How to Solve Reverse Printing Issues in the Printing Process:
Reverse printing is particularly evident in medium to low-speed printing, diminishing significantly at high speeds. The key to resolving reverse printing issues lies in analyzing the root causes. During reverse printing, the ink from the preceding color transfers to the plate of the subsequent color, entering the ink chamber and altering the color, ultimately halting the printing process (e.g., yellow ink gradually turning into light green, red ink transforming into purple-red).
Here are several approaches to address the issue:
Adjust the Diluent Solvent Ratio for the Subsequent Color Ink:
Reduce the dissolving capability of the subsequent color ink when it comes into contact with the preceding color ink. Add a portion of isopropanol when diluting the subsequent color ink and minimize the use of toluene.
Increase Printing Speed:
Higher printing speeds noticeably decrease the contact time between subsequent color ink and preceding color ink. This reduction is particularly significant at low speeds, with minimal to no reverse printing observed at high speeds. Note that printing equipment and environmental factors may limit this approach.
Adjust the Composition of Printing Ink:
Enhance the adhesion of the preceding color ink to BOPP film, ensuring it remains attached when both ink layers come into contact. For inks in the CL-PP system, increasing the CL-PP content is a common solution.
Accelerate the drying speed of the preceding color ink by raising the drying temperature, preventing the presence of residual solvents in the ink film.