Ferroelectric and antiferroelectric LCD's

Ferroelectric and antiferroelectric liquid crystals (FLCs and AFLCs) are a special kind of LCs. Due the inherent permanent polarization of the liquid crystal molecules the ordering and behavior is completely different from normal liquid crystals. The first large difference is the fact that due to the permanent polarization the director of the molecules is located on a cone surface. On top of that they align in layers with the molecules in successive layers parallel (ferroelectrics) or opposite (antiferroelectrics) to each other.

Our research is mainly focused on three aspects of FLCs and AFLCs. Namely ion transport in (A)FLC, model building for grey levels and research on Spatial Light Modulators.

Ion transport in (Anti) Ferroelectric Liquid Crystals

Thanks to the so-called transient current measurements, we are able to determine ion concentration and mobility of up to three ion species. We also study the influence of ion transport on the electro-optical characteristics of these liquid crystals, in particular on FLC when symmetrically driven, on AFLC especially during the holding voltage, and on thresholdless liquid crystals.

Model building for grey levels in AFLC

We consider two possibilities to obtain analog grey levels: 'in-pixel domain switching' and 'continuous director rotation mode.' For the first situation we study domain wall motion. For the second case we developed a very simple theory, the so-called uniform theory, by which we succeeded in explaining the V-shaped switching in AFLC, the V-shaped switching in high P FLC, and the CDR mode in low P FLC material. We are still testing and comparing this simple theory with more accurate programs.

Correlation measurements with an EASLM

The EASLM is fabricated by Displaytech. We have set up a joint transform correlator in two steps of a single EASLM. The Fourier transforms are perfect, but more analysis is needed to do real correlation measurements.

More detailed information about the results we have obtained in our research can be found in our publications.

Contact persons :