Encapsulated toner for heat-and-pressure fixing and method for producing the same

摘要

The encapsulated toner for heat-and-pressure fixing which includes a heat-fusible core material containing at least a thermoplastic resin and a coloring agent, and a shell formed thereon so as to cover the surface of the core material is produced by a process having the step of carrying out in situ polymerization using a thermoplastic resin as a main component of the shell to form a shell having a structure in which a part of the heat-fusible core material is incorporated therein, the thermoplastic resin having a mechanical loss tangent (tan delta ) in the range of from 1.0 to 20.0 based on a dynamic viscoelasticity, when measured with a sine stress having an angular frequency of 25 rad/s at a temperature of from 80 to 120 DEG C. By using the encapsulated toner, good offset resistance can be obtained in the resulting toner even when its fixing speed is slow. Also, the core material is likely to be released from the encapsulated toner upon fixing while retaining good blocking resistance and good shocking resistance.