Brian J. Keefe

Challenges in the development of high-speed true 600-dpi thermal ink-jet printing

Hewlett-Packard Company recently introduced a line of thermal ink jet printers which delivers 6 to 8 pages per minute laser parity text throughput with true 600 X 600 dpi resolution. In the development of this technology, we achieved major breakthrough in many key areas in the design of the HP 51645A ink jet print cartridge. In order to print at true 600 dpi resolution, the dot size has to be reduced proportionally from the previous 300 dpi resolution. To increase the print engine throughput to meet customer needs, firing frequency of the drop generator has to be higher than any previous thermal ink jet designs. As a result of the need to improve print quality and throughput, all fluidic dimensions in the vicinity of the ink jet drop generator have to be redesigned and scaled down. This geometric redesigning and scaling poses significant challenges to the capabilities of our manufacturing processes, leading to the redesign of the orifice plate. Major development work in ink formulation has resulted in significant improvements in printer performance as well. The pigmented ink designed for this new generation of ink jet printers provides the highest optical density and media independency to meet customers print quality needs. The ink formulation also improves dry time so as to meet the pages per minute throughput design objective.