How to Solve Reverse Overprinting Phenomenon During Low-Speed Printing?

Posted on 05-09-2024 by

Reverse overprinting is particularly evident during mid-to-low-speed printing, with a significant decrease in reverse overprinting phenomenon at high speeds. The key to solving the issue of reverse overprinting lies in analyzing its causes. Typically, during reverse overprinting, ink from the preceding color transfers to the plate of the subsequent color, thus entering the ink fountain of the subsequent color and altering its color, ultimately leading to printing interruption, such as yellow ink gradually turning into light green and red ink gradually turning into purplish-red.

Solutions can generally be approached from the following aspects:

1. Adjust the proportion of diluting solvent in the subsequent color ink to reduce its dissolving capacity towards the preceding color ink upon contact. When diluting the subsequent color ink, adding a portion of isopropanol and minimizing the use of toluene is advisable.

2. Increase printing speed. Elevating printing speed significantly reduces the contact time between subsequent color ink and preceding color ink. This explains why reverse overprinting is particularly evident at low speeds but virtually absent at high speeds. However, achieving higher printing speeds may be constrained by printing equipment and environmental factors.

3. Adjust the composition of printing ink formula. Firstly, enhancing the adhesion of preceding color ink to BOPP film can be achieved to ensure that when two layers of ink come into contact, the preceding color ink remains attached to the BOPP film. In ink systems such as CL-PP, increasing the content of CL-PP generally resolves this issue. Additionally, accelerating the drying speed of preceding color ink by increasing the drying tunnel temperature helps prevent the presence of small amounts of unevaporated solvent in the ink film.