One of the critical choices in purchasing product labels is the type of label liner, also called a release liner. Choosing paper when it should be poly, or vice versa, increases costs, delays packaging production, and hurts the bottom line.
There are two primary types of liners—paper liners and film liners. The most common film liners are also known as poly liners or PET liners.
So, which release liner is better, paper or film? There are several factors to consider.
Why Label Liner Choice is Important
A liner is the part of a pressure sensitive label that acts as a carrier for the label. It protects the adhesive until the label is ready to be applied. It’s also treated or coated so that the label releases easily during the application process, whether its manual or automatic.
Labels that are destined for automatic machine application must have liners that stand up to the rigors of machine application.
When label liners tear during automatic application, several things happen.
❌ There is more waste. Every machine re-start requires using labels to re-set the machine.
❌ There is more downtime at the factory. Too much downtime because of defective liners can result in charge backs from the manufacturer.
❌ There may be a shortage of labels to finish the production run. This requires costly reprints and results in additional manufacturing costs. Depending on the situation, penalties might also apply.
Reasons Why the Label Liner Tears During Application
Machine processed labels are done on a roll. Die knives cut through the label and adhesive layers but not through the liner.
When the labels are die cut, the waste is stripped cleanly away from the label and liner as shown in the image below.
The printed, die cut labels are rolled and ready for automatic machine application.
If the setup on the die cutting is incorrect, it causes serious problems with automatic label applicators.
All knives should be set to cut through the label paper and adhesive without going into the liner. If the knife cuts too deep, it penetrates the liner, creating a weak spot.
The illustration above shows a weak spot created by the knife cutting too deep.
Each rotation of the die means there will be a re-occurrence of that weak spot throughout the label roll, any of which can cause a tear as the machine applicator runs.
How to Prevent Label Liners from Tearing
There are two ways to avoid liner problems with your labels.
One – work only with label printing companies who use rigorous manufacturing standards and quality control to ensure that labels never ship with defects in the liner and label.
Two – replace paper liners with polyethylene terephthalate (PET) liners. PET, also called poly liner, is a film liner that is much stronger than paper.
Currently, glassine liner papers have about 36% of the market, poly coated kraft has about 24%, with film liners at 22% according to Label and Narrow Web. Here are the pros and cons of each.
Advantages of Poly Label Liners
Paper is hygroscopic, meaning that it absorbs moisture from the air or releases it, depending on the temperature, the relative humidity, and the moisture content of the paper. It is always seeking a balance. As the relative humidity and temperature changes, so do the dimensions of the paper.
This means that paper products must be properly conditioned to the print shop atmosphere prior to printing. Changes to the paper due to improper conditioning causes problems in printing, die cutting, coating, or lamination. In turn, these problems can cause stoppages in the automatic label application machinery.
✔️ PET is also hygroscopic but to a lesser degree than paper. In fact, moisture stable paper release liners are made by coating both sides of the paper with a polyethylene to inhibit moisture absorption.
✔️ PET is thinner than liner paper. This means the average roll can get up to 20 to 30% more labels on a roll. In turn, this reduces transportation costs.
✔️ More labels per roll means less changeover time, which increases packaging productivity.
✔️ PET is stronger and breaks less frequently than paper. This added strength means machines can run considerably faster with less downtime.
✔️ PET is better than for wet application conditions.
✔️ PET liners reduce waste volume, with liners as thin as 23 microns, or about 0.0009”. Glassine paper liners are typically about 50-70 microns thick.
✔️ PET is less susceptible to curl than paper. Flatness is a key element to high label applicator productivity.
✔️ PET produces less dust than paper liners, which is important in pharmaceutical, electronics, food, health, and cosmetics packaging.
✔️ Because of current paper supply problems, lead times for PET are shorter than paper liners.
✔️ PET is better for labels that are used in harsh environments or that will be exposed to the elements.
Advantages of Paper Liners
There are times when paper liners might be the better choice.
✔️ Paper is more rigid than film and is better in applications in which rigidity is required.
✔️ Paper is more sustainable and has chain-of-custody certification available to track fiber from the forest through its end use. However, film liners are catching up with improved liner recycling processes coming into place.
✔️ Paper liners are generally lower cost.
Final Thoughts on Paper vs Poly Release Liners
There is no single “right” choice when it comes to paper versus PET release liners. Much depends on the end use of the label along with the label application process.
We can work with you to eliminate common mistakes caused by faulty liners, and help you select the product label that’s best for your bottom line.
Call us at 818.709.1220 or Contact Clear Print here to talk about selecting the right release liner for your next job.