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Magnetic Brush Developer Structure

IP.com Disclosure Number: IPCOM000062477D
Original Publication Date: 1986-Nov-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 2 page(s) / 49K

Publishing Venue

IBM

Related People

Dang, CH: AUTHOR

Abstract

For a dual component developer, the magnetic brush magnetic structure is the key component. It determines the developer performance which includes print density, background, print texture, leading or trailing edge uniformity, bead carry out and materials life. The magnetic field of a magnetic brush can be divided into six zones, as illustrated in Fig. 1. The pre-nip, nip and post-nip zones are the most critical. In order to improve print density, more properly charged toner must be introduced to the latent image within the development zone. This could be achieved by increasing carrier bead rotational motion and linear velocity in the direction of mean flow. However, an excessive magnetic force within the nip restricts the bead rotational and lateral motion and also reduces the carrier flow compliancy.

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Magnetic Brush Developer Structure

For a dual component developer, the magnetic brush magnetic structure is the key component. It determines the developer performance which includes print density, background, print texture, leading or trailing edge uniformity, bead carry out and materials life. The magnetic field of a magnetic brush can be divided into six zones, as illustrated in Fig. 1. The pre-nip, nip and post-nip zones are the most critical. In order to improve print density, more properly charged toner must be introduced to the latent image within the development zone. This could be achieved by increasing carrier bead rotational motion and linear velocity in the direction of mean flow. However, an excessive magnetic force within the nip restricts the bead rotational and lateral motion and also reduces the carrier flow compliancy. As a result, the print becomes grainy and fused-on toner and wear problems accelerate. An insufficient magnetic force may not be able to effectively move the carrier beads along the rotating magnetic brush sleeve. This may provide too much bead slippage, which could contribute to a leading or trailing non-uniformity problem. At the post-development zone, a strong magnetic scavenging force is necessary to overcome the centrifugal and electrostatic forces acting on carrier beads. An overly dominant centrifugal force separates carriers from the magnetic brush sleeve and may cause flow build-up and excessive dust due to post-nip flow agitation. All these factors tend to create heavy background by exposing toner to the photoconductor after development, at a very low electric field. An electrostatic force acting...