Relationship between ink film topography and print gloss in offset prints on coated surfaces

• Published in: Nordic pulp & paper research Vol. 23; no. 2; pp. 156 - 163
• Main Authors: Ström, Göran, Karathanasis, Michael
• Format: Journal Article
• Language: English
• Published: De Gruyter 01.01.2008
• Subjects: AFM; Atomic Force Microscopy; Coated paper; Coating; Ink; Print gloss; Printing; Roughness; Scanning Electron Microscopy; SEM
• DOI: 10.3183/npprj-2008-23-02-p156-163
• ISSN: 0283-2631; 2000-0669

Model coatings with different micro roughness but similar and low macro roughness were prepared and laboratory printed. The coating micro roughness strongly affected the print gloss at low inking levels, corresponding to one or two full tone layers. The effect of coating micro roughness decreased with ink amount and was insignificant at inking levels of 3-4 g/m2, which corresponds roughly to three to four full tone layers. A strong correlation between ink film micro roughness and print gloss was established. Remaining ink filament patterns that had survived the ink levelling process were observed with a fast-setting coating but not with a slow-setting coating. The amplitude of the filaments was a few tenths of a urn only and was strongly dependent on ink amount. The filaments were observed in wavelength bands between 15 and 125 ÎŒm, which can be regarded as a sub-macro roughness region. Their impact on print gloss was estimated on some 6 gloss units.