Thin flexible photosensitive cholesteric displays

A novel optically addressable, flexible bistable cholesteric liquid-crystal display (ChLCD) is presented. These displays utilize azo-binaphthalene photosensitive chiral dopants that undergo photo-isomerization upon exposure to light. The isomerization results in a change in the pitch of the cholesteric liquid crystal (ChLC), which enables the creation of inherently high-resolution light-weight displays that are optically written. The displays can be photo-addressed without patterned electrodes or complex addressing schemes. Capitalizing on the dynamic pitch and the bistability of photosensitive ChLCDs, the display is switched with a single pulse at a specific single voltage to drive the region of the display with a shorter pitch to the focal-conic texture and the region of the display with a longer pitch to the planar texture. Once in the different textures, the display can hold an image indefinitely regardless of ambient lighting. As such, these displays are a natural fit for badges, shelf-labels, and point-of-sale cards. In this paper, the photosensitive properties of an encapsulated display system in comparison to an unencapsulated display system is discussed. Properties such a photosensitivity, thermal relaxation, and electro-optical response are studied and reported. In addition, a flexible optically addressable ChLCD is developed and demonstrated.