PHOSPHOR DEVELOPMENT FOR ALPHA-SILICON LIQUID-CRYSTAL LIGHT VALVE PROJECTION DISPLAY

This paper describes the development of a phosphor suitable for effici ently activating an alpha-silicon photoconductor. The photoconductor i s employed to modulate a liquid crystal layer for use in a real-time t elevision projection system. A thorough evaluation of available phosph ors disclosed their unsuitability for this use. The major requirement for this material is that: the spectral emission closely match the alp ha-silicon responsivity curve, have sufficient radiance to activate th e photoconductor efficiently, be resistant to thermal degradation, and exhibit fast decay. An yttrium aluminum oxide phosphor with the yttri um aluminum garnet (YAG) crystal structure and activated by chromium s atisfied the above requirements. The process of making this phosphor i s described with emphasis on producing the YAG phase by the most pract ical means. Products were evaluated for radiance, spectral distributio n, crystal structure, decay time, and ease of screen preparation.