IL33079A - Gas discharge type display panel - Google Patents

Description

/29/16 33079/2 GAS DISCHARGE TYPE DISPLAY PANEL nun ninrnnnrF nrrr ■ Γ ΙΊ Ι Ι Ι r Abstract of Disclosure There is disclosed a multiple gas discharge display/ memory panel having substantially uniform operating voltages, each gas chamber of the panel being filled with a volume of an ionizable gas having a relatively flat Paschen's curve over a selected range. In a specific embodiment there is used an argon-neon gas mixture in a proportion sufficient to significantly lower the operating voltage requirements (magnitude and frequency) relative to other typically used gas mixtures and also increase the uniformity thereof.

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 displays, radar displays, binary words, etc. More particularly, this invention relates to novel gas discharge display/memory panels having substantially uniform 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 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 units are additionally defined by surrounding or confining physical structure such 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 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.

Hereinbefore, the operation of gas discharge panels has typically comprised relatively high, non-uniform operating volt- f.one embodiment off ages. In accordance with this invention, it has been discovered that a multiple gas discharge display/memory panel can be operated at voltages having relatively uniform characteristics. In accordance with a specific embodiment of this invention, such operating voltages are also substantially reduced.

More particularly, it has been discovered that the uniformity of the panel voltage characteristics per discharge unit , can be significantly improved by filling the thin gas chamber or - chambers of a panel with an ionizable gas having a Paschen's curve (breakdown voltage of the gas versus gas pressure times discharge gas distance, V vs. pD) which is relatively flat, e.g., parallel to the pD axis, over a selected wide pD range whereby random dielectric spacing departures between discharge units of the panel do not significantly affect the voltage requirements and characteristics for a given volume of gas positioned at such random spacing departures.

It is contemplated that any ionizable gas may be used provided that such gas has a relatively constant voltage over a relatively wide pD range; that is, a Paschen's curve slope which is approximately zero(O), e.g., a slope value of about -5 volts per centimeter-Torr to about +5 volts per centimeter-Torr over a pD range of about 3 centimeter-Torr to about 30 centimeter-Torr.

In the preferred practice of this invention, the gas pressure within the chamber is about .2 atmosphere to about 5 atmospheres, the upper limit being a function of the structural strength of the panel. Good results have been obtained with a gas pressure of about .2 atmosphere to about 1 atmosphere.

Also in the preferred practice of this invention the discharge gap distance (spacing between the dielectric surfaces) is less than about 10 mils, typically about 4 mils to about 9 mils. With the use of such relatively small dielectric spacing, beneficial results may be obtained particularly with the gas pressures noted hereinbefore.

In accordance with a specific embodiment of this invention, it has been discovered that additional outstanding results, e.g., substantially reduced panel voltage requirements (magnitude and frequency) , are obtained using an ionizable gaseous mixture containing about 99.5 percent atoms of neon and about 0.5 percent atoms of argon to about 99.99 percent atoms of neon and about 0.01 percent atoms of argon.

In a highly preferred embodiment hereof, the gas is a mixture consisting essentially of about 99 „ 9 percent atoms of neon and about 0.1 percent atoms of argon.

Since panels constructed with gaseous discharge mediums as described in the specific embodiment have lower operating voltages and frequency requirements, presently available semiconductor components may be used in supplying operating potentials to the conductor arrays. Moreover, such relatively lower voltage and frequency requirements permit the use of integrated circuitry in designing operating voltage supplies. At the same time the power consumption for a given light output level is reduced with an attendant reduction in operating temperature and possible reductions in stress due to temperature differentials. This beneficial result has a corollary result in further rendering operating voltages for individual discharge units more uniform since there is less warping and deflection of panels due to temperature, thus maintaining uniform spacing, e.g., discharge gaps.

Additional beneficial results can also be obtained since the effects of discharge gap variation between discharge units in a given panel are minimized and the operating voltages rendered more uniform, such that lower memory margins may be used.

In accordance with the practice of this invention, there is used a discharge panel having no physical nor optical isolation of individual discharge units.

Thus, although each discharge unit may be physically and/or optically isolated from each other unit, it has been discovered that such is not essential in the practice of this inven-tion. Where physical and optical isolation of individual discharge units has been deemed necessary in the prior art, rela- tively complex and, difficult manufacturing procedures have been necessary in order to insure precise registration of the isolation device (e.g.., such as a perforated structure positioned between the dielectric members) and each of the matrix conductors. However, in accordance with this invention, such prior art difficulties are reduced by using a panel having no physical nor optical isolation.

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 5 1 - 5^7.

An example of a preferred neon-argon gas mixture embodiment is disclosed in Figure 23, page 114, of an article by M. J. Druyvesteyn. and F. M. Penning, Rev. Mod. Phys. 12_, 87 (1940). " The practice of the specific neon-argon embodiment of this invention enables one to use lower frequencies, e.g., relative to other gas compositions, and still retain memory margin (as defined hereinafter) and adequate panel brightness. The use of lower frequencies may"be preferred because of a resulting decrease in heat buildup and thermal stress in the panel. Furthermore, the specific neon-argon gas mixtures contemplated in the specific embodiment of this invention typically have high visible light or luminous efficiency within the optimum frequency range, e.g., on a plot of frequency versus memory margin, in comparison with other gas compositions.

In accordance with the invention, a continuous volume of ionizable gas having a substantially horizontal Paschen's curve in a selected operating range is confined between a pair of photoemissive 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.x 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 and a copious supply of charges (ions and electrons) during discharge and, preferably, the gas is a mixture of gases at a pressure 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 „ In the panel structure, 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, the re-mote dielectric surface areas struck or impacted by photons emitting electrons to thereby condition the other and remote elemental volumes for discharges at a uniform applied potential.

With respect to the memory function of a given discharge panel, the allowable distance between the dielectric surfaces depends, inter alia, on the frequency of the alternating current supply, the distance being larger for lower frequencies. If the spacing is relatively large then there is insufficient time for charges to transfer to or collect on the elemental or discrete d electric surface areas during a cycle if the frequency is too hi In accordance with the preferred practice of this invention, the spacing or distance between the dielectric surfaces is less than about 10 mils.

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. = —£ vs where Vf is the magnitude of the applied voltage at which a discharge is initiated in a discrete conditioned 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 initiated. It will be understood that basic electrical phenomena utilized in this invention are 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 practice of this invention will be better understood by reference to the accompanying drawings and hereinafter detailed description of an open or unconfined multiple discharge chamber type discharge panel.

Fig. 1 is a partially cut-away plan view of a .gaseous discharge display/memory panel 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 a an isometric view of a larger gaseous discharge display/memory panel.

Fig. 4 is an isometric cross-sectional view (enlarged but not to proportional scale) of a modified form of a gas dis- charge display/memory panel embodying the invention.

As illustrated in the drawings, the panel 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 collectible on the surfaces of the dielectric members at opposed or facing elemental or discrete areas X ' and Y defined by the conductor matrix on 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, in accordance with this invention, the thickness of gas layer 12 as determined by spacer 15 is under 10 mils, typically about 5 to 6 mils, dielectric layers 10 and 11 (over the conductors at the elemental or discrete X and Y areas) are between 1 and 2 mils thick, and conductors 13 and 14 about 8,000 angstroms thick (tin oxide). How- ever, support members 16 and 17 are much thicker (especially in relatively large 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 opera- tion 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, partic ularly 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 1/4" 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 formulae (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 ioniz-able 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» Of course, the bead-like spacers 15B may, if desired, be elongated in the plane of the panel.

In accordance with the present invention the effect of small variations in thickness of gas volume 12 between conductor intersections is made insignificant or eliminated by the gas composition described herein.

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 conductor arrays is about 30 mils Transparent or semi-transparent conductive material such as tin oxide, gold or aluminum can be used to form the conductor arrays. In any event, it is important to select a conductor material that is not attacked during processing by the dielectric material.

It will be appreciated that conductor arrays 13 and 14 may be wires of 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 inven tion. 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 affected during bake-out of the panel.

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.g0, 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 dielec trie 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 less than about 10 mils, typically 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. Such interface and addressing circuitry or system 19 may be relatively inexpensive line scan systems or the somewhat more expensive high speed random access systems.

The gas volume of the panel can be conditioned for operation by continuous discharge of one or more discharge units in open photonic communication with other discharge units or 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 high 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.

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. 3 is a panel having a large number of elemental discharge volumes. 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. 3 but are likewise transparent so that the panel may be viewed from either side.

In the modification shown in Fig. 4 each support member has formed therein a plurality of fine grooves or channels 50A and 50B and in each groove one conductor of each conductor array 13" and 14" is deposited, respectively. Dielectric coating 10" is deposited on each conductor of conductor array 13", respectively, and dielectric coating 11" is deposited on each conductor of conductor array 14". The depth of grooves or channels 50 is greater than the total thicknesses of the conductors and diele-tric coatings so that the mouth 51 of each groove or channel is open for the length of each groove. The support members 16" and 17" are oriented with their respective grooves at right angles to each other with the lands 52 of each groove on support member 16" contacting the lands 53 of each groove in support member 17". Thus, the distance between opposed elemental pairs of dielectric surfaces at conductor crossings is maintained uniform, for gas pressures less than ambient or environmental pressures. In order to eliminate or minimize stresses due to pressure differentials, where the gas pressure is greater than ambient or environmental pressures the contacting lands in the support members may be coated with dielectric or other fusible material and bonded to each other. In this embodiment, the gas 12" under pressure will be continuous along a groove mouth and have a waffle configuration along the groove at each intersection with the conductor bearing channels of the opposite support member. In this case photons can pass freely along the lengths of a pair of channels to impact dielectric coatings along the channels and thereby condition elemental volumes along a pair of crossing channels.

EXAMPLE PREPARATION OF DISCHARGE PANEL A discharge panel having the structure shown in Figures 1 to 3 was prepared.

PREPARATION OF SUBSTRATE MEMBERS 16 AND 17 The substrate glass members 16 and 17 were prepared by cutting 6-1/2 inches x 5 inches x 1/4 inch plates from 24 inches x 24 inches x 1/4 inch twin ground flat glass panes after normal quality inspection. An analysis of the panes with physical properties is given in TABLE I„ TABLE I Component Percent by Weight Si02 72.78 Fe2°3 .148 TABLE I (cont.) Component Percent by Weight Na20 13.15 K20 0.12 CaO 9.33 MgO 2.99 BaO Nil As203 0.05 SO3 0.24 Cr203 0.0008 99.97 The cut edges were beveled on a belt grinder using wet 80 grit silicon carbide cloth, followed by water wash and hand drying. The edges were then acid fortified by brushing an HF < acid paste on the ground areas, etching for 10 - 15 seconds, and then washing in alconox and water. The chemical composition of the acid paste was 70 milliliters of 52% by weight hydrofluoric acid, 20 milliliters of concentrated sulfuric acid, 5 milliliters of aerosol O.T., 20 - 25 milliliters of Dextraglucose (Karo white),' and 18.8 grams of wood flour. The resulting dimensions of the beveled, HF acid fortified members were 6 inches x 5 inches x 1/4 inch.

The members were then scanned for out-of-flat using a Federal Precision Height Gage (standard model 2400). Thickness measurements were taken on both plates at nine points on each member using a Pratt Whitney Supermicrometer Model "B". The flatness and thickness measurement results are summarized in TABLE IIA. The physical properties of the substrates are summarized in TABLE IIB.

TABLE IIA FLATNESS (To 3 Point Zero Reference Plane) Substrate 17 Substrate 16 Max.+ 45 mil Max.+ 1.05 mils Min . - 0 mil Min„- 0 mils Range 45 mil Range = 1.05 mils THICKNESS Max. = .23396" Max. = .23573" Min . = .23386" Min. = .23564 " Range = .00010" Range = .00009" TABLE IIB Softening Point 727°C Annealing Point 548°C Strain Point 505°C Coef. of Expansion 89 (10-7) (0-300°C) Coef . of Contraction 106 (10-7) (A. P. -25°C) Coef. of Contraction 94 (10-7) (435°C-25°C) Transmittance 86-88 Stress Optical Coef. 2.63 mu/cm/kg/cm2 Both substrate members were then ultrasonically cleaned in alconox, water, and alcohol.

APPLICATION OF CONDUCTOR ARRAYS (ELECTRODES) 13 AND 14 Hanovia gold (milled to a -400 mesh and containing a lead borate flux) conductor arrays (electrode lines) were printed on each glass substrate using a screen printing process. The printed electrode lines were air dried for several minutes and the substrates were then fired on 1/2 inch lava bases in an electric recirculating oven under the firing cycle conditions summarized in TABLE III.

TABLE III ELECTRODE FIRING CONDITIONS Heating rate 5°F/min.

Binder Burnout Plateau 650°F/15 min.

Peak Temperature and Time 1150°F/55 min.

Cooling Rate 1.95°F/min.

After the firing cycle, one end of each electrode was shorted using an air dry, acetone soluble, conductive silver paste containing butyl acetate thinner. Line continuity and resistance measurements were then taken using an ohmmeter scanning device. The results are summarized in TABLE IV.

TABLE IV LINE CONTINUITY AND RESISTANCE OF ELECTRODES AFTER FIRING Panel No. 17 Panel No. 16 Line Width 8.0 mils Line Width 7.0 mils Line thickness Line thickness Not measured Not measured Usually 3- .5 mils Usually .3-.5 mils No lines No lines Broken Broken Plate Total Plate Total Out-Of-Flat Out-Of-Flat Scan .50 mils Scan 55 mils Line Line Resistance 4 ohms Resistance 3 ohms APPLICATION OF DIELECTRIC MEMBERS 10 AND 11 After the electrode processing operation the substrates were cleaned by hand in Safety Solvent Solution, wiped dry with Kayday towels, and blown off with filtered air.

Dielectric members 10 and 11 were then formed by applying to each substrate a 4-3/4 inches of 5-3/16 inches by 1-1/2 mil thick layer of lead borosilicate dielectric material consisting of 73.3% by weight PbO, 13.4% by weight B203, and 13.3% by weight S1O2.

Four glass rod spacers having a diameter of 8 mils and a length of 3 inches were placed on approximate centers of 1-1/4 inches in the set dielectric material on substrate 16.

The dielectric material on the substrates was air dried for 10 to 15 minutes and then heat cured by firing the substrates on 1/2 inch lava plates in an electric oven under the conditions summarized in TABLE V.

TABLE V DIELECTRIC HEAT CURING CONDITIONS Heating Rate 4°F/min.

Curing Peak Temp, and Time 1150°F/30 min.

Cooling Rate 1.37°F/min.

An air oxygen purge was used during the heat up and curing temperatures, the purge consisting of a ratio of 15% O2 to 85% air introduced at the rate of 18 liters per minute (by volumes uncorrected to standard conditions) . After the dielectric curing cycle the electrical continuity and resistance of the electrodes were again measured. The results of the measurements are summarized in TABLE VI.

TABLE VI Plate No. 17 Plate No. 16 Diel. Thickness Max. 90 mils Max. 2.26 mils Min. 62 mils Min 2.03 mils Range .28 mils Range 23 mils Average 2.73 mils Average 14 mils Out-Of-Flat Max. 34 mi Max, 56 mils (Diel.) Min. 06 mi Min , mils Range .28 mils RRaannggee = .56 mils Line Resistance 4 ohms 3 ohms Lines Broken 4 3 The physical properties of the dielectric material are TABLE VII DIELECTRIC PHYSICAL PROPERTIES Softening Point 452°C (Glassy Edge) Annealing Point 400°C Strain Point 380°C Coef. of Expansion 83 (0-300°C) (10~7) Coef. of Contraction 105 (A. P. to RT) (10-7) Dielectric Constant 16.1 Dissipation Factor .0028 Loss Factor .0451 Power Factor Δ % .28 The chemical composition of the four glass rod spacers is summarized in TABLE VIII and the physical and electrical prop erties thereof are summarized in TABLE IX.

TABLE VIII GLASS SPACING ROD(S) COMPOSITION Component Percent by Weiqht Si02 56.3 A1203 1.9 K20 8.9 Na20 3.5 CaO >0.1 MgO >0.3 PbO 29.1 TABLE IX PHYSICAL AND ELECTRICAL PROPERTIES OF GLASS SPACING ROD(S) Softening Point 632°C Annealing Point 436°C Strain Point 395°C Coef. of Expansion 90 (0-300°C) x (10~7) TABLE IX (cont.) Coef. of Contraction 103 (A.P.-25°C) x (10~7) Density 3.05 Durability 4.7 (Loss mg . per cm^) (1/5 N H2SO4) Electrical Log Resistivity 250°C 9.9 Log Resistivity 350°C 7.8 ASSEMBLY AND SEALING After the dielectric application the substrates were cleaned and dried. A 3/16 inch wide border of sealing solder glass 15S was applied to a thickness of 11 - 12 mils each substrate. The solder glass vehicle was 50% by weight poly alpha methyl styrene and 50% by weight DuPont Silver Thinner No. 8250. After application the solder glass was cured into the glassy state by firing to 600 - 650°F for 20 minutes with 9°F/minute heating and cooling rates. In this state the thickness was reduced to 6 - 7 mils.

The composition of the solder glass is given in TABLE X. The physical and electrical properties thereof are given in TABLE XI.

TABLE X CHEMICAL COMPOSITION OF SOLDER GLASS Component Percent by Weiqht Si02 5.37 A1203 1.17 B203 7.78 PbO 71.00 ZnO 12.32 BaO 1.82 Na20 .15 TABLE XI PHYSICAL AND ELECTRICAL PROPERTIES OF SOLDER GLASS Physical Properties Coef. of Expansion 87 (10~7/°C) Coef. of Contraction 95 (10~7/°C) Density gms/cc 6.05 Durability H2O — 1.98 (Loss mg. per sq. cm.) HCL 7.66 (1/50N) min. 21°C Gradient Boat Tests Glassy Edge 375°C Crystallization Edge 410°C Glassy Range 35°C Button Flow .970" Electrical Dielectric Constant 21.5 Dielectric Strength 1090 Power Factor Δ% .94 Log Resistivity 250°C 8.5 (P) ohm - cm Log Resistivity 350°C 6.9 A 1/4" hole was drilled in plate 16 at one corner using a water cooled diamond core drill. The drilled hole was then acid fortified by the same procedure used in the edge fortification. The hole was then cleaned by hand in hot water followed by an alcohol rinse.

The substrate plates 16 and 17 were then assembled by matching the glazed solder glass borders, placing them on sealing racks, and weighting the top plate 16 with 1-3/4 pounds of small Lava blocks.

A 1/4 inch tabulation 18 was then placed in the drilled hole of top plate 16 and solder glass (TABLES X and XI) , with amyl acetate - nitro cellulose vehicle, applied to the periphery.

The dimensions, chemical composition, and physical properties of the tubulation 18 are given in TABLE XII.

TABLE XII PROPERTIES OF TUBULATION 18 Dimensions 1/4" Tubing O.D. Max. .255" O.D„ Min. .240" Wall Thickness .050" (+.010") Chemical Composition SiQ2 70.6% by weight B203 0.2% AI2O3 2.0% K20 0.3% Na20 13.4% CaO 7.2% MgO 5.3% As203 0.02% BaO 1.0% Fe203 0.07% S03 0.2% Physical Properties Softening Point 735°C Annealing Point 547°C Strain Point 504°C Coef. of Expansion 83 (0-300 -7< Coef. of Contraction 102 (A.P.- Density 2.52 gm/cc Durability 6.5 (Loss 1 (H2S04) (1/50 N) The plates 16 and 17 and the tubulation 18 were then sealed by heating at 425°C for one hour. The heating and cooling rate was 2°C per minute.

After sealing the panel was tested for leakage using a Vacuum Instrument Corp. leak. detector . Finally, nine point thickness measurements were taken and final spacing calculated. The results are given in TABLE XIII.

TABLE XIII FINAL AVERAGE DIMENSIONS OF SEALED PANEL BEFORE BAKE-OUT BASED ON NINE POINTS MEASUREMENTS Top Substrate 16 Ave. Initial Thickness .23390 mils Range (Max. Thickness Minus Min. Thickness) .00011 mils Ave. Thickness with Dielectric .23663 mils Range (Max. minus Min.) .00031 mils Calc. Ave. Dielectric Thickness 2.73 mils Range (Max. Minus Min.) .28 mils Bottom Substrate 17 Ave. Initial Thickness .23568 mils Range (Max. Thickness Minus Min. Thickness) .00009 mils Ave. Thickness with Dielectric .23784 mils Range (Max. minus Min.) .00018 mils Gale. Ave. Dielectric Thickness 2.14 mils Range (Max. minus Min„) .23 mils Spacing Between Dielectric Members Ave. Spacing 4.70 mils Range (Max. Minus Min.) .56 mils PANEL BAKE-OUT AND GAS FILLING The panel was flamed sealed to a bakeable 4 inch Veeco High Vacuum system and a spark coil used to check for large leaks The device was rough vacuumed to 10 microns of Hg and then high _7 vacuum pumped down to 10 Torr. The panel was then subjected to a bake cycle consisting of a heating rate of 1.08°C per minute, baking at 400°C for 8 hours, and a cooling rate of .34°C per minute down to a baking oven temperature of 93°C.

The panel was then filled with a gas mixture consisting of 99.9% atoms of neon and 0.1% atoms of argon to an absolute pressure of 24.62 inches of Hg . The tubulation 18 was then tipped off and flamed sealed with a torch.

STATIC AND DYNAMIC TESTING OF PANEL ELECTRICAL CHARACTERISTICS After the panel was baked out and gas filled, it was tested for static and dynamic characteristics. In the static test, nine matrices were selected from different areas of the panel, and the magnitude of the sine wave voltage required to turn on all the units in these matrices was measured at a frequency of 50 KHZ. Also, the magnitude of the minimum sine wave voltage which would maintain all the units in the on state was measured. It was found that in the voltage range from 335 to 350 Volts peak to peak all of the units in all the tested matrices were maintained in the on state after having been turned on at a higher voltage; none of the units in any of the tested matrices was turned on by the sine wave signal in the above mentioned sustaining voltage range. Thus, a typical operating, or sustaining, voltage for the panel would be in the range from 335 to 350 Volts peak to peak.

In the dynamic test, a sine wave sustaining voltage within the operating range was applied to nine selected matrices. These nine matrices were similar to, but not precisely identical to, the nine matrices used in the static test. A 2 microsecond pulse, superimposed on the sine wave, was applied sequentially to units within the test matrices to determine how many of the units could be turned on and off with the same sustaining voltage applied to all units of the matrices. It was found that in all cases the percentage of units which could be turned on and off exceeded 95%, and typically exceeded 99%, thereby demonstrating that the voltage characteristics of the units were substantially uniform.

Claims (1)

1. 33079/3 What is claimed 1st 1» A gas discharge panel of the type in which a pair of nominally paralle , thin dielectric members constitute at least a portion of structural members forming charge storage vails of a thin gas chamber and transversely oriented conductor arrays on non-gas chamber surfaces of said thin dielectric members; respectively, are supplied with operating potentials for selectively effecting multiple discharges botween selected cross-points of a pair of conductors of each array and sustaining and terminating discharges once they are initiated?said chamber containing an lonlzable gas medium, characterized in that said gas has a relatively low breakdown voltage which is substantially constant over a selected range of the discharge gap variation, the gas pressure being substantially constant in said chamber over said range* 2· The gas discharge panel as defined in claim 1 characterized In that the thickness of said relatively thin gas chamber Is under about 10 mils thick* 3· She gas discharge panel defined In claims 1 and 2 characterized in that said gas consists essentially of a mixture of at least two gases which coact to produce said breakdown voltage characteristic* 4· The gas discharge panel defined in claim 3 characterised in that said gas is a mixture including two noble gases, at least one of whic* is argon* 5i The gas discharge panel defined In claim 3 characterized that said gas is a mixture of neo and argon gases* 6* The gas discharge panel defined in claim 5 characterised ÷ " -said gas consists of about 99» atoms of neon gas and about ¾. af*^. of argon gas* 33079/3^ 7· The gas discharge panel defined in claim 6 characterized in that said mixture of neon and argon gases is at a pressure greater than 0*2 atmosphere and under about 5 atmosphere* 8* The gas discharge panel defined in claim 7 characterized in that said pressure is from about 0.2 atmosphere to about 1 atmosphere* 9· The gas discharge panel defined in claim 5 characterized in that said pressure is from about 0,2 atmosphere to about 1 atmosphere. 10· The gas discharge panel defined in claim 1 wherein the Paschen*s curve of the gas is about -5 volts per centimeter-Torr to about +5 volts per centimetex*-Torr over a P x D range of about 3 centimster-Torr to about 30 centimeter-Torr* 11. A gas discharge device for the panel defined in claim 1, in which a discharge in a hermetically enclosed ionlzable gas generates charges alternately collectable on a pair of discrete areas of a pair of means having dielectric surfaces to constitute an electrical memory* each of said dielectric surfaces being backed by a conductor array defining a plurality of pairs of opposed discrete areas and means for supplying operating potentials to said conductors, characterized by said pair of means having dielectric surfaces being spaced apart to define a thin discharge chamber, said thin discharge chamber containing a two dimen-sionally uneonfined gas contiguous to said dielectric surfaces, whereby a plurality of discharges can occur within said thin gas chamber in open photonic communication with each other via the space occupied by said gas, and by said gas being at a pressure sufficient to laterally confine charges produced on discharge substantially within the gas volume in which they are generated, and supporting means for supporting said means having dielectric surfaces, said supporting means being sufficiently rugged to withstand stresses on said device due to pressure differential between tiie gas pressure and ambient pressure about the device* 33Q79/3 · 12» The device defined in claim 11 characterized by said means having dielectric surfaces being constituted by thin dielectric coatings on said supporting means* 13* Se device defined in claim 11 characterized by each discharge being an elemental light producing discharge, and at least one of said dielectric surfaces and associated conductor arrays passing the light produced by said elemental light producing discharges* de ice^ 14· Xhefik-vee ea defined in claim 1 characterised by said conductor arrays and said dielectric surfaces being formed in situ on opposing surfaces of said supporting means* said supporting meas having thermal expansion characteristics compatible with the thermal expansion characteristics of said dielectric surface V7ith at least the means supporting the said light passing dielectric surface and conductor array passing light produced by said elemental light producing discharges, Inorganic spacer means spacing said plates to define said two dimensionally unconflned gas volume, and means joining the edges of said plates to form therewith said hermetic enclosure, whereby, after formation of said dielectric surfaces and said conductor array and the joining of said edges of said plates, and prior to placing gas in the enclosure the device may be heated under vacuum to remove impurities from within the enclosure and from the interior vails thereof* device/ 15* The Sim&Bi&m defined in claim 14 characterized by said dielectric surfaces being formed of a thin layer of heat resistant inorganic material* device/ 16* The Saevm defined in claim 11 characterized in that said means for supplying operating potentials to said conductors maintains at least one of said plurality of discharges at all times during operation of said 33079/3 ^ 17» The device defined in claim 11 characterized in that said supporting means are constituted by a pair of elongated glass plates seallngly joined in spaced relation to define said thin gas discharge chamber, said elongated glass plates being oriented such that the axes thereof along tho long dimensions thereof are at transverse angles to each other with the respective ends of said plates extending beyond the side edges of the other plate, and wherein said conductor arrya consist of closely spaced oinear conductors parallel to the long axes of the plates, alternate ones of said conductors being extended toward one edge of the plates, respectively, and the others o ly of said conductors are extended toward the opposite edge of the plates, respectivel * 18· She device defined in claim 17 wherein the long axes of said o plates are at 90 to each other, and said thin gas discharge chamber is square* 1 * The device defined in claim 14 characterized in that said inorganic spacer means comprises at least one bead~like spacer member contacting both dielectric surfaces for maintaining the distances between said dielectric surfaces substantially constant* 20* She method of establishing a uniform firing voltage characteristic and Bdnlmlzing the effect of discharge gap departures for a multiplicity of selectively controlled discrete discharge units in a multiple die* charge gas discharge panel in which a pair of spaced, nominally parallel, thin dieleotrio members constitute at least a portion of structural members forming mils of a thin gas discharge chamber for said multiplicity of selectively controlled discrete discharge units and transversely oriented conductor arrays on non-gas chamber surfaces of said thin dielectric members; respectively, are supplied with operating potentials for selectively aani-pulatlng discharges at discrete discharge units, while at the same time the power consumption is reduced for a given level of light output at lower temperaturef said method comprising the steps of filling said thin gas chamber with a gas exhibiting a characteristic Baschen's curve of breakdown voltage versus the product of pressure and discharge gap distance which gas a substantially zero shape over a sleeted range, whereby random spacing departures across said panel do not afect the firing voltage characteristics for discrete discharge units located at said random spacing departures. 21· The method defined in claim 20 wherein said thin gas chamber has a thickness under about 10 B11B»- 22. The method defined in claim 20 wherein said gas is a mixture of gases consisting essentially of about 99·9$ atoms of neon and about 0*1$ atoms of argon. 2% A gas discharge panel substantially as hereinbefore described and 24» A method of establishing a uniform firing voltage substantially as hereinbefore described and with reference to the annexed drawings*