Liner Guide

The purpose of a release liner is to act as a carrier for the facestock and adhesive. After the label is removed the liner is typically discarded.

Ironically, the liner is usually the most expensive component of a pressure sensitive label. The expense comes from the silicone on the front of the liner. Silicone is the release agent enabling the adhesive to remove cleanly from the liner with the facestock. In order to minimize the silicone expense, dense paper substrates are used to prevent silicone absorption into the liner paper. Paper liners are available in a variety of materials including densified kraft, glassine, and machine finished. Densified kraft is the standard liner material. Glassine is used for additional strength (as are synthetic liners) and machine finished liners provide economy. Silicone can be applied in a variety of thickness in order to control the degree of adhesive release from the liner.

Liners are available in a variety of thickness/weights including 40#, 50#, 60#, 78#, and 90#, among others. Heavier/thicker liners are used for sheeted labels or where additional strength may be required. Such situations included fanfolded labels, or labels being machine applied in damp/wet environments. Both applications place stress on liners.

Liners are available with a variety of treatments, including lay flat, printable, imaging, and piggyback.

1. Lay flat Liners:
There are a number of standard thickness liners now laser qualified. Both 40# and 50# liners are available. More recently, manufacturers are providing MF (machine finished) liners that provide a rougher surface on the back of the liner. This roughness improves feeding in some laser printers using plastic advance rollers. They are also less expensive to manufacture.

2. Printable liners:
It has become more common to print information on the back of the liner. Frequently this is instructions for label or product use.

3. Imaging liners:
These liners are made from self-contained paper. They are utilized in impact printer applications in which an additional copy of the date printed on the label is required.

4. Piggyback liners:
Piggyback liners are created by stacking two liners. They are used in situations in which the label is initially placed in one location and then later moved to another location.

5. Synthetic liners:
Synthetic liners are used when strength and/or stability is required. These liners include bi-axially oriented polypropylene and polyester. They are utilized when labels are automatically applied with high-speed applicators or in extreme humidity situations for sheet or fanfolded labels.