Micro-sizing degree as a property of ink-jet media printability

摘要

As well as supreme image quality realized by specialized paper, industrial and office printing markets demand uncoated general papers compatible with both offset printing and nonimpact printing. The present work aims at clarifying the behavior of a micro-liquid droplet of water-based ink-jet inks or simply water absorbed into uncoated paper. In the experiment, laboratory handsheets were prepared by adding alkyl ketene dimmer (AKD) as a sizing agent at different levels of water repellency; none, 0.05, 0.10 and 0.20 % on dry pulp mass. The landing action and the absorption into paper of micro-droplets of water ejected from an ink-jet head were recorded by the microscopic high-speed video camera system every millisecond. The period of time between the landing and the completion of absorption was defined as "micro-sizing degree". The micro-sizing degree was approximately 2 to 3 ms up to 0.10 % AKD addition. It is lower than that of commercial silica-coated ink-jet papers which was approximately 8 ms although silica-coated papers are known to absorb water very quickly. However, the micro-sizing degree was approximately 45 ms for the handsheets of 0.20 % AKD addition. This result implies that the water-repellency by AKD is distributed over fiber surfaces so homogeneously that micro-water droplets of diameters of as small as a few micrometers are absorbed stably at similar rates.