32.4: Two Modes of LC Parallel Alignment on the Plasma Treated Substrates

Abstract

AbstractWe propose a new alignment procedure for liquid crystals cells that yields both zero and non‐zero pretilt. This procedure is an oblique irradiation of the bounding substrates with the directed plasma flux. As a source of plasma irradiation we use an anode layer thruster producing sheet like plasma fluxes suitable to treat large‐area substrates. Both organic (polymers) and inorganic (glass, ITO) layers can be treated. Plasma beam irradiation results in two types of LC alignment: (1) the easy axis in the incident plane formed by the direction of beam and the normal to substrate; (2) the easy axis perpendicular to the plane of incidence. By increasing the irradiation dose, one can change the alignment direction from the type (1) towards the type (2). In the first type of alignment, the pretilt angle can be controlled by changing parameters such as irradiation angle, ion current density, ion energy, etc. The second type of alignment is characterized by a zero pretilt. The azimutal anchoring energy coefficient is relatively weak (W=10−3 erg/cm2) for the first type of alignment and strong (W>10−1 erg/cm2, comparable to the rubbed polymer substrates) for the second type. The two‐mode alignment feature can be used to generate alignment with desirable parameters as well as to pattern the LC cell substrates. The method is free of certain shortcomings known for the traditional rubbing technique.