Abstract:
In display panels consisting of an envelope formed by a face plate and a base plate sealed together and filled with a gas suitable for supporting cathode glow, and having masking of the sealing material within the envelope to prevent spurious reflection therefrom.

Description:
SUMMARY OF THE INVENTION 
     This invention relates to a gas discharge display that consists of two sheets of glass sealed together about their peripheral edges with a glass frit, creating a sealed envelope. 
     This envelope of glass sheets is then filled with an ionizable gas mixture that, together with a series of electrically charged cathodes printed on one inner face of one of the glass sheets, coacts with associate charged anodes printed on the confronting face of the other glass sheet and forms a visible digital display panel. 
     In the prior art, a problem occurs when the gas is ionized. The glow discharge between the activated cathodes and anodes within the envelope reflect off the inner edges of the sealing material, causing an apparent glowing area in an undesired region of the envelope, particularly when the display is viewed from the front. This reflection can be mistaken for another activated digit. 
     To solve the problem, it was necessary to mask this reflective area from view, and this was accomplished by printing a shield on the anode surface of the glass envelope. This shield obstructed the area of the sealed material from reflecting the glow and resulted in a direct reading of only the activated digits. 
    
    
     DESCRIPTION OF THE DRAWING 
     The information will be best understood by reference to the accompanied drawing which illustrates the preferred mode of construction by which the objects of the invention are achieved and in which: 
     FIG. 1 is a perspective view of the discharge display panel of the invention: 
     FIG. 2 is a plain view of the inner surface of one of the glass sheets of the invention: 
     FIG. 3 is a plain view of the confronting surface of the other glass panel of the invention: and 
     FIG. 4 is a detailed sectional view taken on line 4--4 of FIG. 2. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     A display panel 10 is perspectively shown in FIG. 1 and as such illustrates a sealed envelope consisting of a face plate 11 and a base plate 12. These plates are preferably formed from a thin flat glass sheet which may have substantially any desired size and shape. 
     As shown in FIG. 2, the inner surface 13 of the face plate 11 has screen printed thereon a plurality of anode pads 14. Each of these pads 14 by suitable leads 15 extends into external terminal connections 16 at the exposed edge of the plate. 
     FIG. 3 shows the base plate 12 as having its confronting surface 17 screen printed with cathode segments 18 making up identifiable digits. As shown, the base plate 12 includes a six digit display. Each of the cathode segments 18 are connected by leads not shown to external terminal connectors 19. 
     Each of the confronting surfaces of the face plate 11 and base plate 12 has a viewing area defined by a sealing element 20 comprised of a glass adhesive mixture. The glass adhesive mixture is applied as a fluid mixture of powdered glass in a suitable binder or carrier. 
     As noted in the drawings, this sealing element 20 embraces the anodes 14 and their leads 15 as well as the cathode segments 18 and their leads. When the plates 11 and 12 are mated into a complete panel, as shown in FIG. 1, the adhesive mixture of the sealing element 20 when heated creates a sealed envelope between the face plate and the base plate 12. This envelope is sealed with a well-known ionizable gas such as neon, argon, xeron, in a manner well-known in the art. 
     When a suitable current is applied from an external source through the terminal 16 and 19 and the respective leads of the anodes 14 and cathode segments 18, there will be provided an electrical discharge which will then ionize the enclosed gas and result in cathode glow adjacent to the energized cathode segment which, in turn, will display the desired digit. 
     The foregoing is a description of a known form of construction for a gas discharge display. However, it has been found that spurious glow reflection from the adhesive mixture, particularly along the opposite ends of the panel adjacent to the elongate cathode segments, becomes apparent upon a frontal viewing of the display. This reflection in the past has been mistaken for an additional digit, which is highly undesirable. 
     To overcome this inherent problem, the anode sealing surface of the face plate 11 is provided with a printed opaque anode mask that has horizontally and vertically extending portions which are positioned between outer edges of the anode pads 14 and the sealing element 20. The portions of the anode mask can be positioned and dimensioned to block any undesirable cathode glow reflections from the sealing element which would otherwise be viewed for example on the top, bottom or side edges of the display. As shown in FIG. 2, portions 21 of the anode mask may be positioned between the sealing element 20 and the outer side edges of the anode pads at the ends of the display to block end reflections from the sealing element. 
     This example, defining a distinctive digit display, illustrates a simple yet efficient method of masking glow discharge from within the panel envelope. The method is economical in manufacturing in that the printing of the masking areas can be accomplished during the construction of the face plate, with such masking following the outline of certain of the anodes without additional indexing. The method also permits a semi-variable placement of the glass frit by which the plates are sealed together to form the display envelope. 
     While I have illustrated and described the presented form of construction for carrying my invention into effect, this is capable of variation and modification without departing from the spirit of the invention. I therefore do not wish to be limited to the precise details of construction as set forth, but desire to avail myself of such variations and modifications as come within the scope of the appended claims.