Study on the Effect of Small Molecule Photosensitizer and Photoinitiator on Alignment Behavior of Photosensitive Polyimide

In order to improve the photosensitivity of photosensitive polyimide (PSPI) and greatly reduce the exposure time of non-polarised ultraviolet light (NPUVL). A novel PSPI (ODPA-PI-CA) with flexible main chain is successfully synthesised via esterification of PI containing hydroxyl groups with cinnamoyl chloride (CL). A photoinitiator, 2, 4, 6-trimethylbenzoyldiphenyl phosphine oxide (TPO) and a photosensitiser, benzophenone (BP) are doped into ODPA-PI-CA film to prepare ODPA-PI-CA+BP and ODPA-PI-CA+TPO films. When the irradiation time is the same, LC alignment ability of the ODPA-PI-CA+BP films is higher than that of ODPA-PI-CA+TPO films. The ODPA-PI-CA+BP can induce uniform alignment of liquid crystal (LC) after NPUVL exposure for only 5 min. In addition, the possible mechanism of alignment of LC induced by ODPA-PI-CA+BP films is discussed in detail. Furthermore, the pretilt angle of the LC cells is 0.5 degrees.