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

1. A toner comprising:

a colorant;

a release agent; and

a binder resin comprising:

a crystalline polyester resin; and

an amorphous polyester resin comprising:

an amorphous polyester resin A comprising an isocyanurate backbone and at least one of urethane bond and urea bond; and

an amorphous polyester resin B comprising a trimellitic acid backbone and at least one of urethane bond and urea bond,

wherein

a glass transition temperature of the amorphous polyester resin B is 30° C. or higher and lower than 70° C.,

a content of the crystalline polyester resin is from 3 to 20 parts based on 100 parts of the toner,

a content of the amorphous polyester resin A is from 1 to 10 parts based on 100 parts of the toner,

a content of the amorphous polyester resin B is from 3 to 15 parts based on 100 parts of the toner, and

a ratio of polyester resin A to polyester resin B is from 1/1 to 1/5.

2. The toner of claim 1 , wherein the amorphous polyester resin A comprises a structure selected from the group consisting of structural formulae 1) to 3):

R1-(NHCONH—R2) n -;  1)

R1-(NHCOO—R2) n -; and  2)

R1-(OCONH—R2) n -,  3)

wherein

n represents an integer of 3,

R1 represents an isocyanurate backbone, and

R2 represents a group derived from a polyester comprising a polycarboxylic acid and a polyol or from an isocyanate-modified polyester.

3. The toner of claim 1 , wherein a parameter T1/2 of the toner is from 105° C. to 125° C., wherein the parameter T1/2 is measured according to a temperature rising method by a flow tester.

4. The toner of claim 1 , wherein a glass transition temperature (Tg1st (toner)) of the toner is from 50° C. to 65° C., wherein the Tg1st (toner) is determined from an endothermic curve obtained in a first temperature rising in a measurement by a differential scanning calorimeter.

5. A toner storage unit comprising:

a container; and

the toner of claim 1 stored in the container.

6. 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 of claim 1 , configured to develop the electrostatic latent image formed on the electrostatic latent image bearer with the toner to form a visible image.

7. An image forming method comprising:

charging an electrostatic latent image bearer;

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

developing the electrostatic latent image bearer into a toner image with the toner of claim 1 ;

primarily transferring the toner image formed on the electrostatic latent image bearer onto an intermediate transfer medium;

secondarily transferring the toner image transferred onto the intermediate transfer medium onto a recording medium;

fixing the toner image on the intermediate transfer medium by application of heat and pressure; and

removing residual toner particles remaining on the electrostatic latent image bearer after the toner image has been transferred onto the intermediate transfer medium.

8. The image forming method of claim 7 , wherein, in the secondarily transferring, the toner imager is transferred onto the recording medium at a linear velocity of from 100 to 1,000 mm/sec and a transfer time of from 0.5 to 60 msec.