Toner

1. A toner, comprising toner particles, each of which has a surface layer containing an organosilicon polymer,

wherein the organosilicon polymer has a partial structure represented by the following formula (T3),

R—Si(O 1/2 ) 3   (T3)

wherein R denotes an alkyl group having 1 to 6 carbon atoms or a phenyl group,

wherein the surface layer has an average thickness Dav. of 5.0 nm or more and 150.0 nm or less as measured by observing a cross section of each of the toner particles with a transmission electron microscope (TEM), and

the toner has a ratio (ASi/AC) of 20.00 or more in mapping measurement by focused-ion-beam time-of-flight secondary ion mass spectrometry (FIB-TOF-SIMS), wherein ASi denotes ISi/I, AC denotes IC/I, ISi denotes an intensity of silicon ions, IC denotes an intensity of carbon ions, and I denotes the number of primary ions, the silicon ions and carbon ions being emitted from the toner particles in response to irradiation of the toner particles with the primary ions, and

a concentration of silicon elements on a surface of the toner particles is 5.0 atomic percent or more as measured by electron spectroscopy for chemical analysis (ESCA).

2. The toner according to claim 1 , wherein

a percentage of line segments Ar n (n=1 to 32) having FRA n of 5.0 nm or less is 20.0% or less in observation of a cross section of each of the toner particles with a transmission electron microscope (TEM),

wherein Ar n (n=1 to 32) denotes 32 line segments drawn from a midpoint of a long axis L to a surface of the toner particles at intervals of 11.25 degrees with respect to a line segment a,

the long axis L is a longest chord in the cross section of each of the toner particles,

the line segment a is one of line segments formed by dividing the long axis L at the midpoint thereof, and

FRA n (n=1 to 32) denotes a length of the surface layer along the Ar n (n=1 to 32).

3. The toner according to claim 1 , wherein the organosilicon polymer is produced by polymerization of an organosilicon compound having a structure represented by the following formula (1):

wherein R 1 denotes an alkyl group having 1 to 6 carbon atoms or a phenyl group, and

R 2 , R 3 , and R 4 independently denote a halogen atom, a hydroxy group, an acetoxy group, or an alkoxy group.

4. The toner according to claim 3 , wherein R 1 in the formula (1) denotes a methyl group, an ethyl group, a propyl group, or a phenyl group.

5. The toner according to claim 4 , wherein R 1 in the formula (1) denotes a methyl group.

6. The toner according to claim 3 , wherein R 2 , R 3 , and R 4 in the formula (1) independently denote an alkoxy group.

7. The toner according to claim 6 , wherein R 2 , R 3 , and R 4 in the formula (1) independently denote a methoxy group or an ethoxy group.

8. The toner according to claim 1 , wherein the toner particles are produced by forming particles of a polymerizable monomer composition in an aqueous medium, the polymerizable monomer composition containing a colorant and a polymerizable monomer, and polymerizing the polymerizable monomer.

9. The toner according to claim 8 , wherein the polymerizable monomer composition contains a styrene monomer and an acrylic or methacrylic polymerizable monomer as polymerizable monomers.

10. The toner according to claim 1 , wherein the concentration of silicon elements on the surface of the toner particles is 10.0 atomic percent or more.

11. The toner according to claim 1 , wherein R in the formula (T3) denotes a methyl group.