Security device, method of making a security device and method of authenticating a product

摘要

A method of producing a security device (60) is disclosed. The method comprises inkjet printing a liquid crystal material onto a first region (61) of a substrate and ink jet printing the same liquid crystal material onto a second region (62) of the substrate. The volume of the liquid crystal material printed per unit area of the substrate in the first region of the substrate is different to the volume of the liquid crystal material printed per unit area of the substrate in the second region of the substrate such that the wavelength of the peak reflectance of the liquid crystal material on the first region is different to the wavelength of the peak reflectance of the liquid crystal material on the second region.