Electrophotographic toner and production method therefor
View Patent ↗An electrophotographic toner contains a resin, a colorant and a releasing agent. The releasing agent has a solidifying point of from 79° C. to 109° C., and one peak in an endothermic curve measured by a differential scanning calorimeter. A difference between temperature to give a maximum endothermic peak of the releasing agent and an end-set temperature of the releasing agent is within 10° C. A melt viscosity of the releasing agent at 110° C. is in a range of from 4 mPa·s to 9 mPa·s. The releasing agent in one particle of the toner forms 3 or more domains. Domains having a ratio of a major axis to a minor axis which is in a range of from 5 to 15 occupy 90% or more by number based on the total number of domains.
1. An electrophotographic toner comprising□
a resin;
a colorant; and
a releasing agent,
wherein:
the releasing agent has a solidifying point of from 79° C. to 109° C.,
the releasing agent has one peak in an endothermic curve measured by a differential scanning calorimeter,
a difference between a temperature to give a maximum endothermic peak of the releasing agent and an end-set temperature of the releasing agent is within 10° C.,
a melt viscosity of the releasing agent at 110° C. is in a range of from 4 mPa·s to 9 mPa·s,
the releasing agent in one particle of the toner forms 3 or more domains,
the domains include domains having a ratio of a major axis to a minor axis in a range of from 5 to 15 which occupy equal to or more than 90% by number based on the total number of domains,
the domains include domains having a major axis of 1.5 μm or more which occupy equal to or more than 40% by number based on the total number of domains, and
the domains include domains having 1.0 μm or more which occupy equal to or more than 80% by number based on the total number of domains.
2. The electrophotographic toner according to claim 1 , wherein the releasing agent is a paraffin-type wax, a ratio of an isoparaffin to an n-paraffin in the releasing agent is in a range of from 4% to 10% by weight, and a penetration degree of the releasing agent at 25° C. is equal to or less than 5.
3. The electrophotographic toner according to claim 1 , wherein a ratio of a melt viscosity of the releasing agent to a melt velocity of the resin at 180° C. is in a range of from 1.0×10 −4 to 3.0×10 −4 .
4. The electrophotographic toner according to claim 1 , wherein a content of the releasing agent in the toner is in a range of from 5 to 13% by weight based on the total solid content of the toner.
5. The electrophotographic toner according to claim 1 , wherein an acid value of the toner is in a range of from 10 mg·KOH/g to 50 mg·KOH/g.
6. The electrophotographic toner according to claim 1 , wherein a volume average particle diameter D50v of the toner is in a range of from 3 μm to 9 μm, a volume average particle size distribution index GSDv is equal to or less than 1.30, and the volume average particle size distribution index GSDv is defined by
GSDv =( D 84 v/D 16 v )
where D50v, D84v and D16v each represents a volume average particle diameter showing 50%, 84% and 16% of accumulation when a cumulative distribution curve of volume in divided particle size ranges is constructed starting from a side of smaller diameter.
7. The electrophotographic toner according to claim 1 , wherein the toner has a shape factor SF1 of from 110 to 140 and the shape factor SF1 is defined by
SF1=(ML 2 /A)×(π/4)×100
where ML represents a maximum length of the toner, and A represents a projected area of the toner.