Toner for electrophotography, developer for electrophotography, toner cartridge, image forming apparatus, and image forming method

1. A toner for electrophotography, comprising:

a binder resin, wherein a molecular weight distribution of the binder resin has at least three peaks or shoulders;

a colorant; and

a barium compound,

the toner having:

a relaxation modulus G(t) of from about 2.0×10 2 Pa to about 3.0×10 3 Pa at a fixing time of 220 msec and a fixing temperature of 160° C. as determined by a measurement of dynamic viscoelasticity;

a barium content of from about 0.1% to about 0.5% with respect to a total amount of constituent atoms in the toner as determined by X-ray fluorescence; and

a colorant content of from 4% by mass to 15% by mass based on a total mass of the solids content of the toner.

2. The toner for electrophotography of claim 1 , wherein the barium compound is selected from the group consisting of barium carbonate, barium titanate, barium sulfate, barium borate, and titan nickel barium yellow.

3. The toner for electrophotography of claim 1 , wherein the barium content with respect to the total amount of constituent atoms in the toner as determined by X-ray fluorescence is from about 0.12% to about 0.45%.

4. The toner for electrophotography of claim 1 , wherein the relaxation modulus G(t) of the toner is from about 2.3×10 2 Pa to about 2.8×10 3 Pa.

5. The toner for electrophotography of claim 1 , wherein when the molecular weight distribution of the binder resin is divided at the valley of the peaks or at the shoulder portions in order from the high molecular weight side, and the divided portions are designated as M1, M2 and M3, respectively, from the high molecular weight side, a weight average molecular weight of M1 is from about 5.0×10 5 to about 7.2×10 5 , and a number average molecular weight of M1 is from about 4.0×10 5 to about 5.0×10 5 ; a weight average molecular weight of M2 is from about 8.0×10 4 to about 1.2×10 5 , and a number average molecular weight of M2 is from about 8.0×10 4 to about 9.5×10 4 ; a weight average molecular weight of M3 is from about 1.0×10 4 to about 1.5×10 4 , and a number average molecular weight of M3 is from about 3500 to about 4500.

6. The toner for electrophotography of claim 1 , further comprising an ultraviolet absorbent.

7. The toner for electrophotography of claim 6 , wherein the ultraviolet absorbent is a hydroxybenzophenone-based ultraviolet absorbent.

8. A developer for electrophotography comprising the toner for electrophotography of claim 1 and a carrier.

9. The developer for electrophotography of claim 8 , wherein the toner for electrophotography contains a barium compound selected from the group consisting of barium carbonate, barium titanate, barium sulfate, barium borate, and titan nickel barium yellow.

10. The developer for electrophotography of claim 8 , wherein the relaxation modulus G(t) of the toner is from about 2.3×10 2 Pa to about 2.8×10 3 Pa.

11. A toner cartridge comprising a container accommodating the toner for electrophotography of claim 1 , the toner cartridge being detachable from an image forming apparatus.

12. The toner cartridge of claim 11 , wherein the toner for electrophotography is accommodated in the container in an amount of about 90% or more by volume of the container.

13. An image fowling method comprising:

charging a surface of an electrostatic latent image retaining member;

forming an electrostatic latent image on the surface of the charged electrostatic latent image retaining member;

developing the electrostatic latent image formed on the surface of the electrostatic latent image retaining member with the developer for electrophotography of claim 8 to form a toner image;

transferring the toner image onto a recording medium; and

fixing the toner image on the recording medium.

14. The image forming method of claim 13 , wherein the relaxation modulus G(t) of the toner is from about 2.3×10 2 Pa to about 2.8×10 3 Pa.