We demonstrate a physical model of photoalignment and photopatterning based on rotational diffusion in solid azo-dye nanolayers. We also highlight the new applications of photoalignment and photopatterning in display and photonics such as: (i) liquid crystal (LC) E-paper devices, including optically rewritable LC E-paper on flexible substrates as 3D E-paper, as well as optically rewritable technology for photonics devices; (ii) photonics LC devices, such as LC Switches, polarization controllers and polarization rotators, variable optical attenuators, LC filled photonic crystal fiber, switchable diffraction grating; (iii) patterned micro-polarizer array using photo-alignment technology for image sensor; (iv) electrically tunable liquid crystal q-plates; (v) electrically switchable liquid crystal Fresnel lens; (vi) liquid crystal optical elements with integrated Pancharatnam-Berry phases. We are sure, that in the field of (LC), the main point is no longer display research, but new photonic applications of LC are emerging in telecommunication, fiber optical communication systems, sensors, switchable lenses, LC light converters and other LC photonics devices.

Optically driven liquid crystal displays (ODLCDs) realizes their display function by tuning the easy axis of liquid crystal (LC) molecules under polarized blue light, which has been utilized in some optical devices due to its advantages of ultra-low power consumption. However, a big issue arises in response time, i.e., the rewriting time of the ODLCD. The rewriting time of ODLCD samples was studied. Rotational viscosity plays a very important role for decreasing the rewriting time of the ODLCD. The operating temperature was changed from room temperature to nearly clearing point, the rewriting time decreased a lot as the rotational viscosity decreased for the five different kinds of the LCs. The rewriting time can be decreased from 5.2 s to 0.2 s around 25 times for the LC N4.

It is very difficult to display greyscale for an optically driving liquid crystal display (ODLCD) because the driving unit and display unit are separate, and there are no electronics in the display part of ODLCD. In this paper, two greyscale generation methods are proposed to achieve this goal. Six and nine grey levels are separately achieved through the two methods. Graphical Abstract

For a liquid crystal display device, like optically rewritable (ORW) e-paper, the response time plays a crucial role. In this article, a new method is proposed to increase the rewriting speed of ORW e-paper. Effective rotational viscosity is very important for the dynamic result, the rewriting time can be increased by four times by applying electric field across the liquid crystal cell, i.e. decrease the effective rotational viscosity .