Abstract: Security fibers having enhanced antifalsification features are prepared by a process which comprises the steps of: i) braiding 5 to 30 denier fibers to form a twine; ii) dyeing the twine with a dye or pigment; iii) drying the dyed twine; and then iv) cutting the dried twine to give the security fibers in the form of cut fibers.

Abstract: A partially metallized film having a dyed region and a transparent region alternately at an each regular interval on a major surface thereof is useful as a security thread to be embedded in a security paper. The partially metallized film for a security thread is conveniently prepared by printing a fluorescent pigment or dyestuff at a regular interval on a transparent film, applying a water-soluble ink over the dyed regions and to another selected portions of the film at a regular interval, depositing a layer of a metal on the entire surface of the transparent film including the water-soluble ink layer; and washing the metal deposited film with water to remove the portion of the metal layer deposited on the water-soluble ink layer.