Electrophotographic patterning of an image definition material
View Patent ↗A method is disclosed in the context of a system comprises an electrophotographic subsystem, a transfer subsystem, an imaging member, and an inking subsystem. The electrophotographic subsystem comprises a photoreceptor, a charging subsystem, an exposure subsystem, and a development subsystem. In operation, the photoreceptor is charged areawise. An exposure pattern is formed by the exposure subsystem on the surface of the charged photoreceptor to thereby write a latent charge image onto the photoreceptor surface. The image is developed with an image defining material, such as a dampening fluid. The image defining material forms a negative pattern of the image to be printed. This negative image is then transferred to the reimageable surface. The negative image is then developed with ink. The inked image may be transferred to a substrate.
1. A method for variable data lithography, comprising:
charging a photoreceptor with a first electrostatic charge;
selectively exposing said photoreceptor by an exposure subsystem to thereby form an exposure pattern from regions that are unexposed and exposed by said exposure subsystem on a surface of said photoreceptor, said exposure subsystem causing altering of said first electrostatic charge such that said unexposed regions are caused to have a first electrostatic charge state and said exposed regions are caused to have a second electrostatic charge state;
selectively applying an image defining material layer substantially over regions of said photoreceptor having said first charge state and not over regions of said photoreceptor having said second charge state, to thereby form an image defining material image on a surface of said photoreceptor;
transferring said image defining material selectively applied over said photoreceptor to a reimageable surface, forming regions of image defining material separated by regions of no image defining material on said reimageable surface, and thereby transferring said image defining material image from said photoreceptor to said reimageable surface;
selectively applying ink over said reimageable surface such that said ink preferentially occupies regions of no image defining material on said reimageable surface to thereby form an inked image over said reimageable surface; and
transferring the ink occupying said regions of no image defining material on said reimageable surface to a substrate to thereby transfer said inked image from said reimageable surface to said substrate,
wherein said regions of said photoreceptor having a first electrostatic charge state have a first charge polarity, and wherein said image defining material comprises electrostatically charged particles having a second charge polarity, said first charge polarity being opposite said second charge polarity, and
wherein said image defining material comprises a dampening fluid, said dampening fluid comprising a carrier fluid in which are disposed said electrostatically charged particles.
2. The method of claim 1 , wherein said first electrostatic charge state corresponds to regions not exposed by said exposure subsystem, and second electrostatic charge state corresponds to regions exposed by said exposure subsystem.
3. The method of claim 1 , wherein said exposure subsystem is an optical patterning subsystem such that light emitted by said optical patterning subsystem results in exposure of regions of said photoreceptor.
4. The method of claim 1 , wherein said carrier fluid is electrically insulative.
5. The method of claim 1 , wherein said electrostatically charged particles are organic polymers.
6. The method of claim 1 , further comprising applying an electrostatic charge of a same polarity as that of said first electrostatic charge to said reimageable surface such that said particles are electrostatically attracted to said reimageable surface during transfer thereof from said photoreceptor to said reimageable surface.
7. The method of claim 1 , further comprising applying an electrostatic charge of said second polarity to an element of an image transfer subsystem such that said particles, but not said ink, are electrostatically rejected in a region at which said ink transfers from said reimageable surface to said substrate, and further such that said particles substantially remain on said reimageable surface following said transfer of said ink from said reimageable surface to said substrate.
8. The method of claim 1 , further comprising providing said reimageable surface with a second electrostatic charge of a same polarity as that of said first electrostatic charge.
9. The method of claim 8 , wherein said second electrostatic charge is of a greater value than said first electrostatic charge.
10. The method of claim 1 , further comprising controlling viscosity of said image defining material, by way of a viscosity control subsystem disposed proximate said photoreceptor following said image defining material subsystem in a direction of motion of said photoreceptor.
11. The method of claim 10 , wherein said viscosity control is provided by heating said image defining material prior to transferring said image defining material to said reimageable surface.
12. The method of claim 1 , further comprising:
selectively removing, following applying ink and before transfer of said ink to said substrate, said image defining material, but not said ink, such that said reimageable surface carries substantially only said ink thereafter.
13. The method of claim 12 , wherein said selective removal of said image defining material is performed by a cleaning subsystem, further comprising applying a charge by a charge application device disposed proximate said cleaning subsystem such that said cleaning subsystem selectively removes said image defining material based at least in part on electrostatic attraction of said image defining material to an element of said cleaning subsystem.