IE41581B1 - Gas discharge display panel device and method of manufacturing same - Google Patents

Abstract

1524831 Sealing gas discharge display panels PANEL TECHNOLOGY Inc 29 July 1975 [30 July 1974(4)] 31600/75 Heading C1M [Also in Division H1] The substrate plate 50 on which cathode electrode segments are printed and the anode plate 51 of a gas discharge display panel are sealed together in spaced apart relation by a sealing member 55 which extends around the periphery of the opposed substrates except for an opening 65 therein through which the panel is evacuated and filled with gas as necessary prior to the seal being completed by sealing the opening 65 with a fusible glass plug 66, Figs. 7 and 8 wherein the plug 66 overlies the spaced terminal ends 56, 57 of the sealing member 55 and is completely confined between the plates 50, 51 and is spaced inwardly of the edges thereof. The sealing member 55 is shaped from a cane of bubble-free fibre-optic type glass having a softening temperature of 450‹ C. which during assembly is temporarily held in position on one of the substrates by unfused dielectric. Hard glass spacer rods 58, 59, similarly tacked on to a substrate, define the desired discharge gap between the cathode and anode elements on the substrate. The fusible plug 66 is formed of glass having a fibre softening point below that of the sealing member 55. After the element 55 has been sealed in position with the help of externally applied heat and pressure, one or more of the panels are disposed in a chamber which is first evacuated and then filled at ambient room temperature to 120 torr with the filling gas of 99À5% neon and 0À5% argon, to which radioactive krypton may be added, the devices then being heated so that the glass plug 66 fuses to the sealing member 55 to seal the gas chamber. Also incorporated into the panel is a filamentary glass mercury giver 60 which is disposed opposite a window in the envelope. After sealing a laser beam is projected on to this giver 60 to crack the capsule and release mercury into the envelope.

Description

The present invention is concerned with gas discharge display panels and a process for producing same.

Gas discharge display panels are known which comprise a pair of parallel rigid substrate plate members which define a thin gas chamber therebetween in which, in use, information to be displayed is generated by a plurality of discrete gas discharges between selectively energised electrodes.

In the following description and claims, the term fiber softening temperature in relation to a glass member is defined as that temperature at which the glass melts or softens and just begins to flow so as to fuse or seal with further glass when placed adjacent thereto.

Fabrication of gas discharge display devices of the aforegoing type has been accomplished in the past using one-for-one type operations. That is, individual glass substrates and/or ceramic substrates are provided upon which the conductor runs are printed and then the dielectric masks are printed .over the conductor runs and in the openings in the conductor runs for the cathode electrodes, the cathode materials which interface with the gas discharge medium are printed thereon, all Of these being subsequently fired and cured. Such devices are usually subsequently assembled by the use of a gas filling tubulation. However, in some cases tubulationless devices have been fabricated in which the final hermetic seal of two spaced apart substrates is accomplished by utilization of an unfused sealing frame, evacuating the entire unit and back filling at an elevated temperature and then heating the assembled parts spaced between the electrode elements while retaining the gas in the assembly until the glass parts have beer softened to a sealing temperature to result in a fusion sealing of the frame element and thereby final assembly of the device. This process is difficult and cumbersome and does not lend itself well to batch processing of individual display elements.

In U.S. patent 2,142,106 (Boswau), a gaseous discharge display device having small glass discs carrying shaped cathode elements and individual anode elements are arranged to form a large disc with the interstices between the small discs sealed to prevent electrode interference between one another, a small aperture being left at one point in the periphery by leaving out the sealing operation at this point to provide communication with the main gas chamber formed by an overall glass envelope or bulb. In the Boswau patent, the bulb is subsequently exhausted and filled with the gas at a prescribed pressure, the exhausting and back filling processes extending through and communicating through the aperture to the individual gas chambers formed in the spaced discs.

The aperture is then filled with a suitable sealing material which permits the gas to permeate during the exhausting and filling operation. Thereafter, this individual seal element or plug is sealed, for example by heat.

In accordance with one aspect of the present invention, there is provided a process for manufacturing a gas discharge information display panel device having a pair of parallel rigid substrate glass plate members which define a thin gas chamber therebetween in which, in use, information to be displayed is generated by a plurality of discrete gas discharges betv/een selectively energised electrodes, in which process the sealing of said information display panel is effected by joining said rigid substrate members in spaced apart relation by an elongate sealing member which defines the lateral perimeter of said gas chamber, the terminal ends of sai d member being spaced apart to form a port so that said' chamber is in communication with its ambient atmosphere, placing a glass plug so that it overlies the terminal ends of said sealing member and is completely confined between opposed facing surfaces of the substrate plate members and spaced inwardly of the edges thereof, and, after the chamber has been filled with an ionizable gas, fusing the plug to said terminal ends to close said port and seal the chamber.

In accordance with a second aspect of the invention, there is provided a gas discharge information display panel comprising a pair of rigid substrate glass plate members, sealing means joining said plates in parallel spaced apart relation and defining a thin gas discharge chamber between said plates, an ionizable gas in said chamber and an electrode system for selectively ionizing the gas in said chamber to display information, said sealing means including an elongate first sealing member which defines the lateral perimeter of said thin gas discharge chamber, the terminal end portions of said first sealing member defining a port for enabling the chamber to be evacuated and filled with said gas, and a second sealing member in the form of a glass plug which overlies said terminal end portions of the first sealing member and is completely confined between opposed facing surfaces of said substrate plate members and spaced inwardly of the edges thereof, the glass plug being fused to said terminal end portions to close said port and seal the chamber.

Large numbers of the device may be stacked in trays, with the plugs in the form of small glass rods, bridging the ends of the first sealing members and held in position between the opposing substrates. The diameter of each rod or plug is slightly smaller than the spacing between the opposing substrate surfaces to snugly fit between these opposing substrate surfaces, each rod or plug having a fusion temperature slightly below that of the first sealing member. Both materials are, however, preferably of optical quality and of substantially bubblefree edge surfaces. This initially loose rod seal element or plug permits batch vacuumization (also under bake out conditions if desired) and back filling with any desired gas composition of large numbers of individual devices in a single operation.

In the prior art, in making segmented electrode gaseous discharge display panels, particularly alphanumeric type displays, the individual conductor runs are printed first and fired on the substrate and subsequently, the mask and cathode element electrodes e.g., those elements which are to be in direct conductive contact with the gas, are printed and cured, the printing of the cathode elements being through the apertures or openings in the dielectric mask. In the present instance, instead of using a ceramic substrate, simple, inexpensive glass substrates are preferably used. Conductor elements forming the cathode electrodes which interface with the gas medium are printed first and cured at relatively high temperatures compared with the temperatures used to cure subsequently applied elements so as to ensure that those conductor segments or elements forming the cathodes of the device have a good hard surface at the gas interface so as to minimize sputtering problems and improve the discharge properties of the device.

— ' The typical and classical way.of fabricating, gaseous discharge devices is to vacuum bake the devices so asf.to remove included gaseous contaminants from the interior surfaces of the device. Vacuum baking is a very time consuming and expensive process. In the present instance, several thousand devices can be arranged in trays and placed in a vacuum chamber. A vacuum is applied to the devices without heating to remove substantially all of the free contaminants from the individual gaseous discharge devices and then, at an ambient temperature, the gas filling is admitted to the processing chamber and thereby each individual gaseous discharge element is filled at room or ambient temperature. This ensures proper gas proportions and eliminates the need for accurate and precise calibration at high temperatures of the gas filling. Then, after the gas filling has been introduced to the devices, the devices are heated by Calarod heaters inside the chamber so as to effect a melting of the sealing plugs in the openings described earlier herein. This technique thereby avoids the long period between the filling and heating of the chamber, thereby enabling a production run of thousands of devices in a single chamber to be reduced to no more than six hours. Since this sealing process can be done at a pressure somewhat below ambient, and since the volume of gas in the vacuum chamber can be greater than the cumulative gas volume contained in the devices, there is sufficient heating under somewhat negative pressure conditions to assure good clean up of the device under less than perfect vacuum conditions and at significantly reduced cost and processing time.

Advantageously, small mercury-containing capsules or givers located in the chambers of the devices are activated by the use of a laser beam. To this end, the device is provided with laser transparent windows in each of two glass substrates which thereby permits the use of a laser beam to effectively break the mercury capsule without damaging the device itself.

The invention is described further hereinafter, by way of example, with reference to the accompanying drawings, wherein: Figure 1 illustrates a glass substrate upon which a first conductive pattern has been printed, one such pattern being shown in the top left hand corner thereof ί with the dash lines indicating the positions of a large number of other such patterns not shown in this drawing for purposes of clarity of explanation; Figure 2 illustrates the glass plate of Figure 1 upon which has been printed the first dielectric mask 41581 - 8 " (a black colored dielectric but shown white in Figure ?.); Figure 3 is the plate shown in Figure 2 having the crossover conductors printed on the mask of Figure 2 interconnecting the different elements shown, it being understood that a similar printing has occurred with respect to-the other substrate elements shown in Figure 3; Figure 4 corresponds to Figure 3 but wherein a further dielectric'printing has been effected over the crossover elements shown in Figure 3; Figure 5 is an exploded view showing the sequence of assembly of the different components into a device ready for batch fill and seal operations; Figure 6 is a top plan view of a completely 15 assembled device; Figure 7 is an enlarged sectional view showing the placement of the seal rod bridging the gap on the now fused seal frame; Figure 8 shows the mercury capsule in position 20 with a laser beam directed thereto for fracturing same; and Figure 9 is a process flows chart showing the individual printing and curing operations utilized in the manufacture of the devices.

Referring now to Figures 1 to 8 in conjunction wi th Figure 9, Figure 1 shows a glass plate 10 which, in a specific example, may be ten inches by twelve inches single strength glass, and which has printed thereon individual cathode electrode patterns 11-1, 11-2, 11-N and cathode period elements 12-1, 12-N. Each cathode pattern constitutes a digit position, the illustrated embodimen : being for a nine digit numeric display (n-9). It will bi· appreciated that the invention is equally applicable to alphanumeric segmentation as well as crosspoint matrix display. These elements have cathode electrode segments, 13A, 13B etc. which, in the illustrated embodiment of this invention, constitute the cathode electrode elements defining the glow discharge portions of the display. It will be noted that certain ones of these cathode segments 13A, for example, has a further direct conductive portion 14-A leading to a conductor pad 15-A. In the embodiment of this invention to be described herein, each of the corresponding segments 13-A in all of the digit positions 11-1, 11-2 ... 11-N, are interconnected electrically, some of which are directly interconnected in the initial electrode printing shown in Fig. 1. For example, the center bar segment 13-c is shown as being an interconnected horizontal segment electrode and is connected by a conductor portion 14C to a pad 15-C. Alternate pads are also printed at this time for subsequent connection to the anode elements to be described later herein. In like manner, the cathode electrode 13-B in digit position 11-1 is interconnected with every other cathode segment designated with the numeral B by a conductor portion 14-B and thereby to a pad 15-B.

However, in the present embodiment, some of the cathode segments are not directly connected to conductors extending to the individual pad elements 15. In the illustrated embodiment, a first dielectric mask element 16 shown in Figure 2 is printed over the conductor segments leaving openings or vias 18-1, 18-2, 18-N and 19- 1, 19-2, 19-N and 20-1, 20-N, 21-1, 21-N and 22-1, to 22-N, all of which are in registry with underlying conductor portions or areas. These vias are simply openings or spaces left vacant in the dielectric mask or layer 16. In addition to the vias or openings left for crossover connections, to be described later in connection with Fig. 3, it will be noted that the individual cathode segments 13-A, 13-B, etc. and the periods thereto for 12-1 ... 12N, are left open. No further conductive material is applied to these cathode elements because they have been cured at a temperature as described below which is higher than the temperatures used to cure subsequently applied elements to thereby anneal and/or provide smooth surfaces for the discharge per se. However, the crossover vias, 18-1 ... 18-N, 19-1 ... 19-N, - 1 ... 20N and 22-1 ... 22-N are left open for the purpose of permitting the conductor material which is printed in a manner shown in Figure 4 to make electrical contact with the conductor elements exposed by the vias. These form the electrical crossover connections shown in the pattern of Figure 3. It will be appreciated that conductor patterns may be devised so that the printing of such crossovers is eliminated or minimized. It should be understood that while the dielectric mask is shown as white, it is a black mask for highlighting the glow discharges at the cathode segments, and that the cathode material is white or silver colored in appeararoe and, in fact, is basically a silver in a suitable vehicle Furthermore.·, clear or transparent areas of glass have been stippled. Of course the anode glass substrate covid be translucent.

In addition to the openings or vias to make the crossover connections and in addition to the opening for permitting the cathode segments to be viewed in direct conductive contact with the gas, a pair of windows 25A and 25B are provided so that the glass substrate 10 is directly viewable through these openings 24 and 25.

These openings are for the purpose to be described more fully hereinafter.

Not shown in Figures 1 or 2 are conventional registration marks, such registration marks simply being marks which are printed in dielectric material upon the substrate 10 and in any subsequent printing upon the substrate 10 when the dielectric material is printed so as to ensure registration thereof. The term printing is used principally to encompass stencil screen printing etc., but other forms of printing may be used.

As shown in Figure 3 the crossover interconnecting via 19-1 to via 19-N is designated with the numeral 30 and the crossovers connecting the vias 18-1 ... 18-N are designated 31. In like manner, crossover conductor means 32, 33 and 34 are conductor printings upon the dielectric. The printing operations are simply screening or otherwise applying the conductive material directly upon the dielectric surfaces of the substrate with the conductive material entering the vias and making the electrical contacts with the conductor previously printed. It will also be noted that a pair of crossovers 36 and 37 have also been printed upon the conductor solely for the purpose of making the crossover connections between the conductor elements as shown. 41SS1 - 12 It will be noted that the conductive cathode segments for each of the digit positions remains exposed and these elements are, in effect, continuing to receive the temperature treatments (albeit at lower temperatures) for the curing of the dielectric layer 16 and the individual crossover layers as shown.

In a final printing operation (Fig. 4),the final dielectric layer is applied over the crossover, the windows 25A and 25B being maintained. The purpose of this final printing is, as well known, to avoid any glowing of conductor areas or portions which is it desirable should not flow.

Referring now to Figure 9, it should be noted that an important step in the process just described in the fabrication of the back substrate is that the electrodes which form the cathode segments for the display have been printed in an initial printing operation. This electrode is cured in step 5 as shown in Figure 9 at a much higher temperature than could be effected by prior art techniques in the fabrication of devices of the present type. In other words, by printing the cathode segments first and curing them at a much higher temperature than those used to cure subsequently applied elements to provide an improved cathode-gas interface, the mask which is printed on at a later time, can be cured at lower temperatures without adversely affecting the conducting properties of the different conductor elements used ii providing exterior connections for the device. As shown in Figure 9, the initial mask is printed in a two step operation of, first, printing the mask a first time, drying the mask and then curing the mask. A second mask 4158 1 printing, drying and curing operation is effected but it will be appreciated that these may be done in a single step. In some cases, the mask may be fabricated as a film and transferred to the substrate. However, it is important to ensure that the mask is of a sufficient thickness that the crap adjacent cathode segments is separated by a physical barrier of dielectric material. Thus, this second step is an important insurance that the dielectric between the ends of individual cathode segments is high enough to provide a barrier which avoids or minimizes shorting between nearby cathode segments.

The crossover printing is done with the same conductive material as is used in the first printing operation of conductive material and it will be noted that in each case, the conductive material is dried and then cured at higher temperatures than are used for curing subsequently applied el intents. This material is a frit based thick film paste primarily of silver. The third mask printing operation, while it could have been limited to printing simply over the crossovers, was, in effect, a full printing since this further ensured a sufficient barrier between the individual cathode segments on the substrate. Thus, in addition to being able to print, dry and cure the cathode electrodes at a high enough temperature (a typical conveyor oven being about 50 ft. long, one foot per minute, there being about 15 heat zones with a maximum temperature of 1100°C.) as to ensure a good, clean, smooth silver surface for the cathode electrode, printing the cathode electrodes in a first printing step permits tho building up in the mask areas of sufficient barriers between the individual cathode segments as to 581 reduce the possibility of conductive connections between the individual cathode elements due to sputtering, etc. and thereby to enhance the active life of the device.

As illustrated at box 18 of Figure 9, the device is scribed along the dash-dot lines and separated to provide individual back substrates illustrated in Figure 5 as element 50. Element 50 in Fig. 5 corresponds identically to each of the plurality of elements 50 shown in Figure 4.

Referring now to Figure 5, the back substrate now designated as element 50, is identical to the back substrate component shown in Figure 4. Also shown in Figure 5 is an anode substrate 51 having printed thereon individual anode elements 52-1, 52-2, 52-N, there being one sich anode electrode element for each digit position which is adapted to overlie the individual cathode segments and the cathode period element 12-1 at a given digit position. The anode conductors are transparent tin oxide which are printed and fired on a single strength glass substrate .63. It will be appreciated that the printing and firing of these conductors may be done in a batch process, very much like the printing of the back substrate with cathode elements. The use of tin oxide as a transparent anode element is conventional in the art and is not described in detail herein except to say that the process of printing same with large numbers of devices on a thin glass substrate is useful for the purpose of batch producing devices.

The top substrate or anode plate 51 is joined to the bottom substrate by means of a sealing element or member 55 which has been shaped so as to have the ends thereof 56 and 57 spaced by about a % inch to about 1/16 inch. The sen Iing element 55 is simply placed upon the black dielectric masked element and held in place by drying unfused dielectric. At the same time, small spacer rods 58 and 59 at each end of the device are likewise temporarily held in position by tacking as by the use of unfused dielectric. Spacer rods 58 and 59 consist of a hard glass composition having a higher softening temperature than the sealing element 55. The sealing element 55 is made from a fiber optic type glass which has no bubbles therein and which has a fusing or seal temperature below the melting point of the glass substrate 10 and spacer rods 58 and 59 (a seal temperature of about 45O°C. is used). In addition, a small mercury capsule 60 is held in place in position over window 25A by a white unfused dielectric which is of essentially the same composition as the dielectric forming the mask but which does not have any pigmentation in it. The purpose of using a white unfused dielectric is so that laser energy which is used to rupture the capsule 60 is not absorbed by the black dielectric to create heat in the black dielectric and thereby destroy the device. It is also for this reason that a pair of windows 25A and 25B is provided.

After the sealing member 55 and spacer rods 58 and 59 and mercury capsule 60 have been positioned in the device, the anode plate 51 is positioned over these elements and a weight is applied thereto. The entire assembly is passed through a heating oven to fuse or join the sealing member 55 to anode plate 51 and back substrate plate 50. The resulting device is illustrated in Figure 6 and it will be noted that there is a small gap 65 so the interior of the gas chamber is accessible. A glass rod having a diameter about the same diameter as spacer rods 58 and 59 is simply laid in the gap or crevice between back substrate plate 50 and anode plate 51 so as to be completely confined between the opposed surfaces of these members and to be spaced inwardly of the edges thereof. The rod 66 constitutes the glass plug referred to in block 23 of Figure 9.

It will be appreciated that the spacer rod elements 58 and 59 need not be located in the gas chamber so formed or in the positions shown. They may be located parallel to the horizontal runs of seal 55 as viewed in Fig. 5, parallel to all four runs, between display positions for larger displays (see Baker et al U.S.

Patent 3,499,167); even externally of the chamber and parallel to the horizontal and/or vertical runs of seal member 55. In fact, the spacer may have a perimetrical configuration which is a twin to seal member 55, and only slightly larger or smaller. The only size criteria of the spacer is that it define the discharge gap.

Furthermore, it must be a high melting temperature glass but have a fiber softening temperature (as hereinbefore defined) below that of seal member 55.

As shown in Figure 6 alternate ones of contact pads 15 are connected to the cathode electrode on cathode plate 50 and the intervening ones are connected by means of extruded conductive silver epoxy connectors 70-1, 70-2 It is important to cure the epoxy at a temperature such that bubbles are not formed. Bubbles tend to cause concentrations of current flow in the tin oxide coatings and thereby impair or destroy the connection thereto.

As shown in Figure 8, the mercury giver 60 is a filamentary glass tube (18 mils in outside diameter) which is laser energy transparent. It is positioned between a window 25A and the cathode plate 50 and a transparent portion of the anode plate 51 (which may also be designated as a window) and held in place for assembly purposes by a white dielectric. The aluminium or copper block serves as a heat sink and should not be highly reflective for safety reasons. Instead of a glass capsule the giver may be any other radiant energy actuatable device, such as SAES types 150 giver from the SAES company of Italy.

The gas filling may be a mixture of neon and argon, such as 99.5% neon and 0.5% argon. Radioactive Krypton (Krypton 85) may be added to the ifill mixture to lower the operating voltage. However, it will be noted that there are two unused contact pads 15 which could be used to operate a keep alive discharge.

In a preferred embodiment, the edges 75 and 76 on plates 50 and 51 form a slot or notch for receipt of the seal rod or plug member 66. This permits a simple mechanical retention of the spacer in its desired position during the outgassing and gas filling operation. If desired the top horizontal run of seal member 55 as viewed in Pig. 5 may be located closer to the edge so that upon softening the seal material of element 55 will be pressed flat as shown in Figure 8 and the plug rod 66 held in position by an adhesive such as unfused dielectric. However, the seal member 55 may be formed flat in crosssection and, as before, slightly thicker than the spacer rods. The panel assemblies, with seal rods 66 in the notches or spaces and bridging the ends of the seal elements 55, are arranged in continuous abutting relation to one another in stainless trays with the ports or spaces 65 facing upwards and the glass rods 66 in place and in linear alignment with one another. One of the substrate members can be shorter than the other, in which case a high temperature glass shim, not shown, is located between the lower edge of anode plate 51 to prevent displacement of the shorter of the substrate members and thus to maintain the proper relationship between the anode and cathode plates while the heating of seal rod 66 is performed.

Seal element 55 is a bubble-free glass to avoid worm holes therein. A fiber optic type glass such as Corning type 7570 glass 033 O.D. cane formed as shown in Figure 5 works satisfactorily, it has a relatively low softening temperature of about 45O°C. The glass plugging element or rod 66, placed across the opening or port 65 as shown, has a fiber softening temperature below that of the sealing member 55; a similar glass with a fiber softening temperature 20 to 30 degrees lower is satisfactory.

The gas process procedure involves the evacuation of the system, the introduction of the proper gas at ambient room temperature to the proper pressure, about 120 torr. and the heating of the seal rod 66 so that it closes the envelope with the desired internal gas condition. In the system described above, the production cycle time is 6 hours with 2000 devices produced per cycle. Each production chamber can be large enough to handle as many as 5000 devices. The cycle time may be reduced to hours. If devices fail to seal, they are simply recycled. System gas is recovered by operating two chambers in parallel. After the sealed devices are removed from the gas process system, each one is placed under a laser which is projected through a window in the device to crack the capsule and release mercury into the envelope. As is conventional in the art some panel aging time may be performed before releasing the mercury.

Claims (27)

1. CLAIMS:1. A process for manufacturing a gas discharge information display panel device having a pair of paral lei rigid substrate glass plate members which define a thin gas chamber therebetween in which, in use, information to be displayed is generated by a plurality of dis crete gas discharges between selectively energized electrodes, in which process the sealing of said informatioi display panel is effected by joining said rigid substrace members in spaced apart relation by an elongate sealing member which defines the lateral perimeter of said gas chamber, the terminal ends of said member being spaced apart to form a port so that said Chamber is in communica tion with its ambient atmosphere, placing a glass plug so that it overlies the terminal ends of said sealing member and is completely confined between opposed facing surfaces of the substrate plate members and spaced inwardly of the edges thereof, and after the chamber has been filled with an ionizable gas, fusing the plug to said terminal ends to close said port and seal the chamber.

2. A process as claimed in claim 1 wherein the plugging member is constructed of solid glass whose expansion properties match the expansion properties of said sealing member and which has a fiber softening temperature (as hereinbefore’ defined) below the fiber softening temperature of said sealing member.

3. a process as claimed in claim 2 wherein the panel assembly, comprising the rigid substrate members joined by the sealing member, is firstly placed under a vacuum and secondly in an ambient environment of the desired ionizable gas filling, and said plugging member is then heated to a temperature below the fiber softening temperature of said sealing member and above the fiber softening temperature of said plugging member to thereby seal a predetermined volume of said ionizable gas in said chamber.

4. A process as claimed in claim 1 wherein said sealing member comprises a solid glass member which is performed into the desired perimetrical shape of said chamber with its terminal ends spaced apart to form said port, and in which said sealing member is sandwiched between said rigid platemembers and heat is applied to fuse said sealing member to the opposed facing surfaces of said rigid plate members.

5. A process as claimed in claim 4 including the step of applying spacer means to one of said rigid members prior to joining with the other rigid member, said spacer member having a thickness which is less than the thickness of said sealing member and in which, during the application of heat to join said rigid members, pressure is applied to said members to reduce the thickness of said sealing member.

6. A process as claimed in any of claims 1 to 5 wherein said plugging member is a glass rod and the step of bridging includes placing said glass plugging member between said rigid members.

7. A method of simultaneously producing a plurality of gas discharge information display panels, comprising placing a plurality of panel assemblies formed in accordance with the process claimed in claim 1 in a common chamber and then performing said steps of gas filling and heating.

8. A method as claimed in claim 7 including the step of arranging said panel assemblies in contiguous abutting relation to one another with said plugging 5 members in linear alignment With one another, and at . least during said heating applying pressure to said assemblies to maintain them in said contiguous abutting relation.

9. A method as claimed in claim 7 wherein the 10. Application of said ionizable gas is effected at a temperature corresponding approximately to the operating temperature of the device.

10. A method as claimed in claim 9 wherein said ionizable gas is at a pressure below atmospheric and is 15 introduced into the chamber containing said stacked panel devices during the application of heat to fuse said glass plugging member across said gap, such that sufficient gas is sealed in said panel.

11. A method as claimed in claim 7 wherein said 20 plugging member is retained in position prior to the application of heat by opposed surfaces of said rigid members.

12. A method as claimed in claim 8 wherein said panel devices are arranged with said ports oriented 25 upwardly.

13. A method as claimed in claim 12 wherein one of said rigid bodies is shorter than the other, and in which a shim member is positioned to prevent displacement of the shorter of said rigid members.

14. A process as claimed in claim 1 including 4158 1 forming a laser energy transparent window in each of said bodies which windows face each other in said panel assembly, positioning a mercury giver within said gas i chamber between said windows, and, after sealing of said port, directing a burst of laser energy through one of said windows to cause release of mercury in the gas chamber.

15. A process as claimed in claim 14 wherein each said mercury giver is disposed in a respective laser energy transparent glass capsule.

16. A gas discharge information display panel comprisimr a pair of rigid substrate glass plate members, sealing mi'ans joining said plates in parallel spaced apart relation and defining a thin gas discharge chamber between said plates, an ionizable gas in said chamber and an electrode system for selectively ionizing the gas in sa d chamber to display information, said sealing means inc] uding an elongate first sealing member which defines the lateral perimeter of said thin gas discharge chamber, the terminal end portions of said first sealing member defining a port for enabling the chamber to be evacuated and filled with said gas, and a second sealirg member in the form of a glass plug which overlies said terminal end portions of the first sealing member and is completely confined between opposed facing surfaces of said substrate plate members and spaced inwardly of the edges thereof, the glass plug being fused to said terminal end portions to close said port and seal the chamber.

17. A display panel as claimed in claim 16 wherein said first sealing member is made of a substantially bubble-free glass.

18. A display panel as claimed in claim 16 or 17 wherein said first plug comprises a glass rod located between opposed facing surfaces of said substrate plate member. 5

19. A display panel as claimed in claim 16, 17 or 18 including anode electrodes on one substrate plate member and cathode electrodes on an opposing substrate plate member, contact pads on one of said substrate members, at least some of which are integrally connected 10 to the electrodes thereon, said one of said substrate members having an overhung portion thereof carrying said contact pads, and a conductive, bubble-free extrusion between said plates electrically connecting the electrodes on the other of said substrates with at least one 15 of the contact pads on said overhung portion.

20. A display panel as claimed in claim 19 wherein said conductive, bubble-free extrusion is silver incorporated in an epoxy carrier inserted between said two plates at said selected contact pads. 20

21. A display panel as claimed in claim 19 wherein said cathode electrodes are printed with conductive silver paste on one of said substrates, which is made of glass, and said conductive silver paste is then heated to a firing temperature higher than any temperature subsequently 25 used in the fabrication of the panel so as to substantially eliminate cathode porosity and provide a smooth cathode surface.

22. A display panel as claimed in claim 19 wherein said cathode elements printed on said substrate are co30 planar and some of which have a short spacing therebetween, a dielectric layer being printed on the latter 4158 1 substrate of a sufficient thickness as to form a sputter barrier between the cathode elements having said short spacing.

23. A display panel as claimed in claim 16 including a laser energy activatable giver means, at least one laser energy transparent window in one substrate member, said laser energy activatable giver means being located within the gas chamber adjacent to said window, and means retaining said giver means in position between said window and the opposing substrate.

24. A display panel as claimed in claim 23 wherein the space between the substrates, which defines the discharge gap, is approximately twenty thousandths of an inch, the giver means comprising a filamentary hollow glass tube element made of a laser energy transparent glass and having an outside diameter under twenty thousandths of an inch, said tube element being sealed at both ends and being filled with elemental mercury, the length of said tube and the internal cross-section; 1 area of a hollow portion thereof being selected to contain a predetermined quantity of said mercury in a liquid state.

25. A process for manufacturing a gas discharge information display panel device, substantially as hereinbefore particularly described with reference to the accompanying drawings.

26. A method of simultaneously producing a plurality of gas discharge information display panels, substantially as hereinbefore particularly described with reference to the accompanying drawings.

27. A gas discharge information display panel, constructc d substantially as hereinbefore particularly described with reference to and as illustrated in the accompanying drawings.