GB964695A - Improvements in and relating to multiple colored printing inks and methods of printing using such inks - Google Patents

Abstract

A dry, free-flowing printing ink comprises a mixture of dyes, two or more of which are of different colours and are preferentially soluble in different solvents. Magnetic particles or electrostatically chargeable particles, e.g. iron powder or glass beads, may be added. The inks are applied to a substrate, e.g. in a magnetic or electrostatic printing process, and the image fixed in the desired colour by applying as vapour, liquid or spray a solvent to dissolve one dye preferentially permitting its solution to make the substrate, and then after evaporation of the solvent brushing off the residue of undissolved dye. Suitable solvents are water, methanol, ethanol, acetone, benzene, toluene, hexane, chloroform, ethylene dichloride, carbon tetrachloride, and "Freons" (Registered Trade Mark) or mixtures thereof. In examples the following inks and solvents are used with magnetic iron particles in magnetic printing processes. (1) Sudan black and Sudan yellow or 1,1,2,2-tetrachloro-1,2-difluoroethane gives black images, and trichlorotrifluoroethane olive drab ones. (2) Sudan black, Sudan yellow and du Pont oil red. Trichloromonofluoromethane gives deep red violet printing and trichlorotrifluoroethane gives reddish-orange printing. (3) Sudan black, Sudan yellow and Amaplast red. A mixture of trichloromonofluoromethane and 1,1,2,2-tetrachloro-1,2-difluoroethane gives chocolate brown printing and trichlorotrifluoroethane gives yellowish-brown printing. (4) Sudan black, Sudan yellow and Amaranth. A mixture of trichloromonofluoromethane and 1,1,2,2-tetrachloro-1,2-difluoroethane gives black printing. Steam or water vapour gives red printing. (5) Latyl violet and Polar red. Toluene gives violet printing and ethanol orange printing. (6) Alizanine direct Violet and Cibacet red. Steam leaves blue printing and benzene, red. (7) Hexover blue and Fast light red. Ethanol gives violet printing, and steam gives red. (8) Leather brown and Hexover blue. Steam gives brown printing, and acetone blue. In Example 9 a mixture of Alizanine direct violet, Cibacet red and glass beads is used in an electrostatic printing process. Fixing with steam gives blue printing whereas benzene gives red printing. Example 10 uses a carrier-free mixture of Hexover blue and Fast light red in an electrostatic process. Ethanol fixes a violet image and steam a red one. Specifications 841,148, 848,217, U.S.A. Specifications 2,776,907 and 2,894,799 are referred to.