SBIR Phase II: Thresholdless Ferroelectric Liquid Crystals

Displaytech Incorporated, Longmont CO

Investigators

Abstract

This Small Business Innovation Research Phase II project's goal is a commercial quality liquid crystal exhibiting V-shaped switching with no hysteresis. This LC will be used in gray-scale displays and telecommunications optical switches. Ferroelectric liquid crystals (FLCs), due to their fast switching speed and wide viewing angle, have inherent advantages over the more commonly used nematic liquid crystals. However, when used in displays, they have a disadvantage - they generally can be driven to only two states, on and off. Since displays require intermediate gray states, FLCs currently attain gray scale by rapidly switching on and off. This project uses a new type of FLC which, in addition to its speed and viewing angle advantage, also shows analog switching. This type of material, previously known as a "thresholdless antiferroelectric", is now known to be an FLC with a linear optical response to applied field (also known as "V-shaped switching"). This project's objective is to make new liquid crystal compounds and mixtures that exhibit V-shaped switching. Towards that end, a variety of cores, chiral tails, and achiral tails, all of which are either known or suspected to promote a de Vries-type smectic A, have been proposed. About 50 - 100 liquid crystals will be synthesized by combining these various components. These new LCs will be combined with LCs made in the Phase I or earlier, giving mixtures that ideally will have not only a de Vries smectic A phase, but also a wide room-temperature smectic C phase, good low-voltage analog electrooptic response, good alignability, and fast hysteresis-free switching. An optimal alignment layer configuration will be determined. The newly formulated mixtures will be placed in cells containing this alignment layer to give V-shaped switching displays. This project could be instrumental in advancing our knowledge of the root causes of V-shaped switching in FLC and, by extension, add insight into the responses of self-assembling molecules to applied forces. In addition, since the interaction of the alignment layer with the liquid crystal is crucial for V-shaped switching, much more so than for typical FLCs, this project will provide a better understanding of the alignment layer-LC interactions.