An X-ray Study of Devices Containing a N*???SmC*Liquid Crystal Mixture

Abstract

The structure of a ferroelectric liquid crystal mixture with an N∗ → SmC∗ transition in skew aligned cells has been studied by X-ray diffraction measurements of the layer normal distribution. The rubbing directions of the cells were set parallel, and skewed at ±9°, ±18° and ±40°. The cell with parallel alignment directions showed two sets of layers with normals twisted in-plane by ∼±20° from the rubbing direction. The layer normal distribution of each set of layers was consistent with a chevron-like structure but with an additional untilted region, probably at the apex. It was also observed that the tilt of the chevron arms was weakly temperature dependent, with their normals tilting out of the plane of the device by an angle of 9° to 12° on cooling. The cells with alignment skewed by ±9° and ±18° also showed chevron-like structures which are probably developed in the middle of the cell with each arms tilted by ∼20° and with normals slightly twisted in-plane by ±4° with respect to the mean rubbing direction. However, there were additional components of the layer-normal distribution, which are believed to be a continuous distribution of layer orientations between the middle of the cell and layers near the substrate with normals twisted further away from the mean rubbing direction. The cell with alignment directions skewed by ±40° showed only a chevron structure with the normals to its two arms twisted with respect to each other by 2° and tilted out of plane by ∼17°.