We have found that liquid crystals can be aligned on a polyimide surface exposed to a low energy and neutral Argon ion beam. The energy of the incident ions were varied between 75 and 500 eV, the integrated current density from 100 μA/cm 2 to 500 mA/cm 2 , and the angle of incidence over which alignment was measured was between 10 and 20 degrees. The pretilt angle of the liquid crystals could be varied between 0 and 8 degrees, by controlling the processing conditions. Degradation of the polyimide, which leads to charge migration, can be avoided by operating at low accelerating voltages.

https://iopscience.iop.org/article/10.1143/JJAP.37.L55/pdf

Atomic beam alignment of liquid crystals

The present invention provides a plasma enhancement method and apparatus for electric arc vapor deposition. The plasma enhancement apparatus is positioned to act upon plasma generated from a plasma source before the plasma reaches a substrate to be coated by the plasma. The plasma enhancement apparatus includes a magnet disposed about a magnet axis and defining a first aperture, and a core member disposed about a core member axis and at least partially nested within the first aperture. The core member defines a second aperture, and the plasma enhancement apparatus is arranged and configured in such a manner that the evaporated cathode source material passes from the cathode source and through the second aperture toward the substrate to be coated by the evaporated cathode source material. The plasma is favorably conditioned as it passes through the plasma enhancement apparatus.

Plasma enhancement apparatus and method for physical vapor deposition

We create planar-periodic alignment in nematic liquid crystal (LC) cell by using a command layer of azo-dye molecules directly deposited on the cell substrates and exposed with two interfering laser beams of opposite circular polarizations. Permanent high efficiency polarization gratings are thus created. The diffraction efficiency of those gratings is controlled by a uniform electric field applied across the cell. The electro-optical properties of such polarization gratings are studied. Obtained gratings can be used for electrically controlled discrimination and detection of polarized components of light.

Optical polarization grating induced liquid crystal micro-structure using azo-dye command layer.

A substrate (20) is treated prior to use to induce a near-perpendicular orientation of a liquid crystal director (26) relative to the substrate. A layer of silica (38) is deposited upon the substrate (20) by in-line magnetron sputtering as the substrate (20) is moved past the sputtering target (78), and the silica-coated substrate (20) is thereafter treated with a long-chain alcohol. The alcohol-treated substrate (20) is covered with a layer of liquid crystal (22), the director (26) of the liquid crystal (22) assuming a field-off state tilted about 1-3 degrees from the perpendicular toward an azimuthal direction (30) parallel to the direction of movement of the substrate (20) during deposition.

Inducing tilted perpendicular alignment in liquid crystals

An interposed layer of amorphous carbon promotes the adhesion between conductive substrates and electrochemically deposited polymers. Such a carbon layer may be deposited directly onto the conductive substrate by conventional methods such as, for example, chemical vapor deposition. The subsequently applied electrochemically deposited polymer adheres more tenaciously to the amorphous carbon coating than if it had been electrodeposited directly onto the conductive substrate.

Use of amorphous carbon to promote adhesion between electroactive polymer films and conductive substrates

Electrode surfaces are coated with a passivating material (silicon dioxide, aluminum oxide or titanium dioxide) or with a reflecting material (chromium or chromium and gold) or with a special alignment material (carbon) using standard vacuum sputtering, vacuum evaporation, electrodeposition, or chemical vapor deposition techniques. After sufficient thickness of material has been deposited, the substrate is exposed to a broad or narrow beam of neutralized argon ions of a few kilo-electron-volts energy. The beam of argon ions is incident at a grazing angle to the surface, typically 20°. Exposure of the overcoating results in a microscopic condition believed to comprise a "corrugated" surface with "ridges" and "valleys" parallel to the direction of the incident beam. These microscopically fine grooves or streaks are (1) reproducibly effective in causing parallel alignment of the liquid crystal molecules, (2) are durable to repeated cleaning procedures and air-bake treatments, and (3) are amenable to production applications in conjunction with vacuum deposition equipment.

Yat-Shir Lee

Papers

Means and method for inducing uniform parallel alignment of liquid crystal material in a liquid crystal cell