Film-backed pressure-sensitive adhesive tape that resembles conventional creped paper-backed masking tape but can be torn cleanly with the fingers, is prepared by extruding an isotactic polypropylene film (11), passing it through the nip between a rubber roll and a water-cooled embossed steel roll at a temperature and rate such that predominantly crystalline film is obtained. The embossed roll (10) imparts a ridge-and-valley configuration to one surface (13) of the film, valleys extending crosswise of the tape and having a depth greater than half the total film thickness. When the smooth face (12) of the film is coated with pressure-sensitive adhesive (14), the resultant tape can be torn readily, using only the fingers, in a straight line crosswise of the tape. When subjected to a stretching force in the machine direction (at right angles to the ridges and valleys), the tape elongates uniformly without "necking down." A specific embodiment of this invention is a sterilization indicator tape made with the above described film.
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