Toner
A toner having a toner particle including a toner base particle and an organosilicon polymer coating the toner base particle, wherein when S1 (μm 2 ) is a total area of a non-coated part not coated with the organosilicon polymer on an outermost surface of the toner particle, S2 (μm 2 ) is a total area of a coated part coated with the organosilicon polymer on the outermost surface of the toner particle, and SA1 (μm 2 ) is a total of areas of non-coated part domains D1 with an area of not more than 0.10 μm 2 in size in the non-coated part not coated with the organosilicon polymer, formulae (1) and (2) below are satisfied. 0.45≤[ S 2/( S 1+ S 2)]≤0.65 (1) ( SA 1/ S 1)≥0.50 (2)
1. A toner comprising a toner particle comprising
a toner base particle, and
an organosilicon polymer partially-coating the toner base particle, wherein,
when S1 (μm 2 ) is a total area of a non-coated part which is not coated with the organosilicon polymer on an outermost surface of the toner particle,
S2 (μm 2 ) is a total area of a coated part which is coated with the organosilicon polymer on the outermost surface of the toner particle, and
SA1 (μm 2 ) is a total of areas of non-coated part domains each of which has an area of not more than 0.10 μm 2 , in non-coated part domains D1,
formulae (1) and (2) below are satisfied:
0.45≤[ S 2/( S 1+ S 2)]≤0.65 (1)
( SA 1/ S 1)≥0.50 (2)
where, in scanning electron microscope observation of the outermost surface of the toner particle, when a backscattered electron image of the 1.5-μm square on the outermost surface of the toner particle is obtained, brightness of each pixels constituting the backscattered electron image is assigned to one of 256 gradations from brightness 0 to 255, and the brightness is plotted on a horizontal axis and the number of pixels is plotted on a vertical axis to obtain a brightness histogram,
two local maximum values P1 and P2, and a local minimum value V between the P1 and the P2 occur in the brightness histogram, and brightness yielding the local maximum value P1 is less than brightness yielding the local maximum value P2,
a peak containing the P2 is a peak derived from the coated part, while
a peak containing the P1 is a peak derived from the non-coated part, and
in a binarized image obtained by binarizing the backscattered electron image into a region W derived from the peak containing the P1 and a region B derived from the peak containing the P2, with the local minimum value V being a boundary between the regions,
the non-coated part domains D1 are domains derived from the non-coated part, while
coated part domains D2 are domains derived from the coated part, and
the S1 (μm 2 ) is a total of areas of the non-coated part domains D1, and the S2 (μm 2 ) is a total of areas of the coated part domains D2.
2. The toner according to claim 1 , wherein when SB1 (μm 2 ) is a total of areas of non-coated part domains each of which has an area of not less than 0.50 μm 2 , in the non-coated part domains D1, formula (5) below is satisfied:
( SB 1/ S 1)≤0.20 (5).
3. The toner according to claim 1 , wherein when SC1 (μm 2 ) is a total of areas of non-coated part domains each of which has an area of not more than 0.01 μm 2 , in the non-coated part domains D1, formula (6) below is satisfied:
( SA 1− SC 1)/ S 1≥0.35 (6).
4. The toner according to claim 1 , wherein a content of the organosilicon polymer in the toner particle is 2.00 to 5.00 mass %.
5. The toner according to claim 1 , wherein
the organosilicon polymer has a structure of alternately binding silicon atoms and oxygen atoms, and
the organosilicon polymer has a T3 unit structure represented by formula (7) below:
R a —SiO 3/2 (7)
where R a is a C 1-6 alkyl or phenyl group.
6. The toner according to claim 5 , wherein in 29 Si-NMR measurement of the organosilicon polymer, a ratio of an area of peaks derived from silicon having the T3 unit structure relative to a total area of peaks derived from all silicon elements contained in the organosilicon polymer is 0.60 to 0.90.