Toner, developer, toner storage unit, and image forming apparatus
AssigneeRicoh Company, Ltd.
InventorsKeiji Makabe, Tsuneyasu Nagatomo, Kohsuke Satoh, Kenji Yoneda
Life of this patent
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Abstract
A toner is provided. The toner includes toner particles each including a mother particle and external additive particles covering the mother particle. In a SEM image of the toner, toner particles having a ratio Sd/St of from 5% to 50% are present at a frequency of 15% or more, where Sd representing an area of a largest recessed portion D of each toner particle and St representing whole area of the toner particle, Sd and St determined from the SEM image magnified and binarized to discriminate recessed portions and projected portions of the toner particle from each other. An external additive coverage rate Ca at the largest recessed portion D is from 30% to 100%.
Claims7
A toner comprising:
- toner particles each comprising:
- a mother particle comprising a binder resin comprising an amorphous resin and a crystalline resin;
- and
- external additive particles covering the mother particle,
- wherein, in a SEM image of the toner, toner particles having a ratio Sd/St of from 5% to 50% are present at a frequency of 15% or more, where Sd representing an area of a largest recessed portion D of each toner particle and St representing whole area of the toner particle, Sd and St determined from the SEM image magnified and binarized to discriminate recessed portions and projected portions of the toner particle from each other,
- wherein an external additive coverage rate Ca at the largest recessed portion D is from 30% to 100%, and
- wherein the external additive particles have a number average particle diameter of from 0.03 to 0.10 μm, and a particle diameter distribution of the external additive particles indicated in a Rosin-Rammler diagram has a gradient of from 0.8 to 1.6.
Dependencies are inferred from the claim text.