Display tube having a display window with an interference filter

Details Display tube having a display window with an interference filter Display tube having a display window with an interference filter

1985-06-10

1987-03-03

Moore, David K.

Electric lamp and discharge devices

Cathode ray tube

Screen

350 16, 358253, H01J 2928, H01J 2989

Patent

active

046478124

ABSTRACT:
A display tube comprising in an evacuated envelope (1) a display screen (7) provided on the inside of a display window (2) in the wall of the envelope (1), which display screen (7) comprises luminescent material (13), and a multilayer interference filter (12) is provided between this material and the display window and compises a number of layers (HL) which alternately are manufactured from a material having a high (H) and a material having a low (L) refractive index. If the filter is composed substantially of 14 to 30 layers, each having an optical thickness nd, wherein n is the refractive index of the material and d is the thickness, which optical thickness is between 0.2 .lambda..sub.f and 0.3 .lambda..sub.f and preferably between 0.23 .lambda..sub.f and 0.27 .lambda..sub.f, wherein .lambda..sub.f is equal to p x .lambda., wherein .lambda. is the desired central wavelength which is selected from the spectrum emitted by the luminescent material (13) and p is a number between 1.18 and 1.36, a display tube is obtained in which the luminous efficiency in the forward direction and at small angles for the central wavelength of the phosphor is at least 40% larger than in a tube without such a filter. Color improvement and gain in contrast also occur.

REFERENCES:
patent: 3902012 (1975-08-01), Dalton et al.
patent: 4310783 (1982-01-01), Temple et al.
patent: 4310784 (1982-01-01), Anthon et al.

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