Printing Plastics not a Slam Dunk with UV
I spent last week at a customer completing some testing on various plastic substrates with the goal of achieving the best possible result for one of its new clients. We tested everything from inks and coatings to lamp energy, settings and placement. All of which had an effect on the final outcome.
The objective is to use a sufficient amount of energy to dry the inks correctly, but not to distort the plastic so it looks like a potato chip.
You have to keep in mind that just because you have invested all that money into UV capabilities, it doesn’t give you the guarantee that you will have instantaneous success with printing on non porous substrates.
Dyne levels of the plastics along with chemistry compatibility continue to have a large effect on successful adhesion and end result. It continues to be as important as it is with conventional printing.
You will realize the end result much quicker as the sheets fall into the delivery, but if you don’t take into consideration the complexity of the project at the finishing end, the outcome could be devastating.
It's one thing to print a transparent menu for your local hotdog stand or a liquor advertisement for your local grocery store window, but it’s another matter entirely to create a packaging piece that not only scores, folds ands glues but also gets a coupon attached to the outside of the carton with a removable adhesive.
I can assure you that if the ink doesn’t stick while you’re running the job, it’s not going to get a great deal better after the fact. You have to verify the adhesion on press. You may use a UV coating to cover the sheet, but is this process giving you the feeling of a true or false adhesion? Chances are, false.
Most ink companies manufacture a series of UV inks that are formulated specifically for plastics, much as they do with the conventional process. Many times this set of ink will give you the best results. I realize this constitutes an additional wash up, but the alternative is the job having to be rerun on a substrate that could cost upwards of $2 per each 40˝ sheet.
What costs less—the testing of chemistry and a possible additional wash up or the plastic itself? You decide.