Toner
A toner includes a plurality of toner particles each including a core and a shell layer entirely covering a surface of the core. The core contains a foamable polymer having a foamable group that is foamable through heating. A first foaming amount is at least 7 mL. The first foaming amount is an amount of gas collected over water during a period from when heating of the toner up to 120° C. is started at 30° C. to when a temperature of the toner has been kept at 120° C. for 30 minutes after the heating. A second foaming amount is at least 6 mL. The second foaming amount is an amount of gas collected over water during a period from when the heating is started at 30° C. to when the temperature of the toner reaches 0° C. through cooling after the liquid has been kept at 120° C. for 30 minutes.
1. A toner comprising a plurality of toner particles each including a core and a shell layer covering a surface of the core, wherein
the core contains a foamable polymer having a foamable group that is foamable through heating, and
the shell layer entirely covers the surface of the core.
2. The toner according to claim 1 , wherein
the foamable group is an azido group, and
the core generates nitrogen through an exothermic reaction of the azido group.
3. The toner according to claim 1 , wherein
the foamable polymer includes a unit represented by formula (1) shown below,
where in formula (1), R 16 and R 17 each represent, independently of one another, a hydrogen atom, a halogen atom, or an optionally substituted alkyl group, at least one of R 11 , R 12 , R 13 , R 14 , and R 15 represents an azidomethyl group, and the others each represent, independently of one another, a hydrogen atom, a halogen atom, a hydroxyl group, an optionally substituted alkyl group, an optionally substituted alkoxy group, or an optionally substituted aryl group.
4. The toner according to claim 3 , wherein
the foamable polymer further includes a unit represented by formula (2) shown below,
where in formula (2), R 21 and R 22 each represent, independently of one another, a hydrogen atom or a methyl group, and R 23 represents an optionally substituted alkyl group having a carbon number of at least 1 and no greater than 8.
5. The toner according to claim 1 , wherein
the core further contains a non-foamable polymer.
6. The toner according to claim 1 , wherein
the shell layer contains a thermosetting resin which is a copolymer of at least two vinyl compounds including at least a compound represented by formula (3) shown below,
where in formula (3), R 3 represents a hydrogen atom or an optionally substituted alkyl group.
7. The toner according to claim 1 , wherein
the core has a glass transition point of at least 35° C. and no greater than 45° C.