Claims
- 1. A process for making an electrophotographic toner comprising:(a) uniformly mixing at least one particulate metal oxide selected from titanium dioxide, silicon dioxide, and mixtures thereof with toner particles to form a mixture having 5 to 15 weight percent metal oxide; and (b) mixing the product of step (a) with additional toner particles at a mixing intensity ≧500,000 (cm/minute) minute sufficient to embed the at least one metal oxide particles into the toner particles and decrease the concentration of the at least one metal oxide on the surface of the toner particles; wherein in the mixed product of (b) the metal oxide is 0.1 to 5.0 weight percent of the mixed product; and the toner particles have on their surfaces:when titanium dioxide is employed, a metal oxide concentration in a ratio of 1.0-3.0:1.0 with respect to titanium dioxide on the surface of the toner particles (determined in terms of atomic percent titanium based on total atomic elements present as measured by x-ray photoelectron spectroscopy):total bulk titanium dioxide in the mixed product; and when silicon dioxide is employed, a ratio of 10.0-25.0:1.0 with respect to silicon dioxide on the surface of the toner particles (determined in terms of atomic percent silicon based on total atomic elements present as measured by x-ray photoelectron spectroscopy):total bulk silicon dioxide in the mixed product.
- 2. The process of claim 1 wherein the metal oxide concentration in step (a) is 8 to 12 weight percent.
- 3. The process of claim 1 wherein the mixing intensity in step (b) is ≧1,000,000 and the metal oxide is titanium dioxide.
- 4. The process of claim 1 wherein the metal oxide in the mixed product of step (b) is 0.1 to 2.0 weight percent.
- 5. The process of claim 1 wherein the metal oxide in the mixed product of step (b) is 0.15 to 0.35 weight percent.
- 6. The process of claim 1 wherein the ratio of titanium dioxide on the surface of the toner particles:titanium dioxide in the mixed product of step (b) is 2.0-2.5:1.0.
- 7. The process of claim 1 wherein the ratio of silicon dioxide on the surface of the toner particles:total silicon dioxide in the mixed product of step (b) is 20.0-25.0:1.0.
- 8. A process of making an electrophotographic developer comprising process of claim 1 and the added step of adding magnetic ferrite carrier particles to the mixed product.
- 9. An electrophotographic developer as in claim 8 wherein the magnetic ferrite is iron strontium ferrite.
- 10. The process of claim 1 wherein the at least one metal oxide includes silicon dioxide and titanium dioxide.
- 11. A process for making an electrophotographic toner comprising uniformly mixing at least one metal oxide selected from titanium dioxide, silicon dioxide, and mixtures thereof with toner particles at a mixing intensity sufficient to embed the at least one metal oxide particles into the toner particles and decrease the concentration of the at least one metal oxide on the surface of the toner particles, said mixing thereby forming a metal oxide—toner mixture, the metal oxide—toner mixture having a bulk metal oxide content of from 0.1 to 5.0 weight percent of the total mixture; and the toner particles have on their surfaces, when titanium dioxide is employed, a metal oxide concentration in a ratio of 1.0-3.0:1.0 with respect to titanium dioxide on the surface of the toner particles (determined in terms of atomic percent titanium based on total atomic elements present as measured by x-ray photoelectron spectroscopy):total bulk titanium dioxide in the mixture; and, when silicon dioxide is employed, a ratio of 10.0-25.0:1.0 with respect to silicon dioxide on the surface of the toner particles (determined in terms of atomic percent silicon based on total atomic elements present as measured by x-ray photoelectron spectroscopy):total bulk silicon dioxide in the mixture.
- 12. The process of claim 11 wherein the mixing intensity is greater than or equal to 500,000.
- 13. The process of claim 11 wherein the mixing intensity is greater than or equal to 1,000,000.
- 14. The process of claim 11 wherein the metal oxide content in the metal oxide—toner mixture is 0.1 to 2.0 weight percent.
- 15. The process of claim 11 wherein the metal oxide content in the metal oxide—toner mixture is 0.15 to 0.35 weight percent.
- 16. The process of claim 11 wherein the ratio of titanium dioxide on the surface of the toner particles:titanium dioxide in the mixture is 2.0-2.5:1.0.
- 17. The process of claim 11 wherein the ratio of silicon dioxide on the surface of the toner particles:total silicon dioxide in the mixture is 20.0-25.0:1.0.
- 18. A process of making an electrophotographic developer comprising process of claim 11 and the added step of adding magnetic ferrite carrier particles to the metal oxide—toner mixture.
- 19. An electrophotographic developer as in claim 18 wherein the magnetic ferrite is iron strontium ferrite.
- 20. A process for making an electrophotographic toner comprising:(a) uniformly mixing at least one metal oxide selected from titanium dioxide, silicon dioxide and mixtures thereof with toner particles to form a mixture having 8 to 12 weight percent metal oxide; and (b) mixing the product of step (a) with additional toner particles at a mixing intensity of greater then or equal to 1,000,000 (cm/minute) minute; wherein in the mixed product of (b) the metal oxide is 0.1 to 0.5 weight percent of the mixed product; and the toner particles have on their surfaces: when titanium dioxide is employed, a metal oxide concentration in a ratio of 1.0-3.0:1.0 with respect to titanium dioxide on the surface of the toner particles (determined in terms of atomic percent titanium based on total atomic elements present as measured by x-ray photoelectron spectroscopy):total bulk titanium dioxide in the mixed product; and when silicon dioxide is employed, a ratio of 10.0-25.0:1.0 with respect to silicon dioxide on the surface of the toner particles (determined in terms of atomic percent silicon based on total atomic elements present as measured by x-ray photoelectron spectroscopy):total bulk silicon dioxide in the mixed product.
RELATED APPLICATIONS
U.S. patent Ser. No. 09/452,087, pending filed on even date herewith entitled “Electrophotographic Toner Surface Treated with Metal Oxides”, is a related application.
US Referenced Citations (8)
Non-Patent Literature Citations (2)
Entry |
Schinichi Sata, et al. Study on the Surface Properties of Polyester Color Toner, IS&T NIP 13, 149-152 (1997). |
Nash, R. and Muller, R.N. “The Effect of Toner and Carrier Composition on the Relationship Between Toner Charge to Mass Ratio and Toner Concentration”, IS&T NIP 13, 112-120, (1997). |