Method of forming improved pressure sensitive transfer media

Claim 1

In the formation of pressure sensitive indicia transfer sheets having a predetermined requisite wax content of 5 to 40 percent in a transfer coating thereon, the steps of applying a uniform dispersed hot suspension of a solvent having the requisite wax content of a wax-like material initially dissolved therein, an inert mineral filler having a particle size in the range of 0.1 to 50 microns, and coloring matter to a substrate at a temperature above the cloud point of the wax-like material in the solvent to form a thin coating thereon, said initial solution of solvent and wax-like material dissolved therein being characterized by a cloud point below 150*F, a solubility of wax-like material greater than 30 percent by weight at temperatures above 100*F and less than 10 percent by weight at about 100*F, and an asymptotic solubility curve having a shape such as to permit rapid precipitation of at least 60 percent of said requisite wax content therefrom within a temperature Drop of 10*F during cooling below the cloud point thereof, and having suspended therein said filler and coloring matter in a total amount to constitute between about 50 to 95 percent by weight of the finished coating, rapidly cooling said applied suspension below the cloud point with concurrent evaporation of said solvent to effect selective precipitation of at least 60 percent of said requisite wax content within a temperature drop of 10*F during the cooling from said solvent in said applied coating, and continuing evaporation of said solvent from said coating to provide a finished film having less than 10 percent of said wax-like material remaining in solution in the remaining solvent at a temperature of about 72*F.