DOPED BLACK INK WITH INCREASED LIGHT SCATTERING EFFICIENCY FOR NOZZLE HEALTH DETECTION

摘要

A method of monitoring nozzle condition in an array of inkjet nozzles comprises ejecting at least one black ink drop from an inkjet nozzle, wherein the black ink comprises a black colorant and a colloidal metal or metal-containing dopant. Light from a collimated light source is directed onto an ink drop-in-flight, and light-scatter from the drop is detected. The dopant increases light-scatter by the ink drop of an incident collimated light beam relative to the same ink without the dopant. From the detected light-scatter, an operational condition of the inkjet nozzle is determined. The dopant is visually undetectable in a printed mark made by the black ink, and the ink has a printed black optical density which is substantially the same as that of the same ink without the dopant.