Spontaneous layer reorientation in smectic C liquid crystals

A defect structure has been observed for certain ferroelectric liquid crystal mixtures in the surface stabilised device geometry when cooled towards ambient temperature. X-ray and electro-optic studies suggest that the sample, initially in the chevron layer structure, forms a uniformly tilted layer structure spontaneously. This seriously degrades device contrast and switching properties. The effect of both liquid crystal composition and alignment layer pretilt are reported and recommendations made to ensure that the defect does not occur, thereby allowing good device performance to be maintained.