A recording head having an ejection portion group for ejecting a black ink, and ejection portion groups for ejecting color inks is used. When a black image to be printed by the black ink is present adjacent to a color image to be printed by the color ink, a black image portion adjacent to the ...http://www.google.de/patents/US5748207?utm_source=gb-gplus-sharePatent US5748207 - Ink jet recording system for preventing blurring at color boundary portion 
