Display tube provided with an interference filter
US4634926A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Oct 18, 1984 |
| Grant date | Jan 6, 1987 |
| Priority date | — |
| Expiry date | Oct 18, 2004 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH01J29/28
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
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.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.