US3792300A

US3792300A - Cathode ray tube having a conductive metallic coating therein

Info

Publication number: US3792300A
Application number: US00263297A
Authority: US
Inventors: D Benda; D Kerstetter
Original assignee: GTE Sylvania Inc
Current assignee: GTE Sylvania Inc
Priority date: 1972-07-15
Filing date: 1972-06-15
Publication date: 1974-02-12
Anticipated expiration: 1991-02-12
Also published as: US3802757A; DE2333796A1; CA997819A; BE802367A

Abstract

An improved color cathode ray tube of the shadow mask type is provided wherein localized areas of a primary conductive substance are disposed on the interior surface of the envelope funnel and neck portions separately covering the high voltage button and gun assembly contact areas. A substantially continuous secondary reflective coating of gas-sorbtive electrically conductive metallic material, providing advantageous life performance results, is disposed over the back surface of the shadow mask and over the interior surface of the funnel portion to provide a final anode coating effecting a peripheral unipotential field for the tube and electrically connecting the mask-screen area and the aforementioned localized primary coated areas. A thin tertiary film of high-efficiency gas-adsorbing getter material is disposed over at least a portion of the secondary conductive coating material.

Description

United States Patent Benda et al.

[ CATHODE RAY TUBE HAVING A Primary Examiner-James W. Lawrence CONDUCTIVE METALLIC COATING Assistant Examiner-Saxfield Chatmon, Jr. THEREIN Arigriey Aglenti: or;i KNEE-[Norman J. OMalley; Ro-

a a t rc R 75 Inventors: David Benda, Geneva, N.Y.; Donald s 6 re R. Kerstetter, Emporium, Pa.

57 ABS A [73] Assignee: GTE Sylvania Incorporated, Seneca 1 TR CT Falls, Del. An improved color cathode ray tube of the shadow mask t e is rovided wherein localized areas of a ri- [22] Filed: June 1972 mary c giiduc t ive substance are disposed on the inFer- [21] Appl. No.: 263,297 ior surface of the envelope funnel and neck portionsseparately covering the high voltage button and gun assembly contact areas. A substantially continuous [52] Cl 313/85 a y/ 2 0 3 secondary reflective coating of gas-sorbtive electrisl 1 t Cl 6 29/46 cally conductive metallic material, providing advanta- 85. geous life performance results, is disposed over the l 1 e 0 care 1 1 217 back surface of the shadow mask and over the interior surface of the funnel portion to provide a final anode coating effecting a peripheral unipotential field for the [56] References C'ted tube and electrically connecting the mask-screen area UNITED STATES PATENTS and the aforementioned localized] primary coated ar- 2,093,699 9/1937 Varian et a]. 313/85 R eas. A thin tertiary film of high-efficiency gas- 2.532,322 1/1952 Evans t 3/85 R adsorbing getter material is disposed over at least a 3279941 10/1966 Foster at 313/174 X portion of the secondary conductive coating material. 3,432,712 3/1969 Benda 313/181 7 Claims, 2 Drawing Figures ll, 33 H k 35 I I, 3 77 29 X,3| 25 i h F! 1 I r\ r 4 a5 68 I /1 23 s1 g 2 57 I3 83 \v I f' s7 47 4 43 l 45 49 A j 1 CATIIODE RAY TUBE HAVING A CONDUCTIVE METALLIC COATING THEREIN BACKGROUND OF THE INVENTION This invention relates to cathode ray tubes and more particularly to a color cathode ray tube employing a substantially open metallic member positioned adjacent to the screen and having a metallic coating discretely disposed therein to provide a final anode coating effecting a plurality of advantages for improving the life performance of the tube.

As conventionally manufactured, color cathode ray tubes of the type employing a multiple opening metallic member, such as a foraminous shadow mask or grid, positioned adjacent the patterned phosphor screen, usually have an extensive opaque coating of electrically conductive colloidal graphite disposed on the interior surface of the envelope funnel portion. This conductive graphite deposit, commonly referenced as Aquadag, is applied to the funnel portion prior to tube assembly and subsequently provides several functions in the finished tube. First, the funnel covering material, being connected to the terminal anode electrode of the electron gun assembly, provides a continuation of the anode in the form of a final anode coating, whereof a peripheral unipotential field is established to surround the accelerated electron beam as it is projected from the gun toward the screen. The extensive application of the Aquadag coating affords a common means for electrically connecting the high voltage button funnelconnection with the terminal electrode of the electron gun and the mask-screen region of the tube. Further, this internal coating, in conjunction with a conductive coating. applied to the exterior surface of the funnel portion, forms a filter capacitor for the high voltage power supply. Additionally, this conductive internal coating provides shielding for the electron beam or beams and prevents secondary emission charging of the glass of the envelope.

This graphite or Aquadag coating being extensively applied over the internal surface of the funnel portion, sometimes tends to minutely peel or flake thereby releasing deleterious speck-like particles into the interior 'of the finished tube. These contaminating particles are free'to migrate to vulnerable regions of the tube, e.g., the screen area where they may be evidenced as minute but annoying overshadows, or to the foraminous mask region where they may lodge blocking one or more apertures therein, or to the region of the electron gun where the particulate material may cause devastating leakage, arcs or shorts between electrodes. In addition to the loose particle shortcomings, application of the graphite coating to the interior of the funnel requires a separate manufacturing procedure utilizing specialized applicating equipment and labor, and as such adds to the manufacturing costs of the tube.

OBJECTS AND SUMMARY OF THE INVENTION A It is an object of this invention to reduce the aforementioned disadvantages and to provide an improved color cathode ray tube having enhanced operational and life performance characteristics.

A further object is to produce a color cathode ray tube that evidences a minimum of loose particulate material therein.

Another object is to provide a color cathode ray tube having improved efficiency for internal gas cleanup; the structure of which lends itself to expeditious and economical fabrication procedures.

An additional objectis to provide an expeditious and economical method for manufacturing an improved color cathode ray tube.

The foregoing objects are achieved in one aspect of the invention wherein an improved color cathode ray tube of, for example, the shadow mask type, has localized areas of a primary conductive substance disposed on the interior surface of the envelope funnel and neck portions separately covering the high voltage connection and electron gun assembly contact areas. A substantially continuous secondary reflective coating of gas-sorbtive electrically conductive metallic material is applied over the interior surface of the shadow mask and the interior surface of the funnel portion. This secondary coating overlays and electrically connects the aforementioned areas of primary conductive coating and provides the peripheral final anode coating for the tube. A thin tertiary film of a high-efficiency gasadsorbing getter material is disposed over at least a por tion of the final anode coating of conductive secondary material. An expeditious and economical method is provided for fabricating an improved color tube wherein there is a minimum of loose particulate contaminate material.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view of a shadow mask color cathode ray tube utilizing the invention; and

FIG. 2 is a perspective view of one type of material effusing structure.

DESCRIPTION OF THE PREFERRED EMBODIMENT For a better understanding of the-present invention, together with other and further objlects, advantages and capabilities thereof, reference is made to the following disclosure and appended claims in connection with the above description of some of the aspects of the invention.

With reference to the drawings, there is shown in FIG. 1, for example, a shadow-mask type of color cathode ray tube 11 having an envelope 13 integrally comprising a face panel 15, a funnel portion 17, and a neck portion 19. A patterned cathode-luminescent screen 21 of selected electron responsive phosphor materials is formed on the interior surface of the face panel 15. To enhance the screen imagery, a film of aluminum 22 is normally applied over the screen and the adjacent interior surface of the panel, such being accomplished by a vaporization procedure before the panel is attached to the funnel portion 17.

Adjacent to the screen and spaced therefrom is the I of which are shown as mating with compatibly oriented support studs 31 located in the wall or skirt 33 of the face panel member 15. The aforementioned aluminum film' 22 disposed on the interior of the panel also covers the projecting support studs 31 thereby effecting electrical connection between screen 21 and the adjacent shadow mask 23; The apertured member 27 is formed of relatively thin metal such as, for example, low carbon steel material having a thickness in the order of 0.005 to 0.006 of an inch. The multitudinous number of holes or apertures effect a mask transmission that is in the order of about 18 percent at the center which may diminish to about 12 percent at the edge. Thus, the solid web of mask material 35 constitutes about 82 to 88 percent of the area of the apertured member 27.

Disposed within the neck portion 19 of the tube is the electron gun assembly 37 while not fully detailed as to structure, comprises'at least one and usually two or more electron beam generating means. The plural beam convergence means 39, which is terminally oriented on the gun assembly, has a plurality of resilient support and connective means or snubbers 41 that are formed to make contact with the interior of the neck portion 19. The electron gun assembly is further positionally supported by a plurality of conductive pins (of which only four are shown) 43,44, 45, and 46 which traverse and are hermetically sealed in the stemwafer closure member 47. This member, in turn, is integrally sealed to the open end of the neck portion 19. An exhaust tubulation incorporated in the closure member is shown as being hermetically sealed 49 in the completed tube structure. Prior to sealing, this tubulation is connected to a conventional vacuum or gas evacuation system, not shown, which is part of the tube processing procedure.

Disposed on" the interior surface of the funnel and

neck portions

17 and 19 are three discrete localized areas or patches of a primary conductive substance 53, for example, Aquadag or a suitable metallic material such as a .gold, silver, or aluminum substance. One of the discrete areas covers the high voltage button region 55, extending substantially perimetrically therefrom to afford adequate areal contact with a subsequently applied metallic coating superjacently disposed thereover. A second area is disposed in substantially the neck-funnel transition zone 57 of the envelope, in the region immediately forward of the electron gun assembly 37 wherein the support snubbers 41 terminally associated with the gun assembly make electrical contact therewith. This transition-zone area 57 is usually in the shape of a substantially annular band forming a closed onductive loop. A third contact area 59 is disposed on the forward region of the interior surface of the funnel portion 17 adjacent to the periphery of the shadow mask frame 25. A resilient connective means 61 is attached to the mask frame and oriented in a manner to make a firm electrical connection with a portion of the adjacent contact area 59.

A secondary substantially continuous reflective coating 63 ofa gas-sorbtive and electrically conductive metallic material, such as for example, magnesium or magnesium alloy, is extensively and predeterminately disposed over the interior or back surface of the shadow mask 23 and over substantially the whole of the interior surface of the envelope funnel portion 17. This extensive secondary metallic coating, differing in composition from that of the primary conductive substance; provides several advantageous functions. Firstly, the conductive secondary coating overlays and electrically connects the before-described discrete primary coated substantially patch-

like areas

55, 57 and 59, extending therebeyond to cover the glass wall of the funnel and thus provide a continuous final anode coating 60 for the tube. Secondly, this secondary exemplary magnesium coating is evaporatively applied to the interior surface after the cathode ray tube has been exhaust processed. Such deposition provides a marked advantage, as during dispersal the magnesium is especially active in gettering residual oxygen that may be present within the vacuous space of the tube. This beneficial gas-sorbing action, provided by the deposition of the final anode coating, improves tube performance by relieving the gas-sorbing load of the later-applied regular barium containing getter. Thus, a large portion of the regular gettering cpaacity is retained for maximum and longer gas-sorbing activity which is a promoting factor for longer life performance of the tube. Thirdly, the exemplary magnesium, being flashed in the ambient vacuum of the tube, provides a highly reflective mirrorlike coating on the interior surface of the shadow mask, and as such, acts as a heat radiator during tube operation. This reflective characteristic tends to lower the operating temperature of the mask thereby reducing the mask shift effect during tube operation thusly providing an added advantage to overall tube performance.

A secondary material giver or source, 67 from which the secondary gas-sorbing reflective and conductive coating is evaporated, may be in the form of a stainless steel channelized ring or loop. One such giver is shown as attached to the frame 25 of the shadow mask 23 by suitable support means 68 and oriented in a manner to disperse the secondary coating 63 over the interior of the funnel. Depending upon the size and shape of the funnel, two or more of such sources may be utilized to adequately achieve the uniform coverage desired. Additionally, in FIG. 2, there is illustrated a channelized giver" 69 which is oriented, for example, on a support 71 attached to the beam convergence means 39 of the electron gun assembly 37. Being so located, the evaporable material 73, contained in the channel 75, is directed to cover the interior surface of the shadow mask, e.g., the interstitial webbing thereof in particular.

There are instances in the prior art, in particularly monochrome cathode ray tubes, where metallic coatings of materials such as platinum, palladium, or aluminum were disposed on the interior surface of the tube envelope. Such deposition was usually achieved in the envelope per'se by a separate-step evaporization or sputtering procedure prior to tube assembly since specialized high temperature vaporization sources were required. Thus, such metallic coatings, being priorly dispersed on the interior of the envelope and subsequently exposed to atmosphere during tube assembly, did not possess the efficient gas-sorbing and rearreflective characteristics as effected by the invention.

A thin tertiary film 77 of high-efficiency gas-sorbing getter material, such as barium or barium alloy, is disposed as a third layer over at least a portion of the secondary or final anode coating 60. Usually, some of this getter film material 77 also deposits on the interior of the mask, but it also is highly reflective or mirror-like, being evaporated in a vacuum environment. in FIG. 1, a conventional source of getter material 81 is shown positioned on an antenna-type support 83 affixed to the electron gun assembly 37.

A method of fabricating the aforedescribed improved color cathode ray tube comprises a plurality of related steps as ensuingly described.

The patterned cathodoluminescent screen 21 is formed on the interior of the face panel by tech niques familiar to the art, wherein the openings in the spatially positioned shadow mask are utilized to produce the patterned areas of the screen. Usually, the screened panel has a film of aluminum 22 applied interiorly 'thereover by a separate step employing specialized aluminizing equipment embodying a vacuum environment and a high temperature vaporization source.

The three discrete localized areas or

patches

55, 57, 59 of primary conductive substance 53, such as Aquadag, are applied to the aforenoted respective regions of the envelope funnel and neck portions.

The shadow mask structure 23, with at least one giver or secondary material source 67 attached thereto, is spatially positioned within the screened and aluminized panel 15. The panel portion is then peripherally frit sealed, as at 85, to the lip of the funnel portion 17.

Next, the electron gun assembly 37 is inserted into the neck portion 19 of the tube and the supporting closure member 47 is sealed to the open end thereof as at 87. The tube is then heated to substantially degas the envelope l3 and the tube structural elements, e.g., 23 and 37, contained therein. Simultaneously, the tube is evacuated of gases through the exhaust tubulation 48, shown in phantom as extending from the closure member 47. Upon termination of processing the tubulation is hermetically sealed as indicated at 49, which effects complete closure of the envelope 13.

The secondary material source or sources 67 are activated by localized induction heating emanating from suitably energized coils oriented exteriorly of the envelope. This activation effuses the gas-sorbtive electrically conductive magnesium material into the interior of the envelope in a manner to overlay the discrete pri- There is thus provided an improved color cathode ray tube that evidences a minimum of loose particulate material, has improved efficiency for internal gas cleanup, exhibits enhanced operational and life performance characteristics, and one wherein the structure lends itself to expeditious and economical tube fabrication procedures.

While there has been shown and described what are at present considered the preferred embodiments of the invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the scope of the invention as defined by the appended claims.

What is claimed is:

1. An improved color cathode ray tube having an envelope including face panel, funnel and neck portions wherein a patterned cathodoluminescent screen is disposed on the interior surface of the face panel with a metallic member having a multitude of openings therein positioned spatially adjacent thereto, and wherein at least one electron gun is oriented in said neck portion in a manner to beam electrons toward said screen, said improvement comprising:

a primary conductive substance disposed on the interior surface of said funnel and neck portions over at least two discrete localized areas, one of said discrete areas covering at least the high voltage button area inthe funnel portion, and a second of said dis- Crete areas being disposed substantially in the neck-funnel transition zone of said envelope in the region immediately forward of said electron gun assembly wherein the terminal electrode of said gun assembly has associated connective means to make electrical contact therewith;

a secondary substantially uniform and continuous reflective coating of gas-sorbtive and electrically conductive metallic material disposed over the interior surface of said metallic member and substantially the whole of the interior surface of said funnel portion overlaying the discrete areas of primary conductive coating thereon to provide a final anode coating for the tube effecting means for establishing a peripheral unipotential field therein and electrically connecting said screen and metallic member region and said afore-rnentioned first and second discrete primary coated areas; and

a thin tertiary film of high-efficiency gas-sorbing getter material disposed over at least a portion of said final anode coating of gas-sorlbtive electrically conductive secondary material.

2. The cathode ray tube improvement according to claim ll wherein said second discrete area of said primary conductive substance is in the shape of a substantially annular band forming a closed conductive loop.

3. The cathode ray tube improvement according to claim 1 wherein said secondary gas-sorbtive electrically conductive metallic final anode coating material is substantially magnesium.

4. The cathode ray tube improvement according to claim ll wherein a third localized discrete area of said primary conductive substance is disposed on the for ward region of the interior surface of said funnel portion adjacent the periphery of said metallic member whereof connective means associated with said pluralopening metallic member makes electrical contact therewith.

5. The cathode ray tube improvement according to claim ll wherein said primary conductive substance is of a composition differing from that of said secondary gas-sorbtive conductive metallic material.

6. The cathode ray tube improvement according to claim 1 wherein at least one source of said secondary gas-sorbtive conductive metallic final anode coating material is oriented relative to said metallic member.

7. The cathode ray tube improvement according to claim 1 wherein the patterned cathodoluminescent screen formed on the interior surface of said face panel has an aluminum film disposed thereover.

* =l =l l=

Claims

2. The cathode ray tube improvement according to claim 1 wherein said second discrete area of said primary conductive substance is in the shape of a substantially annular band forming a closed conductive loop.
3. The cathode ray tube improvement according to claim 1 wherein said secondary gas-sorbtive electrically conductive metallic final anode coating material is substantially magnesium.
4. The cathode ray tube improvement according to claim 1 wherein a third localized discrete area of said primary conductive substance is disposed on the forward region of the interior surface of said funnel portion adjacent the periphery of said metallic member whereof connective means associated with said plural-opening metallic member makes electrical contact therewith.
5. The cathode ray tube improvement according to claim 1 wherein said primary conductive substance is of a composition differing from that of said secondary gas-sorbtive conductive metallic material.
6. The cathode ray tube improvement according to claim 1 wherein at least one source of said secondary gas-sorbtive conductive metallic final anode coating material is oriented relative to said metallic member.
7. The cathode ray tube improvement according to claim 1 wherein the patterned cathodoluminescent screen formed on the interior surface of said face panel has an aluminum film disposed thereover.