Siegfried Aftergut

Dependence of absorption and optical contrast of a dichroic dye guest on the pitch of a chiral nematic host

Absorption of unpolarized light by a dichroic dye dissolved in a chiral nematic host increased with a decrease in pitch of the host, accompanied by a proportionate increase in contrast ratio, in qualitative agreement with a theoretical analysis by White and Taylor. Identical experimental values of order parameter of the guest‐host system were obtained by two independent methods.

Brightness and contrast ratio of black‐and‐white reflective dichroic liquid‐crystal displays

Reflectance and contrast ratio of a black liquid‐crystal display made from a solution of dichroic dyes in a cholesteric host were measured as function of incidence angle and liquid‐crystal layer thickness. The experimental data were in reasonable agreement with theory.

Decay time of twist cells with liquid crystals of shortened pitch

Chiral nematogens of natural pitch p0 and layer thickness d were investigated over the regime d<p0<4d in cells with π/2 twist imposed by wall orientation. The decay times in this regime were smaller than for p0⩾4d.