Materials which “carry” the adhesive. The backing also reinforces the adhesive tape and improves handling and processing properties. Most commonly used backing types are film backings (e.g. PET, PP, PVC, PE), paper based backings (e.g. non-woven, tissue), foam backings (e.g. PU, PE and PVC foams).
A specialty adhesive tape type is a transfer tape which has no backing. The adhesive is directly coated on the liner.