U.S. patent number 3,846,670 [Application Number 05/067,604] was granted by the patent office on 1974-11-05 for multiple gaseous discharge display-memory panel having decreased operating voltages.
This patent grant is currently assigned to Owens-Illinois, Inc.. Invention is credited to Robert F. Schaufele.
United States Patent |
3,846,670 |
Schaufele |
November 5, 1974 |
MULTIPLE GASEOUS DISCHARGE DISPLAY-MEMORY PANEL HAVING DECREASED
OPERATING VOLTAGES
Abstract
There is disclosed a multiple gaseous discharge display/memory
panel having an electrical memory and capable of producing a visual
display, the panel being characterized by an ionizable gaseous
medium in a gas chamber formed by a pair of opposed dielectric
material charge storage members which are respectively backed by a
series of parallel-like conductor (electrode) members, the
conductor members behind each dielectric material member being
transversely oriented with respect to the conductor members behind
the opposing dielectric material member so as to define a plurality
of discrete discharge volumes constituting a discharge unit, the
dielectric having at least one electron emissive substance applied
to the surface thereof in an amount sufficient to decrease the
operating voltages of the panel. Typical electron emissive
substances contemplated include Group IA elements, Group IA oxides,
barium, GaAs, GaP, InAs, InSb, InP, NiO, CsF, CsI, AgOCs, and
AuOCs.
Inventors: |
Schaufele; Robert F. (Okemos,
MI) |
Assignee: |
Owens-Illinois, Inc. (Toledo,
OH)
|
Family
ID: |
22077150 |
Appl.
No.: |
05/067,604 |
Filed: |
August 27, 1970 |
Current U.S.
Class: |
315/169.4;
257/103; 313/533; 313/586; 345/71 |
Current CPC
Class: |
H01J
11/12 (20130101); H01J 11/40 (20130101) |
Current International
Class: |
H01J
17/49 (20060101); H05b 037/00 () |
Field of
Search: |
;313/95,106,54
;315/169R,169TV |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Lake; Roy
Assistant Examiner: Dahl; Lawrence J.
Attorney, Agent or Firm: Wedding; Donald K. Holler; E.
J.
Claims
I claim:
1. As an article of manufacture, a dielectric material body for a
gaseous discharge display/memory device, said dielectric body
containing a surface deposit of at least one electron emissive
substance having a thickness of at least about 100 angstrom units
to provide substantially decreased gaseous discharge operating
voltages without substantially affecting the memory margin of said
device, said electron emissive substance being selected from Group
IA elements, Group IA oxides, barium, GaAs, GaP, InAs, InSb, InP,
NiO, CsF, CsI, AgOCs, and AuOCs.
2. In the operation of a gaseous discharge display/memory device
characterized by an ionizable gaseous medium in a gas chamber
formed by a pair of dielectric material members having opposed
charge storage surfaces, which dielectric material members are
respectively backed by a series of parallel-like electrode members
insulated from said ionizable gaseous medium by said dielectric
material members, the electrode members behind each dielectric
material member being transversely oriented with respect to the
electrode members behind the opposing dielectric material member so
as to define a plurality of discrete discharge volumes constituting
discharge units in open photonic communication, and wherein the gas
is selectively ionized within each discharge unit by operating
voltages applied to the transversely oriented electrode members,
the improvement which comprises substantially decreasing the
operating voltages over a given period of operating time of the
device and increasing the effective operating life of the device by
coating each opposed dielectric material charge storage surface
with a deposit of at least one electron emissive substance to a
thickness of at least about 100 angstrom units without
substantially affecting the memory margin of said device, said
electron emissive substance being selected from Group IA elements,
Group IA oxides, barium, GaAs, GaP, InAs, InSb, InP, NiO, CsF, CsI,
AgOCs, and AuOCs, being insulated from said electrode members by
said dielectric material members and being exposed to said gaseous
medium.
3. The invention of claim 2 wherein the electron emissive substance
is deposited on the dielectric surfaces in an amount sufficient to
decrease the operating voltage of said device by at least 50
percent.
4. The invention of claim 1 wherein the electron emissive substance
is a combination of at least one member selected from the group
consisting of GaAs, GaP, InAs, InSb and InP, and one member
selected from the group consisting of Cs and Cs.sub.2 O.
5. The invention of claim 2 wherein the electron emissive substance
is a combination of at least one member selected from the group
consisting of GaAs, GaP, InAs, InSb and InP, and one member
selected from the group consisting of Cs and Cs.sub.2 O.
6. The invention of claim 1 wherein the electron emissive substance
is present on the surface of said dielectric body in an amount
sufficient to decrease the operating voltage of said device by at
least 50 percent.
Description
This invention relates to novel multiple gas discharge
display/memory panels which have an electrical memory and which are
capable of producing a visual display or representation of data
such as numerals, letters, television display, radar displays,
binary words, etc. More particularly, this invention relates to
novel gas discharge display/memory panels having substantially
lower operating voltages. As used herein, voltage is defined as any
voltage required for operation of the panel including firing and
sustaining voltages as well as any other voltages for manipulation
of the discharge.
Multiple gas discharge display and/or memory panels of the type
with which the present invention is concerned are characterized by
an ionizable gaseous medium, usually a mixture of at least two
gases at an appropriate gas pressure, in a thin gas chamber or
space between a pair of opposed dielectric charge storage members
which are backed by conductor (electrode) members, the conductor
members backing each dielectric member being transversely oriented
to define a plurality of discrete discharge volumes and
constituting a discharge unit. In some prior art panels the
discharge unit are additionally defined by surrounding or confining
physical structure as by cells or apertures in perforated glass
plates and the like so as to be physically isolated relative to
other units. In either case, with or without the confining physical
structure, charges (electrons, ions) produced upon ionization of
the gas of a selected discharge unit, when proper alternating
operating potentials are applied to selected conductors thereof,
are collected upon the surfaces of the dielectric at specifically
defined locations and constitute an electrical field opposing the
electrical field which created them so as to terminate the
discharge for the remainder of the half cycle and aid in the
initiation of a discharge on a succeeding opposite half cycle of
applied voltage, such charges as are stored constituting an
electrical memory.
Thus, the dielectric layers prevent the passage of any conductive
current from the conductor members to the gaseous medium and also
serve as collecting surfaces for ionized gaseous medium charges
(electrons, ions) during the alternate half cycles of the A.C.
operating potentials, such charges collecting first on one
elemental or discrete dielectric surface area and then on an
opposing elemental or discrete dielectric surface area on alternate
half cycles to constitute an electrical memory.
An example of a panel structure containing nonphysically isolated
or open discharge units is disclosed in U.S. Pat. No. 3,499,167
issued to Theodore C. Baker et al.
An example of a panel containing physically isolated units is
disclosed in the article by D. L. Bitzer and H. G. Slottow entitled
"The Plasma Display Panel - A Digitally Addressable Display With
Inherent Memory," Proceeding of the Fall Joint Computer Conference,
IEEE, San Francisco, California, Nov. 1966, pages 541-547.
In the operation of the panel, a continuous volume of ionizable gas
is confined between a pair of electron emmisive dielectric surfaces
backed by conductor arrays forming matrix elements. The cross
conductor arrays may be orthogonally related (but any other
configuration of conductor arrays may be used) to define a
plurality of opposed pairs of charge storage areas on the surfaces
of the dielectric bounding or confining the gas. Thus, for a
conductor matrix having H rows and C columns the number of
elemental discharge volumes will be the product H .times. C and the
number of elemental or discrete areas will be twice the number of
elemental discharge volumes.
The gas is one which produces light (if visual display is an
objective) and a copious supply of charges (ions and electrons)
during discharge. In an open cell Baker, et al type panel, the gas
pressure and the electric field are sufficient to laterally confine
charges generated on discharge within elemental or discrete volumes
of gas between opposed pairs of elemental or discrete dielectric
areas within the perimeter of such areas, especially in a panel
containing non-isolated units.
As described in the Baker et al patent, the space between the
dielectric surfaces occupied by the gas is such as to permit
photons generated on discharge in a selected discrete or elemental
volume of gas to pass freely through the gas space and strike
surface areas of dielectric remote from the selected discrete
volumes, such remote, photon struck dielectric surface areas
thereby emitting electrons so as to condition other and more remote
elemental volumes for discharges at a uniform applied
potential.
With respect to the memory function of a given discharge panel, the
allowable distance or spacing between the dielectric surfaces
depends, inter alia, on the frequency of the alternating current
supply, the distance typically being greater for lower
frequencies.
While the prior art does disclose gaseous discharge devices having
externally positioned electrodes for initiating a gaseous
discharge, sometimes called "electrodeless discharges," such prior
art devices utilize frequencies and spacings or discharge volumes
and operating pressures such that although discharges are initiated
in the gaseous medium, such discharges are ineffective or not
utilized for charge generation and storage in the manner of the
present invention.
The term "memory margin" is defined herein as
M.M. = V.sub.f -V.sub.s /V.sub.s
where V.sub.f is the magnitude of the applied voltage at which a
discharge is initiated in a discrete conditioned (as explained in
the aforementioned Baker, et al patent) volume of gas defined by
common areas of overlapping conductors and V.sub.s is the magnitude
of the minimum applied periodic alternating voltage sufficient to
sustain discharges once initiated. It will be understood that basic
electrical phenomena utilized in this invention is the generation
of charges (ions and electrons) alternately storable at pairs of
opposed or facing discrete points or areas on a pair of dielectric
surfaces backed by conductors connected to a source of operating
potential. Such stored charges result in an electrical field
opposing the field produced by the applied potential that created
them and hence operate to terminate ionization in the elemental gas
volume between opposed or facing discrete points or areas of
dielectric surface. The term "sustain a discharge" means producing
a sequence of momentary discharges, one discharge for each half
cycle of applied alternating sustaining voltage, once the elemental
gas volume has been fired, to maintain alternate storing of charges
at pairs of opposed discrete areas on the dielectric surfaces.
The above, as well as other objects, features and advantages of the
invention will become apparent and better understood by reference
to the following detailed description when considered in connection
with the accompanying drawings. FIGS. 1 - 4 and the description of
these figures are from the above mentioned Baker et al., Pat. No.
3,499,167.
FIG. 1 is a partially cut-away plan view of a gaseous discharge
display/memory panel embodying the invention as connected to a
diagrammatically illustrated source of operating potentials;
FIG. 2 is a cross-sectional view (enlarged, but not to proportional
scale since the thickness of the gas volume, dielectric members and
conductor arrays have been enlarged for purposes of illustration)
taken on lines 2--2 of FIG. 1;
FIG. 3 is an explanatory partial cross-sectional view similar to
FIG. 2 (enlarged, but not to proportional scale);
FIG. 4 is an isometric view of a larger gaseous discharge
display/memory panel incorporating the invention; and
FIG. 5 is an explanatory partial cross-sectional view similar to
FIG. 3 (enlarged, but not to proportional scale) illustrating the
present invention.
The invention utilizes a pair of dielectric films or coatings 10
and 11 separated by a thin layer or volume of a gaseous discharge
medium 12, said medium 12 producing a copious supply of charges
(ions and electrons) which are alternately collectable on the
surfaces' of the dielectric members at opposed or facing elemental
or discrete areas X and Y defined by the conductor matrix or
nongas-contacting sides of the dielectric members, each dielectric
member presenting large open surface areas and a plurality of pairs
of elemental X and Y areas. While the electrically operative
structural members such as the dielectric members 10 and 11 and
conductor matrixes 13 and 14 are all relatively thin (being
exaggerated in thickness in the drawings) they are formed on and
supported by rigid nonconductive support members 16 and 17
respectively.
Preferably, one or both of nonconductive support members 16 and 17
pass light produced by discharge in the elemental gas volumes.
Preferably, they are transparent glass members and these members
essentially define the overall thickness and strength of the panel.
For example, the thickness of gas layer 12 as determined by spacer
15 is under 10 mils and preferably about 5 to 6 mils, dielectric
layers 10 and 11 (over the conductors at the elemental or discrete
X and Y areas) is between 1 and 2 mils thick, and conductors 13 and
14 about 8,000 angstroms thick (tin oxide). However, support
members 16 and 17 are much thicker (particularly larger panels) so
as to provide as much ruggedness as may be desired to compensate
for stresses in the panel. Support members 16 and 17 also serve as
heat sinks for heat generated by discharges and thus minimize the
effect of temperature on operation of the device. If it is desired
that only the memory function be utilized, then none of the members
need be transparent to light although for purposes described later
herein it is preferred that one of the support members and members
formed thereon be transparent to or pass ultraviolet radiation.
Except for being nonconductive or good insulators the electrical
properties of support members 16 and 17 are not critical. The main
function of support members 16' and 17 is to provide mechanical
support and strength for the entire panel, particularly with
respect to pressure differential acting on the panel and thermal
shock. As noted earlier, they should have thermal expansion
characteristics substantially matching the thermal expansion
characteristics of dielectric layers 10 and 11. Ordinary one-fourth
inch commercial grade soda lime plate glasses have been used for
this purpose. Other glasses such as low expansion glasses or
transparent devitrified glasses can be used provided they can
withstand processing and have expansion characteristics
substantially matching expansion characteristics of the dielectric
coatings 10 and 11. For given pressure differentials and thickness
of plates the stress and deflection of plates may be determined by
following standard stress and strain formulas (see R. J. Roark,
Formulas for Stress and Strain, McGraw-Hill, 1954).
Spacer 15 may be made of the same glass material as dielectric
films 10 and 11 and may be an integral rib formed on one of the
dielectric members and fused to the other members to form a
bakeable hermetic seal enclosing and confining the ionizable gas
volume 12. However, a separate final hermetic seal may be effected
by a high strength devitrified glass sealant 15S. Tubulation 18 is
provided for exhausting the space between dielectric members 10 and
11 and filling that space with the volume of ionizable gas. For
large panels small bead like solder glass spacers such as shown at
15B may be located between conductors intersections and fused to
dielectric members 10 and 11 to aid in withstanding stress on the
panel and maintain uniformity of thickness of gas volume 12.
Conductor arrays 13 and 14 may be formed on support members 16 and
17 by a number of well known processes, such as photoetching,
vacuum deposition, stencil screening, etc. In the panel shown in
FIG. 4, the center to center spacing of conductors in the
respective arrays is about 30 mils. Transparent or semitransparent
conductive material such as tin oxide, gold or aluminum can be used
to form the conductor arrays and should have a resistance less than
3000 ohms per line. It is important to select a conductor material
that is not attacked during processing by the dielectric
material.
It will be appreciated the conductor arrays 13 and 14 may be wires
or filaments of copper, gold, silver or aluminum or any other
conductive metal or material. For example 1 mil wire filaments are
commercially available and may be used in the invention. However,
formed in situ conductor arrays are preferred since they may be
more easily and uniformly placed on and adhered to the support
plates 16 and 17.
Dielectric layer members 10 and 11 are formed of an inorganic
material and are preferably formed in situ as an adherent film or
coating which is not chemically or physically effected during
bake-out of the panel. One such material is a solder glass such as
Kimble SG-68 manufactured by and commercially available from the
assignee of the present invention.
This glass has thermal expansion characteristics substantially
matching the thermal expansion characteristics of certain soda-lime
glasses, and can be used as the dielectric layer when the support
members 16 and 17 are soda-lime glass plates. Dielectric layers 10
and 11 must be smooth and have a dielectric strength of about 1000
v. and be electrically homogeneous on a microscopic scale (e.g., no
cracks, bubbles, crystals, dirt, surface films, etc.). In addition,
the surfaces of dielectric layers 10 and 11 should be good
photoemitters of electrons in a baked out condition. However, a
supply of free electrons for conditioning gas 12 for the ionization
process may be provided by inclusion of a radioactive material
within the glass or gas space. A preferred range of thickness of
dielectric layers 10 and 11 overlying the conductor arrays 13 and
14 is between 1 and 2 mils. Of course, for an optical display at
least one of dielectric layers 10 and 11 should pass light
generated on discharge and be transparent or translucent and,
preferably, both layers are optically transparent.
The preferred spacing between surfaces of the dielectric films is
about 5 to 6 mils with conductor arrays 13 and 14 having center to
center spacing of about 30 mils.
The ends of conductors 14-1 . . . 14-4 and support member 17 extend
beyond the enclosed gas volume 12 and are exposed for the purpose
of making electrical connection to interface and addressing
circuitry 19. Likewise, the ends of conductors 13-1 . . . 13-4 on
support member 16 extend beyond the enclosed gas volume 12 and are
exposed for the purpose of making electrical connection to
interface and addressing circuitry 19.
As in known display systems, the interface and addressing circuitry
or system 19 may be relatively inexpensive line scan systems or the
somewhat more expensive high speed random access systems. However,
it is to be noted that a lower amplitude of operating potentials
helps to reduce problems associated with the interface circuitry
between the addressing system and the display/memory panel, per se.
Thus, by providing a panel having greater uniformity in the
discharge characteristics throughout the panel, tolerances and
operating characteristics of the panel with which the interfacing
circuitry cooperate, are made less rigid.
One mode of initiating operation of the panel will be described
with reference to FIG. 3, which illustrates the condition of one
elemental gas volume 30 having an elemental cross-sectional area
and volume which is quite small relative to the entire volume and
cross-sectional area of gas 12. The cross-sectional area of volume
30 is defined by the overlapping common elemental areas of the
conductor arrays and the volume is equal to the product of the
distance between the dielectric surfaces and the elemental area. It
is apparent that if the conductor arrays are uniform and linear and
are orthogonally (at right angles to each other) related each of
elemental areas X and Y will be squares and if conductors of one
conductor array are wider than conductors of the other conductor
array, said areas will be rectangles. If the conductor arrays are
at transverse angles relative to each other, other than 90.degree.,
the areas will be diamond shaped so that the cross-sectional shape
of each volume is determined solely in the first instance by the
shape of the common area of overlap between conductors in the
conductor arrays 13 and 14. The dotted lines 30' are imaginary
lines to show a boundary of one elemental volume about the center
of which each elemental discharge takes place. As described earlier
herein, it is known that the cross-sectional area of the discharge
in a gas is affected by, inter alia, the pressure of the gas, such
that, if desired, the discharge may even be constricted to within
an area smaller than the area of conductor overlap. By utilization
of this phenomena, the light production may be confined or resolved
substantially to the area of the elemental cross-sectional area
defined by conductor overlap. Moreover, by operating at such
pressure charges (ions and electrons) produced on discharge are
laterally confined so as to not matarially affect operation of
adjacent elemental discharge volumes.
In the instant shown in FIG. 3, a conditioning discharge about the
center of elemental volume 30 has been initiated by application to
conductor 13-1 and conductor 14-1 firing potential V.sub.x ' as
derived from a source 35 of variable phase, for example, and source
36 of sustaining potential V.sub.s (which may be a sine wave, for
example). The potential V.sub.x ' is added to the sustaining
potential V.sub.s as sustaining potential V.sub.s increases in
magnitude to initiate the conditioning discharge about the center
of elemental volume 30 shown in FIG. 3. There, the phase of the
source 35 of potential V.sub.x ' has been adjusted into adding
relation to the alternating voltage from the source 36 of
sustaining voltage V.sub.5 to provide a voltage V.sub.f ', when
switch 33 has been closed, to conductors 13-1 and 14-1 defining
elementary gas volume 30 sufficient (in time and/or magnitude) to
produce a light generating discharge centered about discrete
elemental gas volume 30. At the instant shown, since conductor 13-1
is positive, electrons 32 have collected on and are moving to an
elemental area of dielectric member 10 substantially corresponding
to the area of elemental gas volume 30 and the less mobile positive
ions 31 are beginning to collect on the opposed elemental area of
dielectric member 11 since it is negative. As these charges build
up, they constitute a back voltage opposed to the voltage applied
to conductors 13-1 and 14-1 and serve to terminate the discharge in
elemental gas volume 30 for the remainder of a half cycle.
During the discharge about the center of elemental gas volume 30,
photons are produced which are free to move or pass through gas
medium 12, as indicated by arrows 37, to strike or impact remote
surface areas of photoemissive dielectric members 10 and 11,
causing such remote areas to release electrons 38. Electrons 38
are, in effect, free electrons in gas medium 12 and condition each
other discrete elemental gas volume for operation at a lower firing
potential V.sub.f which is lower in magnitude than the firing
potential V.sub.f ' for the initial discharge about the center of
elemental volume 30 and this voltage is substantially uniform for
each other elemental gas volume.
Thus, elimination of physical obstructions or barriers between
discrete elemental volumes, permits photons to travel via the space
occupied by the gas medium 12 to impact remote surface areas of
dielectric members 10 and 11 and provides a mechanism for supplying
free electrons to all elemental gas volumes, thereby conditioning
all discrete elemental gas volumes for subsequent discharges,
respectively, at a uniform lower applied potential. While in FIG. 3
a single elemental volume 30 is shown, it will be appreciated that
an entire row (or column) of elemental gas volumes may be
maintained in a "fired" condition during normal operation of the
device with the light produced thereby being masked or blocked off
from the normal viewing area and not used for display purposes. It
can be expected that in some applications there will always be at
least one elemental volume in a "fired" condition and producing
light in a panel, and in such applications it is not necessary to
provide separate discharge or generation of photons for purposes
described earlier.
However, as described earlier, the entire gas volume can be
conditioned for operation at uniform firing potentials by use of
external or internal radiation so that there will be no need for a
separate source of higher potential for initiating an initial
discharge. Thus, by radiating the panel with ultraviolet radiation
or by inclusion of a radioactive material within the glass
materials or gas space, all discharge volumes can be operated at
uniform potentials from addressing and interface circuit 19.
Since each discharge is terminated upon a build up or storage of
charges at opposed pairs of elemental areas, the light produced is
likewise terminated. In fact, light production lasts for only a
small fraction of a half cycle of applied alternating potential and
depending on design parameters, is in the nanosecond range.
After the initial firing or discharge of discrete elemental gas
volume 30 by a firing potential V.sub.f ', switch 33 may be opened
so that only the sustaining voltage V.sub.5 from source 36 is
applied to conductors 13-1 and 14-1. Due to the storage of charges
(e.g., the memory) at the opposed elemental areas X and Y, the
elemental gas volume 30 will discharge again at or near the peak of
negative half cycles of sustaining voltage V.sub.5 to again produce
a momentary pulse of light. At this time, due to reversal of field
direction, electrons 32 will collect on and be stored on elemental
surface area Y of dielectric member 11 and positive ions 31 will
collect and be stored on elemental surface area X of dielectric
member 10. After a few cycles of sustaining voltage V.sub.5, the
times of discharges become symmetrically located with respect to
the wave form of sustaining voltage V.sub.5. At remote elemental
volumes, as for example, the elemental volumes defined by conductor
14-1 with conductors 13-2 and 13-3, a uniform magnitude or
potential V.sub.x from source 60 is selectively added by one or
both of switches 34-2 or 34-3 to the sustaining voltage V.sub.5,
shown as 36', to fire one or both of these elemental discharge
volumes. Due to the presence of free electrons produced as a result
of the discharge centered about elemental volume 30, each of these
remote discrete elemental volumes have been conditioned for
operation at uniform firing potential V.sub.f.
In order to turn "off" an elemental gas volume (i.e. terminate a
sequence of discharge representing the "on" state), the sustaining
voltage may be removed. However, since this would also turn "off"
other elemental volumes along a row or column, it is preferred that
the volumes be selectively turned "off" by application to selected
"on" elemental volumes a voltage which can neutralize the charges
stored at the pairs of opposed elemental areas.
This can be accomplished in a number of ways, as for example,
varying the phase or time position of the potential from source 60
to where that voltage combined with the potential form source 36'
falls substantially below the sustaining voltage.
It is apparent that the plates 16-17 need not be flat but may be
curved, curvature of facing surfaces of each plate being
complementary to each other. While the preferred conductor
arrangement is of the crossed grid type as shown herein, it is
likewise apparent that where an infinite variety of two dimensional
display patterns are not necessary, as where specific standardized
visual shapes (e.g., numerals, letters, words, etc.) are to be
formed and image resolution is not critical, the conductors may be
shaped accordingly.
The device shown in FIG. 4 is a panel having a large number of
elemental volumes similar to elemental volume 30 (FIG. 3). In this
case more room is provided to make electrical connection to the
conductor arrays 13' and 14', respectively, by extending the
surfaces of support members 16' and 17' beyond seal 15S', alternate
conductors being extended on alternate sides. Conductor arrays 13'
and 14' as well as support members 16' and 17' are transparent. The
dielectric coatings are not shown in FIG. 4 but are likewise
transparent so that the panel may be viewed from either side.
In accordance with this invention, it has been surprisingly
discovered that the operating voltage of a gaseous discharge panel
may be significantly decreased by the application of at least one
electron emissive substance to the surface of the dielectric
material. More particularly, at least one electron emissive
substance is applied to each dielectric charge storage surface of a
gaseous discharage panel in an amount sufficient to provide
substantially lower gaseous discharge panel operating voltages.
As used herein, electron emissive refers to the processes of
photoemission, secondary electron emission of ion and/or electron
bombardment, and thermionic electron emission.
In the practice of this invention, it is contemplated using at
least one electron emissive substance selected from Group IA
elements (lithium, sodium, potassium, rubidium, cesium, and
francium); oxides of Group IA; barium; GaAs; GaP; InAs; InSb; InP;
NiO; CsF; CsI; AgOCs; and AuOCs. In one specific embodiment hereof,
there is used an electron emissive combination comprising at least
one member selected from GaAs, GaP, InAs, InSb, or InP and one
member selected from Cs or Cs.sub.2 O.
The selected electron emissive substance (or a source thereof) is
applied to each dielectric surface by any convenient means
including not by way of limitation vapor deposition; vacuum
deposition; chemical vapor deposition; wet spraying upon the
surface a mixture or solution of the substance (or source thereof)
suspended or dissolved in a liquid followed by evaporation of the
liquid; dry spraying of the substance upon the surface; electron
beam evaporation; plasma flame and/or arc spraying and/or
deposition; sputtering target techniques; application of the
substance as a molten melt followed by cooling in an inert or
oxidizing environment.
The selected electron emissive substance is applied to each
dielectric surface as a very thin film or layer, the thickness of
such film or layer being sufficient to provide substantially
decreased panel operating voltages, usually at least about 100
angstrom units, typically at least about 1000 angstrom units. As
used herein, the terms "film or layer" are inclusive of all similar
terms such as deposit, coating, finish, spread, covering, etc. The
thin film or layer 70 applied to the surface of each dielectric 10,
11 is shown in FIG. 5.
In one preferred embodiment hereof, the electron emissive substance
is selected from Group IA alkali metals (as defined hereinbefore)
and oxides of Group IA. In the practice of such embodiment, the
Group IA metal or oxide thereof is applied to the dielectric
surface by any convenient means (as defined hereinbefore),
especially a molten melt technique. It is also contemplated that
the Group IA oxide may be formed in situ on the surface of the
dielectric, e.g., by applying a Group IA alkali metal to the
surface followed by oxidation. One such in situ process comprises
applying a Group IA melt to the dielectric followed by cooling in
an oxygen rich environment. Another in situ process comprises
applying an oxidizable source of the Group IA metal to the surface.
Typical of such sources include minerals and/or compounds
containing one or more Group IA metals, especially those inorganic
or organic compounds which can be readily heat decomposed or
pyrolyzed. However, as already noted, it is also contemplated that
Group IA oxides may be directly used.
In the fabrication of a gaseous discharge panel, the dielectric
material is typically applied to and cured on the surface of a
supporting glass substrate or base to which the electrode or
conductor elements have been previously applied. The glass
substrate may be of any suitable composition such as a soda lime
glass composition. Two glass substrates containing electrodes and
cured dielectric are then appropriately heat sealed together so as
to form a panel.
In one embodiment of this invention, the selected electron emissive
substance is applied to the surface of the cured dielectric before
the panel heat sealing cycle.
In another embodiment of this invention, the electron emissive
substance is applied to the dielectric surfaces after the
fabrication of the panel.
Depending upon the specific electron emissive substance or
combinations thereof utilized, the practice of this invention may
be especially beneficial over given periods of panel operating
time; that is, best results may be realized after appropriate aging
of the panel, the required amount of aging being a function of the
electron emissive substance used. Panel aging is defined as the
accumulated total operating time for the panel.
The following example is intended to illustrate one of the best
embodiments contemplated by the inventor in the practice of this
invention.
EXAMPLE
A gaseous discharge panel device of the Baker et al kind was
constructed, e.g. as generally described hereinbefore. The panel
dielectric composition was a lead borosilicate consisting of 73.3
percent by weight PbO, 13.4 percent by weight B.sub.2 O.sub.3, and
13.3 percent by weight SiO.sub.2. The panel glass substrates were
of a soda lime composition containing about 73 percent by weight
SiO.sub.2, about 13 percent by weight Na.sub.2 O, about 10 percent
by weight CaO, about 3 percent by weight MgO, about 1 percent by
weight Al.sub.2 O.sub.3, and small amounts (less than 1 percent) of
Fe.sub.2 O.sub.3, K.sub.2 O, As.sub.2 O.sub.3, and Cr.sub.3
O.sub.3. The electrode lines or conductor arrays were of hanovia
gold. The panel was filled with 375 torr of an inert ionizable gas
consisting of 99.9 percent atoms of neon and 0.1 percent of
argon.
A sealed elemental cesium metal reservoir was attached to the gas
filling aperture so as to permit cesiation of the dielectric
surfaces. The dielectric surfaces were heavily cesiated to a
thickness of at least 100 angstrom units by opening the cesium
reservoir, heating the metal to a molten state, and permitting the
molten cesium to flow into the sealed, gas filled panel. The excess
metal was drained from the panel.
Panel turn-on and turn-off voltages were measured for quarter areas
of the panel utilizing a 50 KC sinusoidal sustaining voltage,
before and after the addition of the cesium. The results, as shown
in TABLE I, illustrate that the voltages were decreased by over 50
percent for the cesiated surface.
TABLE I ______________________________________ Turn-On Turn-Off
______________________________________ uncesiated surface 132 .+-.
1 volts 103 .+-. 1 volts cesiated surface 60 .+-. 1 volts 48 .+-. 1
volts ______________________________________
The memory margin of the panel was insensitive to cesiation,
decreasing from 0.28 to 0.25. The uncesiated areas of the
dielectric remained essentially at their higher initial voltage
values.
Heating of the cesiated device from 298.degree.K to 383.degree.K,
increased the partial pressure of the cesium metal from
10.sup.-.sup.6 to 10.sup.-.sup.2 torr, but produced no measurable
change in the panel voltages, demonstrating that the voltage
reductions in TABLE I are induced by the electron emissive cesiated
surfaces.
* * * * *