Abstract

The filled nematics consist of small solid particles of pyrogenic silica dispersed in a nematic liquid crystal.¹ Displays made with this material have bistable optical properties. A strong scattering state can be achieved by optical addressing using a laser diode. The laser light is absorbed by a dye in the liquid crystal or by an inorganic layer. Applying an AC voltage erases the written information and aligns the liquid crystal homeotropically into a transparent state. Both the scattering and the transparent state are stable in space and time. Local erasing is possible by applying a moderate voltage and directing a simultaneous laser pulse at the pixel to be erased. Grey scaling can be achieved by variation of the laser power during the writing process. For the writing process it is necessary that the laser power is absorbed. In transmission displays this is achieved by a dye, which is dissolved in the liquid crystal. For reflection displays a thin-film reflector-absorber has been developed.

© 1994 IEEE