Abstract:
The display panel comprises a gas-filled envelope containing a series of fine, closely-spaced cathode lines connected in groups so that they can be energized sequentially and individually. The panel also includes an anode film supported on the face plate and aligned with and in operative relation with the series of cathode lines. The anode and cathodes are closely spaced and the panel contains an ionizable gas at relatively high pressure.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a Continuation of application Ser. No. 428,126, filed Dec. 26, 1973, now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     The principles of the invention are particularly useful for displaying analog signals, and, although devices are known in the prior art for providing a visual display of analog signals, none of these devices is as compact and as simple in construction and operation as the device of the invention. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a plan view of a display panel embodying the invention; 
     FIG. 2 is a sectional view along the lines 2--2 in FIG. 1; and 
     FIG. 3 is a plan view of a modification of the invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A display panel 10 embodying the invention is of generally elongated rectangular shape and includes an insulating base plate 20 of glass, ceramic, or the like, and a face plate 30 of glass or the like and comprising a viewing window for the panel. The base plate and face plate are hermetically sealed together along a predetermined perimeter by means of a glass frit seal (not shown), as is well known in the art. 
     The base plate 20 includes top and bottom edges 22 and 24, respectively, and left and right side edges 26 and 28, respectively, (FIG. 1). The base plate also includes a top surface, on which is formed a light-absorbing, opaque, preferably black, insulating layer 44 which is provided to optimize the viewing contrast of the panel. A series of short, closely spaced, parallel lines 50A, 50B, 50C of a conductive material are formed on the layer 44, preferably by a silk-screen process. The conductive lines are sufficiently close so that, when the lines are operated as cathodes, the glow of one cathode will appear to merge with the glow of an adjacent cathode. Typically, the cathode lines have a width of about 10 to 12 mils, and they are spaced apart about 5 to 8 mils. 
     In one arrangement, the conductive lines 50 are oriented perpendicular to the long axis of the base plate, and they are connected in groups, with the lines 50A, 50B, and 50C being in separate groups. Thus, each two A lines are separated by B and C lines, each two B lines are separated by A and C lines, and each two C lines are separated by A and B lines. 
     All of the A lines are connected to a single common conductor 60A which extends parallel to the longitudinal axis of the base plate to the lower edge 24 where it terminates in a contact pad 70A. Similarly, lines 50C are connected to a longitudinal common conductor 60C which terminates in a terminal pad 70C at edge 24 of the base plate. An insulating layer 80 is formed over conductor 60A, with apertures 84 overlaying each of the lines 50B, and a single longitudinal conductor 60B is formed on the insulating layer 80 in contact with each line 50B and terminating in terminal pad 70B. Insulation 80&#39; (FIG. 2) covers line 60B. 
     A similar insulating layer 83 is formed over the conductor 60C and portions of the conductive lines 50C. In addition, the layers 80 and 83 are spaced apart a suitable distance to provide a desired visible length of each of the conductive lines 50A, B, and C between them. The exposed lengths of these conductive lines, shown as solid black lines in FIG. 1, are the portions which glow in operation of the panel. 
     The panel includes an auxiliary &#34;reset&#34; cathode line 50R positioned parallel and adjacent to the first line 50A in the series. The conductive line 50R is connected to contact pad 70R, and it is turned on first before the adjacent line 50A in an operating cycle to provide excited particles which insure that the first line 50A itself will turn on when it is electrically energized. In addition, the panel includes a keep-alive cell 85 comprising a small-area anode 50KA and a small-area cathode 50KK disposed adjacent to the lower edge 24 of the base plate and connected to suitable terminal pads 60KK and 60KA. The keep-alive electrodes are positioned in close proximity to reset cathode 50R to provide excited particles therefor. Usually, the keep-alive electrodes are connected to a power source V and are always ON and generating excited particles. 
     The face plate of the panel includes, on its lower surface, a transparent conductive film anode 90 of tin oxide, gold or the like which comprises a rectangular strip which extends from the upper edge to the lower edge of the panel and overlays the exposed cathode lines 50A, B, and C. The anode is also in operative relation with cathode 50R. 
     If desired, suitable masks are provided to shield the keep-alive cell 85 and reset cathode 50R from view. Such masks may be opaque films on the face plate, or they may be mechanical shields suitably disposed inside the panel. 
     In panel 10, the base plate and face plate are spaced apart a distance of the order of 20 to 25 mils, and the gas in the panel is provided at a pressure of the order of 400 Torr. One suitable gas mixture comprises 99.8% neon and 0.2% xenon. Another suitable gas filling is pure neon. With this arrangement of gas pressure and close spacing of base plate and face plate, as each cathode line 50 and the anode 90 are energized, cathode glow can be limited to the close vicinity of a single energized cathode even though the cathodes are connected in groups, and, as glow is transferred from cathode to cathode, no spurious glow develops at undesired locations. This is because the ionized particles, including metastable states, are limited in their ability to diffuse and are neutralized by the closely spaced base plate and face plate. 
     One suitable circuit for operating panel 10 is shown schematically in FIG. 1 and includes a source 100 of an analog signal, to be displayed, coupled into a differential amplifier 110 along with a ramp or control voltage from source 120. A separate cathode driver 130A, 130B, 130C, is connected to each of the groups of cathode lines 50 by a connection to one of the cathode pads 70 and thus to one of the common connectors. In addition, a reset cathode driver 130R is connected to reset cathode pad 70R, and voltage source V is connected between the electrodes 50KK and 50KA of keep-alive cell 85. In operation of panel 10, as thus connected, the keep-alive cell provides a constant source of excited or ionized particles, and, at the beginning of a scanning cycle, reset cathode driver 130R is operated to apply operating potential to reset cathode 50R to cause it to glow and generate excited particles, and then operating potential is applied by the other cathode drivers 130 sequentially to each of the other cathodes 50 in turn, beginning with cathode 50A adjacent to the reset cathode 50R. Simultaneously, operating potential is applied to the anode 90 from the output of the differential amplifer. As long as there is an output from the differential amplifier, energization of the cathode lines extends from the beginning of the series along the series until the analog signal and the ramp signal are equal. At this time, there is no output from the differential amplifier, and the anode is de-energized; however, the series of cathodes is energized to the end to insure uniform duty cycle each time cathodes are energized. During this time period, the cathodes glow up to a line in the cathode series determined by the magnitude of the analog signal and the length of time during which the anode is energized. Thus, a line of glow is seen extending along a length of the cathode lines representative of the amplitude of the analog signal. This operation is repeated cyclically at such a rate that a stationary but changeable length of light appears to glow in the panel. 
     Other circuits may also be used to operate the panel 10. For example, a digital clock, controlled by the input analog signal, may be used to sequentially energize the series of cathodes and to simultaneously energize the anode. When the analog signal terminates, the anode is de-energized to cut off cathode glow as described above. 
     In a modification of the invention illustrated in FIG. 3, a display panel 10&#39; includes two series of cathode lines, one disposed along each of the opposite long edges of the panel base plate. As in panel 10, the cathodes include cathodes 50A, B, and C, with cathodes 50A interconnected by a common conductor 60A which extends around the perimeter of the base plate and terminates in pads 70A, and with the cathodes 50B connected across the base plate to each other and to a common conductor 60B and to pad 70B, and with the cathodes 50C, connected across the base plate to each other and to a commmon conductor 60C and pad 70C. Using a silkscreen process, the various cathodes and their common conductors can be formed at the same time and of the same material. As described above, suitable insulating layers 140 are provided to insulate cathodes 50B from cathodes 50C and to cover the cathodes to mask them and to provide two series of cathode lines, of suitable length, along each long edge of the base plate. In this case, the face plate has two anode films 90, each overlaying one of the series of cathode lines. In addition, the face plate may be provided with opaque films (not shown) to provide a desired visible pattern for the conductive lines and, for example, to cover auxiliary reset cathode lines 50R positioned adjacent to the first lines 50A and the two keep-alive cells 85 including cathodes 50KK and anodes 90AK and positioned adjacent to both reset cathodes 50R. 
     The panel 10&#39; is operated in essentially the same way as panel 10 and provides two similar lengths of light representative of an analog input signal. 
     It is clear that modifications may be made in the specific structural features described above. For example, the anode electrodes may be formed on the face plate, or they may be formed on one of the insulating layers carried by the base plate of the panels described. As an example, anodes 90&#39; are shown in dash lines on layers 80&#39; and 83 in FIG. 2. In addition, a single keep-alive cell could be provided in the panel 10&#39; suitably placed to provide excited particles for both reset electrodes.