| 摘要 |
PROBLEM TO BE SOLVED: To provide the developer free from occurrence of deteriorated image density and uneven image density even with images formed after being left in high temperature and high humidity. SOLUTION: This developer contains at least a binder resin and a magnetic material and an insoluble fraction in tetrahydrofuran in an amount of 0.1-20 weight %. The above binder resin is a polyester resin having a melt index of 1-15 g/10 min, a glass transition point of 50-70 deg.C, a molecular weight peak in the tetrahydrofuran soluble fraction of 3000-7000, an acid value of 3-20, a hydroxyl value of 1-20. The above magnetic material has a polyhedron of 10-26 hedron, a residual magnetization of 3.0-6.0 Am2/kg under 796 kAm, and a P/Fe ratio of 0.1-1 weight %. |
