Deficiencies of Pigment Yellow 74, the most widely used yellow inkjet pigment, include poor lightfastness, limited colloidal stability in presence of organic cosolvents due to ripening/recrystallization processes and problems with chemical surface modification. This promotes a search for better yellow pigments for inkjet applications. The known class of quinolonoquinolone (QQ) pigments had been studied at Cabot as one of the possible alternatives to PY74. Specifically, several new asymmetric monohalogenated QQ's had been prepared, characterized and evaluated. Pigment Yellow 218 (3-Fluoro-QQ), Pigment Yellow 220 (2-Fluoro-QQ) and Pigment Yellow 221 (3-Chloro-QQ) were found to be especially suitable for surface modification by using Cabot's diazonium chemistry methods and had been succesfully converted into stable nanosized inkjet dispersions. These three pigments, being of comparable strength and shade with PY74, demonstrate outstanding lightfastness of prints, matching that of copper phthalocyanine and quinacridones. Dispersions of these QQ's have very high colloidal stability and are not sensitive to cosolvents or humectants. QQ synthesis had been studied and the key step was significantly improved to maximize the yield of asymmetrically substituted component by preventing randomization in the course of preparation.
Alex Shakhnovich, "New Inkjet Yellow Pigments – Halogenated Quinolonoquinolones" in Proc. IS&T Int'l Conf. on Digital Printing Technologies and Digital Fabrication (NIP25), 2009, pp 276 - 278, https://doi.org/10.2352/ISSN.2169-4451.2009.25.1.art00077_1