Not all materials are ideal printing substrates. The printing characteristics of surfaces are determined by factors such as surface tension and the extent to which a water drop will spread on it.
On untreated film surfaces, inks will tend to run making it a challenge to print on smooth and non-porous materials such as plastics. Most plastics that are used to produce film labels have a non-polar (chemically inert) and water-repellent surface on which it is difficult to get inks to adhere.
In order to produce good printing results on film labels, the labels must be pretreated on the side on which they are to be printed. There are two processes that have become standard techniques in practice; the application of a permanent top coat and the more cost-effective corona treatment.
The corona treatment involves exposing the film surface to a high frequency discharge that both increases the surface tension of the material and enhances its bonding characteristics. Such pretreated films can be permanently printed with smear-resistant text. However, as the surface energy dissipates over time, the bonding capacity of the material also decreases.
But there is a solution to this problem. To achieve optimal printing results, the surface energy of corona-treated materials can be replenished in special corona systems immediately prior to printing.
At Weber Marking Systems, we have the corresponding equipment for use in the production of our own labels so that our comprehensive range includes both top-coated film labels and the more inexpensive corona-treated film labels. Corona-treated films are perfectly suitable for many printing applications and the results are absolutely satisfactory.