Method and apparatus using two different black inks to reduce intercolor bleeding and provide high quality edge definition with thermal ink jet systems

DETAILED DESCRIPTION It is an object of the present invention to provide an ink jet system and method of use that reduces intercolor bleeding of composite color images by using two different black inks having different drying rates and definition qualities.
The above and other objects are achieved according to a first aspect of the invention by a color printing device for producing a composite color image having reduced intercolor bleeding comprising: liquid ink spot producing means for depositing color ink in at least three colors, the colors including a slow drying black ink, a fast drying black ink and at least one non-black color ink; determining means for determining black portions of an image; and control means for depositing a partial tone of the black portions of the image using the fast drying black ink and subsequently depositing a whole tone of the black portions of the image superposed on the partial tone using the slow drying black ink.
This objective is further achieved by the preceding device further comprising: digital imaging means for producing and storing a digital representation of the color image to be reproduced; analyzing means for analyzing each black pixel of the digital color image and a surrounding matrix of neighboring pixels surrounding each said black pixel; determining means within the analyzing means for determining for each black pixel if any of the neighboring pixels contain colors other than black and white; and control means for reproducing the black pixels of the color image onto a recording substrate, the control means printing each one of the black pixels according to predetermined criteria.
The criteria includes printing a black pixel using slow drying black ink if none of the surrounding matrix of neighboring pixels for the black pixel were determined to contain colors other than black and white and printing the black pixel using fast drying black ink if one or more of the surrounding matrix of neighboring pixels for the black pixel were determined to contain colors other than black and white