Toner
A toner comprising: a toner particle that contains a binder resin and a colorant: and an external additive, wherein (1) the average circularity of the toner is at least 0.960; (2) the fixing ratio of the external additive on the toner particle is from 75% to 100%; and (3) in a differential curve obtained by the differentiation, by load, of a load-displacement curve where the horizontal axis is load (mN) and the vertical axis is displacement (μm), the load-displacement curve being provided by measurement of the strength of the toner by a nanoindentation procedure, a load A that provides a maximum value in the differential curve in a load region from 0.20 mN to 2.30 mN is from 1.15 mN to 1.50 mN.
1. A toner, comprising:
a toner particle containing a binder resin and a colorant; and
an external additive, a fixing ratio of the external additive on the toner particle being from 75 to 100%, wherein
the average circularity of the toner is at least 0.960, and
a load A that provides a maximum value in a load region from 0.20 to 2.30 mN is from 1.15 to 1.50 mN in a differential curve obtained by the differentiation, by load, of a load-displacement curve where the horizontal axis is load (mN) and the vertical axis is displacement (μm), the load-displacement curve being provided by measurement of the strength of the toner by a nanoindentation procedure.
2. The toner according to claim 1 , wherein a coverage ratio X1 of the surface of the toner particle by the external additive is from 40.0 to 80.0 area % as measured with an x-ray photoelectron spectrometer.
3. The toner according to claim 2 , wherein a diffusion index indicated by the formula Diffusion index=X1/X2 satisfies the formula
Diffusion index≥−0.0042×X1+0.62
where X2 is a theoretical coverage ratio of the surface of the toner particle by the external additive.
4. The toner according to claim 1 , wherein the Total Energy is from 200 to 400 mJ when the surface of a powder layer of the toner produced in a measurement vessel by application of a vertical load of 0.88 kPa is penetrated by a propeller-type blade while rotating the propeller-type blade at a peripheral velocity of 10 mm/second at the outermost edge thereof using a powder flowability measuring apparatus.
5. The toner according to claim 1 , wherein the external additive contains an external additive having a number-average particle diameter of from 40 to 200 nm.
6. The toner according to claim 1 , wherein the methanol concentration at a transmittance of 40% is from 40 to 62 volume % when the wettability of the toner relative to a methanol/water mixed solvent is measured using the transmittance of light having a wavelength of 780 nm.
7. The toner according to claim 1 , wherein the external additive contains at least one selected member from the group consisting of silica fine particles and organic/inorganic composite fine particles.
8. The toner according to claim 1 , wherein the fixing ratio of the external additive on the toner particle is from 80 to 100%.
9. The toner according to claim 1 , wherein the fixing ratio of the external additive on the toner particle is from 80.2 to 100%.