On estimation of complex refractive index and colour of dry black and cyan offset inks by a multi-function spectrophotometer

The optical properties of inks have much importance in quality inspection of prints. For instance, gloss and gloss mottling of a print depend not only on the surface roughness of the print but also on the spectral properties such as the wavelength-dependent complex refractive index of the ink. We have developed a device, the so-called multi-function spectrophotometer (MFS), that allows the measurement of reflectance and thereby assessment of the complex refractive index of the dry ink. Here, we report on the complex refractive index of dry black and cyan offset inks. Such information has importance in the study of gloss of prints. Furthermore, we show that the colour of these dry inks can be obtained with our apparatus by using light scattering data from the dry ink.