Electric lamp and discharge devices – Cathode ray tube – Screen
Patent
1984-10-18
1987-01-06
Moore, David K.
Electric lamp and discharge devices
Cathode ray tube
Screen
350163, 358253, H01J 2928, H01J 2989
Patent
active
046349260
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 comprises 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 6 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 0.25.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 1.15 and 1.45, a display tube is obtained in which the luminous efficiency in the forward direction 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.
Brandsma Titus E. C.
Rijpers Johannes C. N.
Spruit Johannes H. M.
Vriens Leendert
Moore David K.
Spain Norman N.
U.S. Philips Corporation
Wieder K.
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