Liquid crystal alignment layers studied by reflection anisotropy spectroscopy

Reflection anisotropy spectroscopy (RAS) achieves surface specificity by sensing optical anisotropy. While surface specificity is prized, it is often rather difficult to relate optical anisotropy to properties of more direct interest. This fact, together with its inability to study isotropic surfaces, can be considered weaknesses of RAS. Here, on the contrary, the application of studying liquid crystal (LC) alignment layers is presented. In this, RAS directly probes the key characteristic and suppression of the isotropic optical response is essential. In the commercial fabrication of LC displays, defects in alignment layers cannot be detected until the construction of the device has been completed. The potential of RAS to detect improperly processed regions and therefore predict the quality of displays during the fabrication process is demonstrated.