Copy paper sheet and method of making the same

Abstract From the Canadian patent

A copy paper sheet capable of forming a colored image after contact with a master sheet carrying a pattern of a suitable, weakly colored or colorless dye precursor is prepared on a paper machine from stuff which, in addition to web forming fibers predominantly consisting of cellulose contains a coll-, oidal dispersion of a hydrated clay or by sizing a web of the, fibers on the sizing press of the machine with an aqueous composition containing the hydrated, colloidal clay. Upon drying of the sheet, the fibers throughout the sheet thickness or at least adjacent the sized surface are substantially completely enveloped by a hydrogel of the clay which develops the color of the dye by interaction …