US3802757A

US3802757A - Method of fabricating a cathode ray tube having a conductive metallic coating therein

Info

Publication number: US3802757A
Application number: US00393931A
Authority: US
Inventors: D Benda; D Kerstetter
Original assignee: Hayden Trans-Cooler Inc
Current assignee: Hayden Trans-Cooler Inc
Priority date: 1972-07-15
Filing date: 1973-09-04
Publication date: 1974-04-09
Anticipated expiration: 1991-04-09
Also published as: BE802367A; DE2333796A1; US3792300A; CA997819A

Abstract

A method of fabricating 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 gassorbtive electrically conductive metallic material, providing advantagesous 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

[111 3,802,757 Apr. 9, 1974 United States Patent U91 Benda et al.

Primary Examiner Roy Lake METHOD OF FABRICATING A CATHODE Assistant Examiner.l. W. Davie Attorney, Agent, or Firm-Norman J. O'Malley; Frederick l-l. Rinn; Cyril A. Krenzer R. Kerstetter, Emporium, Pa.

' ABSTRACT, I

A method of fabricating an improved color cathode [73] Assignee: Hayden Trans-Cooler, Inc. Corona,

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 gassorbtive electrically conductive metallic material, pro- .mm W M 1 .m o C .S mm M FA D U NH NH 22 6 5 viding advantagesous life performance results, is disposed over the back surface of the shadow mask and 316/10 [51] Int. HOlj 9/38 316/3 ,'4, 5, 6, 7, 8, 9,

over the interior surface of the-funnel portion to pro- Field 'of vide a final. anode coating effecting a peripheral uni potential field for the tube and electric entioned localized primary coated areas. A thin tertia efficiency gas- -316/10, 11, 12, 14, 17, 18, 19, 20, 25; 313/64 ally connecting themask-screen area and the aforem [56] References Cited UNITED STATES PATENTS ry film of highadsorbing getter material is disposed Benda.........

over at least a portion'ofthe secondary conductive coating material.

3 Claims, 2 Drawing Figures METHOD OF FABRICATING A CATHODE RAY TUBE HAVING A CONDUCTIVE METALLIC COATING THEREIN CROSS-REFERENCE TO RELATED APPLICATION BACKGROUND OF THE INVENTION This invention relates to cathode ray tubes and more particularly to a method of fabricating 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 afinal 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 tinished 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 wheere 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 1 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 It is an object of this invention to reduce the aforementioned disadvantages and to provide a method of fabricating an improved color cathode ray tube having enhanced operational and life performance characteristics.

A further objects is to provide a method of fabricating a color cathode ray tube that evidences a minimum of loose particulate material therein.

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

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

The foregoing objects are achieved in one aspect of the invention wherein a method is provided for fabricating an improved color cathode ray tube of, for example, the shadow mask type, having localized areas of a primary conductive substance disposed on the interior surface of the envelope funnel and neck portions in a manner to separately cover 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 interiorsurfaceof 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-efficienct gasadsorbing' getter material is disposed over at least a portion 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 coritaminate material.

BRIEF-DESCRIPTION OF THE DRAWINGS 7 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 objects, 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 l3 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 thepanel is attached to the funnel portion 17 Adjacent to the screen and spaced therefrom is the foraminous shadow mask structure 23 which is a metallic member having a multitude of openings'therein. The

described shadow mask structure; per se, is not to be considered limiting, as related structures, intended to be within the scope of the invention, include other multiple opening grid-like constructions that are similarly oriented relative tothe screen. As illustrated, the shadow mask 23 comprisesa supporting frame 25 to which the substantially domed apertured member 27 is suitably attached. Peripherally integrated to the mask frame 25 are a plurality of positioning means 29, two 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 electricalconnection 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 orderof 0.005 to 0.006 of an inch. The multitudinous number of holes or apertures effect a mask transmismake a firm electrical connection with a portion of the adjacent contact area 59. v

A secondary substantially continuous reflective coating 63 of a 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

sion that is in the order of about 18 percent at the cen- Thus, the solid web of inask material 35 constitutes about 82 to 88 percent of the area of the apertured member 27.- v

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 isterminally oriented on-the gun assembly, has a plurality of resilient support and connective means or snubbers 41 that are ter which may diminish to about 12 percent at the edge.

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 nected 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 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 conductive-loop. A third contact area 59'is disposed on 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 emplary magnesium, being flashed in the ambient vacuum of the tube, provides a highly reflective mirror-like 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 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 ensuingly described. I

The patterned cathodoluminescent screen 21 is formed on the interior of the face panel 15 by techniques familiarto the art, wherein the openings in the spatially positioned shadow mask are utilized to produce the patterned areas of the screen. Usually, the

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. I 7

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 13 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 inphantom 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 primary

coated areas

55, 57 and 59 and provide the substantially uniform final anode coating 60 for the tube. This is followed by activating the source of highefficiency barium gettering material 81, by induction heating means, to dispose the thin tertiary gas-sorbing film over at least a portion of the final anode coating.

There is thus provided an expeditious and economical method of fabricating an improved color cathode ray tube that evidences a minimum of loose particulate material, has improved efficiency for internal gas cleanup, and exhibits enhanced operational and life performance characteristics.

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. A method of fabricating an improved color cathode ray tube having an envelope including a face panel,

funnel and neck portions and a multiple opening metal lic member spatially related to said face panel portion, said tube having therein at least one electron gun assembly, at least one effusive source of a gas-sorbtive conductive metallic material and at least one source of a high-efficiency gettering material, said method comprising the steps of:

forming a patterned cathodoluminescent screen on the interior surface of said face panel according to the multiple openings of the metallic member spatially positionedrelative thereto; applying a primary conductive substance on the interior surface of said funnel and neck portions over at least two discrete localized areas, one of said discrete areas coveringthe high voltage button area in said funnel portion, and a second of said discrete areas being disposed substantially in the neckfunnel transition zones of said envelope;

sealing said screened panel with said multiple open-' ing metallic member spatially positioned therein to said funnel portion, said metallic member having'at least one source of evaporable conductive metal positioned thereon; Y

inserting said electron gun assembly supported by a closure member into the open end of said neck portion, the terminal electrode of said gun assembly having associated connective means oriented to make electrical contact with-said second discrete area;

sealing said closure member to said neck portion;

heating said tube to substantially degas the envelope and the tube structural elements contained therein;

substantially evacuating said tube of said gases through an exhaust tubulation in said closure member;

sealing said tubulation to effect a hermetic'seal for said substantially evacuated envelope;

activating said source of gas-sorbtive electrically conductive secondary metallic material to dispose a substantially continuous reflective coating of an electrically conductive metallic materialover the interior surface of said multiple opening metallic member and substantially the whole of the interior surface of said funnel portion overlaying the discrete areas of primary conductive substance thereon to provide a final anode coating for the tube effecting means for establishing a peripheral unipotential field therein and electrically connecting said mask-screen area and said aforementioned first and second discrete primary coated areas; and

activating said source of high-efficiency gettering material to dispose a thin tertiary gas-sorbing film over at least a portion of said final anode coating electrically conductive secondary material. 2. The method of fabricating an improved color cathode ray tube according to claim 1 wherein the activation of said source of the secondary reflective gasdary reflective gas-sorbtive electrically conductive metallic final anode coating material issubstantially magnesium, and wherein said high-efficiency getter material is substantially barium.

Claims

2. The method of fabricating an improved color cathode ray tube according to claim 1 wherein the activation of said source of the secondary reflective gas-sorbtive electrically conductive metallic final anode coating material is accomplished by localized induction heating.
3. The method of fabricating an improved color cathode ray tube according to claim 1 wherein the secondary reflective gas-sorbtive electrically conductive metallic final anode coating material is substantially magnesium, and wherein said high-efficiency getter material is substantially barium.