Resin-coated carrier, two component type developer, and developing method

A two component type developer comprising a toner and a resin-coated carrier;

• said resin-coated carrier comprising carrier particles having a carrier core material and a coat layer which covers the surface of the carrier core material;
• said resin-coated carrier having a 50% particle diameter C (D.sub.50) of from 25 .mu.m to 70 .mu.m, containing carrier particles smaller than 22 .mu.m in particle diameter in an amount of from 0.1% by number to 20% by number and containing carrier particles of 62 .mu.m or larger in particle diameter in an amount of from 2% by number to 35% by number;
• and
• said carrier core material having a BET specific surface area SW1 where the coat layer has been removed and said resin-coated carrier having a BET specific surface area SW2, the SW1 and SW2 satisfying the following expression (I), and said resin-coated carrier satisfying a shape factor SF-1 of the following expression (II) and a shape factor SF-2 of the following expression (III),
• 80.ltoreq.SW1-SW2.ltoreq.650(cm.sup.2 /g) (I)
• 110.ltoreq.SF-1.ltoreq.160 (II)
• 105.ltoreq.SF-2.ltoreq.150 (III).

A developing method comprising the steps of;

• rotating a developing sleeve carrying thereon a two component type developer having a toner and a carrier;
• and
• developing an electrostatic latent image formed on the surface of a photosensitive member, by the use of the toner of the two component type developer;
• wherein a resin-coated carrier comprising carrier particles having a carrier core material and a coat layer which covers the surface of the carrier core material is used as said carrier;
• said resin-coated carrier having a 50% particle diameter C (D.sub.50) of from 25 .mu.m to 70 .mu.m, containing carrier particles smaller than 22 .mu.m in particle diameter in an amount of from 0.1% by number to 20% by number and containing carrier particles of 62 .mu.m or larger in particle diameter in an amount of from 2% by number to 35% by number;
• and
• said carrier core material having a BET specific surface area SW1 where the coat layer has been removed and said resin-coated carrier having a BET specific surface area SW2, the SW1 and SW2 satisfying the following expression (I), and said resin-coated carrier satisfying a shape factor SF-1 of the following expression (II) and a shape factor SF-2 of the following expression (III)
• 80.ltoreq.SW1-SW2.ltoreq.650(cm.sup.2 /g) (I)
• 110.ltoreq.SF-1.ltoreq.160 (II)
• 105.ltoreq.SF-2.ltoreq.150 (III).