BLEED ALLEVIATION IN THERMAL INK JET INKS
Original Publication Date: 1997-Feb-28
Included in the Prior Art Database: 2004-Apr-08
Xerox Disclosure Journal
Disclosed is a method and composition for bleed alleviation in Thermal Ink Jet (TU) inks and ink printing processes. Inter-color bleeding of ink jet inks is one of the most serious print quality deficiencies seen with thermal ink prints made with waterbased inks with viscosities of 1 to 5 cps. The most noticeable case is that of black ink printed on or just touching yellow. The phenomena is extremely paper dependent and can be solved or greatly reduced by the use of special coated papers. The effect can also be solved or greatly reduced by the use of special algorithms, multipass printing and heating the paper just before and/or during printing. A partial solution is the use of four so called "fast dry" inks which penetrate into the paper in about 1 second or less, before the inks have time to intermix. The print quality tradeoff is a greater edge raggedness for these inks, an increase in MidFrequency Line Edge Noise (MFLEN) of a factor of 2 to 10. If bleed were not a factor, a four color set of slow dry inks would be preferred due to much smaller levels of edge raggedness produced when such inks are printed against a paper background. Since slow dry inks take from 30 to > 100 seconds to penetrate/dry to the point of no offset, the printing of a four color slow dry set with boundaries that touch, results in very objectionable bleed on may "plain" papers. A compromise is the use of a slow dry black ink for improved text edge sharpness with three fast dry colors to reduce bleed when black is printed against a color. A further refinement is utilized in the Canon BJC4000 printer where some black pixels at edges are replaced by cyan (fast dry) pixels. This approach apparently allows the black ink to behave more like a fast dry ink at the blackkolor boundary. Ideally, one would like to use a set of four slow dry colors which behave like fast dry colors only at intercolor boundaries, which is the basis of this disclosure.