Label Construction Explained

Pressure-sensitive labels are the most widely-used media type for the identification of all types of items, from shipping cartons to automobiles. A label's construction can vary significantly depending on the intended application and environment. Does it need to go into a freezer? Does the label need to be repositionable? How long will the label be exposed outdoors? The construction of a pressure-sensitive label consists of a number of layers, each with its specific function and qualities designed for the intended application.

Label Liner

The label's liner acts as the carrier for the label. It stays with the label and protects the adhesive layer until the label is ready to be applied to the surface. The release coating on the liner is what allows the label to be removed from the liner.

Liners are available in different thicknesses – generally a thicker liner is used for sheeted and fanfolded labels to help them maintain their lay-flat characteristics.

Liner Examples	Application
Paper	Standard liner type most commonly used
Synthetic	Used when cleanroom properties are required

Label Adhesive

The label's adhesive is the layer that enables the label to bond to the intended surface when pressure is applied. Selecting the correct adhesive is dependent on the intended surface the label is to be applied to as well as the environmental conditions the label will be exposed to. As the wrong adhesive will result in label falling off the applied surface, choosing the right type of adhesive is critical to the label's success in its intended application.

Adhesives are available in a range of adhesion strengths, including permanent and removable/repositionable. Adhesives can also meet certain qualifications for approval in an intended application, such as FDA approval for food or skin contact.

Adhesive Examples	Application
Rubber	Most commonly used in short-term or everyday indoor labeling applications
Acrylic	Has advanced chemical, heat and UV resistance, different formulations can be used for harsher environment application indoor and outdoor
Silicone	Recommended for applications with extreme temperature requirements

Label Substrate

Also known as the "label face stock", the substrate is the material that is the base for the construction of the label. The substrate is usually what is used to classify the type of label (paper labels, polyester labels, etc.) The label substrate provides the basis for printing, coverage, and resistance to abrasion and moisture.

Substrates are available in a variety of materials, thicknesses, and other qualities. They can range from opaque white to clear. The most common label substrates are listed below:

Substrate Examples	Application
Paper	Most common, used for a wide variety of indoor labeling applications including shipping, package and carton labels
Vinyl	Excellent tear resistance as well as resistance to UV and moisture, minimal heat resistance
Polypropylene	Highly durable and conformable with excellent tensile strength, good for labels that require an extended use life
Polyester	Excellent for harsh environments, very resistant to UV, abrasion, moisture and decay
Polyolefin	Excellent chemical resistance and printability, good indoors and outdoors
Polystyrene	Excellent electrical insulating properties, as well as moisture resistance
Polyimide	Also known as Kapton®, ideal for high temperature applications, particularly suited for labeling printed circuit boards

Label Topcoat

Topcoats are treatments applied to the surface of the substrate, usually during the substrate manufacturing or converting process. Typically available in a glossy or matte finish, topcoats primarily increase the ability of the ink to adhere to the label substrate. Certain topcoats can also enhance the label's resistance to UV, moisture, chemicals or abrasion.

Topcoat Examples	Application
Solvent-based	Most commonly used, provided the greatest range of print receptiveness across all mediums
Water-based	More environmentally-friendly, used in more specialized applications

Label Over-Laminates

Over-laminates, varnishes and specialty coatings are optional elements that are used to enhance the label's strength, appearance, printability and/or protection from moisture, chemicals, UV and abrasion.

Over-Laminate Examples	Application
Film over-laminate	Can be applied after printing to seal in and protect the printed surface
Varnish	Commonly used to add abrasion resistance, available in matte or gloss finishes
Specialty coatings	Can be applied to the entire surface of the label or to specific areas to enhance the appearance or performance of the label