Arrangement of discharge openings in a printhead of a multi-color ink printer

An ink jet printhead for multi-color printing having ink reservoirs linked by ink channels to ink driving means, the printhead being movable with respect to a recording medium, comprising:

• a first vertical row of black ink discharge openings connected by said ink channels to one of said
• ink reservoirs for holding black ink, said black ink discharge openings being equally spaced from adjacent black ink discharge openings,
• the length of said first vertical row defining a write line on said recording medium;
• a second vertical row of first color discharge openings parallel to said first vertical row,
• said first color dischagre openings being connected by ink channels to another one of said ink reservoirs for holding a first color ink, said first color discharge openings being spaced from adjacent first color discharge openings by an amount equal to the spacing of said black ink discharge openings, said first color discharge openings being fewer in number than said black ink discharge openings,
• the length of said second vertical row being at least half the length of said first vertical row,
• a third vertical row of second color discharge openings parallel to said first vertical row,
• said second color discharge openings being connected by ink channels to another one of said ink reservoirs for holding a second color ink, said second color discharge openings being spaced from adjacent second color discharge openings by an amount equal to the spacing of said black ink discharge openings, said second color discharge openings being fewer in number than said black ink discharge openings,
• the length of said third vertical row being equal to the length of said second vertical row and;
• a fourth vertical row of third color discharge openings parallel to said first vertical row,
• said third color discharge openings being connected by ink channels to another one of said ink reservoirs for holding a third color ink, said third color discharge openings being spaced from adjacent third color discharge openings by an amount equal to the spacing of said black ink discharge openings, said third color discharge openings being fewer in number than said black ink discharge openings,
• the length of said fourth vertical row being equal to the length of said second vertical row;
• whereby draft quality printing is produced by a first pass of said printhead over a write line and near-letter quality printing is produced by two passes of said printhead over a single write line.

An arrangement of discharge openings in a printhead of a multicolor ink printer in which the discharge openings are connected to ink reservoirs through ink channels, the ink reservoirs having ink of a black color and ink of at least three primary colors, the discharge openings for ejecting ink droplets of the black ink form a vertical row, the discharge openings for ejecting ink droplets of the other primary colors form further vertical rows, a piezo transducer provided at every ink channel which when individually driven drive individual droplets from the discharge openings, the printhead being movable across a recording medium in a line direction and the recording medium being movable perpendicular to the line direction, comprising:

• a plurality of the discharge openings for ejecting black ink having a number and mutual spacing such that characters can be represented on the recording medium over the height of a write line in draft quality, the number of said black ink discharge openings being greater than the number of discharge openings for each respective primary color,
• the discharge openings in each of the further rows for ejecting the other primary colors corresponding in spacing to the spacing of the black ink discharge opening, and
• the recording medium being moved in a direction perpendicular to the line direction after recording a respective write line by at least half a write line height for recording in draft quality and by a value corresponding to half the mutual spacing of the discharge openings in a row for recording in near letter quality.