Title:
METHOD OF MAKING DISPLAY DEVICES
United States Patent 3580654


Abstract:
A method of making a gas discharge display device comprising assembling the component parts of the device and providing a tabulation through which the device can be filled with the desired gas. A capsule containing an antisputtering agent such as mercury is mounted within the tabulation, along with suitable means by which it may be heated. The device is suitably baked out and otherwise preliminarily processed; the desired gas is introduced; and the tubulation is sealed off with the capsule remaining therein. After any other processing steps are carried out as required, the material is freed from the capsule, and, with the entire assembly heated to a suitable temperature to cause the anitsputtering agent to enter the working area of the device, the tubulation is sealed off at an area close to the device itself and with the capsule within the portion of the tubulation which is removed.



Inventors:
KUPSKY GEORGE A
Application Number:
04/764983
Publication Date:
05/25/1971
Filing Date:
10/02/1968
Assignee:
BURROUGHS CORP.
Primary Class:
Other Classes:
220/2.2, 445/43
International Classes:
H01J9/26; H01J9/395; (IPC1-7): H01J9/38
Field of Search:
316/20,24,26,17,18 141
View Patent Images:



Primary Examiner:
Campbell, John F.
Assistant Examiner:
Lazarus, Richard Bernard
Claims:
I claim

1. A method of manufacturing a display tube of the type including

2. The method set forth in claim 1 further including the step of removing the tubulation beyond the point of the second seal and also removing the remainder of the vaporizable material.

3. The method set forth in claim 1 wherein the step of placing a supply of vaporizable material in the tubulation involves placing a sealed capsule containing the vaporizable material together with an attached wire in said tubulation, and wherein the step of activating said vaporizable material involves passing a current through said attached wire to heat the enclosed vaporizable material and crack said capsule.

4. The method defined in claim 1 and including, at a convenient time after sealing said tubulation, the step of aging said tube by applying voltages to said electrodes according to a predetermined program.

5. The method defined in claim 1 and including the step of sealing said tubulation a second time at a region between said envelope and the point at which said vaporizable material was originally placed.

6. The method defined in claim 1 wherein said vaporizable material is mercury.

Description:
BACKGROUND OF THE INVENTION

It has become standard practice in cold cathode display devices to utilize argon and neon and the like as the preferred medium for providing glow discharge, and, ever since J. H. McCauley's invention, it has become good practice, in addition, to provide a small quantity of mercury vapor to minimize cathode sputtering. Display tubes of the type having relatively large envelopes which contain relatively large cathode characters such as numerals, letters, or the like, have utilized these features and have become commercially successful. In tubes of this type, the mercury is provided in a capsule which carries a heating wire and is permanently mounted within the tube with the heating wire connected to two tube pins. The mercury is released from the capsule at a desired stage in the manufacturing process by means of heat generated by current flow through the heating wire. When the mercury is released, its vapor readily fills the tube envelope. In this type of tube, tube pins are provided for an anode, for each of ten cathodes, and for two decimal points, and, in addition, two extra tube pins are required for connection to the capsule heating wire. Moreover, space must be available inside the envelope for the mercury capsule.

For a long time, there has been a need for a display device of the flat panel type which includes a large number of tiny cells formed in a unitary panel and utilizing cold cathodes and gaseous glow. These devices use a gas of the type described above, and, in addition, require mercury to minimize cathode sputtering. However, because of the type of construction used in these devices and because of the small size of the cells, known procedures for introducing the gases and for introducing the mercury are not satisfactory. For example, pins are not available for providing heating current for a capsule, and space is not available in the device for a mercury capsule.

SUMMARY OF THE INVENTION

Briefly, the invention comprises a method making a gas discharge display device including the steps of assembling the parts of the device, baking out the device, introducing an ionizable gas into the device aging the electrodes of the device, introducing an antisputtering agent which has relatively high molecular weight and vaporization temperature, treating the device to cause the anitsputtering agent to vaporize and enter all portions of the device, and then sealing the device.

DESCRIPTION OF THE DRAWING

FIG. 1 is a perspective view of a display device prepared according to the invention; and

FIG. 2 is a side view of the device of FIG. 1 and apparatus used in the manufacture thereof.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The principles of the invention are applicable to display devices of different types. However, for purposes of illustration, only one type of device, a flat panel device, is shown and described. Panel devices of this type are illustrated in detail in a concurrently filed application of G. A. Kupsky.

A display device 10 embodying the invention, shown in FIG. 1, includes a central plate 20 of insulating material such as glass or ceramic which is provided with rows and columns of apertures or cells 30. Top and bottom glass cover plates 40 and 50 are secured to the center plate 20 with parallel row electrodes 60 between bottom plate 50 and plate 20, and parallel column electrodes 70 between top plate 40 and center plate 20. Each row electrode 60 is aligned with a row of cells 30, and each column electrode 70 is aligned with a column of cells 30, and a cell is located at each crossing of a row electrode and a column electrode. In device 10, the row electrodes 60 are cathodes, and the column electrodes are anodes. Plates 20, 40, and 50 are preferably rectangular, and the row and column conductors 60 and 70 extend beyond the edges of the plates so that electrical connection can be made to them.

In one typical panel 10, the central plate 20 is about 1 mm. in thickness, the top and bottom plates are about 1 to 3 mm. in thickness, and the cells are about 0.04 inch in diameter at a density of about twelve cells per linear inch. The conductors 60 and 70 are about 0.05 inch wide and about 5 mils thick.

In manufacturing device 10, the various glass plates are provided with plate 40 carrying a glass tubulation 80 in which is positioned a small glass capsule 90 which contains a tiny droplet of mercury 92. The capsule 90 is supported by a wire conductor 100 which is wrapped around it and has its ends extending through the wall of the capsule for subsequent connection outside the capsule to a source of power 106.

With the glass plates and electrodes assembled and held together mechanically, the various plates are sealed together along their edges by means of a glass frit or the like to provide a gastight seal.

Next, the panel is pumped out and baked out by way of the tubulation 80, and it is filled with a gas suitable for sustaining cathode glow. Gases such as argon and neon are suitable, with one satisfactory gas mixture comprising about 5 percent argon, 95 percent neon, and a trace of krypton. The gas pressure is in the range of about 40 to about 80 Torr at room temperature. After the panel is baked out and then filled with its gas, the tubulation 80 is sealed off below the mercury capsule as at 120. The panel is then aged by cyclically firing each of the rows of cells in order, with about 50 to about 100 ma. of current flowing per row of cells. This aging step is carried out for a few hours.

Next, the mercury is released from its capsule 90 by means of heat applied to the capsule to cause it to crack and release the mercury. The necessary heat is generated by current flow in conductor 100. If the device 10 is not at an elevated temperature, the mercury initially deposits on the wall of the tubulation above the capsule 90, and, according to the invention, in order to force the mercury into all of the cells 30 of the panel, the panel is baked in an oven at about 200° C. for several hours. With the panel held at this temperature, the portion of the tubulation containing the mercury capsule is removed, and the tubulation is sealed off at 130. The first aging step is then repeated.

If desired in the foregoing process, the device 10 may be heated to about 200° C. before the mercury is released from its capsule, and then when the mercury is released, it travels into the cells 30 directly without first condensing in the tubulation.

It is customary to use two or more aging steps with gas devices as described; however, this is not a requirement and one step could be used.

It will be clear to those skilled in the art that the capsule 90 could be made of metal, and it could be heated by induction. It could also be of a material which can absorb infrared radiation, such radiation then being used for heating and breaking the capsule. Other modifications may also be made within the scope of the invention.