Gas discharge display device with at least one spacing frame which limits the post-acceleration chamber

A gas discharge display device has a discharge chamber and a post-acceleration chamber which are separated by a perforated control disc having line and column conductors thereon. The post-acceleration chamber is limited at its lateral boundary by at least one spacing frame which leaves the post-acceleration chamber support-free in its active volume. The inner boundary of the lateral spacing frame substantially coincides with the outer boundary of an active luminescent screen surface which limits one side of the post-acceleration chamber, and the frame has a width such that the inner frame boundary is free of sealing material and which further maintains a separation between the outer edge regions of the potential layers on the opposite sides of the post-acceleration chamber. A high post-acceleration voltage can thus be employed in the post-acceleration chamber without producing arcing.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to gas discharge display devices having a gas 
filled sealed chamber which is divided by a control disc into a gas 
discharge chamber and a post-acceleration chamber, and in particular to 
such a gas discharge display device having a spacing frame for the 
post-acceleration chamber which allows use of high post-acceleration 
voltages without arcing. 
2. Description of the Prior Art 
Gas discharge display devices are known in the art which consist of a gas 
filled chamber which is terminated in gas-tight fashion on one side by a 
front plate and on the opposite side by a rear plate and which is 
subdivided by a control disc parallel to the front and back plates into a 
gas discharge chamber on the cathode side and a post-acceleration chamber 
on the anode side are known in the art. The control disc for such devices 
has electrode paths which are separately driveable which are disposed on 
one side of the disc as parallel row conductors and on the opposite side 
as column conductors, which together form a matrix with the disc being 
perforated at the intersection points of the rows and columns for 
permitting controlled plasma flow therethrough. The interior of the front 
plate has a luminescent screen provided with an anode layer and the 
interior of the rear plate has one or more cathodes which are insulated 
with respect to each other. A spacing frame is provided between the 
control disc and the luminescent screen, as well as between the control 
disc and the cathode(s). 
A gas discharge display device of the type described above having a cathode 
consisting of parallel cathode strips which are insulated from one another 
and are separately driveable is disclosed in German OS No. 26 43 915, 
corresponding to U.S. Pat. No. 4,130,778. The division of the cathode into 
separated cathode strips which are insulated from one another is an 
improvement over a similar device employing a plate cathode which is known 
from German OS No. 24 12 869 corresponding to U.S. Pat. No. 3,956,667. 
This device is utilized for picture reproduction on so-called flat screens 
as well as in gas discharge displays. 
Display devices of this type function according to the principle of the 
spatial separation of electron generation and electron acceleration. As 
stated above, the device is divided into two chambers which are connected 
with one another via a conductor matrix formed on a perforated control 
disc by intersecting lines and columns of conductors. The chamber between 
the cathode or cathodes at the rear plate and the line conductors, which 
serve as auxiliary anodes, on the conductor matrix is the chamber wherein 
gas discharge takes place. The other chamber is the post-acceleration 
chamber which is between the column conductor side of the control disc and 
a flat annode which may be a luminescent screen electrode. By selectively 
driving one of the auxiliary anodes, a wedge-shaped gas discharge volume 
arises between the cathode and the auxiliary annode over the entire line 
length. By simultaneously driving one of the strip-shaped matrix column 
electrodes, plasma electrons which are generated in the gas discharge area 
are drawn through the perforation at the intersection point of the line 
and column conductors into the post-acceleration chamber and are 
accelerated to the anode. At the point of impact on the screen, a light 
point arises on a luminescent material layer which is deposited on the 
anode which corresponds to the image of the intersection point of the 
matrix which was selectively driven. The column and line conductors on the 
control disc are selectively driven according to a time-related course and 
intensity whereby symbols and pictures can be presented on the luminescent 
screen. 
A further gas discharge display device having spacing elements is known 
from German OS No. 27 50 587 wherein ridges having a constant wall 
thickness are provided between the control disc and the post-acceleration 
anode, those ridges extending in the plane of the control disc past which 
the control disc perforations are guided and which run in segments 
alternatingly parallel and diagonally to the conductors which are facing 
the ridges. 
For maintenance of spacing in a gas discharge display device between the 
control disc and the luminescent screen, it has been proposed in German 
patent application No. P28 55 108.8, corresponding to U.S. co-pending 
application Ser. No. 096,920 to arrange several perforated glass foils 
adjacent to each other which each have metallized surface layers. The 
metal layers carry floating potentials and thereby homogenize the 
acceleration field. 
In each of the devices described above, it is a problem to make use of a 
high post-acceleration voltage in the post-acceleration chamber without 
bringing about arcing or flash over. Such arcing generally occurs between 
supports which may be present between the anode and the control disc in 
order to maintain a proper spacing therebetween, or may occur between the 
control disc and the material used to seal the post-acceleration chamber 
in a gas tight fashion. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to provide a gas discharge display 
device having a gas tight chamber divided into a gas discharge chamber and 
a post-acceleration chamber by a perforated control disc which makes use 
of a high post-acceleration voltage in the post-acceleration chamber 
without the occurrence of arcing or flash over. 
The above object is inventively achieved in a gas discharge device having 
at least one spacing frame which maintains a specified spacing between the 
control disc and the anode in an otherwise support-free manner and which 
limits the lateral boundary of the post-acceleration chamber. The inner 
boundary of the spacing frame generally coincides with the outer boundary 
of the active luminescent screen surface on the anode and has a width such 
that the inner frame boundary remains free of sealing materials utilized 
to achieve a gas-tight bond between the frame and the anode and the frame 
and the control disc. The spacing frame further separates the outer edge 
regions of the potential layers which limit the post-acceleration chamber. 
The spacing frame is preferably surrounded by a second outer spacing frame 
which serves for the air tight sealing of the post-acceleration chamber. 
The spacing frames may be comprised of glass which has a thermal 
coefficient of expansion which is matched to that of the luminescent 
screen glass. 
The above inventive gas discharge display device has the advantage that a 
high post-acceleration voltage can be used in the post-acceleration 
chamber without bringing about arcing or flash overs. Because such arcing 
generally occurs at insulators in the vacuum, at significantly lower field 
strengths in comparison with the field strength in the vacuum, a 
support-free post-acceleration chamber is desired so that the critical 
region in which insulator arcing can occur is limited to the lateral 
boundary of the post-acceleration chamber.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
A gas discharge display device is shown schematically in FIG. 1 with 
portions thereof not pertinent to the present invention being omitted. The 
portion of the device shown in FIG. 1 consists of a post-acceleration 
chamber 1 having an overly wide spacing frame 2 disposed between a 
luminescent screen 4 and a control disc 5 for increasing the high voltage 
stability of the device. The post-acceleration chamber 1 is maintained air 
tight by adhesive seams 6 between the spacing frame 2 and the screen 4, as 
well as between the frame 2 and the control disc 5. The spacing frame 2 
projects laterally over the adhesive seams 6. The high voltage stability 
is measured by the maximum voltage which can be achieved before arcing 
occurs. The high voltage stability of the structure shown in FIG. 1 for a 
one millimeter long acceleration path is increased from 2.5 kV to 6 kV 
when a spacing frame 2 is utilized having a thickness of 0.8 millimeters 
and which laterally projects over the adhesive seam 6 by approximately 5 
millimeters. 
A more detailed embodiment of the structure shown in FIG. 1 is shown in 
FIG. 2 with elements corresponding to those in FIG. 1 identically 
numbered. As shown in FIG. 2, the spacing frame 2 extends close to the 
active portion of the luminescent screen 4 which is provided with a 
potential layer 7 and a luminescent material layer 8. The control disc 5 
also carries a potential layer 7 and the two potential layers 7 which 
limit the post-acceleration chamber 1 are separated from each other at 
their edge regions by the inner part of the spacing frame 2. The inner 
edge of the spacing frame 2 is free of sealing material such as, for 
example, glass solder. That portion of the spacing frame 2 which is 
directed toward the outer boundary of the gas discharge display device 
serves for air tight sealing of the chamber. 
Optimal clearance during the construction of such gas discharge display 
devices is achieved when the spacing frame is divided into an inner and 
outer frame corresponding to the above two functions of separating and 
sealing. The luminescent screen 4 may have a number of adjusting pins 9 
connected thereto which serve to align the luminescent grid 8, the 
photoform plate and the control disc 5 during the glass soldering process. 
FIGS. 3 through 5 represent different embodiments of this basic structure. 
In FIG. 3, a second outer spacing frame 3 is shown which has a height which 
is greater than the height of the post-acceleration chamber 1 and serves 
to seal additional control grids in air tight fashion without additional 
glass solder seams. In the construction of the outer spacing frame 3, 
presintered glass solder rods may be utilized which are shaped as needed 
during the glass soldering process by the plastic deformation of the glass 
solder in contact therewith. 
If, however, an especially stable glass solder seam is needed, the outer 
spacing frame 3 may be comprised of glass in order that the thickness of 
the glass soldering seam be as small as possible. Other similar variations 
to the structure shown in FIG. 3 in order to meet varying stability 
requirements can be undertaken without departing from the inventive 
concept herein. 
In the embodiment of FIG. 3, an additional control grid 10, which has a 
potential layer 7, is disposed between the screen 4 and the control disc 
5, each of which also have a potential layer 7, in the post-acceleration 
chamber 1. 
Assembly of the device shown in FIG. 3 is as follows. The control grid 10 
is first brought into the correct position relative to the control disc 5 
and is fixed in that position with a temperature adhesive at several 
points, such as the adhesive seams 6. The inner spacing frame 2 is then 
also fixed in relative position on the control grid 10 with several drops 
of a high-temperature adhesive. For air tight sealing of the structure, 
four pre-sintered glass solder rods each having a width of approximately 
10 millimeters and a thickness of 2.5 millimeters to 3 millimeters are 
placed around the outside of the inner spacing frame 2. The entire 
structure is then subjected to a tempering process. The glass solder, 
which is initially present in access, flows against the luminescent screen 
4 as the screen is lowered to a level determined by the control grid 10 
and the inner spacing frame 2 and fills any gaps which may still remain 
and in this manner generates a close bond between the control disc 5 and 
the luminescent screen 4. The adjustment pins 9, as described above, 
facilitate alignment of all parts. 
As shown in the embodiment of FIG. 4, two spacing frames may be utilized. 
The inner spacing frame 2 limits the post-acceleration chamber 1 between 
the luminescent screen 4, which has a potential layer 7 and a luminescent 
material grid 8, and the control grid 10, which is also provided with a 
potential layer 7. The control grid 10 is disposed on the control disc 5, 
which also has a potential layer 7 in the form of column conductors. The 
spacing frame 2, the control grid 10 and the control disc 5 are adjusted 
as to position relative to each other by the pins 9 and are fixed in place 
by the adhesive seams 6 which may be a high-temperature adhesive. The 
outer spacing frame 3 is comprised of two opposing sides of glass strips 
which are coated with glass solder 11 and two further opposing sides 
consisting of glass solder. It is preferable to use the glass strips where 
the control disc 5 extends relatively far out of the display device and 
must be supported. 
A luminescent screen glass with an integrated spacing frame for the 
post-acceleration chamber 1 is shown in FIG. 5. The screen 4 has sides 
integrally formed thereon and a potential layer 7 so that the separate 
outer spacing frame 3 is not necessary and its function is accomplished by 
the vertical walls of the screen 4. The inner spacing frame 2, which 
prevents high voltage arcing, and which projects into the interior of the 
post-acceleration chamber 1 in the form of glass strips, is directly 
fastened to the sides of the screen 4 by, for example, glass solder 11. 
The spacing frame 2 is attached to the screen 4 in the embodiment of FIG. 
5 after all of the layers for the functioning of the screen 4 have been 
applied to the screen glass. The adjusting pin 9, also applied to the 
screen 4, again serves to adjust the relative positions of the control 
disc 5, the control electrode 10 (which is also provided with a potential 
layer 7) and the spacing frame 2. 
A further embodiment is shown in FIG. 6 wherein the inner and outer spacing 
frames are combined in a single unitary structure referenced at 2. Other 
elements common to the embodiments previously discussed are referenced 
with identical numerals. Again, the adjusting pin 9 extends from the 
luminescent screen 4 through the spacing frame 2 and the control disc 5 to 
fix the relative positions of those elements. The spacing frame 2 is 
attached in air tight fashion with the control disc 5 and the luminescent 
screen 4 by glass solder layers 11. 
Although modifications and changes may be suggested by those skilled in the 
art it is the intention of the inventors to embody within the patent 
warranted hereon all changes and modifications as reasonably and properly 
come within the scope of their contribution to the art.