Liquid crystals ͑LCs͒ in flexible cell were aligned on polyimide ͑PI͒ surface treated by a paperlike plasma beam. The beam had energy of 450 eV and incident angle of 70°with respect to normal flexible indium-zinc oxide-coated substrate. The pretilt angle and anchoring energy of LCs on plasma-aligned PI surface were almost identical to the angle and energy of the rubbing PI. However, optical performance of the plasma-aligned cell was superior to the rubbing cell under various bending conditions. Furthermore, such noncontact alignment technology is suitable for large area and roll-to-roll fabrication of flexible LC films.

A plasma-beam-irradiated PI film has been used in flexible liquid crystal display manufacturing. The beam had energy of 450 eV and incident angle of 70 o with respect to normal flexible indium-zinc-oxide coated substrate. The pretilt angle and anchoring energy of LCs on plasma aligned PI surface were almost identical to those on rubbing aligned PI surface. However, the optical performance of plasma aligned cell was superior to the rubbing cell under various bending conditions. Furthermore, such non-contact alignment technology is suitable for large area and roll-toroll fabrication of flexible LC films.

We demonstrate a plasma-beam-processed polyimide ͑PI͒ surface to effectively align liquid crystal ͑LC͒ molecules. The pretilt angles of LCs can be varied between 0 and 3.5°, and the PI surface energy can be adjusted by controlling the plasma beam with an energy of 450 eV at an incident angle varying from 0 to 80°with respect to the normal direction of the substrate. Additionally, a method was developed to quickly evaluate the level of anchoring force of LC when compared with a rubbed-aligned LC cell. The performance of this method should be under LC cells with the same alignment materials.Controlling liquid crystal ͑LC͒ alignment is one of the most important manufacturing processes in liquid crystal display ͑LCD͒ technology. Many alignment techniques for inducing anisotropy on the surface of the LC alignment layer have been reported. 1-4 Generally, polyimide ͑PI͒ is used in LC cells to align them using a mechanical rubbing method. However, the rubbing process damages the alignment film, which limits the yields and stability of LCDs. Drawbacks of mechanical brushing including generation of dust and electrostatic charges are well-known. The rubbing process also damages bus lines and leads to electrical static discharges on thin film transistors in LCDs. Although the rubbing of the PI layers remains the current method of choice for the production of LCDs, noncontact alignment technologies have attracted much attention in the LCD manufacturing sector. They have great potential for future generations of large, high resolution LCDs. To avoid damage in aligning layers of the LCDs, noncontact alignment methods, such as photo alignment, 5-7 ion beam alignment, SiO 2 alignment, 8-12 and plasma alignment, 13,14 have been proposed for LC alignment. However, the photo alignment method is unreliable, the ion beam alignment method has issues related to uniformity, and SiO 2 oblique deposition system has trouble with large substrates.In this article, a simple LC alignment technique that uses a collimated plasma beam is proposed. The beam is used to treat commercial PI surfaces and then to align LC on a glass substrate. An LC can be homogeneously aligned on commercial PI surfaces using the appropriate incident angle and energy of the plasma beam. The pretilt angle and threshold voltage ͑V t ͒ of the twist nematic ͑TN͒ LCDs can be controlled by adjusting the plasma beam parameters. Moreover, we propose a new method that can quickly evaluate the level of anchoring force of LC by stressing the LC cell at an applied voltage of 10 V for 10 min when the integral area difference of voltage-transmission curves before and after stresses are done. The anchoring force of the Ar-plasma-beam-aligned LC cell at incident angle of 60°is in accordance with that of the mechanical rubbing aligned LC cell. ExperimentalThe alignment layers were composed of PI ͑4170 R2, Nissan Chemical͒, which was printed on 10 ⍀/ᮀ indium tin oxide ͑ITO͒-coated glass substrates ͑50 ϫ 50 mm͒. They were softly baked at 80°C for 10 min to evaporate the solvent within the...