Photocopying – Contact printing – Light boxes
Patent
1990-10-09
1992-08-25
Moses, R. L.
Photocopying
Contact printing
Light boxes
427 13, 355326, 355239, 430120, G03G 1506
Patent
active
051423375
ABSTRACT:
An electrophotographic printing process enables a two-color printer having only binary printing capability to produce high-quality monochrome grey-scale output having, for example, up to 100 grey levels in a 3.times.3 super-pixel through the use of a second toner comprising a mixture of opaque black, opaque white, and clear toner. A layer of the second toner is applied so as to overlie the first toner layer on the substrate, the first toner comprising black toner. The composition of the second toner may be, for example, 9 percent opaque black toner, 9 percent opaque white toner, and 82 percent clear toner. Another embodiment extends this concept to the high-quality, enhanced grey-scale printing of a color other than black. In another embodiment, the layer of the second toner is comprised of a mixture of equal amounts of opaque black toner and opaque white toner and is applied so as to overlie the first toner layer on the substrate, the first toner layer comprised of black toner having a charge-to-mass ratio in the range of 2 to 10 times less than the second toner. This embodiment is also extended to high-quality, enhanced grey-scale printing of a color other than black. The use of these concepts is also extended to a full-color printer, in which each color is printed using enhanced grey-scale.
REFERENCES:
patent: 3236776 (1966-02-01), Tomanek et al.
patent: 4385823 (1983-05-01), Kasper et al.
patent: 4845524 (1989-07-01), Okamoto et al.
patent: 4855204 (1989-08-01), Fujii et al.
Publication W. Lama, et al., in "Hybrid (Gray-Pixel) Halftone Printing", J. of Imaging Technology, vol. 15, No. 3, Jun. 1989.
Karidis John P.
Reiley Timothy C.
Schein Lawrence B.
International Business Machines Corp.
Moses R. L.
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