As printhead and inkjet technology are progressing, the demand for characterisation of inks regarding their pigment size, the presence of single oversized grains and overall colloidal stability is increasing. The size of pigments has a significant impact on factors like printability, printhead blockages, sharpness of text, optical density and colour gamut.
A toolbox of different methods for the characterisation of pigment sizes is available. Depending on whether the analysis takes place in development, process or quality control, complimentary technologies can be used.
Laser Diffraction is the most popular method of particle size analysis for incoming raw materials and for the milling process, allowing close control and optimisation of pigment size. This method has the greatest measuring range, but dilution will be required for suspended pigments in order to obtain sufficient light transmission through the ink. A growing number of specialists uses the combination of laser diffraction and Dynamic Image Analysis, which can be combined in a single instrument. Integrated Image Analysis is able to detect single oversized particles or clumps which cause a risk of printhead nozzle blockages. Finally, Heterodyne Dynamic Light Scattering can be used to measure the size of nano-pigments and dyes in the final product with little dilution, as it is able to handle higher concentrations, especially when using backscatter systems with Reference Beating. The formulation stability and the risk of formation of aggregates can be evaluated by Zeta Potential analysis.
My presentation at the IMI Europe Inkjet Ink Development Conference will describe the latest advances in the key techniques of Laser Diffraction, Dynamic Image Analysis and Heterodyne Dynamic Light Scattering. We will discuss experiences of using these technologies with inkjet inks and show some case studies of the control of pigment sizes related to inkjet ink performance.
I look forward to meeting you in Lausanne!
Dr Thomas Benen