Magnetic glass carrier materials

An electrostatographic developer mixture comprising finely-divided toner particles electrostatically clinging to the surface of low density, magnetic carrier particles, said carrier particles comprising alumino-boro-silicate glass containing about 40 molar percent SiO.sub.2, about 30 molar percent B.sub.2 O.sub.3, about 20 molar percent CaO, and about 10 molar percent Al.sub.2 O.sub.3, said alumino-boro-silicate glass also containing from between about 10 to about 15 molar percent Fe.sub.2 O.sub.3 in which superparamagnetic Fe.sub.3 O.sub.4 ferrite crystallites having an average particle size of up to about 500 A have been precipitated by heat treatment of said glass at temperatures in the range of between about 600.degree. C. and about 800.degree. C. for up to about 24 hours, wherein said carrier particles have a resistivity on the order of about 10.sup.6 to about 10.sup.12 ohm/cm and display soft magnetic properties with a lack of hysteresis behavior.

An electrostatographic imaging process comprising the steps of providing an electrostatographic imaging member having a recording surface, forming an electrostatic latent image on said recording surface, and contacting said electrostatic latent image with a developer mixture comprising finely-divided toner particles electrostatically clinging to the surface of low density, magnetic carrier particles, said carrier particles consisting essentially of a boro-silicate glass further containing about 20 molar percent CaO, about 10 molar percent Al.sub.2 O.sub.3, and from between about 10 to about 15 molar percent Fe.sub.2 O.sub.3 in which superparamagnetic Fe.sub.3 O.sub.4 ferrite crystallites having an average particle size of up to about 500 A have been precipitated by heat treatment of said glass at temperatures in the range of between about 600.degree. C. and about 800.degree. C. for up to about 24 hours, wherein said carrier particles have a resistivity on the order of about 10.sup.6 to about 10.sup.12 ohm/cm and display soft magnetic properties with a lack of hysteresis behavior, whereby at least a portion of said finely-divided toner particles are attracted to and deposited on said recording surface in conformance with said electrostatic latent image.

An electrostatographic imaging process comprising the steps of providing an electrostatographic imaging member having a recording surface, forming an electrostatic latent image on said recording surface, and contacting said electrostatic latent image with a developer mixture comprising finely-divided toner particles electrostatically clinging to the surface of low density, magnetic carrier particles, said carrier particles comprising alumino-boro-silicate glass containing about 40 molar percent SiO.sub.2, about 30 molar percent B.sub.2 O.sub.3, about 20 molar percent Cao, and about 10 molar percent Al.sub.2 O.sub.3, said alumino-boro-silicate glass also containing from between about 10 to about 15 molar percent Fe.sub.2 O.sub.3 in which superparamagnetic Fe.sub.3 O.sub.4 ferrite crystallites having an average particle size of up to about 500 A have been precipitated by heat treatment of said glass at temperatures in the range of between about 600.degree. C. and about 800.degree. C. for up to about 24 hours, wherein said carrier particles have a resistivity on the order of about 10.sup.6 to about 10.sup.12 ohm/cm and display soft magnetic properties with a lack of hysteresis behavior, whereby at least a portion of said finely-divided toner particles are attracted to and deposited on said recording surface in conformance with said electrostatic latent image.