Security thread and process for the preparation thereof

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.

1 . A partially metallized film for a security thread having a dyed region and a transparent region alternately at an each regular interval on a major surface thereof, the regions being in the form of a figure, character or pattern.  
     
     
         2 . The partially metallized film for a security thread according to  claim 1 , wherein the film is prepared by a process comprising the steps of 
 (i) printing a fluorescent pigment or dyestuff at a regular interval on a major surface of a transparent film in the form of a figure, character or pattern;    (ii) applying a water-soluble ink over the pigment or dyestuff-printed regions and to another selected portions of the major surface of the film at a regular interval in the form of a figure, character or pattern;    (iii) depositing a layer of a metal on the entire surface of the transparent film including the water-soluble ink layer; and    (iv) washing the metal deposited film with water to remove the portion of the metal layer deposited on the water-soluble ink layer.    
     
     
         3 . The partially metallized film for a security thread according to  claim 2 , wherein the metal is selected from the group consisting of aluminum, tin, silver and an alloy of cobalt and nickel.  
     
     
         4 . The partially metallized film for a security thread according to  claim 1 , wherein the film has a thickness ranging from 15 to 35 μm and a width ranging from 0.5 to 5 mm.