Sticker Printing Paste Issue: Small fonts, especially those below size eight, often experience ink drying on top due to the narrow spacing between fine lines. This leads to the problem of graphics and text sticking together and becoming indistinguishable, mainly because the ink dries too quickly.
Our company currently uses a well-known resin plate ink with high viscosity. Coupled with high temperatures, the ink dries quickly, resulting in a phenomenon known as dry plate, especially in the case of very detailed stickers in flexographic printing.
To address this issue, we need to start by examining the resin plate itself. Ideally, the bottom of the resin plate's characters should feel smooth and not sticky. However, due to insufficient exposure, the bottom of the characters becomes sticky, easily trapping the ink. As a result, more ink accumulates and dries within the fine lines. Discarding the plate would be wasteful, so a post-treatment solution can be applied using a resin plate post-treatment liquid.
This post-treatment liquid contains sodium hypochlorite and hydrochloric acid, effectively hardening the character bottoms and resolving the stickiness issue. The fundamental solution lies in determining the accurate exposure time to produce resin plates that meet the standard.
For exceptionally fine fonts, it's advisable to consider switching to copper-zinc plates. Fonts on copper-zinc plates are less prone to ink drying between characters, and the characters are harder, making it easier to achieve clear strokes.
In terms of the operating environment, reducing air convection is crucial. If the issue persists, adding an appropriate slow-drying agent to the ink can decrease the drying speed. Additionally, moderately increasing the printing speed can prevent excessive ink drying.