Toner and image forming method using the toner

1. A toner, comprising:

binder resins, including a crystalline polyester resin and an amorphous polyester resin; and

a colorant;

wherein:

the toner is prepared by a method, comprising:

dissolving or dispersing at least the binder resins and the colorant in a solvent to prepare a toner constituent liquid;

emulsifying or dispersing the toner constituent liquid in an aqueous medium comprising a particulate resin to granulate; and

removing the solvent;

the toner comprises from 1 to 30% by weight of the crystalline polyester resin based on a total weight of the binder resins;

the toner has a circularity of from 0.97 to 0.995; and

the toner satisfies the following relationships:

40° C.< T 1<80° C.; and

10° C.<( T 1- T 2) <47.9° C.;

wherein T 1 represents a glass transition temperature of the toner before melting when heated from −20° C. to 150° C. at a heating speed of 10° C./min, and T 2 represents a glass transition temperature of the toner after melting after being heated from −20° C. to 150° C. at a heating speed of 10° C./min, cooled to −20° C. at a cooling speed of 10° C./min and heated again at a heating speed of 10° C./min.

2. The toner of claim 1 , wherein the crystalline polyester resin has an endothermic peak temperature of from 50 to 150° C. when measured by a differential scanning calorimeter.

3. The toner of claim 1 , wherein the crystalline polyester resin has orthodichlorobenzene soluble components having a weight-average molecular weight (Mw) of from 1,000 to 30,000, a number-average molecular weight (Mn) of from 500 to 6,000 and a ratio (Mw/Mn) of the weight-average molecular weight (Mw) to the number-average molecular weight (Mn) of from 2 to 8 when measured by a gel permeation chromatography.

4. The toner of claim 1 , wherein the crystalline polyester has the following formula (1):

[—O—OO—(CR 1 —CR 2 ) L —OO—O—(CH 2 ) n —] m   (1)

wherein R 1 and R 2 independently represent a hydrogen atom or a hydrocarbon group, L represents an integer of from 1 to 3, and n and m represent repeat unit numbers.

5. The toner of claim 1 , wherein the crystalline polyester has an infrared absorption spectrum such that an absorption due to the δ CH (i.e., out-of-plane angle-changing vibration) of an olefin is observed at 965±10 cm −1 or 990±10 cm −1 .

6. The toner of claim 1 , wherein the toner has a volume-average particle diameter (Dv) of from 3 to 8 μm, and a ratio (Dv/Dn) of the volume-average particle diameter (Dv) to a number-average particle diameter (Dn) of the toner of from 1.00 to 1.25.

7. The toner of claim 1 , wherein the T 1 is higher than 45° C. and lower than 80° C.

8. The toner of claim 1 , wherein the melting point is higher than 50° C. and lower than 150° C.

9. The toner of claim 1 , wherein the melting point is higher than T 1 .

10. The toner of claim 1 , wherein the Q 1 is larger than 2 J/g and less than 30 J/g.

11. An image forming method comprising:

forming an electrostatic latent image on an electrostatic latent image bearer;

developing the electrostatic latent image with the toner according to claim 1 to form a toner image thereon;

transferring the toner image onto a recording medium; and

fixing the toner image thereon.

12. The toner of claim 1 , wherein the toner satisfies the following relationship:

0< Q 2/ Q 1 <2/3

wherein Q 1 represents an endothermic quantity at a melting point of the toner before melting when heated from −20° C. to 150° C. at a heating speed of 10° C./min, and Q 2 represents a an endothermic quantity at a melting point of the toner after melting after being heated from −20° C. to 150° C. at a heating speed of 10° C./min, cooled to −20° C. at a cooling speed of 10° C./min and heated again at a heating speed of 10° C./min.

13. The toner of claim 1 , wherein the crystalline polyester resin and the amorphous polyester resin are at least partially compatible with each other.