CA1159873A - Dielectric insulator for gaseous discharge device - Google Patents

Abstract

IMPROVED DIELECTRIC INSULATOR FOR GASEOUS DISCHARGE DEVICE
Abstract of the Disclosure A high resolution gaseous discharge display and/or memory device comprises a panel array of bistable charge storage areas designated gaseous discharge cells or sites, each cell having an associated pair of coordinate orthogonal conductors which, when appropriately energized, pro-duce a confined gaseous discharge in the selected cell. The conductors are insulated from direct contact with the gas by a dielectric insulator, and the dielectric insulator may be composed of or include a layer of refractory material having high secondary emission characteristics such as an alkaline earth metal oxide to prevent degradation of the dielectric layer during operation, to reduce the required discharge voltage and to extend the life of the gaseous discharge panel.
Cross Reference to Related Applications Canadian Application Serial No. 162,719 for "Improved Method and Apparatus for a Gas Display Panel" filed by Tony N. Criscimagna et al, December 15, 1969.
Background of the Invention Plasma or gaseous discharge display and/or storage apparatus has certain characteristics such as a flat display surface and an inherent capability which render it particularly desirable for alphanumeric display apparatus. One example of a known gaseous discharge device is disclosed in U.S. Patent 3,559,190, "Gaseous Display and Memory

Description

Cross Reference to Related Applications Canadian Application Serial No. 162,719 for "Improved Method and Apparatus for a Gas Display Panel" filed by Tony N. Criscimagna et al, December 15, 1969.
Background of the Invention Plasma or gaseous discharge display and/or storaye apparatus has certain characteristics such as a flat display surface and an inherent capability which render it particularly desirable for alphanumeric display apparatus. One example of a known gaseous discharge device is disclosed in U.S. Patent 3,559,190, "Gaseous Display and Memory 1 15~73 Appara~us", patented Januar~ .26 0 1971 by Donald L. Bltzer

2 et al and a~3~igned ~o ~ihe Univer~lty of Illinoi~. Such panels

3 may lnclude an inner gla~3 layer of phy~ically lsol~ted cells

4 or comprise an op~n panel conPlgu.ratlon of electrically isolated but not phy~ically iE~ola~ed gas cell~. In th~
6 latter form o ga~eou~ d.i~charge display appaxatus, a ~ealed 7 gaseous envelope compo~ed of dielectric ma~erial and contalnlng 8 an ionlzable illumln~ble gas, ~uch a8 a mixtur4 o neon and 9 argon or nitrogen, ha~ orthogonal conductors dl~po~ed on opposite side~ thereof~ P.n alternating potentlal connected to 11 selected pair~ of conducto:rs i8 capac~tively coupled to the ga~
12 through the dielet~trlc mat:er~al, produclng an alternating 13 voltage across the gas i.n the xegion defined by the lntersectlon 14 o the conductors. If, vn a particular hal:~-cycle of the 1 5 al'cernating potentlal connected to the conductors, thQ gac~
16 voltage exceeds a br~akdo~"rl voltage V3~, the gas becomes 17 conductive through the vol~a.ge- induc~d productlon of electron~
18 and gas ion~, and th.e selac:ted ce~ 1 is ~aid to have broken 19 down. In this conduc~lve s~ce, ~lectxons ln th~ ga~ migrate to the wall which is tem3?oxar~1y po~1t~ve, a.ns~ the 1OIIB to 21 the wall which is temporar:lly negative. The chargs~d p~rticles 22 collected on the di~lectrlc w~ , or "wall charge, " produce 23 a potential between the dielectrlc suxface and the conductor~
24 which oppose~ the externally applied potentlal, elnd thu~
2 5 reduc~s the ga3 voltage, A~ current sontinuz s to f low 26 thxough the ga~, the wall chaxge increases until the ga~
27 voltage drops below ~hat nece3sary to malntain the ga~ ln a 28 conductive stat~, and ~he r~ur;cent d~ sch~rg~ i9 extingulshed.
29 On the nex~ half-cy~:aQ o~ lthe alternatlng external potentlal having a po:! arilty opposlte ~at of the preceding 31 hal:E-cycle, the vol ~age prod.uced by ~he wall charge sdds Ki971008 -~-~ ~59~73 1 to that produced externally, so that the gas voltage is augmented. Thus the breakdown voltage VB of the gas is obtained at a lower value of external potential, a current discharge of opposite sense to the initial discharge is initiated, and a wall charge of opposite sign to the initial wall charge is established of sufficient magnitude to cause the discharge to be extingu;shed. After initial breakdown, the wall charge condition may be maintained in selected cells by application of a lower potential designated the sustain signal which, combined with the wall charge, causes the selected cells to be reignited and extinguished con-tinuously at a relatively high frequency to maintain a continuous display.
Light output for display purposes is produced during the passage of the discharge current. Since the present invention is primarily concerned with the fabrication and structure rather than the operation of a gaseous dis-play panel, the above information is considered adequate for an under-standing of the instant invention. For additional details regarding operation of gaseous discharge panels in write, sustain and erase modes, reference is made to the aforenoted copending application 162,719.
In the conventional gaseous discharge apparatus the conductors are isolated from direct contact with the gas by a layer of dielectric material which may comprise the gas envelope. The capacitance of the di-electric layer is determined by the thickness of the layer, the dielectric constant of the material and the geometry of the drive conductors. The dielectric material must be an insulator having sufficient dielectric strength to withstand the voltage produced by the wall charge and the ex-ternally applied ~' ~ 159~73 1 potential. ~he dielectrlc should be a relatively good 2 emitter of ~econdary elec~ron~, be tr~nspaxant or tran~lucent 3 on the display side ~o tran~mi~ ~he ligh~ generated by the 4 di~eharge for dl~play purpo8e~, and be susceptible to S fabrlcation without reac~ing wi~h the conductor metallurgy.
6 Flnally, the coefficient o~ expansion of ~he dieleetrie 7 should be compatible wlth tha~ of the gla~s sub~trate on whlah 8 the dlelectrla l~yer i8 fOrnled.
9 One material po~e~sing the above char~cterl~tic~ with re~pect to a ~oda-lime~~ilica~e substrate i9 lead-borosilicate 11 solder glass, a gla~ contalning ln exca~s of 75 pereent 12 lead oxlde. In an embodiment construc~ed in aecordance wi~h 13 the teaehing of the present invention, a dieleetric compri~ing 14 a layer of lead borosilic~ts gla~ wa~ employed a~ the insulator. However, chemical ~nd phy~ical reaetlon on the 16 surface of the lead-boro~ili¢ate glass under di~eharge 17 condltions produced degradatlon or decompo~ition of the lsad 18 oxide on the dialactrlc ~urface, thereby produelng a change 19 ln the electrical charaetari~tics o~ ~he ga3eou8 display p~nel on a cell-by-cell ba~is~ Thi3 degr~dation caused ~h~
21 electrlc~l p~ram~ters o~ the cell~ ln the gaseous discharge 22 de~ice to vary a~ a funct~on o~ the cell history ~uch th~t 23 over ~ period of time the required f~ring voltag~ for 24 indivldual cell~ fell out~ide the normal operatinq r~nge, and the firing voltage varied on a cell-by-cell basis.
26 5ummary of the Invention 27 In order to improve the ~econdary emi~ion chara~teri~tics 28 o~ the cell wall~ and to ~Yold the chemlcal and phy~ical 29 reactlon of the diel~ctrlc layer ~urface of a gaseou~
di~charge device re~ulting fr~m r~petitive ga8 d~charge o~

Ri971008 -4-l 1~9~73 1 selected cells, a layer of alkaline earth metal oxide having both re-fractory and high secondary emission characteristics from a class in-cluding ma~nesium oxide, beryllium oxide and calcium oxide is deposited over the dielectric layer to form the cell walls. In an embodiment con-structed in accordance with the teaching of the instant invention, a coating of magnesium oxide, a refractory material characterized by a high coefficient of secondary emission, is applied over the entire inner surface of the dielectric layer. A refractory material is one which resists ordinary treatment, is difficult to reduce and has a high binding energy such that its constituents remain constant even after prolonged use. By utilizing a layer of refractory material having high secondary emission characteristics, th secondary electron emission characteristics dominate the electric operating conditions in the gas panel, resulting, as more fully described héreinafter, in gaseous discharge operation with lower operating voltages. A thin layer of magnesium oxide has a thermal charac-teristic compatible with that of the lead-borosilicate insulator, thus simplifying the fabrication process. An additional advantage from the magnesium oxide coating is that an imperfect or nonuniform magnesium oxide layer provides satisfactory operation. Finally, the refractory aspect of the magnesium oxide coating is highly resistant to chemical reaction due to the discharge process, thus maintaining the panel operating voltages substantially constant with time and extending the useful life of the gas panel.

1 ~59~73 1 Accordingly, a prlmary ob~ect of the present invention 2 is to provide an improved gaseous discharge di~play panel.
3 Ano~her o~ject of the pre~ent inventlon is to provide 4 an improved gaseous d~charge di~play panel utilizing a layer of refractoxy material having a high ~econdary 6 emis~ion characteri~ic adjacant to and in continuou~
7 contact with the gas to lower the operating potential of 8 the device.
~ Still another ob~ect of tl~e present invention i~ to provide an improved gaseou~ discharge dlsplay panel having 11 an inner layer of magnesium oxid~ in contact wi~l the ga~ to 12 prevent d~gxadation of the dielectric material, to ~xtend 13 panel life and to x~duce th~ opexating potential~ relIuired 14 for ga~ panel operation.
The for~o~ng and oth~r ob~ects, feature~ and 16 advanta~es of th~ pre~ent lnv~ntion wlll be apparent Erom 17 the ~ollowlng de~crip~ion of a preferred em~odiment of the 18 invention a~ illu~trated in ~le acco~panying drawing~.
19 Brie Description of the Drawinys Figure 1 i6 an l~ometric view of a ga~eou~ di~charge 21 panal broken away to illu~trate d~tail~ of t~e pres~nt 22 invention.
23 ~igure 2 i8 a top view of the gaseous di~charge panel 24 illus~rated in Figure 1.
~ r~E~ of a Preferr~d hm~odiment 26 Re~erring now to th~ drawings and more particularly to 27 Figure 1 thereo~, there i~ illustrated a ga6 panel 21 28 compri~ing a plurality of lndividual ga~ cells or 6ite~
2g defined by the inter~ection o~ vertical ~rive line~ 23A-23N

Ki971008 -6-l 1~9~73 and horizontal drive lines 25A-25N. The structure of the preferred embodiment as shown in the drawings is enlarged, although not to scale, for purposes of illustration; however, the physical parameters of the inYention defined in the instant application are fully described in detail hereinafter. While only the YieWing portion of the display panel is illustrated in the interest of clarity, it will be appreciated that in practice the drive conductors extend beyond the viewing area for interconnection to the driving signal source.
The gas panel 21 includes an illuminable gas such as a mixture of neon and argon within a sealed envelope, the vertical and horizontal conductor arrays being disposed in orthogonal relationship on opposite sides of the envelope.
Gas cells within the envelope are selectively ignited or fired during a write operation by applying to the associated pair of conductors coincident potentials having a magnitude sufficient to cause the gas voltage to exceed the breakdown voltage VB. In the preferred embodiment, the control potentials for write, read and erase operations are rectangular a.c. signals of the type described in aforenoted copending Application Serial No. 162,719. Typical operating potentials for a gaseous discharge panel using a neon-argon gas mixture are 200 volts for write, 140 volts for sustain.
Once the wall charge has been established, the gas cells are maintained in the discharge state by a lower amplitude periodic sustain signal. Any of the selected cells may be extinguished, termed an erase operation, by first reducing the potential difference across the cell to zero, then applying an erase pulse corresponding in amplitude but 0 opposite in polarity to that of the last sustain alteration, B

l 15~73 l and malntaining th~s zero po~ential for a ~ixed period 2 following terminat~on o~ ~he erase pulse. By selective wrlte 3 operatlon~, infonmation may be generated and dl~played as a 4 sequence of lighted cells or site~ in the form of alph~numeric or graphlc data and ~uch inormatlon may be regenerated a~
6 long as desired by th~ su~tain operatlon.
7 The gas panel envelope, a~ hereto~ore lndicated, ls a 8 relatively thln or fragile sheet of dielectric material g such that a palr of gla88 substr~tes 27, 29, front and rear, is employed as supporting member~ on opposite sides of the 11 panel. The only requirement ~or such ~upport members is 12 that they be nonconductive and good insulators, and 13 substantially transp~rent for display purposes. Ordinary 14 l/4" commercial grade sod~-lime silicate ~lass i~ ~ltllized in the preferred embodiment.
16 Shown al~o in cut~way are the conductor arrays 23, 25 17 which ~re interposed between the glass substrates 27, ~9 18 and associated dielectric member~ 33, 35. Conductor arrays 19 23, 25 may be formed on sub~trate~ 27, 29 by a number of well known processes such as photoetching, vacuum deposition, 21 stencll screening, etc. Transparent, semi-tran~parent or 22 opa~ue conductive material such a~ tin ox~de, gold, aluminum 23 or copper can be used to form th~ conductor arrays. The 24 conductor arrays 23, 25 may be wires or filaments o copper, gold, silver or aluminum or any other conduct~ve matal or 26 material. However, formed in sltu conductor arrays are 27 preferred, ~lnce they may be more easily and more uniformly 28 deposlted on and adhered ~o the substrates 27, 29. In the 29 embodiment constructed in accordance with the in~tant invention, opaque chrome-copper-chrome conductors are Ki971008 -8-1 iL59873 1 utili~ed. A center conductor of copper utilizes a lower 2 layer of chrome to provide adhenlon to the soda-lime-~ilicate 3 substrate, while the upper layer of chrome over the copper 4 protects the copper conductor from attack by the lead-boro~llicate in~ulator.
6 Dielectric layers 33, 35, layer 33 of which iB broken 7 away in Fig. 1, are formed ln situ in the preferred 8 embodiment directly over conductor arrays 23, 25 of an 9 inorganic material having an expansion coefficient closely rel~ted to that o the substrate member~. One preferred 11 dielectrlc matexial, a0 previously lndicated, i8 12 lead-borosilicate solder glas~, a material containing a 13 hlgh percentage of lead oxlde. To fabricate the dlelectric 14 area, lead-boro~llicate gla88 frlt 1~ sprayed over the conductor array and the plate placed in an oven where the 16 gla~s frlt is reflowed and monitored to ensure appropriate 17 thickness. Alternatlvely, the dlelectric layer could 18 be formed by electron beam evaporation, chemical vapor 19 deposition or other ~ultable means. The requirement~ for the dielectric layer have been specifled, but additionally 21 the surface of the dielectric layers ~hould be electrlcally ~2 homogeneou~ on a micxo~copic scale, i.e., should be preferably 23 fre~ from cracks, bub~le~, cry~tal~, dlrt, surface films or 24 any impurity or imperfection.
F~nally, the problem of degradation occurring on the '6 dieleotric surface during operation of the panel resulting in vary~ng the electrlcal characteristics of individual '8 cells ~ignificantly r2duced panel lifa. The ~olution !9 ut~llzQd in the preferred embodiment was the deposition o~ a ~o homogeneous layer of a material hsving a high ~econdary Ki971008 -9-~ 1~98~3 1 emission characterlstlc between the dielectric surface and the 2 gas. A coating of such material, ln the fonm of an alkaline 3 earth metal oxide, was utilized. In the above described 4 embodlment, a coating of magnesium oxide, which i8 al80 a refractory materlal, was used. The~e layer~ 39, 41 could be 6 applied over the dielectric layer by any conventional mean~ ~uch 7 a~ electron beam evaporation, spraying, spu~tering, eta.
8 Wlth respect to material having a high secondary 9 electron emlssion efflciency, the dominant secondary electron production mechanism i8 de~ined as emis~ion from 11 the conflning boundarie~ of the gas, which ~n the lnstant 12 ~nvention axe the dlelectric electrode ~urfaces. The breakdown 13 voltage in a ga~eous discharge display panel is determined 14 by ths electron amplification of the gas described by a coefficient a and the production of secondary electrons 16 in the volume of the gas and on the confining ~urf~ces or 17 cell wall~. For a specif~ed ga~ mixture, pressure and 18 eleotrode spacing, a is a monotonically increaging function 19 of the voltage in the ordinary range of p~nel operation.
The secondary electron emi8~ on i~ chaxactexized by a 21 coefficient r, which may be a ~trong function of thQ
22 surfac~ material and mod~ of prepRration. Voltage breakdown 23 occurs when the followlng approximate-relationship i8 24 satisfled:
re ad~l 26 where d is the apac~ng between electrodes. Con~ideration 27 of the above equation ~hows that an lncrease in r will 28 xesult in a lower value o~ a at breakdown, and he~ce a 29 lower breakdown or p~nel operating voltage V~. The oxides of the lighter alkaline earth metal~, beryllium, magnesium ~i971008 -10-~ 159873 1 and calcium are preferred for the dielectr$c surface because 2 of their lower chemical reactivlty whereby they are not 3 chemically altered by the actlon of the di~charge. ~his 4 feature also ensureq that the secondary electron emi~sion S remain5 relatively const~nt under prolonged expo~ur~ to the 6 discharge whereby the panel operating voltage~ remain ~ub-7 ~tantially con~tant, thu~ extending the p~nel lifetime.
8 Referring now to Flgure 2, a top view i8 employed 9 to clarify certaln detail~ of the ln~tant invention. Two rigid support members 27 and 29 compri~e the axterlor ll member~ of the dlsplay panel, and ln a preferred embodiment 12 compri~e ordlnary 1/4" commerclal grade qoda-lime-~lllcate 13 gla~s. Formed on the inner walls of the ~ub~trate members 14 27 and 29 are the horizontal and vertical conductor arrays lS 25, 23, re~pectively. The conductor size~ and spacing 16 are obviously enlarged in the interest of clarity.
17 HoweVer, in one pre~erred panel configuration, the center-18 to-cen~er conductor ~pacing in the respecti~e arrays i~
19 about 30 mil~ u~ing 6 mll wlde ohrome-copper-chrome conductors, while the conductors may be typically 2.5 21 miorons in thickn~. Formed dlrectly over the conductor 22 array~ 25, 23 are the dlelectric layers 33 and 35 which, 2~ a~ previou~ly de~cribed, ~re fonmed of an inorganic 24 material having an expanMion coefficient compatible with that of the ~ubstrate member~ 27 and 29.
26 preferred dlelectric materlal for u~e with the above 27 described substrate i9 a solder glass such a~
28 lead~boro#illcate glas~ containing a high psrcentage of lead 29 oxlde. The d~electric member~ belng of nonconductive gla~3 Ki971008 -ll-l 159873 1 function a~ inqulator~ and capacitor~ for ~heir associated 2 conduc~or array3. Lead-boro~ilica~e gla8~ i8 u~ed ~ince it 3 adheres well to other yla8~e8, haB a lower reflow temperature 4 than th2 goda-lime-BiliCate gl~8 3ubstrates on which it iæ
laid, and has a relatively h~gh visco~ity w~th a minimum 6 of interac~ion with the metallurgy of the conductor array~
7 on which it i8 depos~ted, The expansion charact~ri~tic~ of 8 the dielectric mu~t be tailvred to that of the a~ociated 9 substrate members 27 and 29 to prevent bowlng, cracking or di~tortion of the s~b~trate. A~ an overlay or a homogenou~
11 film, the dielectric layers 33 snd 35 are more readily formed 12 over the entire surace of the gaseous dl~chaxge device 13 rather than a cell-by-cell de~inition.
14 Whlle lead-boro~ilicate glas~ po~se~ses the specified dlelectric strength and tempera~ure coefficient, lt ~as 16 found that under actual operating conditions the propertle~
17 of the insulator surface degraded under the influence of 18 the discharge. Thi~ change on the surface of the lnaulator, 19 a~ previously noted, produced a corresponding change ~n the electrical characterlstics on a cell-by-cell b~is 21 wherein the electrical characterlstlcs of a cell varied ln 22 accordance with the coll history. Thus cell~ having a 23 hi~tory of repetitlve fixing produced changes in ~he electrical 24 ch~ra~teri~tic~ requir~nq an increase in the firing voltage ultimat~ly falli~g outside the normal opexat~ng range.
26 In the preerred embodiment, a dielectric layer of 27 approximately 25 microns wa~ ~mployed.
28 The overcoating of a hlgh gamma film of a refractory 29 material such ~8 ~n alkaline earth metal oxide over ~he a~oc~ted dielectric layer i~ shown in Figure 2 as layers 1 159~73 39, 41. Such materlals as the preferred magne3ium oxide 2 c3mblne a high aecondary electron emission efflciency with 3 a resistance to interaction with the di~charge. As ln the 4 dielectric layer with xespect to the sub~trate, the overcoatillg layera 39 and 41 ar~ required to adhere to the ~urface of the 6 dielectr~c layers and r~main ~table under panel ~abrication 7 includlng the high temperature baking and evacuation proce~ses. The hlgh gamma material used in the pre~err~d 9 embodiment, as prevlou31y noted, 1~ magne~lum oxide whlch has a high ~econdary emi~lon yield such that it determines 11 the electrical propertles of the panel, for a given 12 lllumlnable ga~, permltting panel operation at a slgnlficantly 13 lower potential.
14 Magne~ium oxide combines A low work funct~on and a wide band gap, pr~pertie~ which enhance secondary electron 16 emlssion. The alkaline earth metal oxide~ may be used as 17 the ma~or conatltuent of the dlelec~ric layer in the panel 18 or, a~ in the above de~crlbed embodlment, a~ a coatlng 19 applied over a convent~onal gla~ dielectric by ~ny of ~everal means such as spray~ng, evaporating, sputtering, etc.
21 In the preferred embodiment, a panel having a coating of 22 magne~um oxlde of 2000 Angstroms W~B succeesfully operated.
23 Alkaline earth m~tal oxides are good secondary emltter 24 materials, a~d the magn~slum ox$de i8 al80 a re~ractory material, i.e., dif~lcult to reduce such that the ~ur~ace 26 con~tltu~nts remaln constant even after prolonged use. A
27 further adYantage of the magne~ium oxide i8 that the layex 28 need not be a perfect film but may have holes, cracslcs, etc.
2 9 wlthout adYer~ely af fect~ ng the overEIll operation of the panel. In a panel utillzing the ~eaching of the pre~ent 1 inventlon, when the m~gneslum oxide surface 1~ b~mb~rded 2 by lons, photon~ and meta~t~ble atom~ a8 OCCUX~ during 3 di~charga, the magneslum oxide emits electron6 fac~litating 4 the operation of the panel. While the magne~ium oxide coating in the above dQscribed embodlment o~ the in~tant 6 inventlon was applled over the ~ntire surface, lt will be 7 appreclated that it could be Al80 formed on a site-by-~lte 8 definition or alternatively that a~high magneslum oxlde 9 content glass might be utillzed to provide a dielec~ric surface having the deslrad secondary emls~ion characteri~tic6 11 without the necessity of a magnesium oxide overcoat.
12 The final parameter in the lnstant invention relate3 to 13 the gas ~pace 45 between the opposing magne~lum oxide 14 ~urface~ ln which the gas 18 contalned. Thls i8 a relatively critical parameter ln ths gas panel, ~lnce the intenslty of the 16 dlscharge and the interactiona between discharges on ad~cent 17 discharge ~lte~ are functions of the spaclng. In the 18 preferred embodiment of the in~tant lnvention, a Bpacing 19 o~ ~pproxlmately 5 mils i~ utilized between cell wall~.
Since a unlform spaclng distance must be malntalned acro~s 21 ~he entire panel, ~ultable spacer means, lf needed, could 22 be util~zed to maintaln thls unlform spaclng. While the 23 ga~ 18 encap~ulated ~n the envelope, additlonal detail~
24 reg~rding sealing of the panel or fabrication detall~ ~uch as the high temperature bakeout, evacuation and back~lll 26 ~tep~ have been omittad as beyond the 8COpe of the i~tant 27 inYentlon. With respect to the reduction in operati~g 28 voltages wlth a panel using a magnesium oxid~ coating as 29 contrasted to one without, a reduction of discharge slgn~ls from 200 volt~ to a 175-180 volt range wa~ oboerved, while 1 the sustain signal decreased from a level of 140 volts to 115 volts, a most significant reduction.
While the invention has been particularly shown and des-cribed with reference to preferred embodiments thereof, it will be under-stood by those skilled in the art that other changes in form and details may be made therein without departing from the spirit and scope of the invention.

Claims (5)

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

1. In a display device of the gas discharge type, the combination comprising:
a pair of non-conductive support members, conductor arrays formed on the inside of each of said support members, each of said conductor arrays comprising a plurality of parallel conductors, said arrays of parallel conductors being positioned in orthogonal relationship with respect to each other, the intersections of said orthogonal conductors forming discrete charge storage cells, a dielectric member formed over each of said conductor arrays, and a homogeneous layer of an alkaline earth metal oxide deposited on the surface of said dielectric member for providing operation of said gas discharge device with lower amplitude control signals, and protecting said dielectric surface against degradation.

2. Apparatus of the type claimed in Claim 1 wherein said homogeneous layer has a high secondary emission characteristic.

3. Apparatus of the type claimed in Claim 1 or Claim 2 wherein said alkaline earth metal oxide comprises magnesium oxide.

4. In a gaseous discharge device, the combination comprising:
a sealed chamber filled with an ionizable gas, conductor arrays formed on the inner surfaces of said chamber, each of said conductor arrays comprising a plurality of parallel conductors, said conductor arrays being orthogonally related to define discrete gas discharge cells at respective intersections thereof, said gas discharge cells adapted to provide discrete localized discharges when appropriately energized by control signals applied thereto, a dielectric lead oxide glass film of approximately 25 microns in thickness formed over each of said conductor arrays, and a layer of magnesium oxide having a high secondary electron emission characteristic deposited on the surface of each of said dielectric glass films and in contact with said ionizable gas to enable operation of said gaseous discharge device with lower amplitude control signals, said layers of magnesium oxide being also refractory to prevent degradation of the surfaces of said dielectric layers resulting from the discharge in said gas cells.

5. An article of manufacture comprising a dielectric body having a structural configuration for use in a gaseous discharge display/memory device, said dielectric body having at least one electrode on one side thereof and on the opposite side thereof having a deposit of magnesium oxide in direct contact with the surface of the body in an amount sufficient to provide decreased operating voltages in the gaseous discharge device.