U.S. patent number 3,906,285 [Application Number 05/468,065] was granted by the patent office on 1975-09-16 for luminescent display tube anode assembly comprising anode segments each having a tungsten carbide conductive layer.
This patent grant is currently assigned to Nippon Electric Kagoshima, Ltd.. Invention is credited to Masaki Kobayakawa, Kazufumi Yawata.
United States Patent |
3,906,285 |
Kobayakawa , et al. |
September 16, 1975 |
Luminescent display tube anode assembly comprising anode segments
each having a tungsten carbide conductive layer
Abstract
An anode assembly for a luminescent display tube comprises a
substrate and a plurality of anode segments. The anode segments
have layers of a luminescent material deposited in respective
recesses formed in the substrate in conformity with the anode
segments. A layer of tungsten carbide is disposed underlying each
of the luminescent material layers.
Inventors: |
Kobayakawa; Masaki (Izumi,
JA), Yawata; Kazufumi (Izumi, JA) |
Assignee: |
Nippon Electric Kagoshima, Ltd.
(Kagoshima, JA)
|
Family
ID: |
13057545 |
Appl.
No.: |
05/468,065 |
Filed: |
May 8, 1974 |
Foreign Application Priority Data
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|
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May 15, 1973 [JA] |
|
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48-57504 |
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Current U.S.
Class: |
313/496; 313/355;
313/311 |
Current CPC
Class: |
H01J
31/15 (20130101) |
Current International
Class: |
H01J
31/15 (20060101); H01J 001/66 (); H01J
063/02 () |
Field of
Search: |
;313/496,497,355,311 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Demeo; Palmer C.
Attorney, Agent or Firm: Calimafde; John M.
Claims
What is claimed is:
1. An anode assembly for a luminescent display tube, said assembly
comprising a substrate and a plurality of anode segments having
layers of a luminescent material disposed in respective recesses
formed in said substrate in conformity with a desired configuration
of said anode segments, wherein the improvement comprises a layer
of tungsten carbide underlying each of said luminescent material
layers.
Description
DISCLOSURE OF THE INVENTION
BACKGROUND OF THE INVENTION
This invention relates to electronic displays and, more
specifically, to an anode assembly or structure for a luminescent
display tube, also called a fluorescent display tube or a phosphor
indicator tube. The invention is particularly concerned with an
anode assembly for a luminescent display tube of the multi-digit or
multi-figure type.
As described in U.S. Pat. No. 3,508,101 or No. 3,619,694, a tube of
the subject kind comprises an evacuated sealed envelope; an anode
assembly within the envelope and having a base plate or substrate
formed of an insulating material and provided with a plurality of
luminescent anode segments; a cathode disposed in front of the
segments for thermally emitting electrons; a grid between the
segments and cathode; and structure for supplying electric
potentials between the cathode and grid and between the cathode and
selected of the anode segments to have the electrons distributed
substantially uniformly on the selected anode segment to render the
anode segment luminescent. The cathode-anode potential may
simultaneously be applied between the cathode and selected ones of
the anode segments to make the selected anode segments luminesce
together. Conforming with the anode segments, a plurality of
recesses or grooves are formed in the substrate in a geometric
configuration and dimension corresponding to one or more sets of
figures to be selectively displayed. Each anode segment comprises a
layer or film of an electroconductive material on the bottom
surface of the recess and in contact with the anode segment voltage
supplying structure. The anode segment further comprises a layer or
film of a luminescent material covering the electroconductive
material layer.
In sophisticated luminescent display tubes of the type described,
the electroconductive material layers were made by spraying
graphite onto the substrate or otherwise coating the substrate with
graphite. In recent luminescent display tubes, particularly in
those of the multi-digit or multi-figure types, it has become the
practice to resort to tungsten metallizing on forming the
electroconductive material layers in view of the raised efficiency
of manufacture derived thereby. The displays of these recent tubes,
however, are not as bright as those attained with the sophisticated
tube type having the graphite conductive layers. The tungsten
metallized layers may be covered with graphite layers to increase
the brightness of the display. However, this detracts from
simplicity of manufacture, and renders it impossible to utilize
automated equipment for manufacture.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide an
anode assembly for a luminescent display tube which is capable of
providing a bright display, and which may be manufactured as simply
as the recent luminescent display tubes mentioned above.
An anode assembly for a luminescent display tube in accordance with
the instant invention comprises a substrate and a plurality of
anode segments. The anode segments have layers of a luminescent
material disposed in respective recesses formed in the substrate in
conformity with the geometric configuration of the anode segments.
The anode assembly comprises a layer of tungsten carbide underlying
each of the luminescent material layers.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is a front view depicting a set of anode segments; and
FIG. 2 is a cross-sectional view of an embodiment of the instant
invention, taken at section 2--2 of FIG. 1.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to FIGS. 1 and 2, an anode assembly for a luminescent
display tube comprises a substrate 11 of an insulating material on
which a set of anode segments 12 is disposed. In the example
illustrated, seven anode segments a, b, c, d, e, f, and g are
arranged substantially in a figure eight pattern to display any
desired one of the numerals 0 through 9. An additional anode
segment h serves to display the number 4 in a more usual form. An
anode segment DP for a decimal point is also employed.
The substrate 11 comprises a first base plate 21 having holes
formed therethrough in conformity with the geometric configuration
of the anode segments 12 and a second base plate 22 having a
plurality of electroconductive layers 23 formed on one of its
surfaces and extending beyond the cross-sectional areas of the
respective holes. Each of the electroconductive layers 23 has a
lead wire portion 24 extending through the second base plate 22 to
the other surface thereof. The substrate 11 further comprises a
third base plate 26 on which a plurality of leads 27 are formed for
electrically contacting the respective lead wire portions 24. The
anode segments 12 comprise the electroconductive layers 23, and a
layer 29 of a luminescent material covers each of the
electroconductive layers 23. The base plates 21, 22, and 26 may be
made of glass or a ceramic material.
After the base plates 21, 22, and 26 are stacked in the manner
depicted, the holes of the first base plate 21 become recesses or
grooves formed in the substrate 11. The electroconductive layers
23, together with the lead wire portions 24, may be formed by
metallizing or printing. The leads 27 may also be formed by
metallizing or printing. The luminescent material layers 29 may be
formed by deposition in the respective recesses, or by subjecting
the luminescent material to electrodeposition. It will be noted
that the exposed surface of each luminescent material layer 29 is
recessed to provide an inwardly directed area 30 coextensive with
the side or peripheral surface of the associated recess.
For use in a luminescent display tube of the above considered
recent type, the base plates 21, 22, and 26, the electroconductive
layers 23, and the leads 27 may preferably be formed by screen
printing a tungsten paste on green tapes and co-firing the paste
and the tapes into an integral substrate 11 having the conductive
portions 23, 24 and 27. In any event, the holes of the first base
plate 21 become the recesses conforming in geometric configuration
with the anode segments 12. The screen printing and co-firing
techniques facilitate manufacture of an anode assembly for a
luminescent display tube, particularly for a luminescent display
tube of a multi-digit or multi-figure type. Use of a single
tungsten metallized layer for each anode segment has, however, been
objectionable from the view point of the relative lack of
brightness of the display.
In accordance with this invention, the electroconductive layers 23
are made of tungsten carbide. Screen printing and co-firing
techniques are well applicable to this material. In addition, an
anode assembly comprising tungsten carbide conductive layers 23
raises the brightness level of the display by a surprising, very
marked amount. With a tube made in accordance with the instant
invention, it has been confirmed that the display brightness is
about 1.5 times that achieved with the conventional tungsten
layers. Because of the feasibility of utilizing processes similar
to those employed for tungsten metallized layers used in the recent
anode assemblies, it will be appreciated that the anode assembly
according to this invention does not adversely affect simplicity of
manufacture, and is specifically suited for an anode assembly for
use in a multi-digit or multi-figure luminescent display tube where
is it necessary to form a great number of such segments.
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