CA1053311A - Gas discharge display/memory device containing source of lanthanide series rare earth in dielectric - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
mere is disclosed a gas discharge device containing at least two electrodes, at least one of the electrodes being insulated from the gas by a dielectric member. There is particularly 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, each of which is respectively backed by an array of electrodes, the electrodes behind each dielectric material member being oriented with respect to the electrodes behind the opposing dielectric material member so as to define a plurality of discrete discharge volumes constituting a discharge unit. At least one dielectric insulting member contains a predetermined beneficial amount of a source of at least one Lanthanide Series rare earth selected from La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu.
The rare earth may be utilized in any suitable form, such as a compound, mineral, and/or element. Likewise, the rare earth may be incorporated into the dielectric by any suitable means, including being applied as a layer within the dielectric or on the surface thereof.

Description

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This invention relates to novel multiple gas discharge ` .
display/memory panels or units which have an electrical memory and which are capable of producing a visual display or ~:
representation of data such as numerals, l~tters, television display, radar displays, binary words, etc.
Multiple gas discharge display and/or memory panels of one particular type with which the present invention is con- :
cerned are characterized by an ionizable yaseous medium, usually .
a mixture of at least two gases at an appropriate gas pressure, I
1 10 in a thin gas chamber or space between a pair of opposed di~
electric charge storage members which are backed by conductor (electrode) members, the conductor members backing each dielec~
tric member typically being transversely oriented to define a ~.:
plurality of discrete discharge volumes and constituting a discharge unit. In some prior art panels the discharge units .~ are additionally defined by surroun~ing or confining physical structure such as by cells or apertures in perforated glass .
plates and the llke so as to be physicaily isolated relative to .~ .
other units. In either case, with or without the confining physical structure, charges (electrons, ions) produced upon 1 ionization of the gas of a selected discharge unit, when proper .
alternating operating potentials are applied to selected con-.¦ ductors thereof, are collected upon the surfaces of the dielec- .
.~ tric at specifically defined locations and constitute an elec-; trical field opposing the electrical field which created them .:
' so as to terminate the discharge for the remainder of the ., , 30 : ~ - 1- ~ , ,, ,~'.
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half c~cle and aid in the initiation of a discharge on a succeeding opposite hal cycle of applied voltage, such charges as are stored constitutlng an electricaL memory.
Thus, the dielectric la~ers prevent the passage .5 of substantial conductive cuxrent from the conductor members to the gaseous medium and also serve as collecting surfaces for ioni~ed gaseous medium charges (electrons, ions) during the alternate hal~ cycles of the A.C. operating potentials, such charges collectln~ first on one elemental or discrete :L0 dieLectric surace area and then on an opposiny elemental or discrete dielectric surface area on aLternate haLf c~cles to constitute an electrical memory.
An example of a panel structure containing non-physically isolated or open dlscharge units is disclosed in ~ 15 U.S. Letters Patent 3,499~167 issued to I'heodore C. Baker, ; et al~
: An example of a panel containing physically iso-,.;, lated units is discLosed in the article b~ D.L. Bitzer and H.G. Slottow entitled "The Plasma Dls~Lay Panel - A Digital-ly ~ddressable ~ispla~r With Inherent Memory", Proceedingof the Fall ~oin~ Computer Conference, IEEEt San Francisco, California, ~ov. L966, pages 541-547. Also reference is made to U.S. Letters Paten~. 3,559,190.

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In the operation of the panel, a continuous vol-,. .
ume o ionizable gas is confined between a pair o dielec-tric surfaces backed by conductor arrays forming matrix ele-, ments. The cross conductor arrays may be orthogonaLly re-.~ lated (but any other coniguration o conductor aFrays may _ ~ _ .

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be used) to define a pLurality o~ opposed pairs of charge storage areas on the surfaces of the dieLectric bounding or confining the gas. Thus, or a conductor matrix having H
rows and C columns the number of elemental discharge vol-umes will be the product H x C and the number of elementalor discrete areas will be twice the number of elemental dis~
charge volumes~
In additiont the panel may comprise a so-called monolithic s~ructure in which ~he conductor arrays are cre-ated on a single subs~rate and wherein two or more arrays are separated from each o~her and from the gaseous medium by at least one insulating member. In such a device the gas dlscharge takes place not ~etween two opposing members, but between two contiguous or ad;acent members on the same sub strate.
It is also feasible to have a gas discharge de-vice wherein some of ~he conductive or electrode members are in diract contact with the gaseous medium and the re-maining electrode members are appropriately insulated from such gas~
In addition to the matrix configuration, the con-ductor arrays may be shaped otherwise. Accordingly, while the preerred conductor arrangement is o the crossed grid type as shown herein, it is likewise apparent that where a maximal variety of two dimensional display patterns is not necessaryl as where speci1c standardi~ed visual shaped (e~g., numeraLs, lettersJ words~ etc.) are to be formed and image resolution is not critical, the conductors may be shaped accordingly.

, 10$33~1 The gas is one which produces visible light or in-visibLe radiation which stlmulates a phosphor (if visual display is an objecti~e) and a copious supply of charges (ions and electrons) during discharge. In an open aell pan-5 el of the type disclosed in the saker et al patentt the gaspressure and the electrlc fieLd are su~ficient to laterally conine charges generated on discharge within elemental or discrete dieLectric areas within the perimeter o such areas, especialLy in a pan 1 containing non-isolated units As described in the Baker et al patent$ the space between the dielectric surfaces occupiad by the gas is such as to permit photons generated on discharge in a selected ~: dlscre~e or elemental volume of gas to pass freely through the gas space and strike surace areas o~ dielectric remote ;
~rom the selected discrete volumes, such remo~e~ photon struck dielectric sur~ace areas therehy emitting elèctrons so as to condition other and more remote elemental volumes for discharges at a uniform applied potential.
Wi~h respect to the memory function o~ a given dis-charge panel~ the aLlowa.ble aistance or spacing between the dieleetric surfaces depends, inter aLiaJ on the frequency o~
the alternating current supply~ the distance typically being greater ~or lower ~requencies.
While the pr.lor art does disclose gaseous dls-1 25 charge devices ha~ing externally positioned electrodes for ¦ initiating a gaseous discharge, sometimes caLled "electrode-;, . , .: .
less discharge," such prior art devices utiLiæed ~requencies `. `
and spacings or discharge volumes and operating pressures ~;

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such that although discharges are initiated in the gaseous medium, such discharges are ineffective or not utilized for charge generation and storage at higher frequencies; al-though charge storage may be reaLized at lower frequencies, such charge storage has not been utilized in a display/mem- .
ory device in the manner of the Bit~er-Slottow or Baker et al invention. .: .
The term "memory margin" is defined herein as M~M. = ~ . ~:

where V~ is the half amplitude of the smallest sustaining voltage signal which results in a discharge every half cycle, but at which the cell is not Bi-stable and VE is the half ampLikude o the minimum applied voltage su~ficient to sus-tain discharges once lnitiated. ::
It will be understood that basic electrical phe-nomenon utilized in this in~entlon is the generatlon of charges tionS and electrons) alternately stora~le at pairs of opposed or facing discrete points or areas on a pair of dielectric suraces back.ed by conductors connected to a source of operating potential~ Such stored charges result in an electrical ield opposing the fleld produ~ed by the applied potential that created them and hence operate to termlnate ioni~ation in the elemental gas volume between op-posed or ~acing discrete points or areas of dielectric sur-face. The term "sustain a discharge" means producing a se-quence of momen~ary discharges, one discharge for each halfc~cle of applied alternating sustaining voltagel once the ;:

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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 the practice of this invention, ;
there is incorporated into the dielectric a beneficial amount of a source of at least one La~t~ Series rare-earth oxide selected from the lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, `
holmium, erbium, thulium, ytterbium and lutetium. ..
In accordance with a further teaching, an improvement ~:
is provided in a multiple gaseous discharge display/memory panel which has an electrical memory and is capable of pro-ducing a visual display with the panel being characterized by `
an ionizable gaseous medium in a gas chamber formed by a pair :
of opposed dielectric material charge storage members, each :
of the dielectric members is respectively backed by an array .
of electrodes with the electrodes behind each dlelectirc member being oriented with respect to the electrodes behind the opposing dielectric member so as to define a plurality of discrete discharge volumes, each of which constitutes a discharge unit. The improvement which is provided resides in at least one dielectric member containing at leastone Lanthanide -~
Series rare earth oxide selected from La, Ce, Pr, Nd, Pm, Sm, ~.
Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu. ~
As used herein, the phrase "incorporated into" is i intended to comprise any suitable means whereby a source of at .
least one rare ear~h is appropriately combined with the .
dielectric, such as by intimately adding or mixing the source into the dielectric pre melt batch or to the melt; by ion .
exchange; by ion implantation; by diffusion technlques; or by ~
applying one or more layers to the charge storage surface of the - 6 ~

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dielectric, or to the electrode contact surface of the dielec- :
tric, or as an internal layer within the dielectric.
The rare-earth source may be elemental in form or ,~',' ,` '",~ ' ~" , ~
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may be a suitable rare-earth compound, such as a rare-earth oxide or a rare-earth salt.
Typical rare-earth compounds include:
Lanthanum:
Acetate Boride Phosphide ~itride Bromate ~itrate Hexaboride Fluoride Bromide Sulfate Chloride Iodide Carhide Sul~ide -Cerium:
Acetate Chloride Bromate Fluoride ;
: 15 Carbide ~itrate ~itride Selenate Phosphide Iodate :
Boride Iodide ;
5uLfide Oxalate :
Carbonate Sul~ate ~ ;
Praseod~mium:
Acetate Fluoride Bromate Selenate ~ . .
Chloride Sulfate ~eo~ymium:
Acetate Chloride :
Carbide Fluorlde ~;
Bromate ~itrate Bromide Sul~ate ,'~

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Samarlum:
~cetate Chloride Bromate Carbide ..
Fluoride Sulfate Europium:
Sulfate ~itride Carbide ~itrate ChlorIde . Fluoride Gadolinium:
Acetate Boride Bromlde Selenate Caxblde Phosphides : Chloride Sulfate ~itrate L5 Terbium:
Chloride ~itrate :: Fluoride Sul~ate :
DYsprosium: , Acetate Chromate Bromate Nitrake :~ .. ..
Bromide O~alate Chloride Selenate '.1 Fluoride Sul~ate :
Holmium:
Bromide Fluorida Chloride Oxalate Iodide ' `' , , ~ ' ,: ' ,:

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ErbiUm: t Chloride Boride Fluoride Sulfate Nitrate Thulium:
Chloride Boride -~
Fluoride Ytterbium:
Acetate Carbide Titanate Boride Chloride Sulfate ~::
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Fluoride Lutetium:
Sulfate Carblde ,:
FLuoride Boride .

In addition, it is contemplated that various rare- :
: earth minerals and derivatives thereof may be utilized such :',- :, :' ,. . :: .
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as Monazite~ Altaite, Lanthanite, Paristte, Samarskite, Bastnaesite, Euxenite, and MischmetalL.
In one particular em~odiment hereof, the rare-earth source is applied as one or more layers to the charge-storage surface o the dielectric.
As used hereinj the term "layer" is lntended to be all inclusive of other similar terms such as ilm~ de-posit~ coating, finishl spread, covering, ~tc~
The rare-earth source is applied to the dielectric surface tor a previously applied layer) by any convenient means including not by way of limitation vapor deposition;
vacuum deposition; chemicaL vapor deposition; wet spraying upon the suraae a mixture or solution of the layer sub-stance suspended or dissolved in a Liquid ~ollowed by evapo-ration of the Liquid; dry spraying o~ the layer upon thesurface; thermaL evaporakion usiny direct heat, electron beamr or Laser; plaæma 1ame and/or arc spraying and/or ~ deposition; and sputtering target techniques.
; ~ In a ~urther em~odiment hereof, a Layer of rare-ea~th oxide i9 applied to the dlelectric surface, such as by one of the foregoing methods, especially electron beam evaporation.
In still a further embodiment of this invention~
a rare~earth oxide layer is formed in situ on the charge s~orage surface of the dielectric, such a by applying rare-earth metal to the sur~ace followed by oxidation.
Each layer of rare-earth source is applied to the dielectric~ as a surface or sub-layer, in an amount suffi-..

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cient to obtain the desired beneficial result, usually to a thickness of at least about 100 angstrom units with a range of about 200 angstrom units per layer up to about 1 micron (10,000 angstrom units) per layer.
; 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 previ-ously 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 sealed together, e.g. using thermal means, so as to form a panel.
In one pre~erred practice of this invention, each rare-earth containing layer is applied to the surface o~
the cured dielectric before the panel heat sealing cycle, with the substrate temperature during rate-earth applica-tion ranging from about 150F to about 600F.
- In the ~practice of this invention, it has been discovered ~ha~ the use of thin surface films of rare earth oxides on each dielectric charge storage member sur~ace pro-vides several important advantages:
1. Such rare-earth oxide ilms are optically neu-tral in light transmission with low light absorption;
2- Such films have a low index of refraction pro-.
viding low re1ectivity in a muLtipl~ overcoat structure such as a rare-earth oxide layer over a barrier layer of aLuminum oxide;
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3. Such films do not darken as a result of pro~
longed discharge activity (panel aging);

4. The sequioxides of the rare-earth oxide group (La2O3) as opposed to the dioxides (CeO2) tend to pro-vide minimum operating voltages within the general categoryof stable oxide insulators; that is comparable to lead oxide layers as disclosed in U.S. Letters Patent 3,634,719 ytter-bium oxide (Yb2O3) and Lanthanum oxide (La2O3) typically pxovide the lowest operating voltages, especially sustaining voltages; and

5. A properly prepared dielectric charge storage surface of rare earth oxide provides stable operating vol-tages over extended periods of panel operation. In particu-lar, ytterbium oxides exhibit long life properties.
In the drawing there is shown the aging character-istics for a multiple gas discharge display/memory panel of the Baker, et al. type. The panel comprises two opposing dielectric charge storage surfaces, each of which contains a thin (1000 angstrom units thick~ film or layer of ytterbi-um o~ide. A~ter a ~rief preLiminary aging period, both the maximum and minimum sustaining voLtages substantially level off and become relatively constant for over 800 hours of panel operating time.
In addition to the foregoing advantages, it is anticipated that some of the rare-earth oxides will provide inherent ion or other barrier protection thereby eliminating the use of other barrier fiLms or layers.
The use of a rare-earth source, in accordance with ~ , , -12-., ~
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this invention, has many potential beneficial results.
For example, a radioactive, rare-earth source may be used to condition the ionizable gas medium of the gas .
discharge display/memory device; that is, provide free elec~
trons within the gas such that the discharge ~an be initi-ated.
In addition, the rare-earth source~may be used as a luminescent agent, especiaLly as a photoluminescent phos-phor.
- 10 The rare-earth activated phosphors are well known `
in the prior ar~. Typical phosphors include europium-activated yttrium vanadate red phosphor, e.g. with one ~:
europium atom to every nineteen yttrium atoms and europium activated, yttrium oxide.
Also the rare-earths exhibit interesting electri-cal properties, including semi-conductor characterlstics which.make sources thereof particularly suitable for use at the gaseous medium-interface. :~.
Likewise, a.rare-earth source may be utilized in .
coffibination with one or more compounds of other elements, such as Group IIA, Al, Si, Ti, Zr, Hf, Pb, etc., especially ~ .:
as an oxide layer, to achieve various resuLts, e.g. lower operating voltages, thermal stability, decreased aging cycle time, more uniform operating voltages, etc.
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Claims (13)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. In a gas discharge device containing at least two electrodes, at least one of the electrodes being insulated from the gas by a dielectric member, the improvement wherein at least one dielectric member contains a source of at least one Lanthanide Series rare earth oxide selected from La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu.

2. The invention of claim 1 wherein the rare earth oxide is contained within one or more layers on a surface of the dielectric member.

3. The invention of claim 1 wherein the rare earth oxide is contained within one or more internal layers within the dielectric member.

4. The invention of claim 1 wherein the dielectric member contains the rare-earth oxide in the form of a rare-earth sesquinoxide.

5. In 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, each of which dielectric members is respectively backed by an array of electrodes, the electrodes behind each dielectric member being oriented with respect to the electrodes behind the opposing dielectric member so as to define a plurality of discrete discharge volumes, each of which constitutes a discharge unit, the improvement wherein at least one dielectric member contains at least one Lanthanide Series rare earth oxide selected from La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu.

6. The invention of claim 5 wherein the rare-earth oxide is contained within one or more layers on a surface of the dielectric member.

7. The invention of claim 5 wherein the rare-earth oxide is contained within one or more internal layers within the dielectric member.

8. The invention of claim 5 wherein the rare-earth oxide is in the form of a rare-earth sesquinoxide.

9. The invention of claim 5 wherein the rare-earth oxide is ytterbium oxide (Yb203).

10. In a gas discharge device containing at least two electrodes, at least one of the electrodes being insulated from the gas by a dielectric member, the improvement wherein at least one dielectric member contains ytterbium oxide (Yb203).

11. In a gas discharge device containing at least two electrodes, at least one of the electrodes being insulated from the gas by a dielectric member, the improvement wherein at least one dielectric member contains lanthanium oxide (La203).

12. The invention of claims 10 or 11, in which the oxide is on the surface of the dielectric member.

13. The invention of claims 10 or 11 in which the oxide is in the form of a layer within the dielectric member.