Pressure-sensitive labels are plastic or paper labels on the backs of which adhesive has been pre-applied, enabling them to be placed securely on package surfaces. The “pressure-sensitive” designation reflects that the labels, when pressed against a container surface, will adhere. This type of label is a common feature on many rigid plastic, glass and paperboard round containers, as well as on many flexible pouches.
Pressure-sensitive labels are available in both single cut formats for manual application, and in rolls for mechanical application on high-speed production lines. To prevent the adhesive from being activated prematurely, a protective plastic-coated release paper is used to cover the adhesive surface area. This paper is stripped away and discarded shortly before the labels are applied.
When pressure-sensitive labels are marked with production or required regulatory codes, these are usually applied by CIJ (Continuous Inkjet) or laser systems following application of the labels.
In early packaging operations, branding and other required information was often printed directly on to a package surface. This was slow and costly, and restricted containers to very smooth, ink-friendly surfaces. The subsequent development of hand-applied labels increased productivity somewhat and made packaging much more cost-effective. By using varied labels, the packager was able to use the same container format for multiple flavors or formulations of its products, simply changing the label to identify each. The introduction of pre-applied pressure-sensitive adhesives made the labeling function of the packaging operation very efficient.
Early pressure-sensitive adhesives fixed labels permanently in place, much as hand-applied adhesives had. Recycling of rigid glass and plastic packaging requires labels to be removed. As recycling has become more widespread, adhesive manufacturers have developed water-soluble pressure-sensitive adhesives that allow labels to be easily stripped prior to recycling. This capability also provides packagers with the capability to re-use unused labeled packaging by stripping the labels and replacing them with new labeling.
Today, pressure-sensitive labels are by far the most common labels in use on food packaged in rigid plastic and glass containers, and in an increasing number of flexible packages.
Learn more about printing on glass bottles and containers with Continuous Inkjet (CIJ) printers from Videojet.