Electrostatic latent image development employing steel carrier particles

Claim 1

A METHOD OF FORMING A VISIBLE TONER IMAGE COMPRISING THE STEPS OF FORMING AN ELECTROSTATIC LATENT IMAGE ON A RECORDING SURFACE AND CONTAINING SAID ELETROSTATIC LATENT IMAGE WITH A DEVELOPER MIXTURE UNTIL AT LEAD A PORTION OF SAID TONER PARTICLES ARE ATTRACTED TO AND HELD ON SAID SURFACE IN CONFORMANCE TO SAID ELECTROSTATIC LATENT IMAGE, SAID DEVELOPER MIXTURE COMPRISING ABOUT ONE PART BY WEIGHT OF FINELY-DIVIDED TONER PARTILES ELECTROSTATIALLY ADHERING TO THE SURFAE OF ABOUT 10 PARTS TO ABOUT 200 PARTS BY WEIGHT OF HIGHLY SHAPE-CLASSIFIED LOW CARBON HYPEREUTECTOID STEEL CARRIER PARTICLES HAVING AN AVERAGE PARTICLE SIZE BETWEEN ABOUT 50 MICRONS AND ABOUT 1,000 MICRONS AND A SPECIFIC GRAVITY OF AT LAST ABOUT 7 GRAMS PER CUBIC CENTIMETER, SAID STEEL CARRIER PARTICLES HAVING BEEN HEAT TREATED TO A TEMPERATURE MARTENSITIC MICROSTRUCTURE WITH AN AVERAGE HARDNESS OF 40-55 ROCKWELL C IN AN AIR OR OXYGEN ATMOSPHERE AT TEMPERATURES RANGING BETWEEN ABOUT 500*F AND ATBOUT 1,000*F TO PROVIDE AN OXIDE SURFACE LAYER COMPRISING FE3O4 ON SAID STEEL CARRIER MATERIAL, SAID OXIDE SURFACE LAYER HAVING A THICKNESS BETWEEN ABOUT 0.2 AND ABOUT 5.0 MICRONS, SAID STEEL CARRIER PARTICLES COMPRISING CARRIER CORES HAVING A COMPOSITION COMPRISING ABOUT 95.0 TO ABOUT 99.0 PARTS IRON, ABOUT 0.1 ABOUT 2.0 PARTS CARBON, ABOUT 0.5 TO ATBOUT 2.0 PARTS MANGANESE, ABOUT 0.5 TO ABOUT 2.0 PARTS SILICON, ABOUT 0.03 TO ABOUT 0.1 PARTS ALUMINUM, ABOUT 0.01 TO ABOUT 0.05 PARTS PHOSPHOURUS, AND ABOUT 0.02 TO ABOUT 0.05 PARTS SULPHUR, SAID TREATED CARRIER PARTICLES BEING OVERCOATED WITH A RESINOUS COATING MATERIAL CAPABLE OF ELECTROSTATIALLY RELEASING SAID ELECTROSTATICALLY ADHERING TONER PARTICLES TO SAID ELECTROTATIC LATENT IMAGE.

Claim 2

A METHOD OF FORMING A VISIBLE TONER IMAGE COMPRISING THE STEPS OF FORMING AN ELECTROSTATIC LATENT IMAGE ON A RECORDING SURFACE AND CONTAINING SAID ELETROSTATIC LATENT IMAGE WITH A DEVELOPER MIXTURE UNTIL AT LEAD A PORTION OF SAID TONER PARTICLES ARE ATTRACTED TO AND HELD ON SAID SURFACE IN CONFORMANCE TO SAID ELECTROSTATIC LATENT IMAGE, SAID DEVELOPER MIXTURE COMPRISING ABOUT ONE PART BY WEIGHT OF FINELY-DIVIDED TONER PARTILES ELECTROSTATIALLY ADHERING TO THE SURFAE OF ABOUT 10 PARTS TO ABOUT 200 PARTS BY WEIGHT OF HIGHLY SHAPE-CLASSIFIED LOW CARBON HYPEREUTECTOID STEEL CARRIER PARTICLES HAVING AN AVERAGE PARTICLE SIZE BETWEEN ABOUT 50 MICRONS AND ABOUT 1,000 MICRONS AND A SPECIFIC GRAVITY OF AT LAST ABOUT 7 GRAMS PER CUBIC CENTIMETER, SAID STEEL CARRIER PARTICLES HAVING BEEN HEAT TREATED TO A TEMPERATURE MARTENSITIC MICROSTRUCTURE WITH AN AVERAGE HARDNESS OF 40-55 ROCKWELL C IN AN AIR OR OXYGEN ATMOSPHERE AT TEMPERATURES RANGING BETWEEN ABOUT 500*F AND ATBOUT 1,000*F TO PROVIDE AN OXIDE SURFACE LAYER COMPRISING FE3O4 ON SAID STEEL CARRIER MATERIAL, SAID OXIDE SURFACE LAYER HAVING A THICKNESS BETWEEN ABOUT 0.2 AND ABOUT 5.0 MICRONS, SAID STEEL CARRIER PARTICLES COMPRISING CARRIER CORES HAVING A COMPOSITION COMPRISING ABOUT 95.0 TO ABOUT 99.0 PARTS IRON, ABOUT 0.1 ABOUT 2.0 PARTS CARBON, ABOUT 0.5 TO ATBOUT 2.0 PARTS MANGANESE, ABOUT 0.5 TO ABOUT 2.0 PARTS SILICON, ABOUT 0.03 TO ABOUT 0.1 PARTS ALUMINUM, ABOUT 0.01 TO ABOUT 0.05 PARTS PHOSPHOURUS, AND ABOUT 0.02 TO ABOUT 0.05 PARTS SULPHUR, SAID TREATED CARRIER PARTICLES BEING OVERCOATED WITH A RESINOUS COATING MATERIAL CAPABLE OF ELECTROSTATIALLY RELEASING SAID ELECTROSTATICALLY ADHERING TONER PARTICLES TO SAID ELECTROTATIC LATENT IMAGE.