Wide-Band Reflection Of The Cholesteric Liquid Crystals Based On The Chiral Photo-responsible Azobenzene Compound Azo-o-Bi

Cholesteric liquid crystals (CLCs) can selectively reflect the specific band of light due to its self-assembled helical structure which is also named Bragg reflection. The reflection wavelength of the CLCs can be reversibly tuned upon light irradiation by adding the photo-sensitive chiral dopants. However, the reflection bandwidth is around 100 nm owing to the limits of birefringence, which greatly limits the CLCs application in the reflective devices. Broer et al. broadened the reflection band of CLCs under light irradiation, however, there still are some problems such as:instability, irreversibly controlling. The researches about reversibly photo-tuning reflection wavelength and photo-induced wide-band reflection are independently since different devices needs different materials and conditions which limited the application of CLC devices. On account of these points, the research contents of this article include:(1) A new photo-sensitive CLC device was made by adding a chiral photo-responsible azobenzene compound Azo-o-Bi. And the Bragg reflection band of the CLC device was successfully tuning upon light irradiation.(2) We found that the HTP and AHTP of the Azo-o-Bi was bigger in the cholesteric liquid crystal with higher viscosity by studying the influence of liquid crystal viscosity on the chirality of chiral dopant. And we found that the stability of CLC device is better in the device with higher viscosity by studying the light-induced band tuning of CLC device and the stability of the device in the dark condition.(3) The broad-band reflection state was successfully made by controlling the irradiation light. A new approach to control, passively, the reflective wavelength and bandwidth of induced same CLC films for the first time. And the broad-band reflection state was stable in the dark condition.In this research, the reflective wavelength and bandwidth can be reversibly controlled upon light irradiation. And we successfully prepared the red (R), green (G)and blue (B) display device and white-in-black display device. The Bragg reflective band is accurately, sensitive controlled with light irradiation.