Time-Sequential Ultraviolet Exposure to Alignment Layers Embedded with Reactive Mesogen for High-Speed In-Plane Switching Liquid Crystal Cell

We propose a time-sequential ultraviolet (UV) exposure process that can improve the surface anchoring energy of photopolyimide (PI) embedded with reactive mesogen (RM) in high-speed liquid crystal (LC) display devices. To increase the anchoring energy of the PI layer, a separated UV exposure process of polymerization for the embedded RM material and PI layer is required [1]-[8]. In this paper, we propose a novel single-frequency UV exposure method that can perform the separated polymerization of the UV alignment layer and the embedded RM material by optimizing the intensity of the exposure UV light. Using the proposed UV exposure method, we polymerize the RM material during the first 4 s, and then accomplish the polymerization of the UV alignment layer sequentially. To demonstrate the electro-optical performance, we measure the surface anchoring energy and the optical response time of in-plane switching LC cell. The measured results show that the surface anchoring energy and the optical response time are improved by more than 2.5 times and 28.2%, respectively, compared with the conventional UV exposure.