Single-substrate IPS-LCD using an anisotropic polymer film

Most liquid crystal display (LCD) devices use two ITO-glass substrates in order to confine the fluidic LC. To align the LC molecules, the inner surfaces of the substrates were coated with a thin polyimide (PI) layer. These PI layers are mechanically buffed in order to produce uniform molecular alignment. To reduce weight, the single-substrate approach has been explored recently in which the LC device consists of a substrate and a thin polymer film. The major technical challenge is how to align the LC molecules on the polymer film side. In this paper, we demonstrate a new single-substrate IPS-LCD. The LC cell consists of an anisotropic LC polymer film and an interdigitated ITO-glass substrate. The anisotropic film not only behaves as a substrate but also helps align the LC molecules. Compared to the LCD using two glass substrates, the new device has almost the same bright state and the same dark state. Our new device exhibits a higher contrast ratio (∼514:1) because of good LC alignment. The driving voltage is low, and the response time is reasonably fast. The measured rise time is ∼8ms and decay time is ∼63 ms using a 12-μm cell gap and E7 LC mixture. This technology is particularly attractive for making single-substrate displays and also has potential for a double-layered guest-host display and a flexible display using IPS LCDs.