ABSTRACT
Magnetic brush development was invented by Young (1957a, 1957b) and Giaimo (1957) in the 1950s. It is currently used in almost all high-volume copiers and printers. Magnetic brush development can be used with either single-or twocomponent developers. Most current processes, however, use two-component developers. Carriers for magnetic brush development are usually Fe, Co, or Sr ferrites. Figure 11 shows a typical magnetic brush development process. In the process shown in this illustration, the magnets are stationary while the brush roll rotates, bringing the magnetic carrier beads and attached toner particles into contact with the latent image. Key requirements of magnetic brush development are the need to monitor the toner concentration and the addition and mixing of fresh toner. Magnetic brush development processes are described as insulating or conducting. The distinction is due to the conductivity of the developer and largely determined by the composition and geometry of the carrier beads and the thickness of the polymer coating of the beads. Conductive brush development gives better solid area development, whereas insulating development produces better line copy. Conductive brush development is used in many high-volume copiers, while insulating brush development is more common in low-volume applications.
