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Luminescent Thin Film Screen For Display Applications

IP.com Disclosure Number: IPCOM000048701D
Original Publication Date: 1982-Mar-01
Included in the Prior Art Database: 2005-Feb-09
Document File: 3 page(s) / 42K

Publishing Venue

IBM

Related People

Chang, IF: AUTHOR [+2]

Abstract

This technology achieves significant efficiency improvement, better heat conduction, and longer operating life in a structured luminescent thin film screen. It is useful for many display applications such as projection display.

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Luminescent Thin Film Screen For Display Applications

This technology achieves significant efficiency improvement, better heat conduction, and longer operating life in a structured luminescent thin film screen. It is useful for many display applications such as projection display.

The phenomenon of light trapping in a light-emitting thin film is well known and permits the thin film to act as a planar waveguide in which there is trapping of the light propagation within the film due to differences in refractive index n between the thin film and the environment. The angular intensity normal to the film plane is inversely proportional to the square of the refractive index ratio (n(film)/n(ambient)). Typically, the total flux escaping the film to vacuum is about 10 percent of the light generated if the film has a refractive index of 2, which has limited the applications of light-emitting film.

Through a geometrical gain in surface area, the thin film structure which is described herein eliminates efficiency loss due to light trapping and enhances light-emitting efficiency. It can be achieved on a substrate which has anisotropic etching property such as silicon.

Several screens are shown in Figs. 1 to 4 wherein a luminescent pyramidal structure or an inverse pyramidal structure is formed on a substrate such as silicon, glass, or metal which breaks the waveguide-like light propagation and gains back practically all the loss (90 percent loss in a planar film). In a cathodoluminescent display application, an enhancement of light output is realized due to the increased surface area. The surface area gain is 1.44 for a matrix of 45-degree square base pyramid and 2 for a matrix of 60-degree square base pyramid. These gain factors are slightly reduced if spacing is allowed between pyramids or a circular base is used.

Illustratively, a <100> orientation silicon wafer is used b...