US3689792A

US3689792A - Aluminum electron shield coated with powder of one of iron, copper, nickel and cobalt

Info

Publication number: US3689792A
Application number: US84631A
Authority: US
Inventors: Masayoshi Ezawa
Original assignee: Hitachi Ltd
Current assignee: Hitachi Ltd
Priority date: 1969-10-31
Filing date: 1970-10-28
Publication date: 1972-09-05
Anticipated expiration: 1989-09-05

Abstract

An improved electron shield for color picture tubes provided in the space between a supporting section of a color selective electrode, such as a shadow mask, and a gas-tight vessel to prevent unnecessary electrons from bombarding the phosphor screen. The material used for the shield is a surface-roughened aluminum sheet with metal powder not larger than 1 Mu in grain diameter deposited in an alloy-like state on one side of an aluminum sheet as a base material. Thus, both the effective area and the thermal radiation of the electron shield are made large, whereby the temperature rise in the shadow mask is reduced to prevent chromatic aberration.

Description

I United States Patent Ezawa 1 Sept. 5, 1972 [54] ALUMINUM ELECTRON SHIELD 2,806,165 9/1957 Law ..313/92 B COATED WITH POWDER OF ONE OF 3,392,297 7/1968 Schwartz ..313/92 B IRON, COPPER, NICKEL AND COBALT 3,404,303 10/1968 Levin ..313/85 S [72] inventor: Masayoshl Ezawa, Mobara, Japan Primary Examiner Robert Sega] [73] Assignee: Hitachi, Ltd., Tokyo, Japan Attomey-Craig and Antonelli [22] Filed: Oct. 28, 1970 [57] ABSTRACT 2 Appl' 84631 An improved electron shield for colorpicture tubes provided in the space between a supporting section of [30] Foreign Application Priority Data a color selective electrode, such as a shadow mask,

and a gas-tight vessel to prevent unnecessary electrons Oct. 31, 1969 Japan ..44/102932 from bombarding the phosphor screen The material d for the shield is a surface-roughened aluminum [52] US. Cl ..313/85 S 313/41 use 51] Int. Cl ..H0lj 29/06, HOlj 31 20, H01 61/52 F f mt F than 1 9 [58] Field of Search 313/85 S 92 B 41 diameter deposited in an alloy-like state on one side of an aluminum sheet as a base material. Thus, both the effective area and the thermal radiation of the elec- [56 "9" cued tron shield are made large, whereby the temperature UNITED STATES PATENTS rise in the shadow mask is reduced to prevent chro- 2,013,419 9/1935 Moran ..313/41 mm aber'amn' 2,491,284 12/1949 Sears ...2 9/198 1 Claim, 2 Drawing Figures 7 INUMELECTKQ SHI CO W H POWDER OF ONE OF IRON, COPPER, NICgEL AND COBALT BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to improvements in color picture tubes, and more particularly to improvements in an electron shield for such tubes.

2. Description of the Prior Art It has heretofore been common practice that an electron shield for a color picture tube is formed of a metal sheet or foil having glossy surfaces, such as an aluminum sheet or foil. With the prior art electron shield, however, electrons colliding with the glossy surface are reflected. As a result of this, various problems are caused such that the proportion of thermal expansion of the shadow mask is increased to bring-about chromatic aberration and the reflected electrons which pass through apertures in the shadow mask excite the phosphor screen to emit undesired light.

SUMMARY or THE INVENTION It is accordingly an object of this invention to provide a color picture tube of an improved construction, which is free from the various disadvantages mentioned above.

Another object of this invention is to provide a color picture tube in which the effective area as well as the thermal radiation of an electron shield is made large, so that a color selective electrode is not affected by unnecessary electrons.

In accordance with the invention, there is provided a color picture tube comprising a gas-tight vessel, an electron gun disposed in the gas-tight vessel, a phosphor screen emitting colors upon impingement of electron beams thereon, and an electron shield preventing unnecessary electrons from impinging on the phosphor screen, characterized in that the electron shield is constructed of a surface-roughened aluminum sheet having a metal powder formed in an alloy-like state on a surface of the aluminum sheet, one or more kinds of metal powder of iron, copper, nickel, cobalt and the like, which are l p, or smaller in particle size.

Further objects, features and advantages of this invention will become obvious from the detailed explanation given hereinbelow with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a front view, partly broken away, showing a color picture tube embodying this invention.

FIG. 2 is an enlarged view of pertinent portions in FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIG. 1, numeral 1 designates a gastight vessel, 2 an electron gun, 3 a phosphor screen, 4 a color selective electrode such as a shadow mask disposed in close proximity to the phosphor screen 3, 5 a supporting frame for the shadow mask 4, and 6 an electron shield. Details of one form of the electron shield 6 are shown in FIG. 2. More specifically, the shield element 6 uses an aluminum sheet as its base material. On one side of the aluminum sheet is stuck at least one kind of metal powder of iron, copper, nickel, cobalt, etc. in the form of fine grains not larger in particle size than 1 b. The metal powder adhering on the aluminum sheet is baked at a temperature of approximately 550 to 650 C in a hydrogen furnace. Then, the metal powder is deposited like an alloy on the surface of the aluminum sheet. Thus, a surface-roughened aluminum sheet is formed. This is shaped for use into a predetermined configuration. In assemblage, the roughened surface 6a is brought to the side facing the electron gun 2, while the other surface 6b is secured to the supporting frame 5 by any suitable means such as welding or screw clamping. The space 7 between the supporting frame 5 and the envelope 1 is thus shielded.

There will now be explained a concrete example of the method of manufacturing the surface-roughened aluminum sheet for use in the electron shield for color picture tribes according to this invention. v

To about 63 gof nitrocellulose, ml of diethyl oxalate and 680 ml of butyl acetate are added. This mixture is subjected to rolling todissolve the nitrocellulose. To the rolled mixture are then added about 100 ml of rape oil and 330 g of iron powder having a grain diameter of .l p. or smaller, respectively, and these are again subjected to rolling. Thereafter, the material thus twice rolled in applied onto an aluminum sheet. In the next.step, the applied material is dried with eg an ultrared lamp. Finally, the aluminum sheet with the dried material thereon is heated in a hydrogen furnace at about 600C for 5 minutes to thereby finish the manufacture.

The surface-roughened aluminum sheet thus formed is shaped into a desired configuration to obtain the electron shield for a color picture tube.

As described above, the color picture tube according to the invention has its electron shield constructed of a surface-roughened aluminum sheet. Accordingly, the effective area as well as the thermal radiation of the electron shield may be increased, since that surface of the shield element on which unnecessary electrons are bombard becomes a colored and roughened one. It is therefore possible to reduce the temperature rise in the shadow mask and to make its thermal expansion smaller. In addition, the color picture tube is advantageous from the viewpoint of color purity. It is so excellent in practical use.

I claim:

1. A color picture tube comprising a gas-tight vessel, an electron gun disposed in said gas-tight vessel for generating a plurality of electron beams, a color phosphor screen disposed in said envelope opposite said electron gun for emitting colors upon bombardment by said electron beams, a shadow mask electrode mounted in said envelope adjacent said phosphor screen so as to form an annular gap with said envelope, and an electron shield secured to a supporting section of said color selective electrode for shielding the entire annular gap between said supporting section and said gas-tight vessel thereby preventing bombardment of unnecessary electrons onto said phosphor screen, wherein said electron shield is formed of an aluminum sheet having a roughened surface layer arranged on the side facing said electron gun, and wherein said surfaceroughened aluminum sheet comprises an aluminum sheet and powder of at least one metal selected from the group consisting of iron, copper, nickel and cobalt, said powder being deposited on at least the surface of said aluminum sheet facing said electron gun and not exceeding 1 p. in particle size. 5

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