Toner, toner storage unit, image forming apparatus, and method for manufacturing toner

1. A toner comprising:

an amorphous resin;

a crystalline resin dispersed in the amorphous resin; and

a release agent,

wherein the toner satisfies the following inequality:

B/A< 0.8

where A represents a perimeter of the crystalline resin and B represents a length of a part of the perimeter A of the crystalline resin at which the crystalline resin is in contact with the amorphous resin, A and B being measured from a cross-sectional image of the toner observed with transmission electron microscope.

2. The toner of claim 1 , wherein the release agent has a crystallization temperature higher than the crystalline resin by 20° C. or more.

3. The toner of claim 1 , wherein the toner further satisfies the following inequality:

0.05< D/C< 0.4

where C represents a perimeter of the toner and D represents a length of a part of the perimeter C of the toner at which the crystalline resin is exposed, C and D being measured from the cross-sectional image of the toner observed with transmission electron microscope.

4. The toner of claim 1 , wherein the toner further satisfies an inequality 0.5<B/A≤0.6.

5. The toner of claim 1 , wherein the toner further satisfies the following inequality:

0.5< SP 1− SP 2<1.1

where SP1 and SP2 represent solubility parameters of the amorphous resin and the crystalline resin, respectively.

6. The toner of claim 1 , further comprising:

an amorphous hybrid resin comprising:

a composite resin comprising:

a condensation polymerization resin unit; and

a styrene resin unit,

wherein the condensation polymerization resin unit and the styrene resin unit are partially chemically bonded to each other.

7. The toner of claim 1 , wherein tetrahydrofuran-insoluble matter of the toner comprises:

a diol component comprising 50% by mol or more of an aliphatic diol having 3 to 10 carbon atoms based on 100% by mol of alcohol components; and

a cross-linked component comprising an aliphatic alcohol having 3 or more valences,

wherein the toner has a glass transition temperature (Tg1st) in the range of from 20° C. to 50° C. as measured in a first heating of differential scanning calorimetry.

8. A toner storage unit comprising:

a storage unit; and

the toner of claim 1 stored in the storage unit.

9. An image forming apparatus comprising:

an electrostatic latent image bearer;

an electrostatic latent image forming device to form an electrostatic latent image on the electrostatic latent image bearer; and

a developing device comprising the toner of claim 1 , to develop the electrostatic latent image formed on the electrostatic latent image bearer into a visible image with the toner.

10. The toner of claim 1 , wherein the toner is obtained by a process which comprises preparing a composite particle in which the crystalline resin and the release agent are partially combined by recrystallizing the crystalline resin and the release agent without a presence of the amorphous resin.

11. A method for manufacturing a toner, comprising:

dissolving a crystalline resin and a release agent in an organic solvent by application of heat to prepare a solution; and

cooling the solution to prepare a dispersion liquid of a composite particle in which the crystalline resin and the release agent are partially combined by recrystallizing the crystalline resin and the release agent,

wherein the dissolving and the cooling are conducted without a presence of an amorphous resin, and the release agent has a crystallization temperature higher than the crystalline resin by 20° C. or more.

12. The method of claim 11 , wherein a cooling rate of the solution at a temperature below a crystallization temperature of the crystalline resin is smaller than a cooling rate of the solution at a temperature above the crystallization temperature of the crystalline resin.