Note: Descriptions are shown in the official language in which they were submitted.
1145809
THE INVENTION
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 dis-
plays, binary words, etc. More particularly, this invention
relates to novel gas discharge display/memory panels having
substantially decreased 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.
In accordance with this invention, there is provided
in a gaseous discharge display/memory device characterized by
an ionizable gaseous medium in a gas chamber formed by a pair
of opposed dielectric material charge storage surfaces, the
improvement wherein each dielectric surface is coated with a
layer of magnesium oxide, said oxide layer being applied in an
amount sufficient to substantially decrease the operating
voltages of the discharge device.
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Multiple gas discharge display and/or memory panels
of the type with which the present invention is concerned are
characteri~ed 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 bet-~een 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 constitu-ting a discharge unit. In some
prior art panels the discharge uni-ts are additionally defined by
surrounding or confining physical structure such as by cells or
. apertures in perforated gla.ss plates and the like so as to be
: physieally isolated relative to other units. In either case,
with or ~ithout the eonfining physical struc-ture~ charges
(electrons, ions) produced upon ionization of the gas of a
selected d~scharge unit, when proper alternating operating poten-
tials are applied to selected conduetors thereof, are eolleeted
. upon the surfaces of the dielectric at specifically defined
locations and constitute an electrical field opposing the
. 20 electrical field which created them so as to terminate the
discharge for the remaindsr of the half cycle and aid in the
initiation of a discharge on a suceeeding opposite half eycle
of applied voltage, such charges as are stored constituting an
eleetrical memory.
Thus, the dielectrie 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 potenti.a]s, such charges
~0 collecting first on one elemental or discrete dielectric surface
area then on an opposing ~10mental or discr_t~ dielec tric
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sur~ace area on a.lterante half cycles to constitute an electricæl
memory.
An example of a panel structure containing non- .
physically isolated or open discharge units is disclosed in
U. S. Letters Patent 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 dielectric
surfaces backed by conductor arrays forming matrix elements. The
; 15 cross conductor arrays may be orthogonally related (but any other
configuration of conductor arrays may be used) to dsfine 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 colurl~s the number of
elemental discharge volumes will be the product H x C and the .
number of elemental or discrete areas will be twice the number Or
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 be-tween opposed pairs of elemental
or discrete dielectric areas within the perimeter of such areas,
3 especially in a panel containing non-isolated units. .
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¦ 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 elemen-tal volumes for discharges at a l~niform applied
¦po-tential.
¦ With respect to the memory func-tion of a given discharge
¦panel, the allowable distance or spacing between the dielectric
surfaces depends, inter alia~ on the frequency of the alterna-ting
¦ current supply, the distance -typically being greater for lower
I frequencies.
¦ Wh~le the prior art does disclose gaseous discharge
devices having externally positionsd electro~es 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 dis-
2~ ¦ charges are initiated in the gaseous medium, such discharges are¦ ineffective or not utilized for charge generation and storage in
¦ the manner of the present inven-tion. -
¦ The term "memory margin" is defined herein as
l M.M. = Vf-VS
I - Vs
¦ ~rhere Vf is the magnitude of the applied voltage at ~hich a
¦ discharge is initiated in a discrete conditioned (as explained
¦ in the aforementioned Ba~er, et al patent) volume of gas defined
¦ by common areas of overlapping conductors and Vs is the magnitude
~ ¦ of the minimum applied periodic alternating voltage sufficient
¦ to sustain discharges once ini-tiated. It ~ill be understood that
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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 alter-
nating 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.
In accordance with this invention, it has been
suprisingly discovered that the magnitude of the gaseous dis-
eharge panel operating voltage is substantially decreased by
applying a layer of magnesium oxide to the charge storage
surfaee of eaeh dielectrie material in an amount suffieient to
provide substantially decreased gaseous discharge panel operat-
ing voltages.
In one embodiment hereof, the oxide layer is applied
direetly to the surfaee of the dielectric material.
In another embodiment hereof, the oxide layer is
formed in situ on the dielectric surface, e.g., by applying the
magnesium metal (or a source thereof) to the dielectric surface
followed by oxidation. One such in situ process comprises apply-
ing a melt to the dielectric followed by oxidation of the melt
during the cooling thereof so as to form the oxide layer.
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Another in situ process comprises applying an oxidizable source
of magnesium to the surface. Typical of such oxidizable sources
include minerals and/or compounds containing magnesium, especial-
ly organic compounds which are readily heat decomposed or
pyrolyzed.
The oxide layer (or a source thereof) is applied to
the 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 of
solution of the oxide suspended or dissolved in a liquid followed
by evaporation of the liquid; dry spraying of the oxide upon the
surface; electron beam evaporation; plasma flame and/or arc spray-
ing and/or deposition; and sputtering target techniques.
The oxide is applied to (or formed in situ on) the
dielectric surface as a very thin film or layer, the thickness
and amount of the oxide layer being sufficient to substantially
decrease the panel operating voltages. In the usual practice
hereof, the oxide layer is applied to or formed on the dielectric
material surface to a thickness of at least about 100 angstrom
units with a range of about 100 angstrom units up to about 1
micron (10,000 angstrom uni~.
As used herein, the terms "film" or "layer" are intended
to be all inclusive of other similar terms such as deposit,
coating, finish, spread, covering, etc.
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 g~ass 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
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sealed together so as to form a panel.
In the preferred practice of this invention, the oxide
layer is applied to the surface of the cured dielectric before
the panel heat sealing cycle.
The practice of this invention may be especially
beneficial over given periods of panel operating time and best
results are typically realized after appropriate aging of the
panel, the required amount of aging being a function of the oxide
used. Panel aging is defined as the accumulated total operating
time for the panel. ~n a panel without a dielectric oxide layer,
100 hours of panel aging is standard.
The following examples are intended to illustrate one
of the best embodiments contemplated by the inventor in the
practice of this invention.
EXAMPLE I
A layer of magnesium oxide was deposited to a relatively
uniform thickness of about 1000 angstrom units on the respective
exposed surfaces of two cured dielectric material layers, each
dielectric layer having been previously applied and cured onto
(electrodes containing) glass substrates.
The magnesium oxide was deposited by means of an elec-
tron beam evaporation technique. The dielectric composit~on was
a lead borosilicate consisting of 73.3% by weight PbO, 13.4% by
weight B2O3, and 13.3% by weight SiO2. The glass substrates
were of a soda lime composition containing about 73% by weight
SiO2, about 13% by weight Na2O, about 10~ by weight CaO, about
3% by weight MgO, about 1% by weight ~12O3, and small amounts
( %) e23, K2O, As2O3, and Cr2O3. The electrode
lines or conductor arrays were of hanovia gold.
The two substrates were heat sealed together (using a
standard solder glass) so as to form a gaseous discharge panel
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of the open cell Baker et al kind. After an appropriate vacuum
process, the panel was filled with an inert ionizable gas con-
sisting of 99.9% atoms of neon and 0.1% atoms of argon at a
pressure of about 600 Torr. The magnitude of the dynamic
sustaining voltage for the gaseous discharge panel after aging
for about 25 hours was about 120 volts. After aging of the panel
for over 100 hours, the dynamic sustaining voltage dropped to
about 90 volts.
The panel fabrication of Example I was repeated using
no oxide layer on the dielectric. The panel required about 100
hours of aging before the dynamic OEustaining voltage leveled
off at a magnitude of about 140 volts.
The foregoing example illustrates that when a layer of
magnesium oxide is applied to the dielectric surface as in
Example I, the operating voltage for the resulting fabricated
gaseous discharge panel is substantially decreased, e.g., in
comparison with Example II wherein no oxide layer is used.
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