Toner, external additive therefor and image forming method using the toner

A method for preparing an external additive comprising:

• coating a particulate inorganic material with a silicone oil;
• and
• heating the inorganic material,
• wherein after the heating the silicone oil is present on the particulate inorganic material in an amount of Ws by weight and present as a free silicone oil in an amount of Wfs by weight, and a free silicone degree defined as a ratio Wfs/Ws is from 10 to 70%.

A toner comprising:

• a binder resin;
• a colorant;
• and
• an external additive,
• wherein the external additive comprises:
• a particulate inorganic material;
• and
• a silicone oil,
• wherein the silicone oil is present on the particulate inorganic material in an amount of Ws by weight and present as a free silicone oil in an amount of Wfs by weight, and wherein a free silicone degree defined as a ratio Wfs/Ws is from 10 to 70%.

A toner combination for forming a full color image, consisting of a cyan toner, a magenta toner, a yellow toner and a black toner, wherein at least one of the toners comprises:

• a binder resin;
• a colorant;
• and
• an external additive,
• wherein the external additive comprises:
• a particulate inorganic material;
• and
• a silicone oil,
• wherein the silicone oil is present on the particulate inorganic material in an amount of Ws by weight and present as a free silicone oil in an amount of Wfs by weight, and wherein a free silicone degree defined as a ratio Wfs/Ws is from 10 to 70%.