Aging of Liquid Crystal Alignment on Plasma Beam Treated Substrates: Choice of Alignment Materials and Liquid Crystals

Abstract

We studied temporal degradation (aging) of liquid crystal (LC) alignment on plasma beam processed substrates using LC pretilt angle as a measure of this process. It was shown that aging may manifest itself either in pretilt angle decay or pretilt angle growth depending on LC and alignment material. The alteration of electro-optic curves due to alignment aging was revealed. The weakest aging effect was observed for inorganic alignment layers obtained by PECVD method. An important reason of aging is chain scission and generation of low molecular weight reactive species disturbing surface anisotropy of atomic bonds and anisotropy of surface topology.

Stabilization of liquid crystal photoaligning layers by reactive mesogens

“…9 Compared with M1 cells, the LC pretilt angle stability in the M1/RMM256C cells is considerably higher. The pretilt angle shows stabilization trend ͑Fig.…”

Liquid Crystal Alignment on Thin Organic Films Deposited in a Low Pressure Plasma Enhanced CVD Reactor

“…Moreover, polyimide as an alignment layer material requires a baking stage with heat treatments up to 250 °C, and this can damage sensitive electronic parts of the fabricated display. Several alternative methods were developed to overcome these disadvantages like ultraviolet (UV) photoalignment, Kaufman ion beam irradiation, plasma beam irradiation, atmospheric pressure plasma jet treatment, step by step plasma enhanced chemical vapor deposition (PECVD) and treatment with plasma flux, oblique vapor and ion‐beam sputter deposition, etc. All these alternative techniques, except oblique evaporation, use the approach of a two step fabrication method; during the first step alignment, layer material is deposited (polyimide, a‐C:H, a‐Si:H, etc.)…”

Delicate Modification of Poly(dimethylsiloxane) Ultrathin Film by Low-Energy Ion Beam Treatment for Durable Intermediate Liquid Crystal Pretilt Angles

“…In addition, we observed that the initial values of achieved pretilt angles were maintained over 20 days at each treatment condition. This result is unique, since IB treatment generally gives rise to the anisotropic destruction of chemical bonds on the surface of an alignment layer; this, in turn, leads to the degradation of the pretilt angle − (see the Supporting Information). In this study, we closely investigated this uncommon result, focusing on the physicochemical changes of the PDMS surface as a result of IB treatment.…”