Although the consumer never sees it, the liner is a critical component of any pressure sensitive label. A label liner, also known as carrier or backing or “release liner”, serves a very important purpose: carrying the die-cut labels to applicator and releasing the adhesive-backed label onto the product. The diagram below shows how diecut labels are released from the liner.
Why are there so many Liners? Just like adhesives, each type of liner was engineered to meet specific performance criteria. Here are some of the quality and performance criteria used to judge a pressure sensitive label liner:
Liner Performance Criteria
Die-cutting: High speed diecut and stripping
Cost: Relative cost of the liner material
Strength: Liner web strength and durability
Layflat: Resistance to curling after sheeting
Dust: Absence of loose particulates
Types of Liner
Semi-calendered Kraft material. Low cost, all around liner for paper materials. Very good diecutting and stripping, poor layflat. Moderate particulate levels.
Poly-coated Kraft liner has a poly layer that improves die-cutting and strengthens the liner. Is credited with lower incidence of web-breaks due to deep die-cuts. Higher cost than SCK, slightly lower dust particulate. Does not sheet well.
Lay flat liners have excellent stability and resistance to curl for sheeted applications. Higher cost than SCK liners. Moderate particulate levels.
Polyester film liner: durable and good for high speed die-cutting and stripping. Poor sheeting characteristics. Very low particulate. More expensive than paper liners.
Bleached Glassine liner: low cost. For low to medium speed dispensing, not recommended for sheeting.
As you can see, no one liner can do everything. Much like facestock materials, liners must be selected based on the specific label requirements. Sheeted labels require liners designed with lay flat in mind. For roll labels, the applicating equipment will usually drive liner selection. With a robust, modern label applicator a standard SCK or BG liner will work well for the majority of labels. For clean room (zero particulate) and pharmaceutical (high speed application) a polyester liner is often the only option. Ask your Custom Label representative to help you specify the correct liner for your custom labels!