Gloss Development of Spray-coated Systems

A spray-coated system involves any substrate on which a liquid coating is applied in a drop-wise fashion. Inkjet printing is the controlled application of drops to print a surface and is the focus of this work. The gloss of the printed substrate is an important attribute of print quality. Print gloss depends on a number of factors, such as ink and media properties. Non-uniform gloss in different regions of a printed image can cause a decrease in quality of a printed sample. However, a good understanding of the gloss development of spray-coated systems is not available in the literature. Several combinations of inkjet inks and media were characterized in terms of physical properties. Both pigmented and dye-based inks were used with absorbing microporous coated media. These ink/media combinations were printed with an inkjet printer and the final gloss measured. A laser system was used to measure the gloss every millisecond right after printing, around 20 ms after drop impact. Some media were modified with chemicals or other treatments to modify physical and chemical properties. Fiber swelling in paper-based media was found to lower gloss in those media which contain fibers that can contact water. This reduction in gloss occurred one second after printing. Media with protected paper fibers do not exhibit this gloss reduction. Plastic-based media with porous coatings obtained the final gloss at 0.1 seconds. Inks can be destabilized by ions on the media surface that leads to low gloss. Some inks were not sensitive to ions on the media. Light color inks were found to have high gloss values at 50% fill compared to 100% fill while most other inks have the opposite behavior. This phenomenon is likely due to the secondary reflection at the ink/media interface; light is able to transmit through the ink layer and reflect at the media surface.