Patent ID: 9274447
Filing Date: 2016-03-01
CPC Classification: G03G

Claim Text:
1. A two-component color developer containing a toner and a resin-coated carrier, the toner containing at least a polyester resin as a binding resin, an organic pigment as a colorant, and inorganic fine particles as an external additive, wherein the inorganic fine particles have a negative polarity, the toner has a volume resistivity of 40 ×10 9 to 220 ×10 9 Ωcm and a negative polarity, and the carrier has a coat durability of 90% or greater, wherein the coat durability is a value obtained by two different ways to be described below after a prescribed amount of 200 g of the developer is put in a development unit of a full color copying machine, and a magnet roller is blocked and is subjected to idle rotation with a rotation testing machine at a magnet roller rotation frequency of 300 rpm for 24 hours: in the case where the resin-coated carrier has a resin layer made of a silicone-based coating material, the value is obtained by measuring strength of Si and Fe in the carrier obtained by separating the toner from the developer with use of a scanning fluorescent X-ray analyzer and by calculating Si/Fe ratios before and after the idle rotation; or in the case where the resin-coated carrier has a resin layer made of an acryl-based coating material, the value is obtained by measuring a peak area derived from the coating material with use of a gas chromatograph mass spectroscope at a heating temperature set to 500° C. and by calculating a ratio between peak areas before and after the idle rotation.