Comparison of liquid crystal alignment properties resulted from the using novel Photo-fragmentation Activators

Abstract

We proposed novel photo-fragmentation activators to shorten the ultraviolet(UV) irradiation time for the photo-alignment of LCD. The activators fragmented fast and generated active radicals attacking polyimide films. The fragmented activated radicals are responsible for the LC alignment of PI film. Photo-activators were synthesized from the cyclohexanone oxime reacting with three different anhydrides, respectively. The physical aspects of films were identified by measuring the absorbance, contact angle, the pretilt angle and anchoring energy. All three photo-activators had characteristic bimodal shape absorption peaks at 270~280 nm in UV-Vis spectra. The slowest reaction time were less than 5 mins. The short reaction time is very useful for the factory application. The photo-activator using crotonic anhydride (CAP) showed the fastest and highest anchoring energy than others. The double bond of crotonic group made high reactivity due to resonance stabilization.