Levelling during toner fusing: Effects on surface roughness and gloss of printed paper

Abstract

The results of digital printing trials using a Xeikon press on uncoated and coated paper were analyzed using interferometric profilometry to characterize printed paper topography and toner film thickness. Solid print areas were fused at various temperatures, including radiant fusing with and without heated rolls. The overall surface roughness of the prints is slightly higher on the coated than uncoated paper, but is mainly dictated by transferred toner amount and fusing conditions. Increased toner coverage degree, or layer thickness, gives reduced surface roughness, provided the applied fusing power suffices. Increase in radiant fusing temperature yields a decrease in overall print roughness, however, this decrease is more pronounced on coated paper and higher toner amounts. Bandpass analysis of print surface roughness shows that short-sca/e roughness at or below the lateral length scales of toner particle dimensions always decreases with increasing radiant fusing temperature, whereas roughness contributions at wavelengths above 10 μm can increase, with this transition value being shorter on coated paper and at lower toner amounts. Print gloss after radiant fusing is strongly correlated to print roughness on wavelengths up to this transition length scale, and the correlation can extend to order 100 μm if complemented by heated roll fusing.