NOVEL DEVELOPING METHOD OF COLOR FORMERS BY CATION-EXCHANGE MEMBRANESAND ITS STABILITY OF IMAGE DYES

A perfluorinated sulfonate cation exchange membrane was employed as a receiving sheet capable of developing color formers without any develo ping agent. The membranes treated with solutions containing one or two types of metallic ion such as Li+, Na+, Mg2+, and Ni2+ ions acted as developers for spiropyran, azomethine and diphenylmethane color former s. The effect of monovalent metallic ions as counter ions of the membr anes on the developing ability was increased in the order of Li+>Na+>K + ions according to the electronegativity of these metals. The same ef fect was observed in the case of divalent metallic ions, in which the effect was increased in the order of Ni2+>Mg2+>Ca2+ ions. In addition to the effect of these metallic ions, the developing ability of the me mbranes depended on the pH value of the treating solutions for the ion exchange, the water content of the membranes and the developing tempe rature of color formers. The dye forming reactions of these color form ers with the membranes would be similar to the well-known reactions wi th acids. The images so formed with the membranes were extremely stabl e and resistant to dark and light fadings, except for the light fastne ss of spiropyran dye.