The present invention relates to the field of security inks suitable for printing security features on substrates, in particular on security documents or articles as well as security features made from said security inks, and security documents comprising a security feature made from said security inks. In particular, the invention provides UV-Vis radiation radically curable security inks comprising an ink vehicle and pigments comprising a flake-shaped non-metallic or metallic substrate comprising one or more at least partial coating layers, an at least partial surface treatment layer made of one or more surface modifiers selected from fluoro compounds.