Electrophotographic toner and method of preparing the same

1. An electrophotographic toner comprising a latex, a colorant, and a releasing agent, wherein the electrophotographic toner has a weight-average molecular weight of about 50,000 to about 80,000; a complex viscosity of about 1×10 3 to about 5×10 4 (Pa·s) at a temperature ranging from about 100° C. to about 140° C.; and a dG′/dG″ ratio of about 1.10 to about 1.25 at temperatures from about 100° C. to less than 140° C., the dG′/dG″ ratio being defined as ΔG′/ΔG″, where ΔG′ is a first change in G′ and ΔG″ is a second change in G″ over a frequency region of about 0.1 rad/s to about 100 rad/s.

2. The electrophotographic toner of claim 1 , further comprising silicon (Si) and iron (Fe), each independently in a range of about 3 ppm to about 1,000 ppm.

3. The electrophotographic toner of claim 1 , wherein the releasing agent comprises a mixture of a paraffin-based wax and an ester-based wax; or an ester group containing paraffin-based wax.

4. The electrophotographic toner of claim 3 , wherein the releasing agent has a content of an ester group from about 2% by weight to about 10% by weight based on the total weight of the releasing agent.

5. The electrophotographic toner of claim 1 , wherein the toner has a volume average particle diameter of about 3 μm to about 8 μm.

6. The electrophotographic toner of claim 1 , wherein the toner has an average value of circularity of about 0.940 to about 0.980.

7. The electrophotographic toner of claim 1 , wherein the toner has a value of a volume average particle size distribution index (GSDv) and a number average particle size distribution index (GSDp) less than about 1.25, respectively.

8. A method of preparing an electrophotographic toner, the method comprising the steps of:

a) mixing a primary latex particle, a colorant dispersion, and a releasing agent dispersion to prepare a mixture;

b) adding an agglomerating agent to the mixture to prepare a primary agglomerated toner; and

c) coating a secondary latex, prepared by polymerizing one or more polymerizable monomers, on the primary agglomerated toner to provide a secondary agglomerated toner, thus preparing the electrophotographic toner,

wherein the electrophotographic toner has a weight-average molecular weight of about 50,000 to about 80,000; a complex viscosity of about 1×10 3 to about 5×10 4 (Pa·s) at a temperature ranging from about 100° C. to about 140° C.; and a dG′/dG″ ratio of about 1.10 to about 1.25 at temperatures from about 100° C. to less than 140° C., the dG′/dG″ ratio being defined as ΔG′/ΔG″, where ΔG′ is a first change in G′ and AG″ is a second change in G″ over a frequency region of about 0.1 rad/s to about 100 rad/s.

9. The method of claim 8 , wherein the primary latex particle comprises polyester alone; a polymer obtained by polymerizing one or more polymerizable monomers; or a mixture thereof.

10. The method of claim 8 , the method further comprising the step of:

d) coating a tertiary latex, prepared by polymerizing one or more polymerizable monomers, on the secondary agglomerated toner, to provide a tertiary agglomerated toner, thus preparing the electro graphic toner.

11. The method of claim 8 , wherein the polymerizable monomer comprises at least one monomer selected from styrene-based monomers; acrylic acid or methacrylic acid; derivatives of (metha)acrylates; ethylenically unsaturated mono-oletins; halogenized vinyls; vinyl esters; vinyl ethers; vinyl ketones; and nitrogen containing vinyl compounds.

12. The method of claim 8 , wherein the releasing agent dispersion comprises a mixture of a paraffin-based wax and an ester-based wax; or an ester group containing paraffin-based wax.

13. The method of claim 8 , wherein the agglomerating agent comprises Si and Fe containing metallic salts.

14. The method of claim 8 , wherein the agglomerating agent comprises polysilica iron.