U.S. patent number 3,873,171 [Application Number 05/365,404] was granted by the patent office on 1975-03-25 for multiple-digit display device and method of manufacturing the same.
This patent grant is currently assigned to Hitachi, Ltd.. Invention is credited to Masaharu Koyama, Akio Miyamoto, Gen Murakami, Toyokazu Odaka, Kanji Otsuka.
United States Patent |
3,873,171 |
Miyamoto , et al. |
March 25, 1975 |
MULTIPLE-DIGIT DISPLAY DEVICE AND METHOD OF MANUFACTURING THE
SAME
Abstract
A multiple-digit display device comprising an electrode
substrate in which a plurality of sets of cathodes of a desired
pattern constituting a plurality of display sections respectively
and a plurality of sets of anodes associated with the plural sets
of cathodes respectively are multilevel-printed on a dielectric
substrate through dielectric layers, and a front plate provided on
the electrode substrate so as to form a plurality of discharge
spaces on the plural display sections, and a method of
manufacturing the multiple-digit display device.
Inventors: |
Miyamoto; Akio (Mobara,
JA), Koyama; Masaharu (Mobara, JA), Odaka;
Toyokazu (Chiba, JA), Otsuka; Kanji (Kodiara,
JA), Murakami; Gen (Kodiara, JA) |
Assignee: |
Hitachi, Ltd. (Tokyo,
JA)
|
Family
ID: |
12975687 |
Appl.
No.: |
05/365,404 |
Filed: |
May 31, 1973 |
Foreign Application Priority Data
|
|
|
|
|
Jun 1, 1972 [JA] |
|
|
47-54617 |
|
Current U.S.
Class: |
445/24; 445/56;
313/514 |
Current CPC
Class: |
H01J
17/491 (20130101) |
Current International
Class: |
H01J
17/49 (20060101); H01j 009/38 () |
Field of
Search: |
;313/109.5,210,220
;315/169R,169TV ;316/17,18,19,20 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Lawrence; James W.
Assistant Examiner: Nelms; D. C.
Attorney, Agent or Firm: Craig & Antonelli
Claims
What we claim is:
1. A method of forming an electrode substrate for a multiple-digit
display device in which cathodes and anodes are arranged in a
single substrate, comprising the steps of:
a. shaping a pasty composition comprising a dielectric material, a
binder and a solvent into a sheet form of a predetermined thickness
and size;
b. drying the sheet to obtain an unsintered dielectric sheet;
c. multilevel-printing, on said unsintered dielectric sheet, a
plurality of sets of cathodes for respective digits, a plurality of
sets of anodes associated respectively with said cathode sets, a
plurality of cathode terminals for the corresponding cathodes
between said cathode sets, a plurality of anode terminals for said
anode sets, a plurality of wires for the connection of the
corresponding cathodes, between said cathode sets, to said cathode
terminals, a plurality of wires for the connection of said anode
sets to said anode terminals, and a plurality of dielectric layers
to provide an unsintered multilayer electrode structure; and
d. sintering said unsintered multilayer electrode structure to
provide an electrode substrate.
2. A method according to claim 1, wherein a resistor is
incorporated in at least a portion of selected ones of said
wires.
3. A method according to claim 1, wherein said step (c) comprises
the steps of:
c1. printing, on said unsintered dielectric sheet, said cathode
terminals, said anode terminals, and first wires to be connected
respectively to said cathode terminals;
c2. printing, on the structure resulting from step (c1), a first
dielectric layer having predetermined holes therethrough;
c3. printing, on the structure resulting from step (c2), said
cathode sets and second wires connected respectively to the
cathodes thereof, while electrically connecting respectively said
second wires which are connected to the corresponding cathodes
between said cathode sets to said first wires through said
holes;
c4. printing a second dielectric layer on the structure resulting
from step (c3), exposing said cathode sets;
c5. printing, on the structure resulting from step (c4), said anode
sets and third wires connected thereto and to be connected
respectively to said anode terminals; and
c6. printing a third dielectric layer on the structure resulting
from step (c5), exposing said cathode sets and said anode sets.
4. A method of manufacturing a multiple-digit gaseous discharge
display device comprising the steps of:
i. preparing an electrode substrate by
a. shaping a pasty composition comprising a dielectric material, a
binder and a solvent into a sheet form of a predetermined thickness
and size,
b. drying the sheet to an unsintered dielectric sheet,
c. multilevel printing, on said unsintered dielectric sheet, a
plurality of sets of cathodes for respective digits, a plurality of
sets of anodes associated respectively with said cathode sets, a
plurality of cathode terminals for the corresponding cathodes
between said cathode sets, a plurality of anode terminals for said
anode sets, a plurality of wires for the connection of the
corresponding cathodes between said cathode sets to said cathode
terminals, a plurality of wires for the connection of said anode
sets to said anode terminals, and a plurality of dielectric layers
to provide an unsintered multilayer electrode structure, and
d. sintering said unsintered multilayer electrode structure;
ii. locating, on said electrode substrate, a partition plate having
a plurality of spaced openings corresponding individually to the
display sections of said electrode substrate including respectively
said cathode sets therein so as to define respective discharge
spaces;
iii. locating, on said partition plate, a front plate which is
transparent at least at those portions opposite to the respective
display sections;
iv. sealing gastight the outer periphery of the laminate structure
consisting of said electrode substrate, said partition plate and
said front plate; and
v. evacuating said laminate structure and introducing a discharge
medium into said discharge spaces.
5. A method according to claim 4, wherein a resistor is
incorporated in at least a portion of selected ones of said
wires.
6. A method according to claim 4, wherein said step i (c)
comprises:
ic1. printing, on said unsintered dielectric sheet, said cathode
terminals, said anode terminals, and first wires to be connected
respectively to said cathode terminals;
ic2. printing, on the structure resulting from step i (c1), a first
dielectric layer having predetermined holes therethrough;
ic3. printing, on the structure resulting from step i (c2), said
cathode sets and second wires connected respectively to the
cathodes thereof, while electrically connecting respectively said
second wires which are connected to the corresponding cathodes
between said cathode sets to said first wires through said
holes;
ic4. printing a second dielectric layer on the structure resulting
from step i (c3), exposing said cathode sets;
ic5. printing, on the structure resulting from step i(c4) said
anode sets and third wires connected thereto and to be connected
respectively to said anode terminals; and
ic6. printing a third dielectric layer on the structure resulting
from step i (c5), exposing said cathode sets and said anode
sets.
7. In a method of manufacturing a multiple-digit display device
including a single substrate having a plurality of cathodes and
anodes arranged thereon, an improved method of forming said
substrate having said cathodes and anodes arranged thereon,
comprising the steps of:
a. multilevel-printing, on an unsintered dielectric sheet, a
plurality of sets of cathodes for respective digits to be included
in said display device, a plurality of sets of anodes associated
respectively with said cathode sets, a plurality of cathode
terminals to be connected to respective cathodes of said cathode
sets, a plurality of anode terminals to be connected to respective
anodes of said anode sets, a plurality of wires for interconnecting
said cathode terminals to said cathodes, a plurality of wires for
interconnecting said anode terminals to said anodes, and a
plurality of unsintered dielectric layers, to thereby provide an
unsintered multilayer electrode structure; and
b. sintering said multilayer electrode structure to provide a
sintered electrode substrate.
8. An improved method according to claim 7, wherein step (a)
comprises the preliminary steps of:
a1. shaping a pasty composition of a dielectric material, a binder
and a solvent into a sheet having a predetermined size and
thickness, and
a2. drying said sheet to obtain said unsintered dielectric
sheet.
9. An improved method according to claim 7, wherein said step (a)
comprises the steps of:
a1. printing, on said unsintered dielectric sheet, said cathode
terminals, said anode terminals, and first wires to be connected
respectively to said cathode terminals;
a2. printing, on the structure resulting from step (a1), a first
dielectric layer having predetermined holes therethrough;
a3. printing, on the structure resulting from step (a2), said
cathode sets and second wires connected respectively to the
cathodes thereof, while electrically connecting respectively said
second wires which are connected to the corresponding cathodes
between said cathode sets to said first wires through said
holes;
a4. printing a second dielectric layer on the structure resulting
from step (a3), exposing said cathode sets;
a5. printing, on the structure resulting from step a4, said anode
sets and third wires connected thereto and to be connected
respectively to said anode terminals; and
a6. printing a third dielectric layer on the structure resulting
from step (a5), exposing said cathode sets and said anode sets.
10. An improved method according to claim 8, wherein step (a)
further comprises the steps of:
a3. printing, on said unsintered dielectric sheet, said cathode
terminals, said anode terminals, and first wires to be connected
respectively to said cathode terminals;
a4. printing, on the structure resulting from step (a3), a first
dielectric layer having predetermined holes therethrough;
a5. printing, on the structure resulting from step (a4), said
cathode sets and second wires connected respectively to the
cathodes thereof, while electrically connecting respectively said
second wires which are connected to the corresponding cathodes
between said cathode sets to said first wires through said
holes;
a6. printing a second dielectric layer on the structure resulting
from step (a5), exposing said cathode sets;
a7. printing, on the structure resulting from step (a6), said anode
sets and third wires connected thereto and to be connected
respectively to said anode terminals; and
a8. printing a third dielectric layer on the structure resulting
from step (a7), exposing said cathode sets and said anode sets.
11. A method of manufacturing a multiple-digit gaseous discharge
display device comprising the steps of:
a. forming an electrode substrate on which cathodes and anodes are
arranged by
a1. multilevel-printing, on an unsintered dielectric sheet, a
plurality of sets of cathodes for respective digits to be included
in said display device, a plurality of sets of anodes associated
respectively with said cathode sets, a plurality of cathode
terminals to be connected to respective cathodes of said cathode
sets, a plurality of anode terminals to be connected to respective
anodes of said anode sets, a plurality of wires for interconnecting
said cathode terminals to said cathodes, a plurality of wires for
interconnecting said anode terminals to said anodes, and a
plurality of unsintered dielectric layers, to thereby provide an
unsintered multilayer electrode structure; and
a2. sintering said multilayer electrode structure to provide a
sintered electrode substrate;
b. locating, on said electrode substrate, a partition plate having
a plurality of spaced openings corresponding individually to the
display sections of said electrode substrate including respectively
said cathode sets therein so as to define respective discharge
spaces;
c. locating, on said partition plate, a front plate which is
transparent at least at those portions opposite to the respective
display sections;
d. sealing gastight the outer periphery of the laminate structure
consisting of said electrode substrate, said partition plate and
said front plate; and
e. evacuating said laminate structure and introducing a discharge
medium into said discharge spaces.
12. An improved method according to claim 11, wherein said step
(a1) comprises the steps of:
a1-i. printing, on said unsintered dielectric sheet, said cathode
terminals, said anode terminals, and first wires to be connected
respectively to said cathode terminals;
a1-ii. printing, on the structure resulting from step (a1-i), a
first dielectric layer having predetermined holes therethrough;
a1-iii. printing, on the structure resulting from step (a1-ii),
said cathode sets and second wires connected respectively to the
cathodes thereof, while electrically connecting respectively said
second wires which are connected to the corresponding cathodes
between said cathode sets to said first wires through said
holes;
a1-iv. printing a second dielectric layer on the structure
resulting from step (a1-iii), exposing said cathode sets;
a1-v. printing, on the structure resulting from step a1-iv, said
anode sets and third wires connected thereto and to be connected
respectively to said anode terminals; and
a1-vi. printing, a third dielectric layer on the structure
resulting from step (a1-v), exposing said cathode sets and said
anode sets.
13. A method of manufacturing a multiple-digit display device
comprising the steps of:
forming an electrode substrate by multilevel-printing, on a
dielectric substrate through dielectric layer, a plurality of sets
of cathodes of predetermined pattern constituting a plurality of
display sections respectively and a plurality of sets of anodes
associated with said plural sets of cathodes respectively;
disposing, on said electrode substrate, a partition plate having a
plurality of spaced openings corresponding individually to said
display sections so as to define the respective discharge
spaces;
disposing, on said partition plate, a front plate which is
transparent at least at those portions opposite to the respective
display sections;
sealing gastight the outer periphery of the laminate structure
consisting of said electrode substrate, said partition plate and
said front plate;
evacuating said laminate structure and introducing a discharge
medium into said discharge spaces; and
wherein said dielectric substrate and said dielectric layers are
initially unsintered and are simultaneously sintered before the
evacution of said laminate structure.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
The present application relates to subject matter described in
application Ser. No. 365,440 filed May 31, 1973, entitled "Multiple
Digit Display Device and Method of Manufacturing Same" by Akio
Miyamoto, Masaharu Koyama, Toyokazu Odaka, Kanji Otsuka and Gen
Murakami, and assigned to the assignee of the present application,
and it relates to the subject matter described in application Ser.
No. 365,405, filed May 31, 1973, entitled "Multiple-Digit Display
Device," by Akio Miyamoto, Masaharu Koyama, Toyokazu Odaka and also
assigned to the assignee of the present application.
This invention relates to a multiple-digit display device for
displaying a plurality of desired patterns such as figures,
characters and symbols in a juxtaposed state by means of gaseous
discharge and a method of manufacturing such a display device.
In a multiple-digit display device of the kind utilizing a gaseous
discharge for display, a plurality of display sections each
including a plurality of display cathodes arranged according to a
desired pattern and a plurality of anodes associated with these
display cathodes are juxtaposed within the same envelope so that
the desired pattern can be displayed in response to the application
of voltage across selected ones of the display cathodes and
selected ones of the anodes and this multiple-digit pattern display
can be attained by controlling the device in time division
fashion.
Multiple-digit display devices of various structures have been
proposed hitherto, but none of them have been completely
satisfactory. For example, according one of the prior art
proposals, cathodes, cathode leads, etc., are formed on a sintered
dielectric substrate by means of multilevel-printing, and preformed
elements such as anodes and partition walls for individual digits
are mechanically secured to the dielectric substrate. However, due
to the fact that the preformed individual anodes are connected as
by welding to lead wires in the apertures bored in the dielectric
substrate in such a prior art structure, this multiple-digit
display device is not suitable for mass production and the
reliability of the electrical connection is low. Further, there is
a structural limitation in the desired reduction of the thickness
of the display device. Furthermore, due to the fact that the
cathodes and anodes are disposed opposite to each other through a
discharge space, the displayed pattern is observed through the
anodes, and thus, the anodes must be of meshed structure or of
transparent material. However, the use of the meshed anodes is
defective in that not only the display is difficult to observe but
also the number of necessary parts is greatly increased. The use of
the transparent anodes in the form of a film of NESA (a trade-mark)
is also defective in that the transparent film electrode may be
damaged by the heat produced during sealing.
It is therefore an object of the present invention to provide a
multiple-digit display device in which a multilevel wiring
technique and a plug-in system are employed for eliminating the
problem of electrical connection with external circuits and which
can therefore be easily manufactured at low cost.
Another object of the present invention is to provide a
multiple-digit display device which has a very small thickness by
virtue of the fact that electrodes and wires are deposited on a
single substrate by means of multilevel-printing.
Still another object of the present invention is to provide a
multiple-digit display device which can be very easily manufactured
by virtue of the fact that electrodes and wires are formed on a
single unsintered substrate by means of multilevel-printing.
A further object of the present invention is to provide a
multiple-digit display device in which the number of necessary
parts is less than heretofore and which is suitable for mass
production.
In accordance with one aspect of the present invention, there is
provided a multiple-digit display device comprising an electrode
substrate in which a plurality of sets of cathodes of desired
pattern constituting a plurality of display sections respectively
and a plurality of sets of anodes associated with said plural sets
of cathodes respectively are multilevel-printed on a dielectric
substrate through dielectric layers, a partition plate disposed on
said electrode substrate and having a plurality of spaced openings
corresponding individually to said display sections so as to define
the respective discharge spaces containing a discharge medium, and
a front plate disposed on said partition plate and transparent at
least at those portions opposite to the respective display
sections, the outer periphery of the laminate structure consisting
of said electrode substrate, said partition plate and said front
plate being sealed gastight.
In accordance with another aspect of the present invention, there
is provided a method of manufacturing a multiple-digit display
device comprising the steps of forming an electrode substrate by
multilevel-printing on a dielectric substrate through dielectric
layers a plurality of sets of cathodes of predetermined pattern
constituting a plurality of display sections respectively and a
plurality of sets of anodes associated with said plural sets of
cathodes respectively, disposing on said electrode substrate a
partition plate having a plurality of spaced openings corresponding
individually to said display sections so as to define respective
discharge spaces, disposing on said partition plate a front plate
which is transparent at least at those portions opposite to the
respective display sections, sealing gastight the outer periphery
of the laminate structure consisting of said electrode substrate,
said partition plate and said front plate, and evacuating said
laminate structure and introducing a discharge medium into said
discharge spaces.
The above and other objects, features and advantages of the present
invention will become apparent from the following detailed
description taken in conjunction with the accompanying drawings, in
which:
FIG. 1 is a schematic exploded perspective view of a multiple-digit
display device embodying the present invention;
FIGS. 2a to 2h show schematically successive steps for the
manufacture of the multiple-digit display device shown in FIG.
1;
FIG. 3 is a schematic enlarged plan view showing one of the display
sections in the multiple-digit display device manufactured by the
method shown in FIGS. 2a to 2h; and
FIG. 4 is a schematic sectional view taken on the line IV--IV in
FIG. 3.
FIG. 1 is a schematic exploded perspective view of an embodiment of
the present invention and this multiple-digit display device is
constructed to display, for example, thirteen digits. Referring to
FIG. 1, the multiple-digit display device comprises a rectangular
front plate 1 of transparent material such as glass (hereinafter
referred to as a transparent plate), a partition plate 2 having a
plurality of spaced independent openings corresponding individually
to the digits or display sections so as to partition the digits or
display sections from each other and an electrode substrate 3. This
electrode substrate 3 includes a plurality of sets of display
cathodes 4 with each set disposed in the form of (8), a plurality
of pairs of spaced inner anodes 5 with each pair disposed within
the zones defined by each set of these cathodes 4 so as to be
surrounded by the latter, a plurality of outer anodes 6 each
disposed outside of each set of these cathodes 4 so as to surround
the latter, a plurality of auxiliary electrodes 6 for indicating
the decimal point, a plurality of terminals 8 serving as external
connection means for the display cathodes 4, inner and outer anodes
5 and 6 and auxiliary electrodes 7, and many wires (not shown) for
electrically connecting these electrodes to the terminals 8. The
electrode substrate 3 including these electrodes, terminals and
wires is formed by means of multilevel-printing of a conductive
material on a dielectric substrate. Other display sections for
displaying symbols such as plus and minus may of course be provided
on the electrode substrate 3, but such display sections are not
shown herein for conveniences of description and illustration.
Further, the transparent plate 1 may be transparent at least at
those portions opposite to the display sections.
The transparent plate 1, partition plate 2 and electrode substrate
3 having such a structure are successively laminated, and this
laminated structure is sealed gastight at the outer periphery
thereof with a sealing material such as a low-melting glass,
organic binder, special brazing material or solder. After
evacuating the interior of the laminated structure, a discharge
medium which may be a rare gas such as neon or argon or their
mixture is enclosed within the discharge spaces of the laminated
structure to provide the multiple-digit display device.
When voltage is applied across the terminals 8 connected to
selected ones of the display cathodes 4 and the terminals 8
connected to the inner and outer anodes 5 and 6 in the
multiple-digit display device having such a structure, discharge
occurs between the selected display cathodes 4 and the inner and
outer anodes 5 and 6, and the display cathodes 4 provides
illumination of desired pattern. Due to the fact that the
corresponding display cathodes 4 (hereinafter referred to as common
cathodes) in the respective display sections are connected in
common to the same terminals 8 as will be described later, desired
patterns can be displayed on the individual display sections by
successively selecting and applying voltage in time division
fashion to the terminals 8 connected to the inner and outer anodes
5 and 6 in the individual display sections independently of one
another.
Further, the multiple-digit display device according to the present
invention requires a very small number of necessary parts compared
with prior art devices, has a very small overall thickness and is
suitable for mass production due to the fact that it is composed of
only three members, that is, the transparent plate 1, partition
plate 2 and electrode substrate 3. Furthermore, the multiple-digit
display device according to the present invention can be very
easily handled and assembled, and the electrodes and wires can be
simply deposited by means of multilevel-printing due to the fact
that these electrodes and wires are disposed in substantially
coplanar relation in the single electrode substrate 3.
Successive steps for the manufacture of the multiple-digit display
device having the structure above described will now be described
with reference to FIGS. 2a to 2h by way of example.
A binder such as polyvinylbutyral and a solvent such as
butylcarbitol acetate are added to a powdery ceramic material
consisting essentially of, for example, aluminum oxide having a
purity higher than 90 percent to obtain a pasty composition. This
pasty composition is shaped into a sheet form about 2 mm thick and
is then dried to obtain an unsintered dielectric sheet in the form
of a strip or ribbon (hereinafter referred to as a green sheet) as
shown in FIG. 2a. Many jig receiving holes 10 are bored along the
opposite sides of this green sheet for the purpose of ensuring
correct positioning of the sheet in the later steps, thereby
obtaining an unsintered dielectric substrate 11.
Then, as shown in FIG. 2b, a conductive material is deposited by a
screen printing technique on the surface of the unsintered
dielectric substrate 11 for forming cathode terminals 12a to 12h,
wires 13a to 13h extending in the longitudinal direction of the
substrate 11 for connection between common cathodes, wires 14a and
14b to be connected to anodes, cathode lead wires 15, connection
points 16a to 16h positioned at the end of the cathode lead wires
15, anode terminals 17a to 17m, anode lead wires 34, and connection
points 21 positioned at the end of the anode lead wires 34. The
wire 13h in FIG. 2b is provided for connection between the
auxiliary electrodes 7 indicating the decimal point shown in FIG.
1. The conductive material is applied in powder form and may be a
conductive highmelting metal such as tungsten (W), molybdenum (Mo),
manganese (Mn), titanium (Ti) or platinum (Pt) or a mixture of some
of these metals. The conductive material may also be a conductive
paste consisting of a powdery oxide of such metal, a binder such as
polyvinylbutyral and a solvent such as butylcarbitol acetate. The
unsintered dielectric substrate 11 having the above pattern printed
with the conductive material is then subjected to drying in air at
about 120.degree.C for about 15 minutes so that the conductor layer
can be firmly secured to the surface of the unsintered dielectric
substrate 11.
Then, as shown in FIG. 2c a first dielectric layer 18 is printed on
the unsintered dielectric substrate 11 shown in FIG. 2b. In this
case, the first dielectric layer 18 is deposited by screen printing
on the central portion of the substrate 11 except the portions
corresponding to the cathode connection points 19 and connection
points 23a to 23h on the wires 13a to 13h serving as the connection
paths for the common cathodes, anode connection points 20
positioned at the opposite ends of the wires 14a and 14b to be
connected to the anodes, connection points 16a to 16h positioned at
the end of the cathode lead wires 15, connection points 21
positioned at the end of the anode lead wires 34, cathode terminals
12a to 12h, and anode terminals 17a to 17m. These connection points
have a diameter of, for example, about 0.3 to 1.0 mm, and thus, the
holes therefor can be very easily formed by screen printing. The
first dielectric layer 18 is about 10 .mu. to 0.5 mm thick and is
thus very thin compared with the diameter of the holes at the
connection points. This first dielectric layer 18 may be formed
from a material similar to that employed for forming the unsintered
dielectric substrate 11. However, in order to provide a viscosity
suitable for printing and to obviate possible occurrence of
pinholes, it is preferable to employ a composition consisting of,
for example, 50 percent by weight of a powdery ceramic material
consisting essentially of aluminum oxide, 20 percent by weight of
polyvinylbutyral or cetyl cellulose which is a binder possessing
the adhesiveness suitable for printing, and 30 percent by weight of
butylcarbitol acetate which is a solvent giving the required
viscosity.
The unsintered dielectric substrate 11 having the first dielectric
layer 18 printed thereon is subsequently dried under a condition
similar to that described with reference to FIG. 2b. Then, as shown
in FIG. 2d, a conductive material similar to that described
hereinbefore is deposited on the first dielectric layer 18 by
screen printing to provide cathodes 22 slightly spaced from the
cathode connection points 19 and connected partly to the respective
cathode connection points 19, and cathode lead wires 24 disposed
between the connection points 16a to 16h and the connection points
23a to 23h lying on the wires 13a to 13h serving as the connection
paths for the common cathodes respectively. During this screen
printing, auxiliary electrodes 32 are provided and wires 33 for
connecting the auxiliary electrodes 32 to the connection points 19
lying on the wire 13h are also provided. Due to the fact that the
thickness of the first dielectric layer 18 is very small compared
with the diameter of the holes at the connection points, the
conductive material applied to the first dielectric layer 18 flows
readily into these holes during the screen printing so that the
conductive layer can be easily and reliably electrically connected
to the underlying conductive layer through the first dielectric
layer 18. In FIG. 2d, the holes at the connection points 19, 23a to
23h and 16a to 16h are filled with the conductive material. In the
state shown in FIG. 2d, therefore, the common cathodes 22 are
electrically connected to the wires 13a to 13h through the cathode
connection points 19 respectively, and the wires 13a to 13h are
electrically connected to the cathode terminals 12a to 12h through
the connection points 23a to 23h, cathode lead wires 24, connection
points 16a to 16h and cathode lead wires 15 respectively. The
cathodes 22 are deposited in slightly spaced relation from the
connection points 19 because deposition of the cathodes 22 on the
connection points 19 may produce unevenness on the cathode surface
resulting in non-uniform luminescence.
Then, as shown in FIG. 2e, a second dielectric layer 25 is printed
on the first dielectric layer 18 in a manner similar to that
described hereinbefore. This second dielectric layer 25 is
deposited on the portions except the portions corresponding to the
cathodes 22, connection points 20 positioned at the opposite ends
of the wires 14a and 14b to be connected to the anodes, connection
points 21 for the anode terminals 17a to 17m, and auxiliary
electrodes 32 connected to one end of the wires 33.
Then, as shown in FIG. 2f, a conductive material similar to that
described hereinbefore is used to print on the second dielectric
layer 25 a plurality of pairs of inner anodes 26 with each pair
disposed in the respective zones surrounded by the cathodes 22 in
each display section, a plurality of outer anodes 27 each
surrounding the cathodes 22 in each display section and connected
partly to the connection point 20, and wires 28 disposed between
the outer anodes 27 and the connection points 21 for the anode
terminals 17a to 17m. During this printing step, the holes at the
connection points 21 are filled with the conductive material and
the inner anodes 26 are printed to fill the holes at the connection
points 20 lying within the zones surrounded by the cathodes 22. The
printed conductor layer is then dried under a condition similar to
that described with reference to FIG. 2b. In the state shown in
FIG. 2f, therefore, the inner and outer anodes 26 and 27 in each
display section are connected in common to one another by the
connection points 20 and wires 14 a and 14b thereby constituting a
single anode, and these single anodes in the individual display
sections are connected to the anode terminals 17a to 17m by the
wires 28, connection points 21 and wires 34 respectively.
Then, as shown in FIG. 2g, a dielectric material is printed on all
the portions of the second dielectric layer 25 except the portions
corresponding to the cathodes 22, inner and outer anodes 26 and 27,
and auxiliary electrodes 32 so as to provide a third dielectric
layer 29, that is, the outermost dielectric layer in the present
embodiment. The dielectric material employed for forming this third
dielectric layer 29 may be similar to that employed for forming the
first and second dielectric layers 18 and 25. In such a case,
however, light from the light-emitting cathodes may be scattered by
the display surface and the display effect may be reduced due to
the fact that these dielectric layers are generally white in color.
In order to solve such a problem, the third dielectric layer 29,
that is, the outermost dielectric layer should have a color which
provides less reflection of light. When, for example, titanium
oxide is added to the powdery ceramic material consisting
essentially of aluminum oxide, the dielectric layer thus obtained,
is grey or black in color depending on the content of titanium
oxide. The dielectric layer is purple in color when cobalt oxide is
added to the ceramic material, while it becomes pinkish or blackish
when manganese dioxide is added to the ceramic material.
The multilevel-printed unsintered substrate 11 shown in FIG. 2g is
then suitably trimmed at end edges thereof to obtain an unsintered
electrode substrate 30 as shown by the two-dot chain lines in FIG.
2h. The unsintered electrode substrate 30 thus obtained is then
placed and held in a non-oxidizing atmosphere at about
1,400.degree.C to 1,650.degree.C for about 1 hour. As a result of
this sintering treatment, the unsintered substrate 11 consisting
essentially of aluminum oxide, and the dielectric layers and
conductive layers formed by printing are simultaneously sintered to
provide an electrode substrate 30 as shown by the solid lines in
FIG. 2h. During this sintering step, the additives such as the
binder and solvent in the dielectric and conductive materials are
evaporated or ignited resulting in a reduction by about 15 percent
of the original dimensions of the unsintered electrode substrate
30. The electrode substrate 31 having predetermined dimensions can
be obtained by suitably sizing the unsintered electrode substrate
30 taking into consideration the reduction of the dimensions due to
sintering.
A partition plate for defining the display sections is disposed on
the electrode substrate 31 thus obtained and then a transparent
plate is disposed on the partition plate to form a laminate. A
sealing material such as a low-melting plass is applied to the
outer periphery of this laminate and the laminate is heated at a
temperature of about 420.degree.C to 550.degree.C for about 1 hour
to be sealed gastight at the outer periphery thereof. A discharge
medium is then enclosed in the discharge spaces of the laminate to
complete a multiple-digit display device.
The method shown in FIGS. 2a to 2h is merely illustrative of one
form of the present invention and various changes and modifications
may be made therein. For example, the wires 13a to 13h for
connection between the common cathodes in FIG. 2b may be directly
connected to the cathode terminals 12a to 12h so as to eliminate
the cathode lead wires 24 shown in FIG. 2d. Further, the connection
points 21 in FIG. 2b may be directly disposed on the anode
terminals 17a to 17m so as to eliminate the anode lead wires
34.
FIG. 3 is a schematic enlarged plan view of one of the display
sections of the electrode substrate 31 manufactured by the method
described with reference to FIGS. 2a to 2h, and FIG. 4 is a
schematic section view taken on the line IV--IV in FIG. 3. In FIGS.
3 and 4, the same reference numerals are used to denote the same
parts shown in FIGS. 2a to 2h. Referring to FIGS. 3 and 4, the
first conductive layer in the electrode substrate 31 obtained by
the method of the present invention includes the anode terminals
17a to 17m for external connection, cathode terminals 12a to 12h,
wires 13a to 13h for connection between the common cathodes, common
connection wires 14a and 14b for the inner and outer anodes 26 and
27, and cathode lead wires 15. The first dielectric layer 18 is
printed on this first conductive layer except the portions
corresponding to the required connection points. The second
conductive layer is printed on this first dielectric layer 18 and
includes the cathodes 22 (22a to 22h), and wires connected at one
end thereof to the cathodes 22 (22a to 22h) and at the other end
thereof to the wires 13a to 13h in the first conductive layer
through the connection points in the first dielectric layer 18. The
cathodes 22 may have an uneven surface when the connection points
are disposed directly on the cathode portions for connecting the
cathodes 22 to the first conductive layer without providing the
lead wires for connecting the cathodes 22 to the first conductive
layer. In the display of this kind utilizing gaseous discharge,
light is emitted from the cathodes, and thus, presence of slight
unevenness on the cathode surface results in non-uniform
luminescence. In the present invention, the second dielectric layer
25 is disposed on the second conductive layer except the portions
corresponding to the cathodes 22 and required connection points.
This second dielectric layer 25 is provided for covering the
connection points for the cathodes so that the anodes can be
disposed in the vicinity of the cathodes in substantially coplanar
relation with the cathodes. In order to provide the anodes without
employing the second dielectric layer 25, the anodes must be
sufficiently spaced from the cathodes or the anodes must be
directly disposed on the first conductive layer. However, in the
former case, a degree of structural freedom is lost thereby greatly
adversely affecting the electrical properties of the display
device, while in the latter case, discharge is made with
difficulty. The third conductive layer is disposed on the second
dielectric layer 25 and includes the inner and outer anodes 26 and
27, wires 28 for connecting the anodes 26 and 27 to the anode
terminals 17a to 17m, and wires 14a and 14b for connection between
these anodes. The third dielectric layer 29 is then printed on this
third conductive layer except that the portions corresponding to
the cathodes and anodes.
Multilevel-printing is required so that anodes and cathodes for the
display of desired patterns such as figures, characters or symbols
and wires for connecting these electrodes to external circuits can
be provided on a single dielectric substrate, and this is done by
repeatedly printing a plurality of conductive layers and dielectric
layers on the single dielectric substrate. An electrode substrate
having a complex structure can be obtained by increasing the number
of printing, hence the number of layers. At least three conductive
layers and three dielectric layers are required in order to provide
at least two kinds of electrodes with good efficiency and without
deteriorating the desired display effect. An attempt to dispose the
anodes on the first dielectric layer and to dispose the cathodes on
the second dielectric layer results in the loss of the degree of
structural freedom of either the anodes or the cathodes. Therefore,
the best effect can be obtained with the smallest number of steps
when the cathodes are disposed on the first dielectric layer and
the anodes are disposed on the second dielectric layer. The
electrode substrate thus obtained can be used in that form as a
part of the display device utilizing gaseous discharge. However, it
is preferable to plate a metal such as nickel on the electrodes for
smoothing the electrode surface thereby ensuring uniform
luminescence. Further, in the gaseous discharge display device
having the structure above described, a stabilizing resistor having
a resistance of about 10 to 200 kilohms is commonly connected to
each electrode for stabilizing the discharge. In the present
embodiment, a portion or entirety of the cathode lead wires 15 in
FIG. 2b and/or cathode lead wires 24 in FIG. 2d, and anode lead
wires 34 in FIG. 2b and/or anode lead wires 28 in FIG. 2f may be
formed by a resistor. This is advantageous in that the number of
circuit elements is remarkably reduced due to the fact that the
stabilizing resistors are incorporated in the electrode substrate.
In the present embodiment, the display electrodes or cathodes have
been printed in the pattern corresponding to the desired display
pattern in FIG. 2a to 2h. However, due to the fact that the second
dielectric layer is disposed on the second conductive layer
including these display cathodes therein, the shape of the cathodes
themselves may not be limited in any way and the shape of the
portions of the cathodes exposed from the second dielectric layer
may be selected to correspond to the desired display pattern for
attaining the effect similar to that above described. The sealing
material employed in sealing gastight the outer periphery of the
laminate composed of the transparent plate, partition plate and
electrode substrate is preferably a lowmelting glass as pointed out
hereinbefore since the application of high temperatures to the
laminate will result in oxidation of the electrode surface due to
heat, and hence non-uniform luminescence will result.
The embodiment of the present invention has been described with
reference to the use of an unsintered dielectric substrate made of
a ceramic material consisting essentially of aluminum oxide by way
of example. However, the present invention is in no way limited to
such a substrate, and an unsintered green sheet made of a powdery
dielectric material such as powdery forsterite or powdery glass may
be used.
It will be understood from the foregoing detailed description that
the multiple-digit display device and the method of manufacturing
such a display device according to the present invention are
advantageous in that the display device has a very small thickness
and electrical connections between the electrodes and the wires can
be very easily and reliably attained since the cathodes and anodes
are disposed in substantially coplanar relation. Further, in the
present invention the electrode substrate having all the required
electrodes and wires therein is formed by multilevel-printing. The
present invention is advantageous in that the conventional step for
the punching of interconnecting holes is unnecessary, and thus, the
electrode substrate can be formed very simply and reliably.
Furthermore, the present invention is advantageous in that the
dielectric material and conductive material can be economically and
effectively used due to the fact that the thickness of the
dielectric layers and conductive layers can be freely varied by
varying the amount of the paste used in printing. Moreover, the
present invention is advantageous in that the manufacturing process
can be remarkably simplified and the positioning and electrical
connections of the electrodes and wires can be reliably attained
due to the fact that the electrode substrate is formed by
depositing the electrodes, wires and terminals on an unsintered
green sheet by multilevel-printing and then simultaneously
sintering these elements. Further, the present invention in which
the cathodes and anodes are disposed in substantially coplanar
relation is advantageous in that light emitted from the cathodes is
not intercepted by the anodes and the pattern can be displayed more
clearly than heretofore. The multiple-digit display device
according to the present invention can be obtained by merely
laminating the partition plate and transparent plate on the
electrode substrate provided with the cathodes and anodes so as to
form the discharge spaces in the laminate and then sealing gastight
the outer periphery of the laminate. Thus, it is an additional
advantage of the present invention that the number of required
parts is remarkably smaller than heretofore and the display device
can be very easily assembled.
* * * * *