| 摘要 |
PROBLEM TO BE SOLVED: To prevent filming phenomenon due to the use of a resin having a low softening point in the production of a toner by using magnetite having a specified average particle diameter, a specified geometric standard deviation of particle diameter and a specified weight ratio of FeO:Fe3 O4 . SOLUTION: This magnetic powder for addition to an electrophotographic toner is made of magnetite having 0.3-0.5μm average particle diameter, a geometric standard deviation of particle diameter of <=1.5 and a ratio of 3:97 to 15:85 as the weight ratio of FeO:Fe3 O34 . The surface of the magnetic powder is preferably subjected to oxidized film formation treatment. By this treatment, the filing preventing effect of the magnetic powder for addition to an electrophotographic toner is further enhanced. The magnetic powder, as it is excellent in filming preventing effect, is added to a toner used in an electrophotographic developing system and it is stuck to the surface of the toner by mixing, which can be used as magnetic powder for addition. |
