The influence of coating and ink properties on ink setting rate on coated paper.

摘要

The ink setting is the last step of the printing process and determines the final quality of the printed product. In this study, mechanisms that control the rate of ink setting on the porous structure and the coating latex matrix are experimentally and theoretically investigated.; A glossmeter records the ink film gloss dynamics at the exit of the nip. Low initial print gloss is found to correlate with low final gloss and low "print snap". Therefore, the dynamics at short times do influence the final properties. Small coating pigments are found to give low gloss. A mechanism is proposed to explain the results: small pigments are able to pull ink mobile phase from the ink layer that stops the leveling of filament remains. The ink setting on coated paper is determined by the pore structure at low binder content. At high binder level, latex solubility characteristics are found to control the ink setting. An ink with a high viscosity and a fast elastic structure recovery produces low print gloss on plastic film. On a slow setting paper, ink rheology determines ink leveling. Ink formulation strongly influences leveling patterns.; A physical model is proposed to describe the surface-tension-driven leveling of a suspension on a porous surface as some of the fluid phase is removed by capillary pressure and by diffusion into a polymer matrix. Theoretical results are compared to experimental gloss data. The results predict the correct trends in terms of latex type, latex content and pigment size. The model suggests that resistance to vehicle loss is in the filtercake while the removal driving force increases with decreasing pore size.; A novel device follows the change in amplitude and phase angle of an oscillating probe that is in contact with the ink film surface shortly after printing. Oscillation amplitudes decrease sharply and to a low level on fast setting surfaces. The probe can distinguish between fast and slow setting surfaces. The experimental results suggest a filtercake formation type mechanism for ink setting.