Display panel

A display panel includes a group of cathode segments, each segment comprising two cathode bars adapted to glow simultaneously to produce a single segment and circuits for coupling energizing signals to each bar of a segment separately and simultaneously so that if one bar does not light, the other will and proper display will be achieved. The panel also includes anode electrodes.

BACKGROUND OF THE INVENTION 
Gas-filled cold cathode display devices have been in use for many years. 
Most of these devices are relatively small in size, while at the same 
time, there has been a need for either a single panel of wall size or a 
large individual panel which can be used as an element in a wall size 
display. Attempts have been made to build individual panels to display 
large characters using individual segments over one inch in length and 
perhaps one-quarter inch or more in width. However, cathodes of this size 
and area are difficult to turn on uniformly and over their entire lengths. 
The present invention solves this problem by providing display panels using 
multiple stroke cathode segments, each of which is of small area or width 
and can be turned on easily over its entire width. In addition, separate 
power supplies or signal sources are connected to each stroke of a cathode 
segment so that if one segment of a stroke does not light for some reason, 
the other segment will usually light. It would be highly unlikely for both 
segments of a stroke not to light.

DESCRIPTION OF THE INVENTION 
A display panel 10 embodying the invention includes a gas filled envelope 
made up of a glass base plate 20 and a glass face plate 30 sealed together 
hemmetically along their aligned peripheries to form an envelope. 
The panel 10 is made up of two assemblies, one formed on the base plate and 
the other formed on the face plate. The base plate assembly includes a 
plurality of groups of cathodes, each group being operable as a character 
display position. An anode arrangement is provided on the inner surface of 
the face plate overlying each group of cathodes. 
A specific panel structure and method of manufacture are as follows. First 
referring to FIG. 3, an array of parallel conductor runs 40 is screened on 
the top surface 21 of the base plate 20 and an array of contact pads 50 as 
formed along the lower edge 24 of the base plate. The runs 40 and pads 50 
are formed, for example by a screening process with any suitable 
conductive material including silver or nickel or some other metal as is 
well known in the art. 
Next, a black glass insulating layer 60 is formed over the runs 40 with 
openings or vias 70, at selected locations, to which screened cathode glow 
electrodes and other conductors are to be connected. This is illustrated 
schematically in FIG. 5 which shows a few runs 40 and vias 70. 
Next, groups of cathode electrodes for each character position 80 are 
formed on the base plate (FIG. 5). The panel 10 is a segment-type panel. 
That is, each character position 80 is made up of groups of cathode 
segments 82 which can be energized in different combinations to display 
different characters. In panel 10, as shown, each character position 80 
includes an array of cathode segments 82 sufficient in number and location 
to permit the panel to be used for the display of alphanumeric characters. 
According to the invention, in each group of cathodes, each cathode 
segment 82 comprises two similarly shaped cathode bars 90 positioned 
sufficiently close to each other so that when the two bars 90 of a segment 
are energized, their glow blends to produce a wide character. All of the 
cathodes bars 90 are formed by a screening operation with a conductive 
material including nickel, silver or some other suitable metal. Nickel is 
commonly used. 
At the same time that the cathode segments 90 are formed, conductive runs 
100 are also formed on layer 60 and connected through vias 70 (some are 
shown in FIG. 5) to the underlying conductive runs 40 which are thus 
connected to contact pads 50 whereby external electrical connection can be 
made to the runs and thus to their cathodes. 
Next, another black insulating layer 110 (FIG. 3) is screened on the base 
plate covering everything except the cathode bars which are outlined by 
this layer. 
The anodes 120 for the character positions 80 and the groups of cathode 
segments in panel 10 are formed on the inner bottom surface of the face 
plate 30. The anodes are formed in two parts 120A and 120B (FIG. 8) which 
effectively split the group of cathode segments 82 in two groups, an upper 
group and a lower group, The anodes are of transparent conductive material 
such as tin oxide and they are outlined with a conductor 130 such as 
silver to impart strength and greater conductivity. In addition, small 
triangles 140 of the conductive reinforcing material are formed internally 
to further increase the conductivity of the anodes. The anode portions are 
individually connected to edge contact tabs 52 on the face plate by means 
of conductive runs under the insulating layer 110. 
For convenience, the division between the two anode portions is represented 
by solid line 142. 
In assembling the panel 10 a thin, narrow layer of cement 150 (FIG. 1) such 
as pyroceram, is placed along the entire edge of the base plate with 
narrow transverse extensions or arms 160 extending inwardly from the upper 
and lower edges of the panel toward each other between each group of 
cathodes or character positions 80. The cement arms 160 do not extend 
fully across the panel but are sufficiently long to assist in sealing the 
base plate together. A similar array of cementareas is formed on the face 
plate properly located so that when the base plate and face plate are 
coupled together for sealing, the cement on the face plate overlie each 
other exactly and they seal together hermetically with the two plates in 
proper alignement. The auxiliary cement extensions 160 and dots 170 
prevent audible vibrations of the panel, as can occur in operation of some 
display panels. 
In providing the auxiliary extensions of cement 160 and the dots of cement 
170 to prevent audible vibrations, they are positioned so that each unit 
area of the panel, of about one inch by about one inch is provided at its 
corners with support and seals. In other terms, no area greater than, say 
11/2 inches goes without support at its corners. 
It is to be understood that although all of the processing steps are not 
described in detail, various bake-out and other stepsare carried out as 
required and as well known to those skilled in the art. 
After the base plate and face plate have been hermetically sealed together 
by a baking procedure, the panel is filled with an ionizable gas through a 
tubulation 180 secured to the outer surface of the base plate and 
communicating with the inside of the panel through a hole 190 in the base 
plate. The hole 180 is not obstructed by any of the materials placed on 
the base plate. The gas filling mat be argon, neon, xenon or the like, 
singly or in combination, at a suitable pressure in the range of about 100 
to about 400 Torr. Mercury vapor is also introduced into the panel in any 
suitable manner, usually from a capsule 220 held in the tubulation. 
Contact pins 200, some of which are shown in FIG. 1, are cemented to the 
pads 50, and if desired they are further secured in place by means of a 
cement bead which extends along the edge of the base plate over the pads. 
In addition, if desired, the inner ends of the contact pins may be 
positioned in a space between the base plate and face plate, however, this 
arrangement is not shown in the drawings. 
In the panel 10, as shown in FIG. 6. all of the same cathode bars in the 
various groups of segments are connected to the same conductive runs 40 
and 100 and pad 50 so that energizing signals can be connected to all of 
the same bars at the same time when the panel is operated in multiplex 
fashion. All of the anode portions 120A and 120B are separately connected 
to their own edge pads 52 and contact pins 200 are also secured to these 
contact pads 52. 
The panel 10 also includes a keep-alive cathode for each character position 
and these are formed from a single horizontal run 40 which is covered with 
the insulating layers but has small portions 42 exposed at each character 
position (FIG. 1). 
With the cathode bars 90 connected as described above, the panel 10 can be 
operated in a multiplex mode wherein as selected cathode bars in the 
groups are energized, only the bars in the group which has its anodes 
energized will display glow and a character. This operation is carried out 
from group to group and cyclically throughout the panel at such a rate 
that an apparently stationary but changeable message is displayed. 
According to the invention, in operation of the panel 10, as the panel is 
scanned at each character position, the two anodes have generally positive 
potential connected to them and selected cathode segments to be displayed 
have generally negative potential applied to them so that the potential 
difference between a cathode segment and its anode is sufficient to cause 
the segment to glow. 
Further in operation of panel 10, and referring to FIG. 9, if in character 
position, a cathode segment made up of two bars 90A and 90B is to be 
energized and caused to glow, the system applies the same turn-on signal 
from separate sources, to both bars 90A and 90B simultaneously. Similarly, 
if the segment made up of bars 90C and 90D is to be energized to glow, 
then the same energizing signal is applied to these two bars 
simultaneously from separate sources. This principle applies to each 
segment to be turned on in each character position as the panel is 
multiplexed. FIG. 9 represents the principle with separate sources 
connected to each cathode bar and separate anode power sources connected 
to each anode pair. 
With this arrangement, if by chance, one cathode bar of a pair is not 
turned on, for whatever reason, the other bar will normally be turned on 
and no false display will occur. For example, it is possible that a 
failure of cathodes might convert a desired "8" into a false "3". Such an 
incorrect display could be disastrous under certain circumstances. Another 
advantage of the invention is that, in each pair of cathode bars, as an 
example, cathode bars which are 35 mils wide and spaced apart by 35 mils, 
present a stroke width of about 105 mils in operation with economical 
power expenditure. It would be economically and functionally "impossible" 
to attempt to obtain such a stroke width with a single cathode. 
Another advantage of the invention is the use of the split anodes which 
imparts a power advantage in operation of the panel. It is noted that in 
the multiplex mode of operation, both anode portions at each character 
position are energized at the same time. 
It is to be noted that although the term "cathode bar" is used herein, it 
is not necessary that, in each cathode segment, the two "bars" be linear 
in shape. Any similar shape will satisfy the principles of the invention.