PURPOSE: A direct dye of C.I. direct black 19 type is varied in its development diameter ratio in thin layer chromatography by treatment with methanol to control the tone to the desired one stably and easily, thus giving a dye suitably used for an aqueous ink.
CONSTITUTION: A direct dye of C.I. direct black 19 type, with a variety of tones, is treated with methanol to change its development diameter ratio in thin layer chromatography from its original before the treatment to give a dye with such a development diameter ratio as corresponding to the desired tone. The methanol treatment means that the dye is dispersed in methanol and washed under stirring, when it is a powder, or subjected to Soxhlet-extraction, or when the dye is soluble in water, the aqueous solution is gradually dropped in methanol to cause precipitation. The treatment time, the temperature of the methanol, and other factors are varied to control the dye to a desired tone.
FUJII TADASHI
YAMAGUCHI TOMOYUKI
KAWAKAMI TOMIKO
