Ink jet printing with color-balanced ink drops mixed using colorless ink

Abstract

A drop-on-demand ink jet printing system includes a print head having at least one mixing chamber having a nozzle opening. A plurality of sources of color liquid ink and a source of colorless liquid ink communicate with the mixing chamber. A flow controller is adapted to selectably meter ink from the sources to the mixing chamber, whereby ink droplets of selectable color are prepared in the mixing chamber for delivery from the nozzle. The flow controller is further adapted to meter colorless ink into the mixing chamber after a droplet is delivered from the nozzle opening to thereby dilute color ink remaining in the mixing chamber sufficiently such that a next desired color can be attained by adding ink of appropriate color to the mixing chamber. The mixing chamber may be flushed with colorless ink after a droplet is delivered from the nozzle opening and before adding ink of appropriate color to the mixing chamber to attain a next desired color. The flushed ink may be bleached before being returning to the source of colorless ink. The flushed ink may be converted to black by addition of appropriate amounts of color ink before being returning to a source of black ink.

Dependencies are inferred from the claim text.