Toner, developing device, and process cartridge
A toner is provided. The toner includes toner particles each including a binder resin and a release agent. From 20% to 80% by number of the toner particles satisfy the following formula (1) and (2): 2/3≤ T/Dv ≤1.5 (1) 1/3≤ R/Dv ≤1.0 (2) wherein Dv represents a volume average particle diameter of the toner particles; and T and R represent the longest cross-sectional diameters of each toner particle and the release agent contained therein, respectively, measured by observing cross-sections of the toner particles with scanning transmission electron microscope.
1. A toner, comprising:
an external additive; and
mother toner particles, comprising:
a binder resin;
a release agent; and
a plurality of fine resin particles on the mother toner particle surface, each fine resin particle composed of a vinyl polymeric resin;
wherein when a plurality of the toner particles are observed in a scanning transmission electron microscope a first amount by number of the toner particles satisfy formula (1) and a second amount by number of the toner particles satisfying formula (1) also satisfy formula (2) and a number % of the amount of second toner particles of the first amount of toner particles is from 20% to 80%:
2/3 ≤T/Dv≤ 1.5 (1)
1/3 ≤R/Dv≤ 1.0 (2)
wherein Dv represents a volume average particle diameter of the toner particles; and T and R represent the longest cross-sectional diameters of each toner particle and the release agent contained therein, respectively, measured by observing cross-sections of the toner particles with scanning transmission electron microscope, and
wherein
the mother particle has a sea-island structure in which the fine resin particles serve as island portions and constituents other than the fine resin particles serve as sea portions.
2. The toner according to claim 1 , wherein the release agent contained in each cross-section of the toner particles has a shape factor SF-1 of from 100 to 140.
3. The toner according to claim 1 , wherein the toner particles have an average circularity of 0.96 or more.
4. The toner according to claim 1 , wherein each fine resin particle is half embedded in the surface of the mother particle to form surface asperity thereon.
5. The toner according to claim 1 , wherein the binder resin comprises a polyester-vinyl hybrid resin.
6. A developing device, comprising:
a developer bearer having a surface in contact with the toner according to claim 1 to be supplied to a latent image bearer; and
a developer supply member to supply the toner to the surface of the developer bearer.
7. A process cartridge detachably mountable on an image forming apparatus, comprising:
a latent image bearer to bear a latent image; and
the developing device according to claim 6 to develop the latent image with the toner.