Electrostatically charged image developing toner and electrostatically charged image developing two-component developer
An electrostatically charged image developing toner includes a particulate toner matrix containing an external additive on the surface of the particulate toner matrix. The external additive includes silica particles A and silica particles B. The silica particles A have a number average primary-particle diameter in the range of 40 to 100 nm and an average circularity in the range of 0.50 to 0.90, and are surface-modified with silicone oil. The silica particles B have a number average primary-particle diameter of 25 nm or more and smaller than the number average primary-particle diameter of the silica particles A, and are surface-modified with alkylalkoxysilane having a specific structure or silazane.
1. An electrostatically charged image developing toner comprising a particulate toner matrix containing an external additive on the surface of the particulate toner matrix, wherein
the external additive comprises silica particles A and silica particles B,
the silica particles A have a number average primary-particle diameter in the range of 40 to 100 nm and an average circularity in the range of 0.50 to 0.90, and are surface-modified with silicone oil, and
the silica particles B have a number average primary-particle diameter of 36 nm or more and smaller than the number average primary-particle diameter of the silica particles A, and are surface-modified with alkylalkoxysilane having a structure represented by Formula (1) or silazane:
R 1 —Si(OR 2 ) 3 Formula (1)
where R 1 represents a linear alkyl group having 1 or more and 10 or less carbon atoms and has an optional substituent; R 2 represents a methyl or ethyl group.
2. The electrostatically charged image developing toner according to claim 1 ,
wherein the silica particles B are surface-modified with alkylalkoxysilane having a structure represented by Formula (1), and
R 1 in Formula (1) has 4 or more and 8 or less carbon atoms.
3. The electrostatically charged image developing toner according to claim 1 ,
wherein the silica particles B are surface-modified with the silazane, and
the silazane contained is hexamethyldisilazane or hexaethyldisilazane.
4. The electrostatically charged image developing toner according to claim 1 ,
wherein the external additive further comprises titanium oxide nanoparticles having an average aspect ratio in the range of 2 to 15, the average aspect ratio being a ratio of a number average major diameter to a number average minor diameter.
5. The electrostatically charged image developing toner according to claim 4 ,
wherein the titanium oxide nanoparticles have a rutile crystal structure.
6. The electrostatically charged image developing toner according to claim 1 ,
wherein the particulate toner matrix comprises a binder resin containing at least a crystalline resin.
7. The electrostatically charged image developing toner according to claim 1 ,
wherein the silicone oil is dimethylsilicone oil.
8. The electrostatically charged image developing toner according to claim 1 ,
wherein the particulate toner matrix contains an amorphous vinyl resin.
9. The electrostatically charged image developing toner according to claim 6 ,
wherein the crystalline resin contains a crystalline polyester resin.
10. The electrostatically charged image developing toner according to claim 1 , wherein the average circularity of the silica particles A is in the range of 0.50 to 0.83.
11. An electrostatically charged image developing two-component developer, comprising the electrostatically charged image developing toner according to claim 1 and carrier particles.