Addressing Reverse Printing Issues in Medium to Low-Speed Printing
Reverse printing is particularly noticeable in medium to low-speed printing, with a significant decrease in reverse printing observed at high printing speeds. The key to resolving reverse printing problems lies in thoroughly analyzing the underlying causes. During reverse printing, ink from the preceding color typically transfers to the plate of the subsequent color, entering the ink fountain and altering the color of the subsequent ink. This ultimately halts the printing process, transforming, for example, yellow ink into a gradually lighter green hue or red ink into a purplish-red color.
Solutions:
Adjust the Dilution Solvent Ratio of the Subsequent Ink: Modify the ratio of dilution solvents in the subsequent ink to decrease its ability to dissolve the preceding ink upon contact. When diluting the subsequent ink, introduce a portion of isopropanol and minimize the use of toluene.
Increase Printing Speed: Elevating the printing speed significantly reduces the contact time between subsequent and preceding inks. This is particularly effective in minimizing reverse printing at high speeds, where it is more pronounced during low-speed printing. However, this approach may be subject to limitations based on printing equipment and environmental factors.
Adjust the Ink Formulation:
Enhance the adhesion of the preceding ink to BOPP film to ensure it adheres during contact with the subsequent ink. This can be achieved by increasing the content of CL-PP in CL-PP ink systems.
Accelerate the drying speed of the preceding ink by increasing the drying temperature in the drying oven, preventing the presence of residual solvents in the ink film.