Effects of Pigment Type and Pore Structure on Optical Properties & Rotogravure Printability of Light Weight Coated (LWC) Paper, 2000 Coating Conference Proceedings

P. B. Malla, R. E. Starr, T. J. Werkin, S. Devisetti--A statistically designed LWC study was conducted using a cylindrical laboratory coater (CLC) to determine the effects of pigment type and coating pore structure on coated sheet optical properties and rotogravure printability. The results show that delaminated clay improved gloss, brightness, and opacity over talc. Calcined clay further improved brightness, opacity, and rotogravure printability, but reduced gloss. Talc deteriorated gloss, brightness, and opacity, but enhanced rotogravure printability. One or several optimum combinations of these pigments have been identified that would improve overall optical and print properties. Analysis of Croda Red ink absorption, smoothness, and pore structure data indicate that ink absorption does not correlate with rotogravure printability. Printability may or may not correlate with PPS roughness (dynamic roughness) depending on initial roughness (i.e., gloss) and calender conditions. However, pore size data show a definite relationship with rotogravure printability in that printability improves with increases in pore size. However, further study is needed to determine whether this is primarily due to improved ink absorption/transfer and/or improved smoothness/compressibility of the coating film.