THE SETTING OF WATER-BASED INKS ON UNCOATED SUBSTRATES

THE SETTING OF WATER-BASED INKS ON UNCOATED SUBSTRATES

By Wing T. Luu

Thesis Advisor: Dr. Douglas W. Bousfield

A Lay Abstract of the Thesis Presented

in Partial Fulfillment of the Requirements for the

Degree of Doctor of Philosophy

(in Chemical Engineering)

December, 2010

The setting and transfer of water-based inks is important in standard printing process and for ink-jet printing.  Changes in ink chemistry or paper surface properties can have a significant impact on print quality, but a good understanding is not clear in the literature. 

The setting and transfer of water-based inks on various uncoated papers were reported as a function of ink formulation and paper surface properties.  Inks were formulated with different polymers and solvents.  Paper surface properties were changed with a polymer type material commonly used in the paper industry.  Papers were printed with a laboratory printing press at different ink volumes.  A mathematical model for water absorption into paper was proposed.  A new method to improve ink-jet printing using a material known as nano-fibrillated cellulose (NFC) was proposed.  

The amount of ink transferred to the paper and its print quality decreased with changes in paper properties for some inks, while minimal differences were seen for other inks even though the inks had similar properties.  Filtration properties of the inks were found to explain the results.  Changes in surface properties had a large effect on ink transfer and print quality for inks with low filtration properties.  For inks with high filtration properties, paper surface properties had no effect on print quality.

The proposed model predicted absorption rates that were consistent with experimental data.  Diffusion of water into the paper fibers was important for some papers. Surface roughness of the papers contributed a significant amount of water absorbed when comparing to the experimental results.

A combination of a NFC and polymer gave a higher print quality for ink-jet printing.  Microscopy revealed that ink droplets spread or contract on the paper surface depending on its surface properties.  The way in which the ink interacts with the paper surface had a large impact on the final print quality.