A study of the effect of water-pick up of UV curable offset ink on its curing time and its end use properties
Note: imported from RIT’s Digital Media Library running on DSpace to RIT Scholar Works. Physical copy available through RIT's The Wallace Library at: Z247 .F38 1993
The curing time and the end use properties are as important as printing quality for the printer. Shorter curing time equals more jobs and higher productivity each week. The latest available technology for decreasing curing time is Ultraviolet curing technology. This technology uses ultraviolet radiation as the energy source to excite the active site of the monomer in the ink to start the polymerization process. The desired result is a hard polymerized ink film. Another advantage of Ultraviolet curing technology is that the ink is solventless. The screen printing process has the advantage of being a single-fluid printing process. Ink is the only chemical compound to be considered in this printing process. Lithography requires compatibility between ink and fountain solution. Extensive research has been done to better understand the relationship between fountain solution and ink, primarily with conventional ink. The water pickup characteristics of conventional ink is mainly studied for the effect of water on the printing quality. Due to the nature of Ultraviolet ink, the water-ink relation is more complicated. The water pickup by the ink is thought to have an effect on the curing process. This thesis studies the effect of water pickup of ultraviolet ink on curing time and end use properties. The water pickup of the ink was varied by using three levels of acidity for the fountain solution. To simulate the actual printing condition, the fountain solutions used were those commonly used on press. Three resistance properties including film hardness, IX abrasion resistance and adhesion resistance were measured in this study for responses relating to end use. The effect of the substrate absorptivity on the curing time was also reviewed. This study indicates that the higher water pickup of the Ultraviolet ink needed longer curing time. There is a significant effect of acidity of fountain solution on water pickup of the ink. Curing time is considerably affected by the color of the ink or by the transmission properties of the pigment. Cyan acts like a neutral density filter on the printed film. Increased absorptivity of the substrate helps shorten the curing time. Water pickup of the UV inks affects its film hardness. High water pickup decreased film hardness. On the other hand, the effect of water pickup of the ink with regard to abrasion resistance and adhesion resistance is insignificant. Tack as a rheological property of the ink and the curing stages are also reviewed in this study.