Ink-Jet Particle Sizing
The Mastersizer 3000 uses the technique of laser diffraction to measure the size of particles in the range from 0.02 microns to 2000 microns. This is achieved without the need for changes to the optical system.
The technique is therefore ideal for monitoring the size of pigment-based ink-jet inks during milling as the particle size of both the “primary” ink particles and any large agglomerates can be measured as part of the same measurement.
Ink Dispersion and Milling
The production of ink-jet inks is a two stage process. First, the pigment is dispersed in an appropriate mobile phase using a mechanical stirrer. This ensures that any lumps of pigment powder are dispersed. This “pre-mix” sample is then milled using a ball-mill in order to reduce the particle size and cause the break-up of any strongly bound aggregates.
Figure 2 shows the particle size distributions reported by the Mastersizer 3000 during the milling of ink jet ink. The premix dispersion fed into the mill at the beginning of the mill run contained large aggregates.
The Mastersizer 3000 was able to successfully track the break-up of these aggregates during milling. After 180 minutes, a narrow distribution was obtained, centered at around 137nm. At this particle size the risk of jet-blockage and defect formation during printing is minimized.