Shadow mask for color CRT

Details Shadow mask for color CRT Shadow mask for color CRT

1998-06-22

2000-06-06

Patel, J. P.

Electric lamp and discharge devices

Cathode ray tube

Shadow mask, support or shield

313403, H01J 2980

Patent

active

060722703

ABSTRACT:
In a shadow mask employed as a color selection electrode in a multi-electron beam color cathode ray tube (CRT), the surface area of the mask is reduced by increasing the length of the individual elongated beam passing apertures, or slots, while reducing the ratio of the width of the bridge portion of the mask between adjacent apertures to the length of the aperture. Increasing the length of the apertures while reducing the ratio of bridge width to aperture length reduces the surface area of the mask upon which energetic electrons are incident resulting in a corresponding reduction in thermal deformation, or doming, of the shadow mask. Reduction in shadow mask doming results in reduced landing shift of the electron beams incident on phosphor elements disposed on the inner surface of the CRT's display screen for improved video image brightness and color purity. More specifically, in a shadow mask having a thickness in the range of 0.12-0.18 mm with slotted apertures, the length of the slots is in the range of 0.90-10.00 mm and the ratio of bridge width to slot length is in the range of 0.001-0.110. With this invention, electron beam transmission through the shadow mask can be increased by as much as 22% resulting in a reduction in beam landing shift error by as much as 20 .mu.m. Video image brightness is increased by as much as 17% and the color purity adjustment margin is increased to over 10 .mu.m in, for example, a color CRT with a 20 inch display screen.

REFERENCES:
patent: 3735190 (1973-05-01), Say
patent: 4300069 (1981-11-01), Nolan
patent: 5072150 (1991-12-01), Lee
patent: 5126624 (1992-06-01), Ji
patent: 5210459 (1993-05-01), Lee
patent: 5534746 (1996-07-01), Marks et al.

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