Selective Liquid Crystal Driving Mode Achieved by Controlling the Pretilt Angle via a Nanopatterned Organic/Inorganic Hybrid Thin Film

Abstract

Behavior of liquid crystal (LC) is a result of interaction between the geometrical shape restrictions of the adjacent surface and molecular forces among LCs or adjacent surface. For years, continuous efforts have been made to control LC orientation and anchoring with pretilt angle for modulating the electro‐optical characteristics. For now, diverse driving modes have been developed including twisted nematic, optically compensated bend, electrically controlled birefringence, and vertical alignment. However, it has the limitation that different fabrication process should be adopted in different driving mode such as materials of alignment layer and techniques for aligning the LCs. Herein, selective LC modes are achieved by controlling the LC pretilt angle using nanopatterned organic/inorganic hybrid thin films composed of polyimide (PI) and tin oxide (SnO). It is possible to control the surface wettability according to the composition ratio between PI and SnO, thereby adjusting the pretilt angle of the LCs. Fabrication of SnO combined with PI applied via embossing allows for the large‐scale replication for LC alignment and based on consumer demand, devices can be manufactured in various modes through simple configuration changes. Therefore, an inorganic compound combined with an organic one permits designing addressable LC driving modes.

Controlling the Pretilt Angles of Guest–Host Liquid Crystals via a Hydrophilic Polyimide Layer through Oxygen Plasma Treatment

“…Jeng et al demonstrated that the LC molecules can be flexibly aligned on the surface of ZnO nanoparticle arrays, and the pretilt angle can be modified using an annealing temperature . Seo and Liu et al found that the LC pretilt angle in a nanopatterned hybrid film can be controlled by an adjustment of the composition ratio of the PI and sol–gel-based tin oxide …”

“…8 Seo and Liu et al found that the LC pretilt angle in a nanopatterned hybrid film can be controlled by an adjustment of the composition ratio of the PI and sol−gel-based tin oxide. 9 The benefit of surface treatment is that it is highly reliable in achieving the desired surface properties, techniques for which include the baking of the alignment films at different temperatures, ion beam-treated alignment films, and polymer structure-modified substrates. 10−12 However, these methods come with disadvantages, including a difficult production process, high costs, and poor reproducibility.…”

Surface reformed anisotropic polystyrene‐block‐poly(ethylene‐ran‐butylene)‐block‐polystyrene‐graft‐maleic anhydride layer via ion‐beam irradiation for liquid crystals

“…However, owing to the nature of the rubbing process, static electricity or scratches can occur, which may affect the uniformity of the grooves and hence the LC arrangement. To overcome these shortcomings, other nonrubbing methods, such as photoalignment, 6–8 plasma‐beam alignment, 9 atmospheric pressure, 10 ion‐beam (IB) irradiation, 11,12 and nanoimprinting lithography, 13–15 have been studied. Of these, the IB irradiation method is used in the present study and involves applying an Ar + ion‐induced plasma beam onto a film to supply energy to its surface, thereby inducing uniform alignment.…”

Tunable Liquid Crystal Alignment and Driving Mode on Lanthanum Aluminum Zirconium Zinc‐Oxide Thin Film Achieved by Convenient Brush‐Coating Method

“…This method has been widely adopted for functional electronic devices, with excellent electronic and optical characteristics. [14][15][16] It can also affect the morphological characteristics of the deposited film easily. According to Berreman's model, the LC molecules are aligned on the surface with minimal elastic distortion energies.…”