US3037834A - Electron discharge device - Google Patents

Description

June 1952 E. A. LEDERER ETAL 3,037,834

ELECTRON DISCHARGE DEVICE Filed July 30, 1956 WITNESSES I lNVENTOR- Ernest A. Lederer 8 M Carl F. Miller.

United States atent 3,037,834 Patented June 5, 1962 ice 3,037,834 ELECTRON DISCHARGE DEVICE Ernest A. Lederer, Essex Fells, N.J., and Carl F. Miller,

Bath, N.Y., assignors to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Filed July 30, 1956, Ser. No. 600,781 4 Claims. (Cl. 316-19) This invention relates to electron discharge devices and, more particularly, to an electron discharge device suitable for use with a sealing material which cannot be subjected to high temperatures.

Organic resinous (plastic) seals for electron discharge devices have been thought to be desirable for certain uses for many years. One difliculty has been that suitable plastic materials may not be heated above comparatively low temperatures without flowing or decomposing. This has made it necessary to keep the bake-out temperature elow the flow point of the plastic material. However, in order to free the glass or metal envelope of the electron discharge device of most of its absorbed gas and moisture within a reasonable time, it is necessary to bake the device, while maintaining a vacuum, at a temperature on the order of 300500 C. No suitable plastics are known that can withstand such temperature-s.

Even the new materials such as epoxy-resins or silicone resins cannot be heated above 20025() C. Since degassing of glass or metal would take hundreds of hours at such relatively low temperatures, commercial utilization of plastic seals has not been found to be feasible.

In general our invention involves keeping the sealing material and possibly small adjacent portions of the envelope at a temperature consistent with the properties of the sealing material while heating the remainder of the envelope to the extent desired. Thus the temperature limitations of plastic seals are eliminated and modern mass production methods may be utilized.

It is an object of this invention to provide an improved electron discharge device suitable for use with an organic resinous sealing material.

It is another object to provide an improved method of sealing an electron discharge device with an organic resinous sealing material.

It is a further object to provide an improved electron discharge device suitable for use with an organic resinous scaling material, said electron discharge device having a metallic flange member permanently positioned in the seal itself.

It is an additional object to provide an improved method of sealing an electron discharge device with an organic resinous sealing material, said method utilizing a metallic flange member as a cooling or heating agency.

These and other objects of our invention will be apparent from the following description taken in accordance with the accompanying drawing, throughout which like reference characters indicate like parts, which drawing forms a part of this application and in which:

FIGURE 1 is a top view of a cathode ray tube, partly in section, according to one embodiment of our invention;

FIG. 2 is a sectional view of part of the seal portion of FIG. 1 showing the cooling member;

FIG. 3 is a perspective view of an electron discharge device according to another embodiment of our invention;

FIG. 4 is a perspective view of a metallic flange member similar to that shown in FIG. 3; and

FIG. 5 is a sectional view of a part of the seal portion of an electron discharge device and the cooling agency shown during the sealing process according to still another embodiment of our invention.

In FIG. 1 there is shown a cathode ray tube including an envelope member 11, including a face panel envelope portion 13 and a flared envelope portion 15. A metallic flange member 17 is positioned in the seal area between the sealing portions 21 of the face panel envelope portion 13 and the flared envelope portion 15. The metallic flange member 17 includes a flange member projecting portion 19. In this and other embodiments the envelope member 11 may be made of suitable glass or metal material.

In FIG. 2 there is shown a part of the seal portion of FIG. 1 including the face panel envelope portion *13, the flared envelope portion 15 and the sealing portions 21 of the above envelope portion. The metallic flange member has a flange member projecting portion 19 and is positioned in the seal portion. Sealing material 39 is positioned between the flange member 17 and the sealing portions 21 of the envelope member. In physical contact with the flange member projecting portion 19 there is shown a flange cooling member 41 or heat-sink including a clamp member 43 and a screw member 45. The flange cooling member 41 may, if desired, be provided with suitable coolant passages 47.

During the manufacture of a cathode ray tube or other electron discharge device, the ealing material, which will be cscribed below, may be applied to the sealing portions 21 of the envelope portions 13 and 15, or to the metallic flange member 17. The metallic flange member 17 is then inserted between the face panel envelope portion 13 and the flared envelope portion 15. The seal is then made by applying heat and pressure. During the bakeout process, in which the envelope member 11 may be heated to a temperature of from 300 to 500 C., the seal material is cooled by cooling the metallic flange member 17. The metallic flange member 17 may be cooled by placing the projecting portion 1 in contact with a cooling agency such as a water cooled member 41 shown in FIG. 2. Other methods or" cooling include air blasts or contact with any number of suitable cooling members which themselves may be cooled by air or fluid cooling. The sealing process may be accomplished very cheaply in a furnace containing an inert atmosphere, such as argon, in order to prevent oxidation of the interior portions of the electron discharge device. During this bakeout process, of course, the interior of the electron discharge device is under a vacuum.

Also, if the flared portion 15 of the envelope is made from metal a distinct and separate metal flange 17 may be superfluous. In this case the seal-portion of the metal envelope may be placed in contact to the heat-sink or cooling member 41.

In FIG. 3 there is shown a perspective view of an electron discharge device, in this case a triode, including an envelope member 23, envelope portions 25 and sealing portions 27. A metallic flange member 29, including a flange member projecting portion 31, is positioned in the seal. Also shown are heater lead-in wires 33, electrode lead wires 35 and a tipped-off exhaust tabulation 37.

In FIG. 4 there is shown a perspective view of a flange member 29 similar to that shown in FIG. 3. This metallic flange member 29 includes heater lead grooves 49, electrode lead grooves 53 and an exhaust tabulation groove 51. Also shown are positioning members 55, a cleat type spacer member 57 and notch type positioning members 59.

It is possible that if the lead-in wires are in direct contact with a plastic or resinous seal material, overheating of the lead wires during use would result in an air leak through the resinous seal material. Also, in the utilization of the metallic flange member 29 shown in FIGS. 3 and 4, there may be actual contact between the lead-in wires and the metallic flange member 29 or, if not actual contact, there may be a capacitance between the lead-in wires and the metallic flange member 29. Therefore, it

may be desirable to use pie-beaded lead members to avoid direct contact between the metal flange member 29 and the lead members, and also to avoid the possibility of air leaks through the resinous seal material. Prebeaded lead wires may be made by enclosing a portion of an ordinary lead wire in a glass sleeve and may be made on an automatic machine. When these pre-heated lead wires are utilized, the heater lead grooves and the electrode lead grooves should be made somewhat larger than normally would be used. These larger grooves are shown in FIG. 4.

The flange members 29 and 17 should be made of a material having a high heat conductivity, for example, aluminum, copper, silver or molybdenum.

In some cases, it may be desirable not to have a metallic flange member permanently positioned in the seal portion. In FIG. there is shown an embodiment of our invention in which the metallic flange member is not a permanent part of the seal portion, but the sealing material is still cooled adequately without setting up a large thermal gradient in the glass which would lead to strains and cracking. The sealing material 39 is placed between the sealing portions 21 of the envelope portions 28 and a surplus amount of sealing material is positioned on the outside of the seal portion. A metallic flange member 61 is placed in intimate contact with the surplus sealing material and the flange member projecting portion 63 is cooled by a suitable flange cooling member 67 including flange member contact portions 65. After the electron discharge device is sealed, the metallic flange member 61 and the surplus sealing material may be removed.

Among suitable organic resinous sealing materials are those known as epoxy resins. These epoxy resins are glycidyl polyethers and may be prepared by reacting predetermined amounts of at least one polyhydric phenol and at least one epihalohydrin in an alkaline medium. Phenols which are suitable for use in preparing such resinous polymeric epoxides include those which contain at least two phenolic hydroxy groups per molecule. Polynuclear phenols which have been found to be particularly suitable include those wherein the phenol nuclei are joined by carbon bridges, such for example as 4,4'-dihydroxydiphenyldimethyl-methane (referred to hereinafter as bisphenol A) and 4,4-dihydroxy-diphenyl-methane. In admixture with the named polynuclear phenols, use also may be made of those polynuclear phenols wherein the phenol nuclei are joined by sulfur bridges such, for example, as 4,4'-dihydroxy-diphenyl-sulfone.

While it is preferred to use epichlorohydrin as the epihalohydrin in the preparation of the resinous polymeric epoxide starting materials of the present invention, homologues thereof, for example, epibromohydrin and the like also may be used advantageously.

In the preparation of the resinous polymeric epoxides, aqueous alkali is employed to combine with the halogen of the epihalohydrin reactant. The amount of alkali employed should be substantially equivalent to the amount of halogen present and preferably should be employed in an amount somewhat in excess thereof. Aqueous mixtures of alkali metal hydroxides, such as potassium hydroxide and lithium hydroxide, may be employed although it is preferred to use sodium hydroxide since it is relatively inexpensive.

The resinous polymeric epoxide, or glycidyl polyether of a dihydric phenol, suitable for use in this invention has a 1,2-epoxy equivalency greater than 1.0. By epoxy equivalency reference is made to the average number of 1,2-epoxy groups contained in the average molecule of the glycidyl ether. Owing to the method of preparation of the glycidyl polyothers and the fact that they are ordinarily a mixture of if deposited in suflicient thickness,

chemical compounds having somewhat different molecular weights and contain some compounds wherein the terminal glycidyl radicals are ian hydrated form the epoxy equivalency of the product is not necessarily the integer 2.0. However, in all cases it is a value greater than 1.0. The 1,2epoxy equivalency of the polyethers is thus a value between 1.0 and 2.0.

Resinous polymeric epoxides or glycidyl polyethers suitable for use in accordance with this invention may be prepared by admixing and reacting from one to two mol proportions of epihalohydrin, preferably epichlorohydrin, with about one mol proportion of bis-phenol A in the presence of at least a stoichiometric excess of alkali based on the amount of halogen.

The epoxy resins may be applied to the metallic flange member or the sealing portions of the envelope in the form of a powder or paste which softens upon heating.

Silicone resins have also been found to be suitable sealing materials. In addition, other organic plastic or resinous materials exhibiting suitable characteristics may be utilized.

During the'baking of the electron discharge device, the cooling of the metallic flange member may also cool a narrow region of the adjacent envelope portions of the electron discharge device which portions will not be sufficiently degassed. As a rule, these portions are sufiiciently small that the ordinary getter of the electron discharge device will absorb any evolved gas. However, if it is felt that this moisture film will not be sufiiciently removed it may be removed by bombardment by charged particles such as electrons or ions. In order to aid in removing moisture and accumulated gases it may be desirable to coat the inside of the envelope member with a suitable metallic layer. Preferably, this layer should I exhibit an afiinity for water vapor so that the moisture may be absorbed and removed by chemical combination. It may also be desirable to coat the portions of the sealing material itself so that no decomposition of the sealing material occurs due to particle bombardment.

This protective metal film may be evaporated at a lower temperature than the maximum envelope temperatures reached in the degassing processes. Suitable materials which react readily with water but not with resinous seal materials, exhibit good electrical conductivity, so as to protect the plastic material from decomposition by electron or ion bombardment, and have a desirable low vapor pressure include magnesium, calcium, lithium, zirconium, hafnium, titanium, aluminum, zinc, manganese and vanadium. Such a protective metallic film may be electrically connected to the cathode or to another grounded electrode.

The hydrogen removed in the performance of the previous step may be removed by a hydrogen removing getter material which may be evaporated within the envelope after it has been sealed and tipped off. Suitable hydrogen getter materials include beryllium, thorium, cerium, lanthanum, tantalum, colurnbium, and zirconium. Of course, the protective metallic film and the hydrogen removing getters are not limited to the above materials.

We have found that by utilizing the method shown in FIG. 5, it is possible to maintain a seal temperature of 200 C. while the adjacent glass envelope portions reached a temperature of 425 C. Cathode ray tubes using this process have met suitable emission and life tests. If the invention disclosed in this application is utilized in the manufacture of shadow mask color television tubes, the face panel may be joined to the flared envelope portion at a comparatively low temperature without subjecting the shadow mask to the rigorous strain when a molten glass-to-glass or a molten glass-to-metal seal is made.

Since the temperatures reached during the curing cycle of the epoxy resin materials and the temperature reached during the bake out process are approximately the same,

it is feasible to perform both curing and bake out during one heating cycle.

The flange cooling members 41 or 67 or other similar cooling means may be continuous or in several sections and, of course, may be used repeatedly or, if desired, may be an integral part of a suitable exhaust machine. Also, if desired, the interior projection portion 26 of the metallic flange member 29 may be utilized to support getters within the envelope or may obviate the use of a second anode contact in a cathode ray tube. After the electron discharge device is completed, the metallic flange member 17 or 29 may be closely trimmed to conform to the dimensions of the envelope member or, if desired, it may be left full size and be used to cool the seal portion during actual operation of the electron dis charge device.

In a 21 cathode ray tube dimensions of the metallic flange member 17 may be approximately 1%" wide and 0.020 thick. It is obvious, of course, that these dimensions may be modified in many Ways. This invention may also be utilized with other low melting seal materials such as suitable glass solders.

While the present invention has been shown in a few forms only, it will be obvious to those skilled in the art that it is not so limited'but is susceptible of various changes and modifications without departing from the spirit and scope thereof.

,We claim as our invention:

1. A method of exhausting an electron discharge device, said electron discharge device having an envelope member comprising at least two envelope portions, said envelope portions having sealing portions, said method including the steps of coating at least one side of a heat conductive metallic flange member with a sealing material which cannot withstand subsequent high temperature degassing of said device, placing said metallic flange member adjacent said sealing portions so that said sealing material separates said flange member and said envelope portions, sealing said envelope portions together, and then heating parts of said envelope portions to degas said device while artificially cooling said metallic flange member during at least part of said heating step to prevent damage to the seal between said envelope portions.

2. A method of sealing an electron discharge device, said electron discharge device having an envelope member comprising at least two envelope portions, said envelope portions having sealing portions, said method including the steps of placing a heat conductive metallic flange member between said sealing portions, placing a sealing material so that said sealing material is between said metallic flange member and said sealing portions, heating said sealing portions to a first temperature to seal said envelope portions together, heating parts of said envelope portion to a second temperature higher than said first temperature and removing heat from said metallic flange member during at least part of said heating step to maintain said sealing portions at a temperature less than said first temperature.

3. A method of manufacturing an electron discharge device, said electron discharge device having an envelope member comprising at least two envelope portions, said envelope portions having sealing portions, said method including the steps of placing a heat conductive metallic flange member between said sealing portions, said metallic flange member having a portion projecting outwardly from said envelope member, placing a sealing material so that said sealing material is between said metallic flange member and said sealing portion, sealing said envelope portions together, heating parts of said envelope portions to exhaust said parts and artificially cooling said projecting portion of said metallic flange member during at least part of said heating step.

4. A method of manufacturing an electron discharge device, said electron discharge device having an envelope member comprising at least two envelope portions, said envelope portions having sealing portions, said method including the steps of placing a heat conductive metallic flange member between said sealing portions, said meta lic flange member having a portion projecting outwardly from said envelope member, placing an organic resinous sealing material so that said organic resinous sealing material is between said metallic flange member and said sealing portion, heating said sealing portions to seal said envelope portion together, heating parts of said envelope portions to exhaust said heated parts and artificially cooling said projecting portion of said metallic flange member during at least part of said exhaust heating step.

References Cited in the file of this patent UNITED STATES PATENTS 1,873,776 McNeil et a1 Aug. 23, 1932 2,132,783 Goldmark Oct. 11, 1938 2,167,431 Bowie n July 25, 1939 2,178,826 Bowie Nov. 7, 1939 2,219,574 Fraenckel Oct. 29, 1940 2,232,098 Deichman Feb. 18, 1941 2,629,093 Pask et a1. Feb. 17, 1953 2,683,937 Hager July 13, 1954 2,691,457 Longacre Oct. 12, 1954 2,709,147 Ziegler May 24, 1955 2,723,044 Bar asch Nov. 8, 1955 2,753,073 Faulkner July 3, 1956 2,756,892 Bleuze July 31, 1956 2,920,785 Veres Ian. 12, 1960 2,925,189 Martin Feb. 16, 1960 FOREIGN PATENTS 688,121 Great Britain Feb. 25, 1953 OTHER REFERENCES Brown: Abstract of application, Serial Number

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