Toner
Provided is toner that contains a toner particle, and an external additive containing a strontium titanate particle, wherein the toner has an average circularity of at least 0.935 and not more than 0.995, the strontium titanate particle has a number-average primary particle diameter of at least 10 nm and not more than 60 nm, the strontium titanate particle has a peak in the range of 39.700°±0.150° and a peak in the range of 46.200°±0.150° in a CuKα x-ray diffraction spectrum obtained in the 2θ range of at least 10° and not more than 90° where θ is the Bragg angle, and the ratio of the area Sb of the peak at 46.200°±0.150° to the area Sa of the peak at 39.700°±0.150° is at least 1.80 and not more than 2.30.
1. A toner comprising:
a toner particle; and
an external additive containing a strontium titanate particle, the strontium titanate particle having a number-average primary particle diameter of 10 to 60 nm, wherein
the toner has an average circularity of 0.935 to 0.995, and
the strontium titanate particle has peaks at 39.700°±0.150° and 46.200°±0.150° in a CuKα x-ray diffraction spectrum obtained in the 20 range of 10 to 90° where θ is the Bragg angle, and Sb/Sa is 1.80 to 2.30 where Sa is an area of the peak at 39.700°±0.150° and Sb is an area of the peak at 46.200°±0.150°.
2. The toner according to claim 1 , wherein the toner has a glass transition temperature of 50 to 70° C.
3. The toner according to claim 1 , wherein Sr/Ti (molar ratio) for the strontium titanate particle is 0.70 to 0.85.
4. The toner according to claim 1 , wherein a primary particle of the strontium titanate particle has an average circularity of 0.700 to 0.920.
5. The toner according to claim 1 , wherein a methanol concentration at 50% transmittance of light at a wavelength of 780 nm is 60 to 95 volume % in a wettability test of the strontium titanate particle relative to a methanol/water mixed solvent.
6. The toner according to claim 1 , wherein the coverage ratio of the surface of the toner by the strontium titanate particle is, as measured 5.0 to 20.0 area % as measured with an x-ray photoelectron spectrometer.
7. The toner according to claim 1 , wherein the content of the strontium titanate particle per 100 mass parts of the toner particle is 0.05 to 5.0 mass parts.
8. The toner according to claim 1 , wherein the toner particle has a core, and a shell layer present on the surface of the core.
9. The toner according to claim 8 , wherein the shell layer contains at least one kind selected from the group consisting of polyester resins, styrene-acrylic copolymers, and styrene-methacrylic copolymers.
10. The toner according to claim 1 , which satisfies 3×10 −4 ≤E/A≤50×10 −4 where A and E are respectively the amounts (atomic %) of carbon atoms and sulfur atoms present on the surface of the toner particle as measured with an x-ray photoelectron spectrometer.
11. The toner according to claim 4 , wherein the primary particle of the strontium titanate particle has an average circularity of 0.790 to 0.920.