The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Jan. 06, 1987
Filed:
Oct. 18, 1984
Leendert Vriens, Eindhoven, NL;
Johannes H Spruit, Eindhoven, NL;
Johannes C Rijpers, Eindhoven, NL;
Titus E Brandsma, Eindhoven, NL;
U.S. Philips Corporation, New York, NY (US);
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.