Electrographic methods using hard magnetic carrier particles

US6589703B2 · kind B2 · utility

Assignee

• Heidelberger Druckmaschinen AG · DE

Inventors

• Eric C. Stelter · Rochester, US
• Robert D. Fields · Rochester, US
• Thomas A. Jadwin · Rochester, US

Key dates

• Filing date: May 11, 2001
• Grant date: Jul 8, 2003
• Expiry date: May 11, 2021

Classification

• Technology area (CPC G): Physics
• CPC primary: G03G9/1085
• WIPO field: Optics
• WIPO sector: Instruments

Abstract

Disclosed are methods and apparatus for electrographic development which utilize a rotating magnetic core, a toner shell disposed around the rotating magnetic core, and developer compositions disposed on the toner shell which include a hard magnetic material, such as a strontium ferrite. The shell in embodiments has an outer surface with a surface roughness Ra of less than 32 microinches. The methods and apparatus do not require special manufacturing steps to place surface roughness or irregularities on the shell, and, thus, can provide the same or better image quality with relatively less complex manufacturing steps and at reduced cost.