MAGNETIC TONER FOR DEVELOPING ELECTROSTATIC LATENT IMAGE, DEVICE UNIT AND IMAGE FORMING METHOD

摘要

PROBLEM TO BE SOLVED: To obtain a magnetic toner not causing scattering on an image at the time of forming a line or letter image and capable of forming a sharp image. SOLUTION: This magnetic toner contains magnetic toner particles contg. 20-150 pts.wt. magnetic substance based on 100 pts.wt. bonding resin and having such triboelectric chargeability as to ensure 25-40mC/kg absolute value of the quantity of electric charges by triboelectric charge to iron powder passing a 250mesh sieve but not passing a 350-mesh sieve. When the wt. average particle diameter (D4 ) of this magnetic toner is represented by X (μm) and the number% of magnetic toner particles each having <=3.17μm particle diameter in the number distribution is represented by Y (%), the formulae -5X+35<=Y<=-25X+180 and 3.5<=X<=6.5 are satisfied. The magnetic substance has a sphericity () of >=0.80 and 10-56kA<2> m/kg product (σr×Hc) of residual macjnetization [σr (Am<2> /kg)] and coercive force [Hc(kA/m)] in a magnetic field of 795.8kA/m (10kOe).