US3697797A

US3697797A - Process for manufacturing cold cathode gas discharge devices and the product thereof

Info

Publication number: US3697797A
Application number: US109271A
Authority: US
Inventors: Paul J Freyheit; Claude D Lustig
Original assignee: Sperry Rand Corp
Current assignee: WALTER E HELLER WESTERN Inc; Sperry Corp; Microsemi Corp Power Management Group
Priority date: 1971-01-25
Filing date: 1971-01-25
Publication date: 1972-10-10
Anticipated expiration: 1989-10-10

Abstract

The invention comprises a process of manufacturing cold cathode gas discharge devices. A unitary metal electrode structure is inserted through a glass support, the metal and glass having the same coefficient of thermal expansion. The support and electrode structure are heated in the presence of oxygen to effect a seal therebetween. The gas discharge device is completed without removing the oxide coating formed on the electrode surfaces of the structure during the heating step. The resulting gas discharge device, which may be used for display purposes, has a stable oxide coating on electrodes thereof that attenuates display distorting reflections.

Description

United States Patent [151 3,697,797 F reyheit et a1. 14 1 Oct. 10, 1972 [54] PROCESS FOR MANUFACTURING 3,551,721 12/1970 Holz ..315/169 R X COLD CATHODE GAS DISCHARGE 3,603,837 9/ 1971 Turner ..3 15/ 169 R X DEVICES AND THE PRODUCT THEREOF Primary ExaminerRoy Lake Assistant Examiner-Siegfried H. Grimm [72] Inventors: Paul J. Freyhelt, Frammgham Attorney sl Yeaton Center; Claude D. Lustig, Lexing- 1011, both Of Mass. [73] Assign: Sperry Rand Comm-36 The invention comprises a process of manufacturing 22 Filed; Jam 25, 1971 cold cathode gas discharge devices. A unitary metal electrode structure is inserted through a glass support, [211 App! 109371 the metal and glass having the same coefficient of thermal expansion. The support and electrode struc- 52 us. Cl. ..313/217, 29/25.!6, 65/154, we are heated in the presence of yg to effect a 313/109.5, 313/218, 313/221, 313/245 Seal therebetween. The gas discharge device is [51] Int. Cl ..H0l j l/94, H01 j 9/18, H0 1 j 17/48 completed without removing the oxide coating formed [58] Field of Search...313/ 188, 109.5, 189, 210, 217, on the electrode surfaces of the structure during the 313/218, 221, 244, 245, 283, 356; 315/167, heating step. The resulting gas discharge device, which 169 R, 169 TV, 260; 340/324 R, 166 EL; may be used for display purposes, has a stable oxide 65/154; 29/25.15, 25.16 coating on electrodes thereof that attenuates display distorting reflections. 156] References Cited 9 Claims, 2 Drawing Figures UNlTED STATES PATENTS 3,465,194 9/1969 l-lall ..313/2l7 X CATHODE GAS DISCHARGE DEVICES AND THE PRODUCT THEREOF BACKGROUND OF THE INVENTION 1 Field of the Invention The present invention pertains to the manufacture of cold cathode gas discharge devices particularly of the type utilized for display purposes.

2. Description of the Prior Art Methods are known in the manufacture of electron tube devices, and particularly in the manufacture of of manufacturing the devices are often removed to preclude contamination and hence faulty operation. Although'providing clean electrode surfaces in the resulting devices, this welded construction technique is laborious, time consuming and hence expensive. Furthermore, such spot-welds are subject to deterioration under the influence of vibration. Additionally, the step of removing the residual oxide coatings is undesirable since it further complicates the manufacturing procedures.

SUMMARY OF THE INVENTION The present invention eliminates the prior art welded electrode construction as well as any oxide cleaning step required in the prior art methods. The present invention utilizes a unitary metal electrode, such as a rod, comprised of a metal having the same coefficient of thermal expansion as the glass through which the electrode is to be sealed. The steps of the present invention include inserting the electrode through a close fitting glass support. The assembly is heated in the presence of oxygen until the glass softens. Pressure is then applied to squeeze the softened glass against the metal electrode. Oxide formed on the surfaces of the metal during the heating step combines with the softened glass to effect the desired seal. The oxide coating formed during the heating step is not only beneficial in effecting a proper glass to metal seal, but it is stable, adherent and does not significantly afiect the operation of the assembled devices. The invention eliminates the welded electrode construction and the oxide cleaning steps of the prior art resulting in a substantially more economical manufacturing process while providing devices superior to those produced by the prior method. a

Additionally, not only does the oxide coating on the electrode surfaces not interfere with the long lived operation of the devices butthe coating provides an additional beneficial result in devices utilized for display purposes. The oxide coating attenuates reflections from the electrode surfaces which reflections have heretofore tended to distort the displayed information.

2 BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view, partially in section, of a cold cathode gas discharge display device constructed in accordance with the process of the present invention; and

FIG. 2 is a magnified view of a portion of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT Although the present invention has applicability in a wide variety of cold cathode gas discharge devices, the invention will be explained in terms of a gas discharge display device utilizing hollow cathodes. Detailed descriptions of such a device may be had in copending US. Pat. application Ser. No. 27,608, filed Apr. 13, 1970, entitled Gas Discharge Display Apparatus Utilizing Hollow Cathode Light Sources, invented by Claude D. Lustig and assigned to the assignee of the present invention. In particular, the invention will be explained in terms of a hollow cathode structure formed of a metal alloy consisting of 49 percent iron and 5 1 percent nickel sealed in a soda-lime glass support. This alloy may be commercially procured from, for example, the Wilbur B. Driver Company as Niron 52. It is known that this alloy and soda-lime glass have substantially the same coefiicient of thermal expansion thereby providing sound glass-to-metal seals over normally encountered temperature ranges.

Referring to FIG. 1, a cold cathode gas discharge display device 10 utilizing hollow cathodes is illustrated.

The structure and operation of the device 10 is explained in detail in said US. Pat. application Ser. No. 27,608 and will be briefly described here for completeness. The display device 10 comprises a glass support 11 having a matrix of apertures formed therethrough. A hollow cathode rod such as the rod 12 is sealed in each of the apertures of the matrix. A transparent dielectric plate 13 having transparent metal anode strips 14 affixed thereto is sealed to the cathode assembly to form a gastight envelope. Conductors 15 for addressing the cathodes in the manner described in said US. Pat. application Ser. No. 27,608 are connected to the cathodes and anodes. The cathode rods, such as the rod 12 are comprised of a metal alloy consisting of 49 percent iron and 51 percent nickel and the support 11 is comprised of soda-lime glass as previously mentioned. It is known that a metal alloy having this composition and soda-lime glass have the same coefiicient of thermal expansion. Thus, as previously explained, the seal effected between the rod 12 and the glass support 11 is structurally sound over the temperature ranges normally encountered. A portion 16 of the device 10 including a hollow cathode rod 20 is illustrated in magnified view in FIG. 2.

Referring to FIG. 2, in which like reference numerals indicate like components with respect to FIG. 1, the cathode rod '20 is sealed in an aperture 21 of the glass support 11. The cathode 20 has a hole 22 disposed therein, the interior surfaces thereof functioning as the cathodic surfaces of the electrode 20 in the manner described in said US. Pat. application Ser. No. 27,608. The cathode rod 20 further includes a rim 23.

The rod 20 is sealed in the aperture 21 by the method of the present invention which comprises the following steps: The metal structure 20 is inserted into the aperture 21 in the glass support 11. The assembled structure is then heated in the presence of oxygen at atemperature sufficient to soften the glass support 11. Since the heating step is performed in the presence of oxygen, oxide is formed on all of the inner and outer surfaces of the cathode 20. For example, oxide is formed on the outer cylindrical surfaces thereof as well as on the inner or cathodic surfaces of the hole 22 and on the l rim 23. Pressure is then applied to the softened glass support 11. The oxide formed on the portion of the outer surface of the rod 20 that is inserted in the aperture 21 combines with the softened glass to effect a gastight seal between the

members

11 and 20. Subsequent to the heating step, the device 10 (FIG. 1) is assembled, as described in said US. Pat. application Ser. No. 27,608 without removing the oxide coating formed on the rim 23 and the cathodic surfaces of the hole 22. The oxide formed as described above has a mat black surface, is of stable composition and is highly adherent to the surfaces of the cathode rod 20. It is to be noted with respect to FIGS. 1 and 2 that the black oxide coating on the cathodic surfaces of the hole 22 and on the rim 23 is depicted by stippling where clarity is enhanced.

It will be appreciated that the heating step in the presence of oxygen may be performed with the device exposed to the atmosphere which provides the oxygen required to effect the glass-to-metal seal. A glass softening temperature found suitable for the heating step with respect to the above-discussed materials is approximately l,0O C.

Display devices of the type illustrated in FIG. 1 have been operated at high current densities for extended periods without any significant change in the operating conditions thereof. Such changes would have been apparent if there had been any significant degradation in gas composition or cathodic surfaces.

From the foregoing, it is appreciated that significant manufacturing economies are realized in practicing the method of the present invention since the step conventionally performed of spot welding electrodes is eliminated and no steps are necessary to remove the residual oxide coating from the cathodic surfaces. These economies are particularly significant with regard to the gas discharge devices of the type discussed above and in said US. Pat. application Ser. No. 27,608 because of the complex contours of the cathodic surfaces of the hollow cathodes.

Additionally, the method of the present invention provides novel display devices whose glowing cathodes generate the display information. These glowing cathodes are uniquely coated with a stable mat black oxide that is effective in attenuating display distorting reflections while not impairing the normal operation of the device.

, It will be appreciated that the invention comprising the use of a single metal piece to provide both the cathodic surface and the glass-metal seal, such metal piece not requiring cleaning to remove oxide depositions, is applicable also-to devices where the glassmetal seal is accomplished at much lower temperatures by the use of a glass frit.

While the invention has been described in its preferred embodiment, it is to be understood that the words which have been used are words of description rather than limitation and that changes may be made within the purview of the appended claims without departing from the true scope and spirit of the invention in its broader aspects.

We claim: 1. In a process for manufacturing cold cathode gas discharge devices comprising the steps of inserting a metal electrode structure into a glass support, said metal and said glass having the same coefiicient of thermal expansion,

heating said support and electrode structure in the presence of oxygen at a softening temperature of said glass to effect a seal therebetween, and a inserting a metal alloy electrode structure into a glass said alloy consisting of approximately 49 percent iron and 51 percent nickel,

said glass having the same coefficient of thermal expansion as said alloy,

heating said support and electrode structure in the presence of oxygen at a softening temperature of said glass to effect a seal therebetween, and

completing said devices without removing the oxide coating formed on the electrode surfaces of said structure during said heating step.

3. In a process for manufacturing cold cathode gas discharge devices comprising the steps of inserting a metal alloy cathode rod through a glass support,

said alloy consisting of approximately 49 percent lime glass support, said alloy consisting of approximately 49 percent iron and 51 percent nickel,

heating said support and cathode rod in the presence of oxygen at a softening temperature of said glass to effect a seal therebetween, and

completing said devices without removing the oxide coating formed on the cathodic surfaces of said structure during said heating step.

5. In a cold cathode gas discharge display device glass support means, and

metal electrode means sealed in said support means,

the electrode surfaces of said electrode means being coated with a non-reflective oxide formed thereon by heating in the presence of oxygen thereby attenuating display distorting reflections from said surfaces.

6. In the device of claim 5 in which said surfaces comprise the cathodic surfaces of said cathode means.

8. In the device of claim 7 in which said cathode means comprises a unitary piece of said alloy, a portion thereof being sealed to said glass and another portion thereof forming said cathodic surfaces.

9. In the device of claim 7 in which said cathode means comprises a rod of said alloy.

Claims

2. In a process for manufacturing cold cathode gas discharge devices comprising thE steps of inserting a metal alloy electrode structure into a glass support, said alloy consisting of approximately 49 percent iron and 51 percent nickel, said glass having the same coefficient of thermal expansion as said alloy, heating said support and electrode structure in the presence of oxygen at a softening temperature of said glass to effect a seal therebetween, and completing said devices without removing the oxide coating formed on the electrode surfaces of said structure during said heating step.
3. In a process for manufacturing cold cathode gas discharge devices comprising the steps of inserting a metal alloy cathode rod through a glass support, said alloy consisting of approximately 49 percent iron and 51 percent nickel, said glass having the same coefficient of thermal expansion as said alloy, heating said support and cathode rod in the presence of oxygen at a softening temperature of said glass to effect a seal therebetween, and completing said devices without removing the oxide coating formed on the cathodic surfaces of said rod during said heating step.
4. In a process for manufacturing cold cathode gas discharge devices comprising the steps of inserting a metal alloy cathode rod through a soda-lime glass support, said alloy consisting of approximately 49 percent iron and 51 percent nickel, heating said support and cathode rod in the presence of oxygen at a softening temperature of said glass to effect a seal therebetween, and completing said devices without removing the oxide coating formed on the cathodic surfaces of said structure during said heating step.
5. In a cold cathode gas discharge display device glass support means, and metal electrode means sealed in said support means, the electrode surfaces of said electrode means being coated with a non-reflective oxide formed thereon by heating in the presence of oxygen thereby attenuating display distorting reflections from said surfaces.
6. In the device of claim 5 in which said metal comprises an alloy consisting of approximately 49 percent iron and 51 percent nickel, said oxide comprises a mat black oxide formed on said surfaces by heating in the presence of oxygen at a softening temperatures of said glass, and said glass has the same coefficient of thermal expansion as said alloy.
7. In the device of claim 6 in which said glass comprises soda-lime glass, said electrode means comprises cathode means, and said surfaces comprise the cathodic surfaces of said cathode means.
8. In the device of claim 7 in which said cathode means comprises a unitary piece of said alloy, a portion thereof being sealed to said glass and another portion thereof forming said cathodic surfaces.
9. In the device of claim 7 in which said cathode means comprises a rod of said alloy.