Ink Dot Formation in Coating Layer of Ink-Jet Paper with Modified Calcium Carbonate

Abstract

Commercial ink-jet papers are made from silica or alumina as a coating pigment, both of which give high image quality, but are expensive. The present work aims at efficient use of calcium carbonate as an alternative of silica for ink receptive coating layers. Commercial calcium carbonate was ground mechanically or dissolved partially with hydrochloric acid to reduce and equalize the aggregates size. Trial ink-jet papers were prepared and some of them were plasma-etched to give a hydrophilic property. The trial ink-jet papers were evaluated in terms of dynamic behavior of ink droplets ejected from a test ink-jet head visualized by a microscopic high-speed video camera system and of ink penetration depth determined by confocal laser scanning microscope (CLSM). Particle size reduction of calcium carbonate pigment by mechanical grinding and hydrochloric acid dissolution decreased ink dot area and dot roughness on the papers. This result suggests that particle size reduction improves image quality. Based on the criterion standard that the smaller the dot area, the better the image quality, the efficient processes were mechanical grinding, hydrochloric acid dissolution and plasma-etching in the decreasing order. It is concluded that particle size reduction decreases pore size of the coating structures and consequently ink droplets tend to penetrate deep in coatings rather than spread laterally along surfaces.