Influence of laser writing of polyimides on the alignment of liquid crystals

Abstract

The influence of direct laser writing in polyimides on the alignment of organic liquid crystals was investigated. Laser writing was performed below the ablation threshold, which resulted in local melting of the polyimide. A surface relief structure was obtained as a result of the fast heating and cooling cycle during laser writing. No alignment of organic liquid crystals in the vicinity of the surface relief structure was observed as a direct result of the laser writing process. However, it appeared to be possible to wipe out the alignment originating from the rubbing process. This property proved to be useful to generate complex patterns in twisted nematic liquid crystal cells with locally uniaxial alignment. The contrast between the nonpatterned and patterned areas ranged between 40 and 50, which illustrates that the earlier described phenomena are potentially useful in, for instance, personalized security features.