Electric lamp and discharge devices – With luminescent solid or liquid material – Vacuum-type tube
Patent
1994-03-31
1996-02-06
O'Shea, Sandra L.
Electric lamp and discharge devices
With luminescent solid or liquid material
Vacuum-type tube
313497, 313500, 313505, 313512, 313525, 313539, 345 75, 345905, 378121, H01J 2908
Patent
active
054898170
DESCRIPTION:
BRIEF SUMMARY
FIELD OF TECHNOLOGY
The invention concerns an electron-optical image terminal device based on an air-tight vacuum envelope containing a solid-state thin layer element that serves as electron source--the cold cathode--in which the electron emitting region consists of a stack made up of a metal layer that serves as the ground electrode, an insulator film, a semiconductor film and finally another thin metal layer as covering electrode, this stack residing on a non-conducting substrate, plus an electron acceleration space, likewise enclosed within the vacuum envelope.
STATE OF THE ART
The state of the art, which serves as the starting point of the invention, is contained in the publication "Direct Evidence of Ballistic Acceleration of Electrons in ZnS" by G. O. Muller, R. Mach, E. Halden, a paper presented at "The 20th International Conference on The Physics of Semiconductors", Aug. 6-10, 1990, Thessaloniki, Greece (see proceedings 20th ICPS, October 1990, vol. 3, pp. 2510-2513). This paper reports on the results of research on MISM-structures (Metal-Insulator-Semiconductor-Metal) serving as sources of "hot" electrons for electron-optical applications. This work is concerned with a cold cathode, although the authors do not refer to it explicitly as such. Later papers adopt the acronym "HECC" (Hot Electron Cold Cathode) for this arrangement.
This development opens a new way for a variety of applications of electron-optical systems. The efforts that have been undertaken to replace conventional cathode-ray tubes by display devices of better configuration, in particular having a smaller ratio of depth to the useful screen area, have led to the construction of so-called flat panel cathode ray tubes (flat-CRT) employing a variety of working principles, such as hybrid plasma display/CRT and true flat panel displays, in particular liquid crystal, plasma and electro-luminescent displays. A sort of intermediate position is occupied by the so-called vacuum fluorescent displays, in which electrons are emitted from a multiplicity of hot cathodes and accelerated through a multiplicity of control grids to impinge on layers of fluorescent material.
Electrons in cathode-ray tubes are driven to relatively high kinetic energy (5 keV up to 30 keV) required for efficient generation of light in fluorescent materials, whereby high brightness is obtainable if the fluorescence efficiency is adequate. The principle of emission of these electrons from one or a few hot cathodes makes it necessary, however, to provide a deflection system and it is this system that causes the considerable tube depth, or in the case of flat-CRT's requires a complicated construction or technology, and on the other hand forces the dwell-time of the electron beam on each individual pixel to grow shorter, the higher the resolution. The latter circumstance makes it difficult to attain high brightness, since the energy input per pixel and frame cycle is given by the product of beam power and dwell time.
The patent DE-OS 34 32 377 does already describe a flat display device in which an array of thin-layer MIM (Metal-Insulator-Metal) cathodes serve as the electron source. By depositing a sub-atomic thin layer of an electro-positive adsorbate, such as Cs, electron scattering in the covering metal of the cathodes could be reduced. This additional deposited layer leads to instabilities, however, due to redistribution that takes place during operation.
Image converters find application as devices that make visible on a fluorescent screen UV or X-ray images incident on the photo-cathode. Many image converters of conventional construction suffer from the drawback of undesirable phenomena due to back-coupling of the light from the screen with the photo-cathode, from complicated dependence of the electron-optical image formation on the energy with which the photo-electrons are emitted from the cathode, or by the fact that the quantum efficiency of the photo-emission is as a rule much lower than 1, so that weak primary images may only be incompletely reproduced on the d
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Muller Gerd O.
Muller-Mach Regina
Friedman Mark M.
O'Shea Sandra L.
Patel Ashok
Scitex Corporation Ltd.
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