Toner, process cartridge, developer, and image forming apparatus

1. A toner, comprising:

a binder resin comprising a polyester resin,

wherein the polyester resin is a copolymer having an amorphous polyester segment and a crystalline segment, the amorphous polyester segment being obtained by condensation polymerization of an alcohol and a carboxylic acid including an aliphatic dicarboxylic acid and an aromatic dicarboxylic acid,

when the toner is subjected to a pressure of 100 gf at a temperature of 40° C. and a relative humidity of 80%, the toner deforms with a deformation rate of from 1.0% to 5.0%,

when the toner is observed with an atomic force microscope in tapping mode to obtain a phase image and the phase image is binarized by using an intermediate value between maximum and minimum phase difference values to obtain a binarized image, the binarized image consists of first phase-contrast images serving as large-phase-difference portions and second phase-contrast images serving as small-phase-difference portions with the first phase-contrast images dispersed in the second phase-contrast images and the first phase-contrast images having a dispersion diameter of 100 nm or less, and

when the toner is subjected to a differential scanning calorimetric measurement, an endothermic quantity Q1 measured in a first heating is from 10 to 50 J/g, and a ratio Q2/Q1 of an endothermic quantity Q2 measured in a second heating to the endothermic quantity Q1 measured in the first heating is 0.65 or less.

2. The toner according to claim 1 , wherein, in the copolymer, the amorphous polyester segment and the crystalline segment are bound by an urethane bond or an urea bond.

3. The toner according to claim 2 , wherein the amorphous polyester segment has a glass transition temperature of from 50° C. to 70°C.

4. The toner according to claim 2 , wherein a weight ratio of the amorphous polyester segment to the crystalline segment in the copolymer is from 1.5 to 4.0.

5. The toner according to claim 1 , wherein the binder resin further comprises a modified polyester resin.

6. A process cartridge, comprising:

an electrostatic latent image bearer; and

a developing device configured to develop an electrostatic latent image formed on the electrostatic latent image bearer into a visible image with the toner according to claim 1 ,

wherein the process cartridge is detachably mountable on an image forming apparatus.

7. A developer, comprising:

the toner according to claim 1 ; and

a carrier.

8. 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 configured to develop the electrostatic latent image into a visible image with the toner according to claim 1 .

9. The toner according to claim 1 , wherein the copolymer has a glass transition temperature of from 40° C. to 70° C.

10. The toner according to claim 1 , wherein the amorphous polyester segment has a glass transition temperature of from 50° C. to 70° C.

11. The toner according to claim 1 , wherein a weight ratio of the amorphous polyester segment to the crystalline segment in the copolymer is from 1.5 to 4.0.

12. The toner according to claim 1 , wherein the aliphatic dicarboxylic acid is at least one selected from the group consisting of succinic acid, adipic acid, sebacic acid, azelaic acid, dodecanedicarboxylic acid, octadecanedicarboxylic acid, decyl succinic acid, dodecenyl succinic acid, pentadecenyl succinic acid, octadecenyl succinic acid, maleic acid, fumaric acid, citraconic acid, and dimmer acid.

13. The toner according to claim 1 , wherein the aromatic dicarboxylic acid is at least one selected from the group consisting of phthalic acid, isophthalic acid, t-butyl isophthalic acid, terephthalic acid, 2,6-naphthalenedicarboxylic acid, and 4,4′-biphenyl dicarboxylic acid.

14. The toner according to claim 1 ,

wherein the aliphatic dicarboxylic acid is at least one selected from the group consisting of succinic acid, adipic acid, sebacic acid, azelaic acid, dodecanedicarboxylic acid, octadecanedicarboxylic acid, decyl succinic acid, dodecenyl succinic acid, pentadecenyl succinic acid, octadecenyl succinic acid, maleic acid, fumaric acid, citraconic acid, and dimmer acid, and

the aromatic dicarboxylic acid is at least one selected from the group consisting of phthalic acid, isophthalic acid, t-butyl isophthalic acid, terephthalic acid, 2,6-naphthalenedicarboxylic acid, and 4,4′-biphenyl dicarboxylic acid.

15. The toner according to claim 1 , wherein the aromatic dicarboxylic acid is at least one selected from the group consisting of terephthalic acid, isophthalic acid, and t-butyl isophthalic acid.

16. The toner according to claim 1 , wherein the alcohol is at least one polyol selected from the group consisting of ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol, 1,12-dodecanediol, 1,13-tridecanediol, 1,14-tetradecanediol, 1,18-octadecanediol, and 1,20-eicosanediol.

17. The toner according to claim 1 , wherein the copolymer is a block copolymer.

18. The toner according to claim 1 , wherein the copolymer has a melting point of from 50° C. to 75° C.

19. The toner according to claim 1 , further comprising:

at least one selected from the group consisting of a crystalline resin, a colorant, a release agent, a charge controlling agent, and an external additive.

20. The toner according to claim 1 , further comprising:

a crystalline resin.