Toner, developer, toner storage unit, image forming apparatus, and image forming method

1. A toner comprising:

a mother toner particle comprising a binder resin,

wherein, when the toner is observed with an atomic force microscope (AFM) in tapping mode to obtain a phase image and the phase image is binarized with an intermediate value between maximum and minimum phase difference values in the phase image to obtain a binarized image, the binarized image consists of first phase-contrast portions having a large phase difference and second phase-contrast portions having a small phase difference, where the first phase-contrast portions are dispersed in the second phase-contrast portions and a dispersion diameter of the first phase-contrast portions is in a range of from 150 to 500 nm, and

wherein the toner has at least two glass transition temperatures (Tg) in respective ranges of from 40° C. to 65° C. and from −30° C. to 20° C., determined from a DSC curve obtained at a first temperature rise in a differential scanning calorimetric (DSC) measurement by a midpoint method.

2. The toner according to claim 1 , wherein the binder resin comprises at least two resins differing in solubility parameter determined by a Fedors' method by 0.5 or more.

3. The toner according to claim 1 , wherein the binder resin comprises:

a matrix resin; and

a domain resin having a glass transition temperature lower than a glass transition temperature of the matrix resin,

wherein a mass ratio of the matrix resin to the domain resin is from 95/5 to 70/30.

4. A developer comprising the toner according to claim 1 .

5. The toner according to claim 1 , wherein the phase image is obtained by cutting the toner into a section under the following conditions:

Cutting thickness: 60 nm,

Cutting speed: 0.4 mm/sec, and

Knife: Diamond knife (Ultra Sonic 35°), and

observing the section of the toner with the atomic force microscope (AFM) under the following conditions:

Target amplitude: 0.5 V,

Target percent: 5%,

Amplitude setpoint: 315 mV,

Scan rate: 1 Hz,

Scan points: 256×256, and

Scan angle: 0°.

6. The toner according to claim 2 , wherein the at least two resins comprise at least two amorphous polyester resins.

7. The toner according to claim 1 , wherein the dispersion diameter of the first phase-contrast portions is in a range of from 200 to 400 nm.

8. The toner according to claim 1 , wherein the at least two glass transition temperatures (Tg) are in respective ranges of from 50° C. to 60° C. and from −10° C. to 10° C.

9. A developer for replenishment, comprising the toner according to claim 1 .

10. A toner storage unit comprising:

a container; and

the toner according to claim 1 stored in the container.

11. An image forming apparatus comprising:

an electrostatic latent image bearer;

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

a developing device containing the toner according to claim 1 , configured to develop the electrostatic latent image with the toner into a toner image.

12. An image forming method comprising:

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

developing the electrostatic latent image with the toner according to claim 1 into a toner image.