Toner, developer, process cartridge, and image forming apparatus

1. A toner, comprising:

a binder resin comprising a non-crystalline resin (R), which comprises a polyester skeleton;

releasing agent-encapsulating capsules; and

a colorant,

wherein the releasing agent-encapsulating capsules each comprise: a capsule formed of a resin (I) which is different from the binder resin and of a polyolefin resin (D) comprising a vinyl monomer; and a releasing agent (RA) which is encapsulated in the capsule,

wherein an absolute value of a difference between a solubility parameter of the polyolefin resin (D) and a solubility parameter of the release agent (RA) is less than 2,

wherein the releasing agent-encapsulating capsules exist in the binder resin,

wherein 50% to 100% of the releasing agent-encapsulating capsules exist in a region from a surface of the toner to a depth of 0.10 times a volume-average particle diameter of the toner,

wherein the vinyl monomer of the resin (D) comprises an ester group introduced in an oil-soluble component,

wherein an average ester-group concentration of the vinyl monomer calculated by Formula (1) is from 13.2% by mass to 30% by mass:

Ester-group concentration=Σ(44 /Mwi ×Wi )  Formula (1)

wherein Mwi is a molecular weight of the vinyl monomer comprising the ester group, and

wherein Wi is a charge ratio (% by mass) of the vinyl monomer comprising the ester group.

2. The toner according to claim 1 ,

wherein the binder resin further comprises a material (A) which is compatible with the non-crystalline resin (R).

3. The toner according to claim 1 ,

wherein the releasing agent-encapsulating capsules have an average circle-equivalent diameter of 50 nm to 200 nm.

4. The toner according to claim 1 ,

wherein a mass ratio of a mass of the resin (D) to a mass of the releasing agent (RA) [(D)/(RA)] is 0.01 to 2.5.

5. The toner according to claim 1 ,

wherein the releasing agent (RA) comprises a hydrocarbon wax.

6. The toner according to claim 1 ,

wherein the releasing agent (RA) has a melting point of less than 80° C.

7. The toner according to claim 2 ,

wherein the material (A) is a crystalline polyester.

8. The toner according to claim 1 ,

wherein the binder resin further comprises a crystalline resin (C) as a main component.

9. The toner according to claim 8 ,

wherein the binder resin comprises, as the crystalline resin (C): a first crystalline resin (C-1); and a second crystalline resin (C-2) having a weight-average molecular weight Mw greater than that of the first crystalline resin, and

wherein the first crystalline resin (C-1) is a crystalline polyester.

10. The toner according to claim 9 ,

wherein the second crystalline resin (C-2) is a crystalline resin including a urethane bond or a urea bond, or both thereof, in a backbone thereof.

11. The toner according to claim 10 ,

wherein the second crystalline resin (C-2) is a crystalline resin formed by elongation of a modified crystalline having an isocyanate group at an end thereof.

12. The toner according to claim 8 ,

wherein the binder resin comprises, as the crystalline resin (C): the first crystalline resin (C-1); and the second crystalline resin (C-2) having a weight-average molecular weight Mw greater than that of the first crystalline resin, and

wherein the first crystalline resin (C-1) is a crystalline resin including a urethane bond or a urea bond, or both thereof, in a backbone thereof.

13. A developer, comprising:

a toner which comprises:

a binder resin comprising a non-crystalline resin (R), which comprises a polyester skeleton;

releasing agent-encapsulating capsules; and

a colorant,

wherein the releasing agent-encapsulating capsules each comprise: a capsule formed of a resin (I) which is different from the binder resin and of a polyolefin resin (D) comprising a vinyl monomer; and a releasing agent (RA) which is encapsulated in the capsule,

wherein an absolute value of a difference between a solubility parameter of the polyolefin resin (D) and a solubility parameter of the release agent (RA) is less than 2,

wherein the releasing agent-encapsulating capsules exist in the binder resin,

wherein 50% to 100% of the releasing agent-encapsulating capsules exist in a region from a surface of the toner to a depth of 0.10 times a volume-average particle diameter of the toner,

wherein the vinyl monomer of the resin (D) comprises an ester group introduced in an oil-soluble component,

wherein an average ester-group concentration of the vinyl monomer calculated by Formula (1) is from 13.2% by mass to 30% by mass:

Ester-group concentration=Σ(44 /Mwi ×Wi )  Formula (1)

wherein Mwi is a molecular weight of the vinyl monomer comprising the ester group, and

wherein Wi is a charge ratio (% by mass) of the vinyl monomer comprising the ester group.

14. A process cartridge, comprising:

a photoconductor; and

a developing unit which develops an electrostatic latent image on the photoconductor with a developer including a toner to form a visible image,

wherein the photoconductor and the developing unit are integrally supported, and the process cartridge is detachably attached to an image forming apparatus, and

wherein the toner comprises:

a binder resin comprising a non-crystalline resin (R), which comprises a polyester skeleton;

releasing agent-encapsulating capsules; and

a colorant,

wherein the releasing agent-encapsulating capsules each comprise: a capsule formed of a resin (I) which is different from the binder resin and of a polyolefin resin (D) comprising a vinyl monomer; and a releasing agent (RA) which is encapsulated in the capsule,

wherein an absolute value of a difference between a solubility parameter of the polyolefin resin (D) and a solubility parameter of the release agent (RA) is less than 2,

wherein the releasing agent-encapsulating capsules exist in the binder resin,

wherein 50% to 100% of the releasing agent-encapsulating capsules exist in a region from a surface of the toner to a depth of 0.10 times a volume-average particle diameter of the toner,

wherein the vinyl monomer of the resin (D) comprises an ester group introduced in an oil-soluble component,

wherein an average ester-group concentration of the vinyl monomer calculated by Formula (1) is from 13.2 by mass to 30% by mass:

Ester-group concentration=Σ(44 /Mwi ×Wi )  Formula (1)

wherein Mwi is a molecular weight of the vinyl monomer comprising the ester group, and

wherein Wi is a charge ratio (% by mass) of the vinyl monomer comprising the ester group.

15. The toner according to claim 1 , wherein the solubility parameter of the polyolefin resin (D) (SP(D)) satisfies:

8 ≦SP ( D )≦11.

16. The toner according to claim 1 , wherein the toner is obtained by a process comprising:

preparing an oil phase with the releasing agent-encapsulating capsules dissolved or dispersed therein,

dispersing the oil phase in an aqueous phase, thereby preparing an oil droplet dispersion comprising oil droplets that comprise the releasing agent-encapsulating capsules, and

removing the solvent in the oil phase.