Distribution of Offset Ink Constituents in Paper Coating and Implications for Print Quality

The implications arising from the distribution of offset ink components in a paper coating structure are presented. The work focuses on two mechanisms causing differential distribution of ink constituents, namely (a) adsorption chromatography, resulting from coating pigment chemistry and morphology variables, and (b) latex-oil diffusional interaction. Adsorption chromatographic fractionation and resultant distribution of ink constituents in a coating structure are shown clearly to affect print quality parameters like print gloss and density. Latex-oil diffusion and its dependent distribution, however, strongly affect ink setting dynamics but no observable effect was found on print gloss and density. This difference in effects is suggested to be due to the fact that adsorption delays the absorption of slightly polar oils, hence delaying the upconcentration of solved resins at the ink-coating interface, whereas diffusional absorption of the polar oils by latex, usually on a longer timescale occurs in volume terms away from the critical initial upconcentration region of ink setting and cohesive tack build.