The most common way to solve the adhesion of UV curing coating for UV flat printer is to apply a layer of UV primer on the surface of substrate. Due to the requirements of environmental protection, water-based bottom oil has become a logical choice. The basic function of Waterborne UV primer is to ensure the adhesion with substrate and UV coating. In the formulation, the following factors should be paid attention to:

1. Wettability of Waterborne UV primer to substrate: due to the high surface tension of water, an appropriate amount of wetting agent should be added to the formulation of waterborne coating to ensure that the primer evenly covers the substrate and reduce defects.

2. Adhesion of UV base oil to substrate: except that the base oil has good wettability to the substrate, the adhesion to the substrate is mainly determined by the type of resin.

3. Strength after UV base oil curing: the strength requirements after base oil curing come from the coating process on the one hand and the necessity of ensuring adhesion on the other hand.

4. Adhesion of UV base oil to UV paint and ink: this performance is the key to the success of the base oil. On the one hand, the base oil resin fused with UV resin should be used to ensure affinity. On the other hand, appropriate additives can be used to promote the penetration of UV resin in the base oil layer.