Multiple Digit Display Device And Method Of Manufacturing Same

Abstract

A multiple-digit display device comprising a cathode substrate in which a plurality of sets of cathodes of a desired pattern constituting a plurality of display sections respectively and wires for the cathodes are multilevel-printed on a dielectric substrate through dielectric layers, and a front plate having a plurality of transparent anodes and provided on the cathode substrate so as to form a plurality of discharge spaces on the respective display sections, and a method of manufacturing the multiple-digit display device.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application relates to subject matter described in application Ser. No. 365,404 filed May 31, 1973 entitled "Multiple-Digit Display Device and Method of Manufacturing the Same," by Akio Miyamoto, Masaharu Koyama, Toyokazu Odaka, Kanji Otsuka and Gen Murakami, and assigned to the assignee of the present application and to application Ser. No. 365,405, filed May 31, 1973, entitled "Multiple-Digit Display Device," by Akio Miyamoto, Masaharu Koyama, Toyokazu Odaka, and 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 for the manufacture of 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 disposed 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.

A commonly conventionally employed multiple-digit display device of the kind above described comprises a cathode substrate having a plurality of display cathodes embedded therein for constituting a plurality of display sections, an anode substrate formed with a plurality of anodes associated with the corresponding cathodes in the cathode substrate, a transparent plate of material such as glass, a spacer interposed between the substrates, and a wiring board having wires formed thereon for electrically connecting the electrodes of the electrode substrates to external circuits, and these members are laminated to constitute a laminate. In the laminate, holes are bored in the substrates and a conductive material is filled in these holes for electrically connecting the substrates with each other by means of through-hole connections. The laminate is sealed gastight at the outer periphery thereof with a sealing material such as frit glass and a discharge medium is enclosed in the laminate for completing the multiple-digit display device.

However, difficulty has been encountered in such a conventional multiple-digit display device for establishing reliable electrical connections between the substrates. More precisely, the substrates for which the through-hole connections are employed for the electrical connections therebetween have a considerable thickness and there is a great limitation in the diameter of the holes which are filled with the conductive material for establishing the required electrical connections. Thus, extreme difficulty is encountered during filling the conductive material into these holes whose diameter is extremely small. Therefore, the holes are frequently incompletely filled with the conductive material resulting in incomplete electrical connections between the substrates, and the reliability of electrical connections is greatly reduced.

It is therefore an object of the present invention to provide a novel and improved multiple-digit display device of the kind above described in which the electrical connections between the internal electrodes can be very easily and reliably attained.

Another object of the present invention is to provide a method for the manufacture of such a multiple-digit display device which is suitable for mass production, which can be easily manufactured and the number of necessary parts of which is remarkably less than heretofore by virtue of the fact that the cathode substrate is prepared by forming the cathodes and wires on an unsintered dielectric substrate by means of multilevel-printing and then simultaneously sintering these elements.

A further object of the present invention is to provide a multiple-digit display device which is satisfactorily sealed gastight at the outer periphery thereof.

In accordance with one aspect of the present invention, there is provided a multiple-digit display device comprising a cathode substrate in which a plurality of sets of cathodes of desired pattern constituting a plurality of display sections respectively and wires for said cathodes are multilevel-printed on a dielectric substrate through dielectric layers, a partition plate disposed on said cathode substrate and having a plurality of spaced openings corresponding individually to said display sections so as to define the respective discharge spaced 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, said front plate having a plurality of spaced transparent anodes formed on the inner surface of said transparent portions, the outer periphery of the laminate structure consisting of said cathode 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 a cathode 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 wires for said cathodes, disposing on said cathode 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 and in which a plurality of spaced transparent anodes are formed on the inner surface of said transparent portions, sealing gastight the outer periphery of the laminate structure consisting of said cathode 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:

FIG. 1 is a schematic exploded perspective view of a multiple-digit display device embodying the present invention; and

FIG. 2a and 2g show schematically successive steps for the manufacture of the multiple-digit display device according to the present invention.

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, 13 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 3 corresponding individually to the digits or display sections so as to partition the digits or display sections from each other, and a cathode substrate 4. A plurality of spaced independent anodes 6 in the form of a transparent conductive film of material such as NESA (a trade-mark) each having a terminal 5 at one end thereof are formed on the transparent plate 1 at positions opposite to the respective display sections. The transparent plate 1 may be transparent at least at those portions opposite to the display sections. The cathode substrate 4 includes a plurality of sets of display cathodes 7 with each set disposed in the form of (8) for constituting the respective display sections, a plurality of spaced dot electrodes 7 for indicating the decimal point, a plurality of cathode terminals 8a to 8h connected to the common cathodes in the respective display sections, a plurality of anode terminals 9a to 9m, and a plurality of terminals 10 disposed opposite to the terminals 5 of the anodes 6 and electrically connected to the anode terminals 9a to 9m respectively. The cathode substrate 4 including these electrodes and terminals 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 cathode substrate 4, but such display sections are not shown herein for conveniences of description and illustration.

The transparent plate 1, partition plate 2 and cathode substrate 4 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 complete the multiple-digit display device. The sealing may be carried out by heating the laminate at a temperature of about 420.degree. to 550.degree.C for about 1 hour when, for example, the low-melting glass is employed as the sealing material.

When the cathode terminals 8a to 8h and anode terminals 9a to 9m in the multiple-digit display device having such a structure are suitably selected and voltage is applied across these selected cathode and anode terminals, discharge occurs between the selected display cathodes 7 and transparent anode 6 and the display cathodes 7 provide illumination of desired pattern due to the fact that the anode terminals 9a and 9m are electrically connected to the terminals 5 of the corresponding anodes 6 through the respective terminals 10. Due to the fact that the corresponding display cathodes 7 (hereinafter referred to as common cathodes) in the respective display sections are connected in common to the corresponding cathode terminals 8a to 8h 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 anode terminals 9a to 9m electrically connected to the anodes 6 in the individual display sections independently of one another.

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 2g by way of example.

A binder such as polyvinyl-butyral 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 as shown in FIG. 2a. Many jig receiving holes 26 are bored along the opposite sides of this dielectric 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 unsintered dielectric sheet 11 for forming cathode terminals 12a to 12h, anode terminals 13a to 13m, wires 14a to 14h extending in the longitudinal direction of the substrate 11 for connection between common cathodes, cathode and anode lead wires 27, and connection points 17 positioned at the end of these lead wires 27. The conductive material is applied in powder form and may be a conductive high-melting 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 conductive layer can be firmly secured to the surface of the unsintered dielectric substrate 11.

Then, as shown in FIG. 2c, a first dielectric layer 15 is printed on the unsintered dielectric substrate 11 shown in FIG. 2b. In this case, the first dielectric layer 15 is deposited by screen printing on the central portion of the substrate 11 except the portions corresponding to connection points 16, 16a to 16h on the wires 14a to 14h for connection between the common cathodes, and connection points 17 positioned at the inner end of the cathode terminals 12a to 12h and of the anode terminals 13a to 13m. The connection points 16, 16a to 16h and 17 have a diameter of, for example, 0.3 to 1.0 mm, and thus, the holes therefor can be very easily formed by screen printing. The first dielectric layer 15 is about 60.mu. to 0.5mm thick and is thus very thin compared with the diameter of the holes at the connection points 16, 16a to 16h and 17. This first dielectric layer 15 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 15 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 15 by screen printing to provide cathodes 18 slightly spaced from the cathode connection points 16 and connected partly to the respective cathode connection points 16, and wires 19 disposed between the connection points 16a to 16h lying on the respective wires 14a to 14h and the connection points 17 of the respective cathode terminals 12a to 12h. During this screen printing, cathodes 28 indicating the decimal point and wires 29 connecting these cathodes 28 to the connection points 16 lying on the wire 14h are also provided. Due to the fact that the thickness of the first dielectric layer 15 is very small compared with the diameter of the holes at the connection points, the conductive material applied to the first dielectric layer 15 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 15. In the state shown in FIG. 2d, therefore, the common cathodes 18 are electrically connected to the wires 14a to 14h through the connection points 16 respectively and to the cathode terminals 12a to 12h through the connection points 16a to 16h wires 19 respectively. The cathodes 18 are deposited in slightly spaced relation from the connection points 16 because deposition of the cathodes 18 on the connection points 16 may produce unevenness on the cathode surface resulting in non-uniform luminescence.

Then, as shown in FIG. 2e, a second dielectric layer 20 is deposited by screen printing on the first dielectric layer 15.

This second dielectric layer 20 is deposited on the portions except the portions corresponding to the cathodes 18, connection points 17 of the anode terminals 13a to 13m, and cathodes 28 indicating the decimal point. Then, a conductive material similar to that described hereinbefore is deposited by screen printing on the second dielectric layer 29 to provide terminals 21 opposite to terminals of anodes (not shown) in the respective display sections, and wires 22 electrically connecting the terminals 21 to the respective anode terminals 13a to 13m.

Then, as shown in FIG. 2f, a third dielectric layer 23 of material similar to that described hereinbefore is deposited by screen printing on the second dielectric layer 20 except the portions corresponding to the cathodes 18, terminals 21, and cathodes 28 indicating the decimal point. The multilevel-printed unsintered substrate 11 shown in FIG. 2f is then suitably trimmed at end edges thereof to obtain an unsintered cathode substrate 24 as shown by the two-dot chain lines in FIG. 2g. The unsintered cathode substrate 24 thus obtained is then placed and held in a non-oxidizing atmosphere at about 1,400.degree. 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 a cathode substrate 25 as shown by the solid lines in FIG. 2g. 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 cathode substrate 24. The cathode substrate 25 having predetermined dimensions can be obtained by suitably sizing the unsintered cathode substrate 24 taking into consideration the reduction of the dimensions due to sintering.

A partition plate for defining the display sections as shown in FIG. 1 is disposed on the cathode substrate 25 thus obtained and then a transparent plate having transparent anodes formed one the inner surface thereof as shown in FIG. 1 is disposed on the partition plate to form a laminate. A sealing material such as frit glass is applied so as to seal gastight the outer periphery of this laminate, and the terminals of the anodes are electrically connected to the anode terminals 21 on the cathode substrate 25 in FIG. 2g with a material such as a brazing material, solder, conductive glass paste or conductive binder. Subsequently, a discharge medium is enclosed in the discharge spaces of the laminate to complete the multiple-digit display device.

The method shown in FIGS. 2a to 2g is merely illustrative of one form of the present invention and various changes and modifications may be made therein. For example, the wires 14a to 14h 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 19 shown in FIG. 2d.

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 electrical connections between the electrodes and the wires can be very easily and reliably attained. Further, the present invention, in which the wires and cathodes are formed by multilevel-printing, is advantageous in that the conventional step for the punching of interconnecting holes in the spacer is unnecessary, and thus the cathode 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 cathode substrate is formed by depositing the electrodes, wires and terminals on an unsintered green sheet by multilevel-printing and then simultaneously sintering these elements. It is an additional advantage of the present invention that the number of necessary parts is remarkably smaller than heretofore and the display device can be very easily assembled and is suitable for mass production.

Claims

What we claim is:

1. A method of forming a cathode substrate for a multiple-digit display device, in which said cathode substrate including cathodes is arranged opposite to a plate including anodes, comprising the steps of:

a. shaping a pasty composition comprising a dielectric material, a binder and a solvent into a shett form having 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 cathode terminals for the corresponding cathodes between said cathode sets, a plurality of wires for the connections of the corresponding cathodes, between said cathode sets, to said cathode terminals, and a plurality of dielectric layers to provide an unsintered multilayer cathode substrate; and

d. sintering said unsintered multilayer cathode substrate to provide a cathode substrate.

2. A method according to claim 1, wherein said step (c) comprises the steps of:

c1. printing, on said unsintered dielectric sheet, said cathode 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 said second wires which are connected to the corresponding cathodes between said cathode sets to said first wires through said holes; and

c4. printing a second dielectric layer on the structure resulting from step (c3), exposing said cathode sets.

3. A method of manufacturing a multiple-digit gaseous discharge display device, comprising the steps of:

i. preparing a cathode substrate by

a. shaping a pasty composition comprising a dielectric material, a binder and a solvent into a sheet form having 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 cathode terminals for the corresponding cathodes between said cathode sets, a plurality of wires for the connection of the corresponding cathodes between said cathode sets to said cathode terminals, and a plurality of dielectric layers to provide an unsintered multilayer cathode substrate, and

d. sintering said unsintered multilayer cathode substrate;

ii. locating, on said cathode substrate, a partition plate having a plurality of spaced openings corresponding individually to the display sections of said cathode 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 and in which a plurality of spaced transparent anodes are formed on the inner surface of said transparent portions;

iv. sealing gastight the outer periphery of the laminate structure consisting of said cathode substrate, said partition plate and said front plate; and

v. evacuating said laminate structure and introducing a discharge medium into said discharge spaces.

4. A method according to claim 3, wherein said step i (c) comprises:

i. c1. printing, on said unsintered dielectric sheet, said cathode terminals and first wires to be connected respectively to said cathode terminals;

i. c2. printing, on the structure resulting from step (i)(c1), a first dielectric layer having predetermined holes therethrough;

i. c3. printing, on the structure resulting from step (i)(c2) said cathode sets and second wires connected respectively to the cathodes thereof, while electrically connecting said second wires which are connected to the corresponding cathodes between said cathode sets through said holes to said first wires; and

i. c4. printing a second dielectric layer on structure resulting from step (i)(c3), exposing said cathode sets.

5. In a method of manufacturing a multiple-digit display device including a cathode substrate having a plurality of cathodes and a plate having a plurality of anodes facing said cathodes, said plate being so disposed relative to said substrate that said cathodes are spaced apart from said anodes, an improved method of forming said cathode substrate 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 cathode terminals to be connected to respective cathodes of said sets, a plurality of wires for interconnecting said cathode terminals to said cathodes, and a plurality of unsintered dielectric layers, to thereby provide an unsintered multilayer cathode structure; and

b. sintering said unsintered multilayer cathode structure to provide a sintered cathode substrate.

6. An improved method according to claim 5, 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.

7. A method according to claim 5, wherein step (a) comprises the steps of:

a1. printing, on said unsintered dielectric sheet, said cathode 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 said second wires which are connected to the corresponding cathodes between said cathode sets to said first wires through said holes; and

a4. printing a second dielectric layer on the structure resulting from step (a3), exposing said cathode sets.

8. A method according to claim 6, wherein step (a) further comprises the steps of:

a3. printing, on said unsintered dielectric sheet, said cathode 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 said second wires which are connected to the corresponding cathodes between said cathode sets to said first wires through said holes; and

a6. printing a second dielectric layer on the structure resulting from step (a5), exposing said cathode sets.

9. A method of manufacturing a multiple-digit gaseous discharge display device comprising the steps of:

a. forming a cathode substrate 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 cathode terminals to be connected to respective cathodes of said sets, a plurality of wires for interconnecting said cathode terminals to said cathodes, and a plurality of unsintered dielectric layers, to thereby provide an unsintered multilayer cathode structure; and

a2. sintering said unsintered multilayer cathode structure to provide a sintered cathode substrate;

b. locating, on said cathode substrate, a partition plate having a plurality of spaced openings corresponding individually to the display sections of said cathode 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 and in which a plurality of spaced transparent anodes are formed on the inner surface of said transparent portions;

d. sealing gastight the outer periphery of the laminate structure consisting of said cathode substrate, said partition plate and said front plate; and

e. evacuating said laminate structure and introducing a discharge medium into said discharge spaces.

10. A method according to claim 9 wherein step (a1) comprises the steps of:

a1-i. printing, on said unsintered dielectric sheet, said cathode 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 said second wires which are connected to the corresponding cathodes between said cathode sets to said first wires through said holes; and

a1-iv. printing a second dielectric layer on the structure resulting from step (a1-iii), exposing said cathode sets.

11. A method of manufacturing a multiple-digit display device, comprising the steps of:

forming, a cathode 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 wires for said cathodes;

disposing, on said cathode 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 and in which a plurality of spaced transparent anodes are formed on the inner surface of said transparent portions;

sealing gastight the outer periphery of the laminate structure consisting of cathode 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 evacuation of said laminate structure.