POSITIVE CHARGE TYPE MAGNETIC DEVELOPER AND IMAGE FORMING METHOD

摘要

PROBLEM TO BE SOLVED: To provide a positive charge type magnetic developer having good fluidity and containing toner particles having a large quantity of electric charges from the time immediately after the beginning of development and keeping the quantity even when development is repeated many times, and to provide an image forming method using the magnetic developer. SOLUTION: The positive charge type magnetic developer 2 comprises a mixture of at least insulating magnetic toner particles containing a bonding resin and a magnetic powder with fine powder of amorphous silicon-aluminum co-oxide consisting of 85-55 wt.% Al2O3 and 15-45 wt.% SiO2, having 20-200 m2/g BET specific surface area and optionally provided with hydrophobic property. The magnetic developer 2 housed in a developer housing chamber 3 is conveyed as a thin uniform layer regulated to a prescribed thickness by a doctor blade 6 in accordance with the turning of a developing sleeve 4 having an internal fixed magnet roll 5 and develops an electrostatic latent image supported on a photosensitive drum 1 in a developing region.