Furthermore, uniform alignment methods of LCs were also investigated and proposed in a number of different ways, for instance the usage of Langmuir-Blodgett film, e-beam lithography, atomic force microscopy (AFM) nano-rubbing, nano-imprint lithography, and photolithography, respectively. In addition, in the last two decades, both photoalignment and the ion/plasma method as alternatives to the rubbing technique were successfully studied. The most commonly encountered method of orientation of LCs is the rubbing technique, widely used in LCD technology. There are a number of various processing techniques allowing to obtain anisotropy on the surface using them as high-quality aligning layers with certain properties for LC orientation. As a consequence, research on different surfaces as perspective candidates for high-quality alignment of LCs is still continuing. The alignment of liquid crystals (LCs) is an important stage within the production of various LC devices. Comprehensive measurements and comparisons of the azimuthal anchoring energy as well as the pretilt angle for the 1D-LSFL, unstructured gaps, and entire areas depending on the width of unstructured gaps are presented and discussed. Modifying the sapphire surface by an ITO-coating with further deposition of a polyimide film increases the azimuthal anchoring energy by a factor of about four up to W φ ~ 4.25 × 10 −6 J/m 2, when the minimum width of the unstructured gap is 7 µm. It is found that such alignment layers of the sapphire surface lead to a decreasing azimuthal anchoring energy, when the width of the unstructured gap is increased. These periodic structures, employed as alignment layers, have a spatial periodicity of about 980 nm, a modulation depth of about 100 nm, and exhibit a high quality due to being characterized by a high degree of homogeneity and parallelism of the structured features.

One-dimensional LIPSS (1D-LSFL) are generated by infrared femtosecond laser pulses along parallel lines covering an area of 5 × 5 mm 2, with a line spacing that is varied between 7 and 17 µm. In this study, we report on the alignment properties of nematic liquid crystals on various transparent structured sapphire layers formed by laser-induced periodic surface structures (LIPSS).

Singapore Sapphire by A.M. Stuart