Flexographic printing is a printing process that has developed rapidly in recent years. The graphic part of the printing plate is higher than the non-image part, and has elasticity, which can better express the subtle level and contour of the graphic part. In addition, it is suitable for a wide range of printing materials. Except for the traditional paper, some non-absorbent printing material such as plastic film, aluminum foil composite paper, cellophane, etc, can also be taken flexographic printing.

　　There are several things that we should pay attention to when adopting the flexographic printing with UV ink, that is, coloring, curing and adhesion etc, and we should also closely watch out the influence that ink composition has on the ink viscosity and rheology 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 flexographic printing inks are solvent-based and water-based, which requires a large amount of solvent or water to adjust the viscosity. Due to the large amount of solvent used, most flexographic printing inks approximate the Newtonian fluid in terms of rheology, which causes ink to settle down and become unstable. Therefore, proper thixotropy imparted to the flexographic printing ink prevents the pigment from flocculation and sedimentation.

UV flexographic printing inks use reactive diluents to reduce the viscosity of the system. Therefore, in general, their viscosity may be higher than solvent-based flexographic printing inks.

　　Although the viscosity of UV flexographic printing inks is lower than that of screen printing and offset printing inks, the addition of pigments increases the viscosity, especially when the pigments are wet, dispersed, and stable.

　　In addition, the influence of pigment on the rheology of the ink is more important, and proper thixotropy is beneficial because when the molecular crosslinking inside the ink reaches a certain degree and pseudoplasticity occurs, the ink system without the pigment dispersion stabilizer is on the high-speed running ink roller, and the viscosity will drop sharply, but when the ink roller enters the printing portion with a relatively low rate of entry, the viscosity will rise rapidly, and the wetting effect on the surface of the substrate is too poor to be suitable for printing.

　　The ink containing a suitable dispersion stabilizer has a certain stability, and its viscosity is not high. After high shear, the viscosity rises slowly and the printing adaptability is good.