Reverse overprinting is especially noticeable when printing at low and medium speeds. The phenomenon of reverse overprinting is greatly reduced during high-speed printing. The key to solving the problem of reverse overprinting is to analyze the reasons for the clear generation. On the printing plate of the ink, it enters the ink tank of the latter color, and changes the color of the ink of the latter color, which eventually leads to the inability to continue the printing. For example, the yellow ink gradually changes to a light green color, and the red ink gradually changes to a magenta color.
Generally, it can be solved from the following aspects:
1. Adjust the ratio of the diluted solvent of the back color ink to reduce the solubility of the back color ink to the front color ink when in contact with the front color ink. That is, when diluting the back color ink, add a part of isopropyl alcohol and use toluene as little as possible ;
2. Increase the printing speed Increasing the printing speed can significantly reduce the contact time between the back color ink and the front color ink. This is also the reason why reverse overprinting is especially obvious at low speed printing, and there is basically no reason for reverse overprinting during high speed printing. This point may be restricted by printing equipment and printing environment during actual printing;
3. Adjust the formula composition of printing ink
First, you can use the method to improve the adhesion of the front color ink on the BOPP film. When the two layers of ink are in contact, the front color ink still adheres to the BOPP film. In the CL-PP system ink, the CL-PP can generally be increased. Content to be resolved. Secondly, it can increase the drying speed of the front color ink, increase the drying channel temperature of the front color ink, and prevent the presence of a small amount of unvolatile solvent in the ink film.
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