Two-component developer

摘要

Provided is a two-component developer containing: a magnetic carrier obtained by coating a magnetic core with a resin; and toner, in which: the magnetic core contains at least a ferrite component and at least one kind of an oxide selected from the group consisting of SiO2 and Al2O3; the content of the oxide is 4.0 mass % or more and 40.0 mass % or less with respect to the magnetic core; the magnetic core has a specific resistance of 5.0×104 Ω·cm or more and 5.0×108 Ω·cm or less at the time of the application of 1,000 V/cm; the magnetic carrier has an intensity of magnetization in 79.6 kA/m of 40.0 Am2/kg or more and 65.0 Am2/kg or less, and a residual magnetization after the application of an external magnetic field of 79.6 kA/m of 3.0 Am2/kg or less; and the toner has a weight-average particle diameter (D4) of 3.0 μm or more and 10.0 μm or less and an average circularity of 0.940 or more and 0.990 or less.

主权项

1. A two-component developer, comprising:
a magnetic carrier obtained by coating a magnetic core with a resin; and toner, wherein: the magnetic core contains at least a ferrite component and SiO2; a ratio of a length of a longest straight line among straight lines drawable on the ferrite component observed in a reflected electron image photographed with a scanning electron microscope to a maximum diameter of the section of the magnetic core in the reflected electron image is 50% or more and 85% or less; a content of SiO2 is 4.0 mass % or more and 40.0 mass % or less with respect to the magnetic core; the magnetic core has a specific resistance of 5.0×104 Ω·cm or more and 5.0×108 Ω·cm or less at a time of application of 1,000 V/cm under the following measurement conditions; the magnetic carrier has an intensity of magnetization in 79.6 kA/m of 40.0 Am2/kg or more and 65.0 Am2/kg or less, and a residual magnetization after application of an external magnetic field of 79.6 kA/m of 3.0 Am2/kg or less; and the toner has a weight-average particle diameter (D4) of 3.0 μm or more and 10.0 μm or less and an average circularity of 0.940 or more and 0.990 or less: measurement conditions: upper and lower portions in a cylindrical resin container having a measuring space with a sectional area of 2.4 cm2 are provided with upper and lower electrodes each having a measuring surface identical in shape to a sectional shape of the measuring space, 0.7 g of the magnetic core is loaded into a gap between the upper and lower electrodes, and the loaded magnetic core is subjected to measurement while being sandwiched between the upper and lower electrodes at a pressure of 50 g/cm2.