete, and it may be operated by applying electrical signals to
selected parallel lines on each plate thereby to ignite gas cells
defined by the coordinate intersections of such parallel lines
which are disposed orthogonally to each other.
The foregoing and other objects, features and advantages of the
invention will be apparent from the following more particular
description of a preferred embodiment of the invention as
illustrated in the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of a gas panel constructed according
to this invention.
FIG. 2 is a perspective view of one glass plate during the
fabrication process.
FIG. 3 is a cross-sectional view, with parts not shown to scale,
taken on the line 3--3 in FIG. 2.
FIG. 4 is a cross-sectional view, with parts not shown to scale, of
one plate after the parallel conductors are formed thereon.
FIG. 5 is a cross-sectional view, with parts not shown to scale, of
a plate showing a protective coating disposed on the laminated
parallel lines.
FIG. 6 is a perspective view of a lower plate with a frame seal and
spacers disposed thereon.
FIG. 7 is a perspective view of an upper plate which includes
tubulation.
DESCRIPTION OF THE PREFERRED EMBODIMENT
A gas panel constructed according to the novel method of this
invention is illustrated in FIG. 1, and it includes an upper glass
plate 10 separated from and sealed to a lower glass plate 12 with
an intervening chamber which is filled with an illuminable gas.
Electrically conductive parallel lines 21 through 28 are disposed
on the lower side of the glass plate 10, and they serve as an
electrode for supplying a given electrical signal to a selected gas
cell. Electrically conductive parallel lines 31 through 40 are
disposed on the upper side of the glass plate 12, and they serve as
an electrode for supplying a given electrical signal to the other
side of a selected gas cell. Gas cells are defined as the region of
the illuminable gas disposed between the coordinate intersections
of the upper parallel lines 21 though 28 and the lower parallel
lines 31 through 40. A selected gas cell is ignited by supplying a
given electrical signal to one of the parallel lines 21 through 28
and applying a given electrical signal to a selected one of the
parallel lines 31 through 40. The gas cell at the coordinate
intersection of the pair of selected lines is ignited.
The fabrication of the gas panel in FIG. 1 according to the method
of this invention involves numerous operations. In the ensuing
description the basic method steps are outlined first, and
thereafter the various operations involved in the basic steps of
the method are described in detail. The basic steps are summarized
as follows:
1. Two plates of glass which may be soda-lime-silica glass are cut
to the appropriate dimensions according to the desired size of the
gas panel. The plates are overlapped as shown in FIG. 1, and the
overlap area serves as the display or storage portion of the
panel.
2. A first thin film of chromium approximately 1,000 Angstroms
thick is deposited on one side of each glass plate. A second thin
film of copper approximately 10,000 Angstroms thick is deposited on
the first thin film composed of chromium of each glass plate. A
third film composed of chromium approximately 1,000 Angstroms thick
is deposited on the second thin film composed of copper of each
glass plate. The deposition of these thin films to form a laminate
preferably is done by vacuum metalization techniques. The laminate
terminates a given distance from the edges of the glass plates for
reason explained later.
3. A photolithographic process is used to convert the laminate into
a plurality of parallel lines which serve as electrical conductors.
A liquid photoresist material is applied, preferably by roller,
over the outer thin film of chromium and baked dry. The photoresist
material is exposed to a light pattern of art work having the
desired shape of parallel lines to be formed. After the exposure of
the photoresist material is made, the two plates are immersed in a
developer until the exposed resist material is removed. The
unexposed areas of the photoresist remain undisturbed. Each glass
plate is cleaned and then immersed in a solution which etches away
the chromium-copper-chromium laminate from regions not protected by
the resist material. This etching process leaves a plurality of
parallel lines with each line being composed of a
chromium-copper-chromium laminate having an outer coating of
unexposed resist. This resist is exposed and placed in a developer
until it is removed. The resulting parallel lines terminate a given
distance from the edges of the glass plates.
4. The two glass plates are heated in a forming gas atmosphere
composed of 90 percent nitrogen and 10 percent hydrogen and water
vapor. The outer surface of the third thin film composed of
chromium thereby is oxidized, and the chromium oxide surface
prevents a subsequent coating operation from dissolving the
laminated parallel lines. This step is referred to as passivation
since it renders the laminated parallel lines passive during a
subsequent dielectric coating operation.
5. A glass frit is applied over the electrically conductive
parallel lines of each glass plate. The glass frit preferably is a
lead glass. The glass frit is applied to a uniform depth over each
glass by precision spraying. The two glass plates are then fired in
an oven to a temperature sufficient to reflow the glass frit
whereby a glass coating covers completely the parallel lines. The
parallel lines terminate a given distance from the edges of each
glass plate, as pointed out above, and since the lead glass coating
extends beyond the ends of these parallel lines, it follows that
the ends, sides and top of each of the parallel lines are coated
over by the lead glass coating. The covering of the ends of these
parallel lines is done to prevent a reaction in subsequent firing
steps of the process from attacking and destroying end regions of
these lines. The lead glass coating serves also to prevent the
electrically conductive parallel lines from directly contacting the
illuminable gas when such gas is inserted in the completed gas
panel. The lead glass coating serves as a dielectric material which
collects a wall charge when the parallel lines are used
subsequently as electrodes for operating the gas panel.
Furthermore, the lead glass coating provides mechanical strength
and support for the thin laminated conductors which enables them to
withstand thermal and mechanical stress and stock during and after
the fabrication process.
6. The two glass plates are spaced apart a given distance and
sealed around the periphery thereby to form a chamber therebetween
for holding an illuminable gas. The sealing material preferably is
lead glass finely ground and disposed in a cellulose binder which
is cut in the form of a rectangular frame. The inner periphery of
the rectangular frame represents the desired dimensions of the
chamber for holding the illuminable gas. The frame is disposed on
one of the glass panels on top of the dielectric coating, and this
glass plate is heated in an oven until the cellulose binder is
baked out of the sealing material. The binder is baked out of the
sealing material to avoid blistering or darkening of the sealant.
The bake out is done also to remove possible contaminates which
subsequently might invade the illuminable gas. Glass rods of
suitable diameter to maintain proper chamber width are disposed at
given intervals around the inner periphery of the sealing material.
The spacer rods are placed approximately one-sixteenth of an inch
from the inner periphery of the sealing material. The remaining
glass plate is disposed on top of the spacer rods with the lead
glass dielectric coating face down engaging the sealant and spacer
rods. A hollow glass tube is inserted in a hole in the upper plate,
and sealing material is placed around the glass tube. The assembly
is placed in an oven, leveled, and fired until the lead glass
sealing material reflows. The glass plates are sealed to each
other, and the glass tube is sealed to the upper glass plate.
7. The hollow glass tube is connected to a vacuum pump. The chamber
between the two glass plates is evacuated, and simultaneously the
panel is baked thereby to remove moisture from the chamber and
gasses which escape from the lead glass sealing material. After the
chamber is evacuated and the bake off is complete, the chamber is
filled with an illuminable gas. The illuminable gas may be any one
or a combination of several well known gasses used for this
purpose. One suitable conbination is an illuminable gas composed of
99.9 percent neon and 0.10 argon. The evacuated chamber is filled
with the illuminable gas until the pressure in the chamber reaches
a range of 600 to 700 torrs.
8. The dielectric coating and the outer or third thin film composed
of chromium are removed in the end regions of the parallel lines on
each plate so that electrical connections can be made to the
exposed copper lands. The dielectric coating may be removed by
immersion in an etching solution containing hydrochloric acid, and
the third layer composed of chromium may be removed by immersion in
a solution of potassium ferricyanide. The construction of the panel
is complete, and it may be operated by applying electrical signals
to the parallel conductors.
The foregoing summary of the basic steps according to this
invention lays the foundation for a more detailed description of
the basic steps given next. The steps of the succeeding detailed
description are numbered to correspond with the basic method steps
summarized above.
1. The glass plates 10 and 12 in FIG. 1 are cut to appropriate
dimensions thereby to provide an overlap area of a desired size for
use as a display device or a storage device. The upper plate 10
extends beyond the left edge of the lower plate 12 and this
extension provides support for the electrical conductors 21 through
28. The conductors 21 through 28 are not extended to the left edge
of the glass plate 10 for reasons pointed out subsequently. The
glass plate 12 extends beyond the right edge of the plate 10, and
this extension provides support for the electrical conductors 31
through 40. The electrical conductors 31 through 40 likewise are
not extended to the right edge of the lower glass plate 12 for
reasons pointed out subsequently.
The glass plates 10 and 12 preferably are made of a
soda-lime-silica which is one-fourth inch thick and free of chips
or scratches. Lightly scratched plates are acceptable if scratches
exist on one side only. The scratched surfaces are disposed
outwardly so that the unblemished surface is used for depositing
the conductors. The plates 10 and 12 should be checked for
flatness, and the flatness should be 50 millionths or better. A
hole is drilled in the upper plate 10 to permit the subsequent
insertion of a hollow tube 50 which is bifurcated as shown.
Tubulation is essential to permit subsequent evacuation of the
chamber and insertion of an illuminable gas.
The glass plates are thoroughly cleaned. The cleaning may include
degreasing in Freon TF for about 5 minutes, scrubbing in a
detergent, rinsing in tap water, and placing in Freon vapor for 5
minutes. Precise measurements are then made for thickness and
flatness of the plates. After the measurements are made they are
cleaned again. This cleaning may include placing the plates in a
detergent cleaner at 160.degree. Farenheit, applying ultrasonic
energy for thirty minutes, rinsing in hot water for 5 minutes, and
spray rinsing in distilled water for 2 minutes. Further cleaning
may include placing the plates in chromate solution at 160.degree.
Farenheit for 15 minutes, rinsing in hot water for 5 minutes,
rinsing in distilled water for 2 minutes, placing in 10 percent
hydrochloric solution for 15 minutes, rinsing in hot water for 5
minutes, rinsing in distilled water for 2 minutes, and placing in
Freon TF vapors for 5 minutes. The plates are then ready for
deposition of the electrodes.
2. The electrodes preferably are formed on the plates 10 and 12 in
FIG. 1 by successive depositions which form a laminate. The
laminate extends over the entire area of each glass plate out to
the point where the electrodes in FIG. 1 terminate which is about
one-fourth of an inch from the left and right edges of each glass
plate. This is illustrated in FIG. 2 for the lower plate 12. The
laminate 60 covers the entire upper surface of the glass plate 12
except the regions to the left and right of the electrodes 31
through 40 in FIG. 1. The laminate 60 is made by depositing a layer
of chromium 1,000A thick on the glass plate 12. This chromium
deposition on the glass plate 12 is shown as the layer 70 in FIG.
3. FIG. 3 is a cross sectional view taken on the line 3--3 in FIG.
2. Next copper is deposited on the chromium layer 70. This is shown
as the layer 71 in FIG. 3, and the copper layer is about 10,000A.
Another layer of chromium is deposited on the copper layer 71, and
this is shown as the layer 72 in FIG. 3. The chromium layer 72 is
about 1,000A thick. This completes the laminate 60 in FIG. 2 for
the plate 12. A similar laminate is deposited on the lower side of
the plate 10 in FIG. 1. The deposition of the various layers of the
laminate 60 may be accomplished by any one of various well known
techniques, and vacuum metalization is particularly suitable. If
this techique is used, each layer of the laminate is deposited by
inserting the glass plates in a bell jar, evacuating the bell jar,
and heating the metal to be deposited in a crucible until it
vaporizes. The metal vapor condenses on the plates to form a thin
layer of the laminate. This procedure is repeated for each layer of
the laminate.
3. A photolithographic process is used to form the parallel lines
on each glass plate from the laminate 60. A liquid photoresist
coating is applied over the surface of the laminate 60 in FIG. 2 of
glass plate 12, and a similar coating is applied over the laminate
of the plate 10. Before the photoresist coating is applied, the
plates 10 and 12 are pre-baked in an oven for 30 minutes at
180.degree. Farenheit. The plates are allowed to cool to room
temperature. The photoresist material is rolled on by a precision
coater. It is preferable that the pressure of the roll applying the
photoresist material be approximately 18 lbs. per square inch and
that the viscosity of the photoresist material be adjusted to dry
in 50 to 55 seconds. After the photoresist coating is applied, the
plates 10 and 12 are baked in an oven for 1 hour at 190.degree.
Farenheit.
The plates 10 and 12 are then placed in a printer and aligned with
the art work. Exposure of the photoresist material is made under a
vacuum of 10 lbs. per square inch. The light patterns projected
onto the photoresist material are in the form of alternate light
and dark parallel rows.
The glass plates 10 and 12 are immersed in a developer which
removes the exposed photoresist. This takes about 8 minutes. The
plates 10 and 12 are rinsed in tap water, a gentle spray for 30
seconds, again in distilled water, and finally in a gentle spray
for 30 seconds. Nitrogen is blown on the laminate 60 of each plate
until it is dry. Any broken lines in the photoresist material may
be touched up by a fine camel's hair brush dipped in photoresist
material. The plates are again baked in an oven for 30 minutes at
180.degree. Farenheit.
Each plate is immersed in a solution of 50 percent hydrochloric
acid with zinc activation, and this etches the portions of the
upper chromium layer 72 in FIG. 3 not protected by the remaining
photoresist material on both plates. The plates are continuously
observed, and when all of the upper chromium layer 72 is removed,
the plates are withdrawn and rinsed in cold tap water for about 1
minute. The plates are then immersed in a solution containing 681
grams of ammonium persulphate per gallon of distilled water. This
etches the exposed copper from the layer 71 in FIG. 3 of both
plates. The plates are constantly observed, and when the copper is
removed, the plates are withdrawn and rinsed in cold tap water for
about 1 minute.
Both plates are then immersed again in the 50 percent hydrochloric
acid solution which etches the exposed regions of the chromium
layer 70 in FIG. 3 of both plates. The plates are continuously
observed, and when the chromium layer 70 is removed, the plates are
withdrawn and rinsed in cold tap water for about 1 minute. The
plates are then immersed in a solution containing one pound of
potassium ferricyanide and 17 grams of sodium hydroxide per gallon
of distilled water. The plates are removed after about 7 seconds,
rinsed in distilled water for 2 minutes, and then blown dry with
nitrogen.
The plates 10 and 12 are placed in the printer again, and the
remaining photoresist material is exposed. The plates are then
immersed in developer which removes the remaining photoresist
material after which they are removed, rinsed in water and dried
with nitrogen. The laminate regions are wiped with acetone, rinsed
in water, sprayed with isopropyl or ethyl alcohol and then dried
with nitrogen. At this point in the process the laminate 60 of the
glass plate 12 in FIG. 2 has been converted to laminated parallel
lines as shown in cross-section in FIG. 4. The copper layers in
FIG. 4 serve as electrically conductive parallel lines which form
the electrode on the plate 12 in FIG. 1. The copper layers 31
through 40 in FIG. 4 are checked at this point to determine if
there are any open copper lines and to assure adequate deposition
of copper throughout each line. Reference is made to copending
Application Ser. No. 214,150 filed on Dec. 30, 1971.
For Method of Protecting Electrical Conductor Terminations During
Gas Panel Fabrication by Peter R. Wagner et al. for additional
description concerning the parallel conductors in the fabrication
process.
4. The glass plates 10 and 12 are heated in a forming gas
atmosphere composed of 90 percent nitrogen, 10 percent hydrogen and
water vapor. The temperature of the gas is raised 8.5.degree.
centigrade per minute until the temperature rises to 525.degree.
centigrade. That temperature is held for 80 minutes. This keeps the
parts of the plate at the temperature of 525.degree. centrigrade
for about 50 minutes. This atmosphere is then cooled at the rate of
3.2.degree. centigrade per minute to 300.degree. centigrade at
which point cooling may be accelerated, but care should be
exercised to avoid cracking of the glass plates or oven structure.
This operation is done to oxidize the upper surface of the chromium
strips disposed on the copper strips 31 through 40 in FIG. 4. It is
done to passivate or render inactive the upper chromium strips in
FIG. 4 during a subsequent dielectric coating operation.
5. The laminated lands in FIG. 4 are covered with lead glass which
is a dielectric material (1) that protects these parallel lines
from reacting in subsequent steps of the panel fabrication, (2)
that isolates the electrically conductive copper strips from
contact with the illuminable gas when the panel later is operated
with electrical signals, and (3) that provides mechanical support
which enables these lines to survive greater shock and stress. The
manner of adding this coating is described next.
The laminated parallel lines in FIG. 4 are covered with a glass
frit. This covering is preferably done by using a precision spray
gun which has a regulated constant blower pressure, constant vapor
pressure and regulated constant speed which provides accurate
control of the thickness of the dielectric coating. The spray gun
is loaded with a mixture of finely ground lead glass frit and
suspension vehicle. The suspension vehicle is commercially
available from Corning Glass Company under the name suspension
vehicle, and it is composed of a nitrocellulose polymer binder in a
solvent of amyl acetate. The lead glass frit is a powder which is
sufficiently fine to permit spraying. This powder may be made from
small lead glass beads disposed in a jar with alumina balls, and
the jar may be rotated to cause the alumina balls to break up the
glass beads. The process continues until the glass beads are
reduced to a very fine powder sufficiently small to pass through
the nozzle of the spray gun. The mixture used in the spray gun is a
slurry which includes 110 grams of the powdered lead glass and 110
grams of the Corning suspension vehicle. They may be blended by
mixing in a blender at medium speed for three minutes or so. The
mixture is added to the spray gun equipment, and the mixture is
applied uniformly throughout the area of the parallel conductors on
both plates 10 and 12.
The spray gun is operated in a class 100 clean stage or enclosure
having a highly clean atmosphere. A freon vapor generator
preferably is used to provide freon vapor as the propellent for the
spray gun. Liquid freon is heated to produce the vapor, and the
pressure of the vapor to the spray head is regulated to be
constant. Freon is preferable to air as a propellent since it
contains little, if any, contamination. Compressed air from a
compressor, on the other hand, has various contaminants chief of
which is oil. In addition to regulated blower pressure the spray
gun has a regulated constant speed of movement relative to the
upper surface of the glass plates. The thickness of the coating
sprayed on the upper surface of the glass plates is preferably 1.8
mils thick but the thickness of the coating may be varied as
desired. Spraying provides a uniform depth of the coating on the
upper surface of the glass plate because there is uniform
dispersion of powdered glass frit particles per unit volume of the
slurry, and the coating is deposited at a constant rate by
regulating and maintaining constant the speed of the sprayhead
relative to the surface of the glass plates.
The preparation of the powdered lead glass is described next. The
lead glas is received in granular form and milled before use. The
milling is preferably one with alluminum oxide balls. The balls are
cleaned first. This may be done by placing the alluminum oxide
balls in a ceramic jar and immersing them in a solution of 10
percent distilled water and 90 percent hydrochloric acid for 15
minutes. This solution is removed, and the jar is rinsed first with
water and then ethyl alcohol. The jar with the balls therein is
placed in an oven with the top of the jar removed, and the assembly
is baked at 110.degree. centrigrade for one hour at which time the
jar is removed and allowed to cool in air. Next 200 grams of
granular lead glass and 200 grams of alcohol are added to the jar
which may contain 200 alluminum oxide balls, for example. A rubber
gasket is placed on the top of the jar, and the cover is placed on
the jar and tightened to form a tight seal with the rubber gasket.
The ceramic jar is placed on a ball mill and rotated for about 24
hours thereby to mill the granular lead glass to a fine powder. The
content of the jar is poured into a 400 mesh sieve which passes all
particles having a diameter of 0.0015 of an inch or less. The
sieved material is dried overnight at 50.degree. centrigrade in an
exhaust hood. The powdered frit is placed in a clean pyrex dish and
baked at 250.degree. centigrade for 3 hours to assure dryness. It
is then placed in an oven and covered with a clean glass plate and
maintained at 240.degree. Farenheit until used. The powdered frit
thus remains completely dry until ready to be mixed with a
suspension vehicle for a spraying operation.
The spray gun is disassembled and thoroughly cleaned in an
ultrasonic cleaner after each spraying operation is completed. The
parts are then rinsed in acetone and dried. The inside of the spray
gun equipment is cleaned with lint-free paper soaked in acetone.
The paper is removed and replaced with clean paper taped down with
masking tape to prevent contamination. The filters of the spray gun
equipment are replaced when dirty. Various types of spray gun
equipment may be used, and one suitable type is zicon equipment
which is commercially available from Zicon Corporation of Mt.
Vernon, New York. Their R-3 nozzle and RB-5 spreader are adequate
for spraying powdered glass frit, for example. The jet size of the
spray head is 0.030 of an inch in diameter.
After the lead glass frit coating is sprayed on the laminated lands
forming the parallel lines on the plates 10 and 12, they are dried
for approximately 20 minutes at room temperature. The edges of the
glass plates 10 and 12 are wiped after the drying operation with a
lint-free cloth or paper to remove any dielectric from the edges,
and the tubulation hole in the upper plate 10 in FIG. 1 is wiped to
remove any of the spray.
Both plates are placed in an oven on polished lava plates which
previously have been leveled with a machinist's level. Grade "A"
lava plates are preferred which are adjusted to be flat and
parallel within 0.0002 inches per inch or better. The polished lava
plates are wiped with a lint-free cloth soaked in acetone before
use.
The plates 10 and 12 are fired in the oven which is programmed to
provide a temperature rise of 6.degree. centrigrade per minute to
200.degree. centigrade, then 1.degree. centigrade per minute to
604.degree. centrigrade, then holding the temperature at
604.degree. centigrade for one hour, and thereafter decreasing the
temperature 1.degree. centigrade per minute to room temperature.
This cycle is about twelve hours. This operation results in a
dielectric coating 80 as shown in cross-section in FIG. 5, and this
coating preferably is 1.8 mils thick. The parts are not shown to
scale in FIG. 5. Reference is made to copending Application Ser.
No. 214,151 filed on Dec. 30, 1971 for "Improved Method of Gas
Panel Construction" by Thomas J. Murphy et al. for additional
description concerning this dielectric coating operation.
6. The next step is to separate the glass plates a given distance
and seal them around the periphery to form a chamber therebetween
for holding an illuminable gas. A sealing material composed of
powdered glass disposed in a cellulose binder is used. It is
preferably pre-formed in a frame configuration of the desired size.
A pre-formed seal frame 90 is illustrated in FIG. 6, and it is
disposed on the dielectric coating of the glass plate 12. Glass
spacer rods 91 through 96 are disposed around the inner periphery
of the seal frame 90, and these rods are spaced about one-sixteenth
of an inch from the inner periphery of the sealed frame. The glass
rods have the same diameter, and this diameter represents the
desired chamber space between the glass plates 10 and 12 in FIG. 1.
The number of the glass rods used as spacers can be increased or
diminished as needed in order to provide uniform spacing between
the plates 10 and 12.
The glass plate 12 is placed in an oven on a polished lava plate
which has been leveled with a machinist's level. The oven is
operated to increase temperature at the rate of 6.degree.
centrigrade per minute to 70.degree. centigrade, then 1.degree.
centrigrade per minute to 400.degree. centigrade, then maintaining
at 400.degree. centigrade for one hour, then decreasing temperature
at 1.degree. centigrade per minute to room temperature. The cycle
is about 12 hours. This bakeout removes the cellulose binder from
the frame 90 in FIG. 6. The cellulose binder is baked out of the
sealing material to avoid blistering and darkening of the sealant
as well as remove possible contaminates which subsequently might
invade the illuminable gas.
Next tubulation is added to the glass plate 10. This plate is
placed on a piece of lint-free paper or cloth with the dielectric
coated side down as shown in FIG. 7. The tubulation 50 is cleaned
and dried. The cleaning operation may be that described above for
the glass plates 10 and 12. Next powdered glass and suspension
vehicle are mixed with a clean glass rod, and the mixture should
have a heavy cream consistency. This mixture may be stored for
future use. A powdered glass of 325 mesh is preferred, and one
suitable type commercially available is Corning 7,570 powdered
glass available from Corning Glass Company. A bead of this mixture
is applied to a step of the hollow tube 50, and if there is no
step, the paste is applied near the end of the tube 50. The tube is
then placed in the hole of the plate 10 and rotated a small amount
to flow the paste slightly. The bead of paste is shown generally by
the reference numeral 98 in FIG. 7. The tubulation paste is allowed
to dry in air for 15 minutes.
The top plate 10 in FIG. 7 is placed on the bottom plate 12 in FIG.
6 in the manner shown in FIG. 1. The parallel electrical conductors
21 through 28 on the lower side of the top plate 10 extend
orthogonally with respect to the parallel electrical conductors 31
through 40 on the top of the lower plate 12. The plates 10 and 12
in FIG. 1 are separated a given distance from each other by the
glass spacer rods 91 through 96 in FIG. 6.
This assembly is placed in an oven on a polished lava plate which
has been leveled with a machinist's level. A glass weight is placed
on the top plate 10 to yield a pressure of up to 0.5 lbs. per
square inch throughout the sealing area or overlapped regions of
the plates 10 and 12 in FIG. 1. The oven is operated to raise the
temperature 6.degree. centigrade per minute to 200.degree.
centigrade, then 1.degree. centigrade per minute to 500.degree.
centigrade, holding at 500.degree. centigrade for 1 hour, and then
decreasing temperature 1.degree. centigrade per minute to room
temperature. The cycle is about 12 hours. This operation causes the
glass in the seal frame 90 of FIG. 6 to reflow and unite the upper
plate 10 and the lower plate 12 in FIG. 1 in a spaced relationship
as determined by the spacer rods 91 through 96. These glass plates
are hermetically sealed throughout the region of the seal frame 90
in FIG. 6.
It is pointed out that when this firing operation takes place, the
glass coating 80 protects the laminated parallel lines 21 through
28 of the plate 10 and the laminated parallel lines 31 through 40
of the plate 12 from being eroded. If the glass coating 80 were
omitted during this firing operation, then the left ends of the
copper layer of the parallel lines 21 through 28 of the plate 10
and the right ends of the copper layer of the parallel lines 31
through 40 of the plate 12 in FIG. 1 would be pitted or eaten away.
This is undesirable because it would reduce the end area of copper
strip used as an electrical connector, and in some cases there
might not be sufficient copper left at the ends of some of these
lines to make an electrical connection. The glass coating thus
serves the important function of protecting and preserving the ends
of the copper strip which are exposed during this firing
operation.
7. The assembly is placed in an oven again, and the bifurcated
hollow glass tube 50 in FIG. 1 is connected through one branch to a
vacumn pump and through the other branch to a source of illuminable
gas. The source of illuminable gas is isolated from the tube 50.
This may be done by closing an outlet valve. The vacuum pump is
operated to evacuate the chamber between the glass plates 10 and 12
in FIG. 1. The pressure in the chamber between the glass plates 10
and 12 is reduced to 1 .times. 10.sup.-.sup.6 Torr. This low
pressure is reached after about one hour. The oven is fired and
programmed to increase temperature 1.degree. centigrade per minute
to 400.degree. centigrade. This temperature is held for 5 hours,
and the oven then is programmed to decrease temperature 1.degree.
centigrade per minute to room temperature. The cycle is about 17
hours. This evacuation and bakeout operation removes moisture and
gasses which escape from the lead glass sealing material and the
dielectric coating. This insures that the the illuminable gas
subsequently inserted will remain free of contamination from the
sealing material and the dielectric coatings which form the chamber
walls for the gas panel.
With the chamber pressure still at 1 .times. 10.sup.-.sup.6 torrs
the vacuum pump is sealed off from the tube 50, and low pressure in
the chamber persists. An illuminable gas is then admitted through
one branch of the tube 50 to the chamber, and backfilling with the
illuminable gas continuous until the pressure of 600 to 700 torrs
is reached. The illuminable gas is passed slowly to the chamber,
and this may take approximately 20 minutes to completely backfill
to the desired pressure. The tube 50 is then tipped off with a
gas-oxygen flame thereby to seal the chamber completely with the
illuminable gas at the given low pressure. A check on the gas
within the chamber may be made with the use of a spectrometer.
8. The laminated parallel lines 21 through 28 of the top plate 10
in FIG. 1 and the laminated parallel lines 31 through 40 of the
lower plate 12 are covered with the dielectric glass coating as
explained above. It is necessary to remove portions of these
coatings as well as the upper chromium coating of the laminate in
order to expose the copper strips on the top of plate 12 in FIG. 1
and the bottom of plate 10 for electrical connection purposes. The
dielectric coating is removed by dipping the right end of the glass
plate 12 in FIG. 1 in a solution of hydrochloric acid and water in
equal parts for about 30 seconds. The depth of insertion in this
acid bath should be enough to remove the dielectric coating from
the edges of the conductors 31 through 40 in FIG. 1, but the
insertion depth should not be enough for the acid to reach the
plate 40. The panel is removed and dipped in tap water. The
dielectric coating is inspected. If it is not gone, the panel again
is dipped in the acid bath, removed and rinsed in water. If the
dielectric coating is not removed, this dipping continues until it
is removed. Caution should be exercised by watching closely to
prevent attack of the outer chromium layer of the laminated
parallel lines 31 through 40. This is evidenced by bubbles, and
this process should be terminated when bubbles appear.
Next the right side of the lower plate 12 in FIG. 1 is dipped in a
solution consisting of one gallon of distilled water, 17 grams of
sodium hydroxide, and one pound of potassium ferricyanide to the
same depth as in the acid bath above. The panel is gently moved
back and forth in this solution until all of the chromium in the
outer layer of the laminated parallel lines 31 through 40 is gone.
This may take about three hours. The panel is removed, rinsed with
water and blown dry with nitrogen or air. This leaves exposed the
end regions of the copper strips of the laminated lines 31 through
40 of the plate 12 in FIG. 1, and electrical connection can be made
to these exposed copper strips. The preceding two operations are
repeated to remove the dielectric glass coating and the outer
chromium coating from the laminated parallel lines 21 through 28 on
the lower left face of the upper plate 10 in FIG. 1. The
fabrication of the gas panel is complete.
The panel is operated in a test made by applying electrical signals
of 180 to 200 volts to all of the lines 21 through 28 of the upper
panel 10 and all of the lines 31 through 40 of the lower panel 12.
This will ignite all gas cells. Thereafter electrical signals are
applied to selected ones of the lines on the plates 10 and 12 to
ignite selected gas cells defined by the coordinate intersections
of the parallel lines 21 through 28 and 31 through 40 in FIG.
1.
Some of the operations in steps 1 through 7 of the method according
to this invention may be varied, and the order may be changed in
many instances without departing from the essence of the invention.
The fabrication method lends itself to mass production
techniques.
It is seen therefore that a novel fabrication technique is provided
according to this invention for producing gas panels having
uniformity in their mechanical, electrical, and optical
characteristics. The fabrication according to this invention may be
adapted to mass production techniques thereby making the gas panels
relatively less expensive to manufacture. The gas panels, moreover,
are relatively inexpensive to operate as display or storage
devices.
While the method of this invention has been particularly shown and
described with reference to a preferred embodiment thereof, it will
be understood by those skilled in the art that various changes in
form and details may be made therein without departing from the
spirit and scope of the invention.
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