Diaper closure utilizing pressure-sensitive adhesive tape having textured foil backing

Claim 1

In the combination of a diaper and, adhered to one exterior surface thereof, at least one closure tab comprising a strip of sheet material having a coating of normally tacky and pressure-sensitive adhesive firmly bonded to one face thereof, the improvement comprising said sheet material's being a substantially untensilized, tough, ductile foil of crystalline polypropylene or linear polyethylene having a fine grain crystal structure and a calipered thickness of about 100-500 micrometers, said foil having one smooth face and one textured face, the textured face having a pattern of ridges separated by valleys, (a) the average distance between the crests of adjacent ridges being about 250-1,500 micrometers, (b) none of said crests being more than either (1) 100 micrometers or (2) 2/3 the calipered thickness of the foil below the highest crest, (c) the thickness of the foil between the bottom of the valleys and said smooth face being at least about 25 micrometers but not more than about 2/3 the calipered thickness, (d) the void volume included on the textured face of said foil constituting about 10-60% of the apparent volume of said foil, at least some of the ridges extending at an angle of 60° or less to the lateral edge of the closure tab and having a length significantly greater than any valleys they block, said tab being further characterized by having a tensile strength at yield of 2.5 kg/cm width, a stiffness value of no more than about 3 gm-cm perpendicular to its long dimension and no more than about 5 gm-cm parallel to its long dimension so that it is readily conformable, and a tear propagation value perpendicular to its long dimension of at least 100 grams so that it resists inadvertent edge tear resulting from tensile forces even when nicked.