Color toner, method for manufacturing the toner, and image forming apparatus and method using the toner

A method for manufacturing a color toner composition, comprising:

• kneading a first part of a binder resin, a colorant, and water upon application of heat to prepare a master batch pigment;
• kneading a second part of the binder resin, a release agent that is insoluble in the binder resin, and the master batch pigment upon application of heat to prepare a mixture;
• pulverizing the mixture to prepare a color toner,
• mixing the color toner with 0.3 to 1.5 parts by weight of titania having a primary particle diameter of 0.005 to 0.02 μm using a mixer having a mixing blade, for not less than 50 sec, to obtain a color toner composition which comprises
• toner particles comprising:
• said binder resin;
• and
• said colorant and said release agent dispersed in the binder resin, and
• said 0.3 to 1.5 parts by weight of titania having a primary particle diameter of 0.005 to 0.02 μm as an external additive,
• wherein the colorant has an average dispersion particle diameter not greater than 0.5 μm;
• the release agent and the binder resin are insoluble in each other;
• the toner particles satisfy the following relationship:
• 0.05≦Dw/D4≦0.4,
• wherein Dw represents an average dispersion particle diameter of the release agent and D4 represents a weight-average particle diameter of the toner particles;
• and
• the titania has a segregation rate of from 0.5 to 5%.

An image forming method comprising:

• forming at least one electrostatic latent image on a latent-image bearer;
• developing the electrostatic latent image with at least one color developer comprising a color toner to form a color toner image on the latent-image bearer;
• transferring the toner image onto a transfer sheet optionally via an intermediate transfer medium,
• wherein the color toner comprises toner particles comprising:
• a binder resin;
• and
• a colorant and a release agent dispersed in the binder resin, and
• 0.3 to 1.5 parts by weight of titania having a primary particle diameter of 0.005 to 0.021 μm as an external additive,
• wherein the colorant has an average dispersion particle diameter not greater than 0.5 the release agent and the binder resin are insoluble to each other;
• the toner particles satisfy the following relationship:
• 0.05≦Dw/D4≦0.4,
• wherein Dw represents an average dispersion particle diameter of the release agent and D4 represents a weight-average particle diameter of the toner particles;
• and
• the titania has a segregation rate of from 0.5 to 5%.