Cholesteric liquid crystal films

Optically active polymerizable liquid-crystal monomers, (I), providing polymeric cholesteric liquid-crystal films were prepared by Seki et al. (2) and used in optical applications. 

Cholesteric liquid crystal films are applied by painting or spraying a solution of the liquid crystal onto a surface. Cholesteric liquid crystals have been used to measure microwave energy, infrared light (such as in surface thermography), visible... 

Fig. 4.1.15. First and second order reflexion spectra of a cholesteric liquid crystal film (0.45 0.55 mole fraction mixture of 4 -bis(2-methylbutoxy)-azoxybenzene and 4,4 -di-n-hexoxyazoxybenzene) 15 pitch lengths or 11.47 on thick. Angle of incidence 45°. Polarizer and analyser are parallel to the plane of reflexion for and normal to it for measurements. The small oscillations are interference fringes from the two cholesteric-glass interfaces. (After Berreman and Scheffer. )...

S.K.-H. Wei, S.H. Chen, Spatially resolved lasers using a glassy cholesteric liquid crystal film with lateral pitch gradient. Appl. Phys. Lett. 98, 111112 (2011)... 

Schmidtke J, Stille W (2003) Fluorescence of a dye-doped cholesteric liquid crystal film in the region of the stop band theory and experiment. Eur Phys J B Condensed Matter Complex Sy St 31 179... 

D. W. Berreman and T. J. Scheffer, Bragg reflection of light from single-domain cholesteric liquid crystal films, Phys. Rev. Lett., 25, 577 (1970). 

Reflection and Transmission by Single-Domain Cholesteric Liquid Crystal Films Theory and Verificationt... 

We have used a 4 x 4 matrix formulation of the electromagnetic wave equations in stratified media to compute the reflectance and transmittance of single-domain cholesteric liquid crystal films. Our technique is basically equivalent to the 4x4 matrix technique first described by Teitler and Henvis, ) applied by them to... 

Schmidtke J, Stifle W (2003) Photonic defect modes in cholesteric liquid crystal films. Eur Phys J E Soft Matter 12 553-564... 

Optical Properties of Cholesteric Liquid-Crystal Films... 

There are two possibilities of obtaining direct temperature diagrams of objects either the infrared radiation from the object is focused by a suitable optical system onto an infrared-absorbant layer and this layer is in good thermal contact with a cholesteric liquid crystal film, or the object is brought into direct thermal contact with a cholesteric liquid crystal film. The cholesteric film then converts the temperature diagram of the object into visible form. This can either be directly viewed by illuminating with a suitable light source or automatically evaluated. 

Cholesteric liquid crystals can also be used to display sound fields, especially ultrasonic fields [13, 14]. The ultrasonic source is immersed in water and directed at a black foil on the water surface. The upper side of the foil is coated with a cholesteric liquid crystal film. The acoustic irradiation of the indicator foil generates colored images of the ultrasonic source and also various interference patterns. The reason for colors appearing can be attributed to conversion to heat of the ultrasonic energy absorbed by the foil. 

In imaging methods based on the deformation of an insulating viscous film, an electrostatic pattern becomes visible. With a cholesteric liquid crystal film, deformation of the film caused by an electrostatic pattern yields a colored picture. As the electrostatic pattern is controllable by incident light, electrophotographic imaging is obtained [21]. 

See, for example, D. W. Berreman and T. J. Scheffer, Reflection and Transmission by Single-Domain Cholesteric Liquid Crystal Films Theory and Verification, Mol. Cryst. and Liquid Cryst, 11, p. 395 (1970) R. Dreher and G. Meier, Optical Properties of Cholesteric Liquid Crystals, Phys. Rev., A8, p. 1616(1973). 

Ma, J., Zheng, Z., Liu, Y., Xuan, L. Electro-optical properties of polymer stabilized cholesteric liquid crystal film. Chin. Phys. B 20, 024212 (2011)... 

---