Apparatus for electrostatic printing

Claim 2

Apparatus for electrostatic printing comprising: a printing plate including a conductive base having a coating of a semiconductor material thereon, said semiconductor material being capable of varying its resistance from a high resistance condition to a low resistance condition in response to energy applied thereto: a substantially constant DC voltage source one pole of which is conductively connected to said base for providing a charge which is conducted through said semiconductor material in those areas where said semiconductor is in said low resistance condition; writing means for applying energy to selected regions of said coating, in an amount sufficient to vary the resistance of said semiconductor material from said high condition to said low condition to permit passage of said voltage to the surface of said semiconductor material in said selected regions; modulating means for varying the amount of energy applied to other regions of said coating to a level which is insufficient for varying the resistance of said semiconductor material in said other regions to said low condition, developing means for applying particles to said printing plate which cling to said coating at said selected regions; and transfer means for engaging said printing plate with a record medium to transfer at least a portion of said clinging particles to said record whereby an image of said selected regions is printed on said record.

Claim 3

Apparatus as defined in claim 1 wherein said coating has a single stable state in said high resistance condition and shifts temporarily from said high resistance condition to said low resistance condition in response to said energy applied thereto to permit voltage from said source connected to said base to travel through said coating during said temporary shift thereby trapping said charge on said coating when said coating returns to said high resistance condition.

Claim 4

Apparatus as defined in claim 2 further characterized by the addition of a grounding means for removing said charge trapped on said coating after said image is printed on said record.

Claim 5

Apparatus as defined in claim 3 further characterized by the addition of cleaning means for wiping said clinging particles from said coating after said image is printed on said record to prepare said material for printing another image.

Claim 6

Apparatus as defined in claim 1 wherein said coating comprises a semiconductor material which has two stable states, a high resistance state and a low resistance state, and which is capable of being switched between said states in response to said energy applied thereto.

Claim 7

Apparatus as defined in claim 5 further characterized by the addition of means for applying energy to said coating to switch said coating from said low resistance state to said high resistance state.

Claim 8

Apparatus as defined in claim 1 wherein said writing means includes a modulated laser beam.

Claim 9

Apparatus as defined in claim 1 wherein said writing means includes a modulated electron beam.

Claim 10

Apparatus as defined in claim 1 wherein said writing means includes a plurality of slide wires in contact with said coating.

Claim 11

Apparatus as defined in claim 9 wherein an electron beam selectively applies a charge to said slide wires.

Claim 12

Apparatus as defined in claim 1 wherein said coating is an amorphous semiconductor.

Claim 13

Apparatus for electrostatic printing comprising: a rotatable printing drum including a metal cylinder having an amorphous semiconductor coating applied to the outer surface thereof, said amorphous semiconductor having a bistable characteristic including a high resistance state and a low resistance state; drive means for rotating said drum; a constant DC voltage source one pole of which is conductively connected to said base; writing means for applying a pattern of energy to said amorphous semiconductor at selected regions, said pattern having an energy content sufficient to switch said coating from said high resistance state to said low resistance state to permit passage of said voltage to the surface of said amorphous semiconductor material in said selected regions; developing means for dusting said amorphous semiconductor coating with particles of ink as said drum rotates, said ink clinging to said regions of said amorphous semiconductor residing in said low resistance state; printing means for placing a document in contact with said amorphous semiconductor and transferring at least a portion of said ink particles to said document; reset means for applying a uniform field of energy across said amorphous semiconductor, said field having an energy content sufficient to switch said amorphous semiconductor from said low resistance state to said high resistance state; grounding means for removing charge from said amorphous semiconductor coating; and control means connected to said reset means for selectively rendering said reset means inoperative during certain revolutions of said drum, whereby said developing means applies ink to said coating during said certain revolutions, and said printing means prints a plurality of copies of said image.

Claim 14

Apparatus for electrostatic printing comprising: a rotatable printing drum including a metal cylinder having an amorphous semiconductor coating applied to the outer surface thereof, said amorphous semiconductor having a bistable characteristic including a high resistance state and a low resistance state; drive means for rotating said drum; a constant DC voltage source one pole of which is conductively connected to said base; writing means for applying a pattern of energy to said amorphous semiconductor at selected regions, said pattern having an energy content sufficient to switch said coating from said high resistance state to said low resistance state to permit passage of said voltage to the surface of said amorphous semiconductor material in said selected regions; developing means for dusting said amorphous semiconductor coating with particles of ink as said drum rotates, said ink clinging to said regions of said amorphous semiconductor residing in said low resistance state; printing means for placing a document in contact with said amorphous semiconductor and transferring at least a portion of said ink particles to said document; reset means for applying a uniform field of energy across said amorphous semiconductor, said field having an energy content sufficient to switch said amorphous semiconductor from said low resistance state to said high resistance state; grounding means for removing charge from said amorphous semiconductor coating; and control means connected to said reset means for selectively rendering said reset means inoperative during certain revolutions of said drum, whereby said developing means applies ink to said coating during said certain revolutions, and said printing means prints a plurality of copies of said image.

Claim 15

Apparatus as defined in claim 12 further characterized by the addition of cleaning means for wiping said clinging particles from said coating of said drum.

Claim 16

Apparatus as defined in claim 12 wherein said writing means includes a modulated laser beam.

Claim 17

Apparatus as defined in claim 12 wherein said writing means includes a modulated electron beam.

Claim 18

Apparatus as defined in claim 12 wherein said writing means includes a plurality of slide wires in contact with said amorphous semiconductor coating.

Claim 19

Apparatus as defined in claim 16 wherein an electron beam selectively applies a charge to said slide wires.