Electrostatic transfer of magnetically held toner images

Claim 2

A process comprising bringing a substrate capable of maintaining an electrostatic charge into superposed position and intimate contact with an image of uncharged toner particles which have an electrical conductivity of less than about 1×10 -13 mho/cm magnetically adhered to an electrically conductive magnetic imaging member having a resistivity of less than about 1×10 +9 ohm-cm which is adapted to dissipate an electric charge, and applying an electric field at this position whereby said toner particles adhere to said substrate upon separation of said substrate from said electrically conductive magnetic imaging member.

Claim 3

The process of claim 1 wherein the imaging member is grounded.

Claim 4

The process of claim 2 wherein the electric field is generated by applying an electrostatic charge to the side of the substrate away from the toner particles.

Claim 5

The process of claim 3 wherein the electric charge field is generated by spraying ions on the side of said substrate away from the toner particles.

Claim 6

The process of claim 4 wherein the toner particles are fused to the substrate by heat.

Claim 7

The process of claim 4 wherein the image of uncharged toner particles is held by magnetized acicular chromium dioxide.

Claim 8

A process comprising spatially periodically magnetizing a layer of acicular chromium dioxide particles in a binder which particles comprise from 40 to 85 weight percent of a layer from 0.001 to 0.015 mm thick which layer has a resistivity of less than about 1×10 +9 ohm-cm adhered to a grounded electrically conductive layer, bringing said layer of acicular chromium dioxide into superposed position with a document containing thereon indicia which are to be copied, uniformly illuminating said document so that radiant energy is transmitted through said document in the areas of said document not covered by indicia whereby the acicular chromium dioxide in the areas where it is illuminated is heated to above its Curie point and demagnetized while the areas of acicular chromium dioxide covered by the indicia contained on said document are not heated above their Curie point, applying uncharged toner particles which have a low electrical conductivity of less than about 1×10 -13 mho/cm and which comprise ferromagnetic material and a fixable material uniformly to the chromium dioxide layer whereby said toner particles adhere only to the magnetized areas of the chromium dioxide, maintaining said toner particles in the uncharged condition, superposing a dielectric substrate capable of maintaining an electrostatic charge in intimate contact with said acicular chromium dioxide layer, and applying an electric field while said substrate is positioned adjacent said layer of acicular chromium dioxide whereby said toner particles adhere to said substrate upon separation of said substrate from said layer of chromium dioxide.

Claim 9

A process comprising spatially periodically magnetizing a layer of acicular chromium dioxide particles in a binder which particles comprise from 40 to 85 weight percent of a layer from 0.001 to 0.015 mm thick which layer has a resistivity of less than about 1×10 +9 ohm-cm adhered to a grounded electrically conductive layer, bringing said layer of acicular chromium dioxide into superposed position with a document containing thereon indicia which are to be copied, uniformly illuminating said document so that radiant energy is transmitted through said document in the areas of said document not covered by indicia whereby the acicular chromium dioxide in the areas where it is illuminated is heated to above its Curie point and demagnetized while the areas of acicular chromium dioxide covered by the indicia contained on said document are not heated above their Curie point, applying uncharged toner particles which have a low electrical conductivity of less than about 1×10 -13 mho/cm and which comprise ferromagnetic material and a fixable material uniformly to the chromium dioxide layer whereby said toner particles adhere only to the magnetized areas of the chromium dioxide, maintaining said toner particles in the uncharged condition, superposing a dielectric substrate capable of maintaining an electrostatic charge in intimate contact with said acicular chromium dioxide layer, and applying an electric field while said substrate is positioned adjacent said layer of acicular chromium dioxide whereby said toner particles adhere to said substrate upon separation of said substrate from said layer of chromium dioxide.

Claim 10

The process of claim 7 wherein the electric field is generated by applying an electrostatic charge to the side of the substrate away from the toner particles.

Claim 11

The process of claim 8 wherein the electric charge is generated by spraying ions on the side of said substrate away from the toner particles.

Claim 12

The process of claim 9 wherein the substrate is paper.

Claim 13

The process of claim 10 wherein the toner particles are fused to the substrate by heat.

Claim 14

The process of claim 9 wherein the substrate is a fabric.

Claim 15

The process of claim 9 wherein the substrate is a dielectric film.

Claim 16

A magnetic printing apparatus for applying non-conductive ferromagnetic particles to selected areas of a substrate capable of maintaining an electrostatic charge comprising a movable electrically grounded magnetic imaging member containing selectively magnetized areas of ferromagnetic particles and non-magnetized background areas, which magnetic imaging member has a resistivity of less than about 1×10 +9 ohm-cm in both background areas and selectively magnetized areas, drive means to advance said imaging member, means adapted to apply ferromagnetic toner particles in the uncharged condition to said magnetic imaging member, means to bring said substrate into superposed position with and in intimate contact with said magnetic imaging member, means for generating an electric charge on the side of the substrate away from the toner particles where said magnetic imaging member is superpositioned against said substrate and means for removing said substrate from said magnetic imaging member.

Claim 17

A magnetic printing apparatus for applying non-conductive ferromagnetic particles to selected areas of a substrate capable of maintaining an electrostatic charge comprising a movable electrically grounded magnetic imaging member containing selectively magnetized areas of ferromagnetic particles and non-magnetized background areas, which magnetic imaging member has a resistivity of less than about 1×10 +9 ohm-cm in both background areas and selectively magnetized areas, drive means to advance said imaging member, means adapted to apply ferromagnetic toner particles in the uncharged condition to said magnetic imaging member, means to bring said substrate into superposed position with and in intimate contact with said magnetic imaging member, means for generating an electric charge on the side of the substrate away from the toner particles where said magnetic imaging member is superpositioned against said substrate and means for removing said substrate from said magnetic imaging member.

Claim 18

The apparatus of claim 14 wherein said means for generating an electrical charge comprises means for spraying ions.

Claim 19

The apparatus of claim 14 wherein magnetic means are provided to selectively magnetize the movable magnetic imaging member.

Claim 20

The apparatus of claim 14 wherein electrical or thermal stylus means are provided to selectively magnetize at the points of contact of said stylus the movable magnetic imaging member.

Claim 21

The apparatus of claim 14 wherein electrical or thermal stylus means are provided to selectively demagnetize at the points of contact of said stylus areas of the movable magnetic imaging member.