Control of High Pretilt Angle in NLC, 5CB, by the Washing Process on a Polyimide Surface with CF₃ Moieties

Abstract

The washing effects on pretilt angle generation in a nematic liquid crystal (NLC), 4-n-pentyl-4′-cyanobiphenyl (5CB) on a rubbed polyimide (PI) surface with trifluoromethyl moiety have been successfully studied. The pretilt angle of 5CB is increased by the washing process on the rubbed PI surface. The surface tension on the rubbed PI surface increases with the rubbing strength RS and then saturated above RS = 150 mm. The pretilt angle of 5CB for all washing processes on the rubbed PI surface decreases with the surface tension. We have found that the pretilt angle of 5CB on the rubbed PI surface may be attributed van der walls (VDW) dispersion interaction between the LC molecules. and the polymer surfaces having trifluoromethyl moieties.

Keywords:

• Washing effect
• pretilt angle
• nematic liquid crystal
• ven der walls (VDW)

Acknowledgments

This work was supported by National Research laboratory program (M1-0203-00-0008).