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Producing Uniform Brightness Levels of Thin Film Incandescent Filaments

IP.com Disclosure Number: IPCOM000076526D
Original Publication Date: 1972-Mar-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Hochberg, F: AUTHOR

Abstract

The brightness of a tungsten filament is known to be strongly dependent upon its temperature which, in turn, is a function of the current density through the filament. In integrated tungsten display devices, wherein an array of filaments or characters are to be displayed, it is necessary to maintain a uniform brightness level. The method to be described would automatically vary the deposition rates of tungsten on a filament so as to provide a more uniform temperature along the filament length, and automatically compensate for end losses which also cause temperature gradients.

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Producing Uniform Brightness Levels of Thin Film Incandescent Filaments

The brightness of a tungsten filament is known to be strongly dependent upon its temperature which, in turn, is a function of the current density through the filament. In integrated tungsten display devices, wherein an array of filaments or characters are to be displayed, it is necessary to maintain a uniform brightness level.

The method to be described would automatically vary the deposition rates of tungsten on a filament so as to provide a more uniform temperature along the filament length, and automatically compensate for end losses which also cause temperature gradients.

With the filaments placed in a chemical vapor deposition reaction chamber (WF(6)+ H(2)), and a constant current applied to each filament, any temperature nonuniformity along the filament results in different deposition rates, i.e., the higher the temperature, the greater the deposition rate. Thus, the cross-sectional area at regions of higher temperature is increased, thereby acting to reduce the temperature in these regions.

The arrangement may be adjusted, so that when the driving voltage reaches a desired level, the power to the filament shuts off, cooling that filament and halting deposition. The method, accordingly, acts to automatically compensate for filament end losses, repair hot spots by selective deposition, and ease the fabrication problems incident to obtaining good filament uniformity. The method may also b...