Devices for reproducing by photoelectric method

Claim 2

An electrographic device comprising a photoconductive layer, means for placing a layer of electrically chargeable particles against said photoconductive layer, means for exposing said photoconductive layer to a pattern of radiation forming a conductivity pattern in said photoconductive layer, and means for generating across said layer of electrically chargeable particles an alternatively modulated electric field of sufficient strength to transfer alternating electric charges from said conductivity pattern to said layer of electrically chargeable particles whereby said layer of particles receives a pattern of greater and lesser alternating charges, said greater alternating charges reMoving a part of said particles while said lesser alternating charges maintain the remaining particles in said layer of particles thereby developing a stable electrographic image.

Claim 3

A device as defined in claim 1 further including an insulating backing placed against said photoconductive layer so that said photoconductive layer is located between said insulating backing and said layer of electrically chargeable particles.

Claim 4

A device as defined in claim 1 further including an insulating layer placed against said photoconductive layer so that said layer of electrically chargeable particles is located between said insulating layer and said photoconductive layer.

Claim 5

A device as defined in claim 3 wherein said insulating layer is formed from a fluid layer.

Claim 6

A device as defined in claim 1 wherein said means for generating said alternatively modulated electric field includes a first and a second electrode between which said photoconductive layer and said layer of electrically chargeable particles are interposed so that said photoconductive layer is located between said layer of particles and said first electrode.

Claim 7

A device as defined in claim 5 wherein said first electrode is shaped in the form of thin parallel wires.

Claim 8

A device as defined in claim 5 wherein said second electrode is shaped in the form of a grid.

Claim 9

A device as defined in claim 1 further including an image carrier placed against said photoconductive layer so that said layer of electrically chargeable particles is located between said photoconductive layer and said image carrier.

Claim 10

An electrographic device comprising a photoconductive layer, means for exposing said photoconductive layer to a pattern of radiation forming a conductivity pattern in said photoconductive layer so that said conductivity pattern includes maximum and minimum electric conductivities, an image carrier having a uniform electric conductivity between the maximum and the minimum conductivities which are included in said conductivity pattern, means for sandwiching a uniform layer of electrically chargeable particles between said photoconductive layer and said image carrier, and means for generating across said image carrier, said layer of electrically chargeable particles and said photoconductive layer an alternatively modulated electric field of sufficient strength to charge said layer of electrically chargeable particles from said conductivity pattern and said image carrier simultaneously, said layer of electrically chargeable particles thereby receiving electric charges attracting a part of said particles away from said image carrier to develop a first stable electrographic image on said photoconductive layer and opposite electric charges attracting the remaining particles away from said photoconductive layer to develop a second electrographic image on said image carrier.

Claim 11

An electrographic device comprising a photoconductive layer, means for exposing said photoconductive layer to a pattern of radiation forming a conductivity pattern in said photoconductive layer so that said conductivity pattern includes maximum and minimum electric conductivities, an image carrier having a uniform electric conductivity between the maximum and the minimum conductivities which are included in said conductivity pattern, means for sandwiching a uniform layer of electrically chargeable particles between said photoconductive layer and said image carrier, and means for generating across said image carrier, said layer of electrically chargeable particles and said photoconductive layer an alternatively modulated electric field of sufficient strength to charge said layer of electrically chargeable particles from said conductivity pattern and said image carrier simultaneously, said layer of electrically chargeable particles thereby receiving electric charges attracting a part of said particles away from said image carrier to develop a first stable electrographic image on said photoconductive layer and opposite electric charges attracting the remaining particles away from said photoconductive layer to develop a second electrographic image on said image carrier.

Claim 12

A device as defined in claim 9 further including an insulating backing placed against said photoconductive layer so that said photoconductive layer is located between said insulating backing and said layer of electrically chargeable particles.

Claim 13

A device as defined in claim 9 further including an insulating layer placed against said image carrier so that said image carrier is located between said insulating layer and said layer of electrically chargeable particles.

Claim 14

A device as defined in claim 9 further including two insulating layers between which the sandwich, formed by said layer of electrically chargeable particles located between said photoconductive layer and said image carrier, is disposed.

Claim 15

An electrographic device comprising a photoconductive layer, a conductive image carrier, means for coating said conductive image carrier with a layer of loosely adhering electrically chargeable particles, means for placing said coated image carrier against said photoconductive layer so that said layer of electrically chargeable particles is sandwiched between said photoconductive layer and said conductive image carrier, means fOr exposing said photoconductive layer to a pattern of radiation to form a conductivity pattern in said photoconductive layer, means for generating across said conductive image carrier, said layer of electrically chargeable particles and said photoconductive layer an alternatively modulated electric field of sufficient strength to charge said layer of electrically chargeable particles from said photoconductive layer and said conductive image carrier simultaneously, said layer of electrically chargeable particles thereby receiving a pattern of greater and lesser charges, said greater charges attracting a part of said particles away from said image carrier to develop a first stable electrographic image on said photoconductive layer while said lesser charges maintain the remaining particles on said image carrier thereby developing thereon a second stable electrographic image.

Claim 16

An electrographic device comprising a photoconductive layer, a conductive image carrier, means for coating said conductive image carrier with a layer of loosely adhering electrically chargeable particles, means for placing said coated image carrier against said photoconductive layer so that said layer of electrically chargeable particles is sandwiched between said photoconductive layer and said conductive image carrier, means fOr exposing said photoconductive layer to a pattern of radiation to form a conductivity pattern in said photoconductive layer, means for generating across said conductive image carrier, said layer of electrically chargeable particles and said photoconductive layer an alternatively modulated electric field of sufficient strength to charge said layer of electrically chargeable particles from said photoconductive layer and said conductive image carrier simultaneously, said layer of electrically chargeable particles thereby receiving a pattern of greater and lesser charges, said greater charges attracting a part of said particles away from said image carrier to develop a first stable electrographic image on said photoconductive layer while said lesser charges maintain the remaining particles on said image carrier thereby developing thereon a second stable electrographic image.

Claim 17

A device as defined in claim 13 further including an insulating backing placed against said photoconductive layer so that said photoconductive layer is located between said insulating backing and said layer of electrically chargeable particles.

Claim 18

A device as defined in claim 13 further including an insulating layer placed against said conductive image carrier so that said conductive image carrier is located between said insulating layer and said layer of electrically chargeable particles.

Claim 19

A device as defined in claim 13 further including two insulating layers between which the sandwich, formed by said layer of electrically chargeable particles located between said photoconductive layer and said conductive image carrier, is disposed.

Claim 20

A device as defined in claim 13 wherein said photoconductive layer is formed from a material having an electric conductivity superior to 10 11 mho/cm when exposed to the light.

Claim 21

An electrographic device comprising a photoconductive layer, an insulating backig on to which said photoconductive layer is affixed, means for coating said photoconductive layer with a layer of electrically chargeable particles, an insulating layer disposed against said photoconductive layer so that said layer of electrically chargeable particles is located between said insulating layer and said photoconductive layer, means for exposing said photoconductive layer to a pattern of radiation to form a conductivity pattern in said photoconductive layer, means for generating across said insulating layer, said layer of electrically chargeable particles, said photoconductive layer and said insulating backing an alternatively modulated electric field thereby transferring alternating electric charges from said conductivity pattern to said layer of electrically chargeable particles whereby said layer of particles receives a pattern of greater and lesser alternating charges, said greater alternating charges removing a part of said particles while said lesser alternating charges maintain the remaining particles in said layer of particles thereby developing a stable electrographic image.

Claim 22

An electrographic device comprising a photoconductive layer, an insulating backig on to which said photoconductive layer is affixed, means for coating said photoconductive layer with a layer of electrically chargeable particles, an insulating layer disposed against said photoconductive layer so that said layer of electrically chargeable particles is located between said insulating layer and said photoconductive layer, means for exposing said photoconductive layer to a pattern of radiation to form a conductivity pattern in said photoconductive layer, means for generating across said insulating layer, said layer of electrically chargeable particles, said photoconductive layer and said insulating backing an alternatively modulated electric field thereby transferring alternating electric charges from said conductivity pattern to said layer of electrically chargeable particles whereby said layer of particles receives a pattern of greater and lesser alternating charges, said greater alternating charges removing a part of said particles while said lesser alternating charges maintain the remaining particles in said layer of particles thereby developing a stable electrographic image.