Print Gloss Development on Model Substrates, 1996 International Printing & Graphic Arts Conference Proceedings

Travis Glatter and Douglas W. Bousfield

University of Maine

A laser beam-detector system is used to continually record the gloss of an ink film within a tenth of a second of application on a laboratory print tester (KRK). The sample is printed at one to eight meters per second and stopped 0.1 m after the nip exit. About a 100 mm 2 area of ink is monitored at 75° angle with the laser beam. The printing speed and ink film thickness have a strong influence on the results: high speeds (8 m/s) along with high ink levels (5 µm) produce an ink film which levels rapidly but subsequently slows down and produces a lower gloss sample. The leveling of an ink film on a rough surfaces is modeled based on the long-wave approximation to the Navier-Stokes equations. Given the ink film thickness, the substrate roughness, ink surface tension and viscosity, the leveling of the ink film is calculated. The model can start from any initial film profile. The model indicates that the wavelength of the roughness is the most critical parameter in the model: long wavelengths have a slow leveling rate. Thin ink films reduce the leveling rate and in some cases cannot fill up the surface roughness. The model predictions are compared to experiments.