Fion Sze Yan Yeung

Variable liquid crystal pretilt angles by nanostructured surfaces

Variable liquid crystal pretilt angles of any value from 0 to 90° can be obtained by using a nanostructured alignment layer. This layer is robust and reliable. The pretilt angles obtained are stable against high storage and operating temperatures, and have strong anchoring energies.

Fast-response no-bias-bend liquid crystal displays using nanostructured surfaces

We present results of a fast-response no-bias-bend (NBB) liquid crystal display, made possible by using a nanostructured alignment layer. Such alignment layers allow high pretilt angles of over 45° to be fabricated reliably. Thus, a stable bend configuration pi-cell can be achieved without applying any bias voltage to the cell. This NBB cell has a total on-off response time of less than 1.8ms and is faster than the corresponding optically compensated bend cell with a low pretilt angle.

Pi-cell liquid crystal displays at arbitrary pretilt angles

The pi-cell is studied as a function of its pretilt angle. It is shown experimentally and theoretically that the critical holding voltage decreases as the pretilt angle increases. At high pretilt angles, the critical holding voltage becomes zero and the bend cell becomes stable. The measured total response time of the pi-cell decreases with the pretilt angle as well. There is almost a factor of 2 difference between the total response time of conventional pi-cell and the no-bias bend cell.

Liquid crystal pretilt angle control using nanotextured surfaces

A scalable and economical method to control the pretilt alignment of nematic liquid crystal (LC) to ∼45° has long been sought as it constitutes the foundation of some key technologies of LC displays. We demonstrate that nanotextured surfaces fabricated by mixing horizontal and vertical polyimides allow complete LC pretilt control from ∼0° to 90°. Devices made with these surfaces show response times four times superior to the state-of-the-art panel.

Liquid-Crystal Photoalignment by Super Thin Azo Dye Layer

A novel liquid crystal (LC) photoalignment method, based on a super thin azo dye molecular layer is proposed. The basic idea of this method is to form a very neat textile knitwear and uniform alignment by azo dye layer without spin coating and rubbing processes. The thickness of the alignment layer is smaller than 3 nm, which is much thinner than traditional PI alignment film. In addition to the advantages of a conventional photoalignment method, the use of super thin layer simplifies the alignment procedure, making possible a high electrooptical performance, good photo-tolerance and thermal stability, better adhesion on indium tin oxide (ITO) surface and compatibility with roll-to-roll process.

Truly bistable twisted nematic liquid crystal display using photoalignment technology

Truly bistable twisted nematic liquid crystal display has been fabricated using photoalignment. This display can be switched between the −22.5° and 157.5° twist states by breaking the anchoring condition on one of the substrates. The application of a photoalignable polymer SDA-1 was able to achieve the weak anchoring energy necessary for switching. Both theoretical and experimental results show that this mode has excellent contrast ratio and wide viewing angles.

Liquid Crystal Alignment Layer With Controllable Anchoring Energies

We demonstrate a liquid crystal alignment layer with controllable polar and azimuthal anchoring energies. This alignment layer is based on a nanostructured surface formed by mixing a conventional polyimide and a nonaligning polymer. By using this variable anchoring alignment layer, large cell gap bistable twisted nematic LCD requiring asymmetric anchoring can be fabricated.

Simultaneous Determination of Large Pretilt Angles and Cell Gap in Liquid Crystal Displays

A method for the measurement of arbitrary pretilt angles in liquid crystal displays is proposed and demonstrated. The cell gap can also be determined accurately in the same experiment as well. This method makes use of a photo-elastic modulator and is capable of measuring pretilt angles from 0 to 90deg precisely.

Nano-structured liquid-crystal alignment layers (Invited Paper)

— The alignment of liquid crystal by nano-structured surfaces is investigated. It is shown that reliable pretilt angles of any value between 0° and 90° can be produced with these surfaces. The physics and properties of such alignment layers are studied using a variety of techniques. The anchoring energy and temperature stability of the alignment are also measured. Dependence on various processing conditions is also characterized. It is shown that these nano-structured alignment layers are useful for the production of high pretilt angles needed for a variety of applications.

62.2: Dual-Frequency Bistable Bend-Splay LCDs

A bistable liquid crystal display based on the bend and splay configurations has been demonstrated using dual frequency liquid crystal. Unlike the previous three-electrode version, only two regular electrodes are needed in the present case. We also propose and demonstrate a convenient multiplex driving scheme for a BBS matrix display.