Developer for electrophotography, image forming apparatus and process cartridge

1. A developer, comprising:

a toner comprising:

a binder resin comprising a crystalline resin; and

a colorant, and

a resin carrier comprising:

a resin;

wherein the resin carrier has a magnetic particulate material having a magnetic anisotropy, dispersed in

the resin, and

wherein the resin carrier has a saturated magnetization of from 16 to 30 emu/g, a coercive force of from 15 to 40 kA/m and an average particle diameter not less than 15 μm and less than 100 μm,

wherein the binder resin comprises the crystalline resin in an amount not less than 50% by weight.

2. The developer of claim 1 , wherein the toner is prepared by dispersing or emulsifying at least the binder resin and the colorant in an aqueous medium.

3. The developer of claim 1 , wherein the crystalline resin is at least a resin selected from the group consisting of a polyester resin, a polyurethane resin, a polyurea resin, a polyamide resin and a polyether resins.

4. The developer of claim 1 , wherein the crystalline resin comprises at least one of a urethane skeleton and a urea skeleton.

5. The developer of claim 1 , wherein the crystalline resin comprises a crystalline resin (A) and a crystalline resin (B) having a weight-average molecular weight (Mw) different from each other.

6. The developer of claim 1 , wherein the toner satisfies the following relationships:

45 ≦Ta≦ 70, and 0.8 ≦Tb/Ta≦ 1.55

wherein Ta (° C.) is the maximum peak temperature of heat of melting the toner measured by a differential scanning calorimeter, and Tb (° C.) is a softening point of the toner measured by an elevated flow tester; and

1.0×10 3 ≦G ′( Ta+ 20)≦5.0×10 6 and 1.0×10 3 ≦G ″( Ta+ 20)≦5.0×10 6

wherein G′(Ta+20) (Pa·s) is the storage elastic modulus of the toner at the temperature of (Ta+20)° C., and G″(Ta+20) (Pa·s) is the loss elastic modulus of the toner at the temperature of (Ta+20)° C.

7. The developer of claim 1 , wherein the resin carrier comprises the resin and the magnetic particulate material in a weight ratio (binder resin/magnetic particulate material) of from 65/35 to 80/20.

8. The developer of claim 1 , wherein the resin carrier is a rare earth-iron-nitrogen magnet powder.

9. The developer of claim 1 , wherein the resin carrier is prepared by melt-kneading the magnetic particulate material in the resin and then leaving the resultant resin powder for 10 sec or longer in a magnetic flux density of 2 T (tesla) or higher.

10. An image forming method, comprising:

forming an electrostatic latent image;

developing the electrostatic latent image with the developer according to claim 1 to form a toner image;

transferring the toner image onto a transfer paper; and

fixing the toner image thereon.