Antiferroelectric liquid crystals with 45 degrees tilt - A new class of promising electro-optic materials

Antiferroelectric liquid crystals with a tilt angle of 45 degrees have very interesting optical properties, which seem to have been overlooked so far - perhaps because such materials have hardly been available. We have prepar ed a four-component mixture of partially fluorinated compounds with a SmCa* phase in the interval between 27.4 degrees C and 121.6 degrees C, in which the tilt angle theta saturates at 45 degrees for T less than or equal to 8 0 degrees C, and we investigate the optical properties, theoretically and e xperimentally. One of the surprising features of 45 degree materials is tha t they permit a remarkably high contrast by virtue of an excellent dark sta te, in spite of the fact that AFLC materials are notoriously difficult to a lign. This is because a 45 degrees AFLC turns out to be (negatively) uniaxi al instead of biaxial. We describe these properties and propose a number of potentially interesting new applications, including a polarizer-free displ ay mode and a three-level "phase-only" modulator.