Ultraviolet light screen using cholesteric liquid crystal capsules on the basis of selective reflection

Sunscreen can protect human skin from sunlight by decreasing exposure to ultraviolet (UV) light, specifically UV-B and UV-A. In this study, a new type of UV screen system is proposed using cholesteric liquid crystal (CLC) capable of selectively reflecting UV-A within the human skin temperature range of 32-36 °C. Polycaprolactone (PCL) capsules with CLC mixture which had a helical chiral pitch corresponding to the wavelength of UV light were made by a solvent evaporation method. The average diameter of the capsules was about 34 μm. Consequently, it was confirmed that the CLC mixture (COC : CN = 80 : 20) could reflect UV-A light over 350-380 nm within the human skin temperature range. Also, it was confirmed that the CLC/PCL microcapsules could block UV light over 290-400 nm by about 6%.