| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide magnetic iron oxide particulate powder for a magnetic toner which does not drop out from toner particles, ensures good fluidity as a toner and hardly inhibits charging of the toner because of a small area of a magnetic material surface exposed on the toner surface to improve the charging performance of the toner, thereby giving a toner having high image density even in a high-temperature and high-humidity environment and also having high image density-maintaining property. <P>SOLUTION: The magnetic iron oxide particulate powder has a spherical particle shape as a basic shape and has angular protrusions on a particle surface. A method for producing such magnetite particulate powder includes a two-step reaction comprising a reaction of an aqueous ferrous salt solution with an aqueous alkali hydroxide solution to form magnetite seed crystal particles and a growth reaction of the seed crystal particles, wherein pH in the first-step reaction is adjusted to a range of 7.0-8.5, and in the second-step reaction, a ferrous salt solution is added in an amount of 1.0-30.0 at.% relative to the amount of Fe in the first-step reaction. <P>COPYRIGHT: (C)2009,JPO&INPIT |
