UV flexographic ink properties

Flexographic printing is a kind of printing technology that has developed rapidly in recent years. The graphic and textual parts of the printing plate are higher than the non-graphical parts, and they are flexible. They can express the subtle levels and outlines of the graphic parts. In addition, its applicable printing materials are very extensive, in addition to the traditional paper, some non-absorbable printing materials, such as plastic film, aluminum foil composite paper, glass paper, etc. can also use flexographic printing.

The use of UV ink for flexographic printing, in addition to attention should be paid to coloring, curing and adhesion problems, but also must pay attention to ink components on the ink viscosity, rheological effects in order to obtain better printability and stability.

The flexographic printing process determines that the UV ink used should not have a high viscosity. Conventional flexo printing inks are solvent-based and water-based. They require a large amount of solvent or water to adjust the viscosity. Due to the large amount of solvents used, most flexographic printing inks are similar to Newtonian fluids in terms of rheology, causing ink settling and instability. Therefore, imparting appropriate thixotropy to the flexographic printing ink can prevent the pigment flocculating from settling.

UV flexographic printing inks use reactive diluents to reduce the viscosity of the system, and therefore their viscosity may generally be higher than solvent-based flexographic printing inks. Although the viscosity of UV flexo printing inks is lower than that of screen printing and offset printing inks, the addition of pigments will increase the viscosity, especially when the wetting, dispersion, and stability of the pigments are not handled properly. In addition, the influence of pigments on the rheological properties of inks is more important, and the appropriate thixotropy is beneficial because when there is a degree of pseudo-plasticity in the cross-linking of the molecules inside the ink, there is no ink dispersion system for pigment dispersion stabilizers. The viscosity of the ink roller on high-speed operation will drastically drop, but when the ink roller enters the printing position where the ink roller enters a relatively low speed, the viscosity will quickly rise and the wetting effect on the surface of the substrate will be too poor to be suitable for printing. The ink containing a suitable dispersion stabilizer has a certain stability, and its own viscosity is not high, after a high shear, the viscosity rises slowly and the printing adaptability is better.