Developer and image forming apparatus

Abstract

The invention provides a developer used in an image forming apparatus and an image forming apparatus, the developer containing: a toner, and a carrier that charges the toner, the toner containing a core toner, and an external additive that is added to a surface of the core toner, the core toner containing a colorant, a binder resin, a releasing agent, and a charge controlling agent containing Al and Mg, an amount of the charge controlling agent on the surface of the core toner being from 0.2 to 4.0 cps / eV in terms of a Mg amount measured by EDX, the core toner having a circularity of from 0.880 to 0.930, the external additive having a primary particle diameter of from 70 to 200 nm, an amount of the external additive being from 0.2 to 3.0% by weight based on the core toner.

Description

[0001] Cross References to Related Applications [0002] This application is based upon and claims the benefit of priority from prior US Patent Application No. 61 / 044220, filed April 11, 2008, the entire contents of which are hereby incorporated by reference. technical field [0003] The present invention relates to a developer and an image forming apparatus used when an image is formed by electrophotography, for example, in a copier or a printer. Background technique [0004] A two-component developer containing toner and a magnetic carrier for charging the toner is used in an electrophotographic image forming apparatus. Such a two-component developer degrades the carrier during use. Therefore, it is difficult to maintain an initial state such as ensuring necessary chargeability, and it is difficult to obtain a long life. [0005] For example, chargeability decreases due to long-term use, causing problems in that poorly charged toner scatters to contaminate the inside of ...

AI Technical Summary

Problems solved by technology

[0005] For example, due to long-term use, the chargeability is lowered, so that there is a problem that poorly charged toner scatters and contaminates the inside of the machine, thereby causing severe image defects, fogging (blurring) images

However, even if such a charge control agent is added to the toner, the charge amount fluctuates due to changes in the installation environment, so it is difficult to properly control the chargeability.

For example, there arises a problem that although the decrease in charge amount can be suppressed in a high-humidity state, the charge amount excessively increases in a low-humidity state.

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