| 摘要 |
<p>PURPOSE: To provide a developer that is provided with a good chargeability with no electrostatic charge control agent, less in toner scattering and excellent in image quality by comprising a toner and a carrier specified each. CONSTITUTION: The developer comprises a toner and a carrier. Toner grains contain a fixing resin, magnetic powder dispersed in this resin, and a polyester resin. This fixing resin contains a resin with an anionic polar group and its acid number is 4 to 20. The magnetic powder is contained in the rate of 0.1 to 5 pt.wt to 100 parts by weight of the fixing resin. This polyester resin is 500 to 10000 of its weight-average molecular weight and contained as far as 0.5 to 5 pt.wt to 100 parts by weight of the fixing resin. Carrier grains have a core grain and a covered layer. This core grain is made up of a magnetic material expressed by a formula of MOFe2 O3 (M is metal of Cu, Zn or the like). In this connection, the covered layer consists of a resin composition containing a thermosetting resin and thermoplastic resin, and this thermoplastic resin contains a quaternary ammonium group of 0.1 to 20 millimol to 100g of the resin composition.</p> |
