ABSTRACT
The effect of liquid crystal (LC) photoaligning is a direct consequence of the appearance of the photo-induced optical anisotropy and dichroism absorption in thin amorphous films, formed by molecular units with anisotropic absorption properties. As polyimide materials possess high temperature stability and are commonly used in the liquid crystal display (LCD) industry, which is highly desirable to modify them for the photo-alignment applications. The value of the pretilt angle of an LC cell on the substrate is one of the important characteristics for photo-alignment. In most of the electro-optical modes the pretilt angle should be sufficiently high to enable a quality performance of LCD. A new generation of optical security elements based on photo-patterning technology enables the fabrication of optical security devices. The photo-patterned security mark can be applied directly to documents via printing or coating methods as well as indirectly by hot-stamping processes.
