Abstract
We developed an alignment method for control of the polar pretilt angle at the boundaries of a liquid crystal (LC) layer in a continuous range 2–90° by introducing a low-density polymer network. The network was formed as a result of the electric field-induced segregation of a photo-reactive monomer added in concentrations of 0.5–1% to the LC host and subsequent in-situ UV-light-induced polymerization. LC director was “frozen” within a less than a micron-thick layer in the vicinity of the cell substrates at high average tilt angles anchoring the LC in the bulk similarly to a high-pretilt alignment layer. The resultant pretilt angle was determined by the voltage applied before and during polymerization and the duration of voltage application before UV-light exposure. The desired pretilt angle could be set over a small area of a sample which allowed for the fabrication of LC devices with spatially variable optical retardation. Using this method, we fabricated high-pretilt splay and bend LC cells, optically recorded converging lenses and bi-prisms with electrically controlled optical characteristics, and phase diffraction gratings with resolution better than 50lines/mm.
•We developed an effective method of pretilt angle control in nematic liquid crystal cells.•The paper includes our newest results on stabilization of high-pretilt bend structures in π-cells, the fastest display modes.•Our method of pretilt control eliminates a need for a photo-lithographically manufactured electrodes.•We present examples of an optically recorded lens, prism, and phase diffraction grating.•The optical elements demonstrate low light scattering, which allows for the commercial application.