NanoSight

Inks and Pigments

Background

Particle size and particle size distribution remain core measures in determining the functional and handling properties of pigment-based inkjet inks. Colour density, opacity and viscosity depend directly upon particle size. As jet nozzles get smaller and more numerous and the resolution demands of customers grow, the need to fully understand agglomeration and dispersion stability increases. Existing techniques that address particle size in the sub-500 nm range have significant limitations with inkjet systems:

• Dynamic Light Scattering (or Photon Correlation Spectroscopy) is inherently limited in assessing polydisperse suspensions. This is due to the measured signal being strongly intensity-weighted towards larger particles as the scattering from deeply sub- micron particles tends to proportionality to the sixth power of their diameter
• Electron microscopy, whilst providing a detailed insight into morphology, surface structure and much more, it is inherently intrusive in preparation and doesn't necessarily provide information about the sample in its natural state.

Fig.1 Shows an overlay of graphs from a sample of magenta ink pre and post ball milling. Fig.1 shows that the milled sample has a higher concentration of particles as well as a much narrower distribution of particle sizes than the raw material.

Fig.2 Shows a normalised version of Fig.1.

Application Note

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