From the point of view of characterisation, inkjet inks are really interesting systems. They are complex dispersions or emulsions with dyes or pigments, along with other components, all suspended in a continuous phase. If you change the properties of any one of these components it can impact multiple aspects of the final ink. For example, the particle size of the pigment determines the hue, gloss, opacity and weatherability of the coating finish. The particle size and particle size distribution will also determine the stability of the ink as well as flow properties such as viscosity.
Due to the complexity of these systems they can be challenging to measure, however, by using complimentary analytical techniques the properties of the particles and final suspension can be assessed and optimised for each application.
Different analytical techniques can be used at different stages of the inkjet development process. The wide dynamic range of laser diffraction makes it ideal for following the milling process from the premix, which might contain agglomerates larger than 100 microns, to the final primary particle size at around 200 nm. Dynamic light scattering provides the ability to measure the particle size of the primary pigment at concentrations much closer to that of the original sample, which also allows the effect of sample dilution to be investigated.
My presentation at the IMI Europe Inkjet Ink Development Conference will describe how the techniques of laser diffraction and dynamic light scattering work, discuss some of the challenges of applying these technologies to inkjet inks and then present some case studies where these technologies have been used to control production processes and optimise ink performance.
I look forward to seeing you there!
Dr Anne Virden
Product Technical Specialist – Diffraction and Analytical Imaging, Technical Support Supervisor