US 8,007,969 B2 · Tri-level xerography for hypochromatic colorants

Abstract

A xerogrpahic system and method use a tri-level development process in which at least one xerographic imaging unit includes a photoreceptor and a pair of developer units. A first developer unit includes a conventional first toner of a given color (CYMK) and a second developer unit includes a hypochromatic light form of the first toner. By use of a specific tri-level process, excellent color-to-color registration can be achieved for each processed color separation because overlap between colorants can be prevented. Moreover, by use of two forms of the same colorant, a smoother tone reproduction curve can be achieved when an aggressive blending strategy is used. Gamut loss and ink limit violation can be avoided by adjusting the blending curve in certain situations. An exemplary implementation uses a four drum, eight color tandem architecture with formulations of Cyan, Magenta, Yellow and Black, as well as corresponding hypochromatic light colorants of light Cyan, light Magenta, light Yellow, and light Black (gray).

Claims23

Dependent claims

A xerographic printing method, comprising:

uniformly charging a photoreceptor of a tri-level xerographic imaging unit to a predetermined voltage;
creating tri-level electrostatic images including CAD image areas and DAD image areas having different voltage levels, VCAD and VDAD, respectively, on the photoreceptor, where a background discharge level VW is located between VCAD and VDAD in which no image may be developed;
developing one of the CAD image areas and DAD image areas with a first toner of a first color and developing the other of the CAD image areas and DAD image areas with a second toner of a second color that is a hypochromatic light form of the first toner to form a composite separation image of a desired image in which the first and second colors are developed without any overlap;
and
transferring the first composite separation image onto a substrate.

2 more elements

A xerographic machine, comprising:

a photoreceptor;
and
a tri-level xerographic imaging unit including
a charging device for charging the photoreceptor to a predetermined voltage;
an imaging system for obtaining tri-level electrostatic images including CAD image areas on the photoreceptor having a first voltage level VCAD, and DAD image areas on the photoreceptor having a second voltage level VDAD lower than the first voltage level, and a background discharge level VW between the first and second voltage levels at which neither the CAD image areas nor the DAD image areas may be developed;
and
first and second developer units for developing the CAD image areas and the DAD imaging areas with a first colorant toner of a first color from one of the developer units and a second colorant toner that is a hypochromatic light form of the first colorant toner from the other of the developer units, wherein one of the toners is developed in the CAD image areas and the other toner is developed in the DAD image areas to form a first composite color separation of a desired image in which the first and second toners are developed without any overlap.

4 more elements

Dependencies are inferred from the claim text.

Tri-level xerography for hypochromatic colorants

Life of this patent

Tri-level xerography for hypochromatic colorants

Life of this patent

Abstract

Claims23