Fabrication of Defect-Free Ferroelectric Liquid Crystal Cells Using Combination of Different Pretilt Alignment Films Rubbed in Anti-Parallel

Abstract

Fabrication of operable surface-stabilized ferroelectric liquid crystals (SSFLCs) is often hampered by the occurrence of zigzag defects. This defect formation can, to some extent, be controlled or eliminated in SSFLCs in which the rubbing directions are set parallel, because two chevrons have different molecular alignment structures and different energies. In this study, we try to fabricate a defect-free SSFLC with anti-parallel rubbed films which possess different surface anchoring and/or pretilt angle between two cell substrates in order for the energy condition in two types of chevron to be different. In the case using a combination of the same alignment film material, it was confirmed that in all alignment film materials used in this research, the occurrence of zigzag defects can be reduced as the difference of rubbing strengths increases between two alignment films. It is found that the appearance of zigzag defects can be more strongly suppressed as the difference of pretilt angles increases between two alignment films, and then in the case of the large difference, zigzag defect-free SSFLCs can be obtained. Furthermore, it is found that the effect of the pretilt on the suppression of zigzag defect is much stronger than that of the anchoring strength.

Keywords:

• anti-parallel rubbing
• ferroelectric liquid crystal
• pretilt angle
• surface anchoring
• zigzag defect

Acknowledgments

The authors thank Mr. H. Fukuro and Mr. H. Endoh of NissanChem Ind. for supplying polyimide materials. We also thank Dr. T. Takahashi of Kogakuin Univ. for the measurement of the pretilt angle.