Band-Separated UV Exposure on a Photosensitive Polyimide Layer with Embedded Reactive Mesogen for a High-Speed Liquid Crystal Display Device

In general, surface anchoring energy is one of the most important parameters that strongly affect electrooptical performance, especially the optical response time of liquid crystal (LC) displays. In this paper, we proposed a photoalignment method for strong surface anchoring energy by applying double ultraviolet (UV) exposure with a separated bandwidth to a photosensitive polyimide layer with embedded reactive mesogens (RMs) that can increase the anchoring energy during polymerization. We first polymerized the embedded RM molecules using long wavelength UV rays (over 340 nm), and then achieved the ordered photosensitive alignment layer using short UV rays (between 254 and 340 nm). We compared the measured surface anchoring energy and the optical response time by the proposed method with the conventional UV exposure using the in-plane switching LC mode for verification. As a result, we confirmed that the anchoring energy increased two times and the optical response time improved by 22% compared with the conventional pure UV exposure method.