Photo-alignment using a Photo-decomposition Polyimide and Effect of Reactive Monomers

Abstract

Photoreactivity of photo-decomposible polyimde was studied with and without reactive monomer, RM257. Recently photo reactive monomers have been draw attention for better alignment of liquid crystals and broad viewing angle. Interfacial effects as well as macro molecular interaction have been studied to enhance anchoring energy of liquid crystal. After irradiation, polyimide film gives LC alignment, perpendicular to polarization direction of the UV irradiation. LC aligning direction is measured by polar diagram. We had time to adjust during 10min-30 min. And we exposed to linearly polarized UV the angle vertically or horizontally by measured the degree of LC alignment. And we used 253.7 nm UV light by the use of band pass filter. Because this photo-decomposition polyimide film when using the 253.7 nm UV light is active in the reaction. We are the best time of the photo-alignment can be found by dichroic ratio [= (Aper – Apara)/(Aper + Apara)]. Normal photo-decomposition polyimide films were 0.584 dichroic ratio at 15 min and Reactive monomer added photo-decomposition polyimide films were 0.623 dichroic ratio at 10 min. Photo-decomposible polyimide reacts very efficiently with UV light. We have studied photo-alignment with CBDA-DAPM-DA polyimide by irradiating with 253.7 nm UV light. The polarization direction of liquid crystals were perpendicular to the polarization of incident light with and without reactive monomer(RM). The dichroic ratio obtained from the liquid crystal cells assembled with photo-irradiated alignment layer were 0.584 for the 15 min irradiated of UV light without reactive monomer. The dichroic ratio became 0.623 with 10 min irradiated polyimide film with RM.