US 4,448,872 A · Duplex imaging with pressure transfixing

Abstract

Method and apparatus for duplex electrostatic imaging wherein a toner image is transferred and simultaneously fixed to two sides of a receptor medium using high pressure. The first toner image is created on a dielectric image roller and pressure transferred to a transfer roller moving at an identical surface velocity. A second toner image is subsequently formed on the image roller, and the two images are simultaneously transferred and fused to opposite sides of a receptor sheet at the nip. The image roller advantageously includes a hard, very smooth dielectric surface, while the transfer roller has a moderately smooth, compliant surface. The transfer roller surface preferably comprises an engineering thermoplastic or thermoset material characterized by a relatively low coefficient of friction in order to provide high transfer efficiency to the receptor sheet. The duplex imaging apparatus may be incorporated into electrostatic printers and copiers with suitable adaptations in the image generating stages.

Claims18

Dependent claims

A method of duplex imaging which comprises forming a first toner image on the surface of an image roller, said image surface having a smoothness in excess of 20 microinch rms and a modulus of elasticity in compression of at least 10.sup.7 PSI;

transferring said first toner image to the surface of a transfer roller in rolling contact with said image roller under a compressive load, said transfer roller having a surface layer of a material selected from the group consisting of engineering thermoplastic and engineering thermoset materials;
creating a second toner image on the surface of the image roller;
passing an image receptor sheet between said image roller and said transfer roller;
and
transferring said first toner image from said transfer roller to one side of said image transfer sheet and simultaneously transferring said second toner image from said image roller to an opposite side of said image receptor sheet,
wherein the rollers are pressed together sufficiently to fuse the toner images to said image receptor sheet at ambient temperatures.

3 more elements

A method of duplex imaging which comprises forming a first toner image on the surface of an image roller comprised of aluminum anodized to form an oxide surface layer, which is impregnated with a dielectric material and polished to a smoothness in excess of 20 microinch rms;

transferring said first toner image to the surface of a transfer roller in rolling contact with said image roller under a compressive load, said transfer roller having a surface layer of a material selected from the group consisting of copolymers and homopolymers of polyoxymethylene, polyesters, polyvinylchloride, and polycarbonates;
forming a second toner image on the surface of said image roller;
passing an image receptor sheet between said image roller and said transfer roller;
and
transferring said first toner image from said transfer roller to one side of said image receptor sheet and simultaneously transferring said second toner image from said image roller to an opposite side of said image receptor sheet, wherein the rollers are pressed together sufficiently to fuse the toner images to said image receptor sheet at ambient temperatures.

2 more elements

Dependencies are inferred from the claim text.

Duplex imaging with pressure transfixing

Life of this patent

Duplex imaging with pressure transfixing

Life of this patent

Abstract

Claims18