FIELD-INDUCED INCREASE OF PITCH IN PLANAR CHOLESTERIC LIQUID-CRYSTALS

In cholesteric liquid crystals the application of an electric field pa rallel to the helix axis can change the wavelength of selective reflec tion. For decreasing pitch of the studied mixtures, the colour shift b ecomes more stable against the field-induced transformation of the ini tial Grandjean structure into a confocal texture. In compounds with a low crossover frequency, a field induced increase of the pitch was obs erved at the switching between low and high frequency fields. The inve stigations allow new conclusions on the origin of the colour shift.