Optical variable pigment technologies for markings and inks have increased in use as overt protection methods for document and product security. These technologies use optical reflective effects including interference technologies that create angular dependent color changes. Novel developments in different inorganic and organic pigments offer potentially new optical performance for both overt and covert security applications. These developments may lead to unique signature pigment formats that can verify origin and authenticity. Cholesteric Liquid Crystal (CLC) pigment approaches utilize both angular dependent color flop and the unique polarization properties to potentially develop markings with both overt and covert detection mechanisms. Continuous improvement in these technologies may lead to new visible and non-visible applications that when integrated with the graphic design will provide novel protection and graphic impact.
Various single layer reflective polarizers are introduced based on cholesteric liquid crystal materials containing one polymeric liquid crystal component and other non-reactive liquid crystals. A non-linear pitch gradient has been created during a process called polymerization induced molecular re-distribution. The polarizers in the visible exhibits a high extinction ration (over 30:1) over a bandwidth from 400 to 1,000 nm. When tuned to the near infrared, the polarizer reflects from 700 to 2,000 nm. In addition, field controllable broadband polarizers will be briefly introduced. Finally, applications will be described.
The procedure for the preparation of CdSe/CdS/ZnS photoconductors is described, and the results of characterization of photoconductors are presented. It was found that the spectral response peak of the photoconductor can be shifted to the shorter wavelength region by changing the relative content of ZnS. However, this can be done only at the cost of decreasing photosensitivity.
This paper reports an improved laser-addressed LCLV that employs scattering structure of smectic liquid crystal as display background. Its LC layer will not be easily electrically broken down. Full erasure can be achieved within 0.5 - 1 second. We also present a new method utilizing an insulative layer (inert insulative film) that is sandwiched between the LC layer and transparent electrode-absorbing layer. Such structure makes it possible to avoid decreasing LCLVs input sensitivity, which is caused by an increase of LC layer thickness, to improve bearing ability to high voltage and large current, and to achieve fast full erasure. Its highest breakdown voltage reaches 690 Vrms.