Electrostatic image developing toner

1. An electrostatic image developing toner comprising a toner base particle containing at least a binder resin and a colorant, and an external additive, wherein:

the toner base particle has a core-shell structure having a core particle and a shell layer,

the toner base particle has a resin coating layer of a water-soluble resin on the surface of the core particle, and has the shell layer on the resin coating layer, and the shell layer is formed of a particle comprising a resin as a main ingredient, and

when a glass transition temperature of a polymer primary particle to constitute the core particle is referred to as Tg1, and a glass transition temperature of the particle to constitute the shell layer is referred to as Tg2, the Tg1 and Tg2 satisfy the following relationship:

25° C.≦Tg1≦45° C.

55° C.≦Tg2

Tg2−Tg1≧20.

2. The electrostatic image developing toner according to claim 1 , wherein the particle to constitute the shell layer contains a resin having a sulfonic acid group.

3. The electrostatic image developing toner according to claim 2 , wherein charging properties of the core particle and the resin coating layer are in an opposite relationship to each other, and wherein charging properties of the resin coating layer and the shell layer are in an opposite relationship to each other.

4. The electrostatic image developing toner according to claim 1 , wherein the core particle is obtained according to a polymerization method.

5. The electrostatic image developing toner according to claim 1 , wherein charging properties of the core particle and the resin coating layer are in an opposite relationship to each other, and wherein charging properties of the resin coating layer and the shell layer are in an opposite relationship to each other.

6. The electrostatic image developing toner according to claim 5 , wherein a wax contained in a core layer of the core particle having a capsule structure is a wax where the time until the weight loss thereof at 200° C., as measured with a thermogravimetric analyzer, reaches 0.1%, is 15 minutes or more, and wherein a melting point of a wax contained in a shell layer of the core particle having a capsule structure is 70° C. or higher.

7. The electrostatic image developing toner according to claim 1 , wherein the core particle has a capsule structure.

8. The electrostatic image developing toner according to claim 1 , wherein a wax contained in a core layer of the core particle having a capsule structure is a wax where the time until the weight loss thereof at 200° C., as measured with a thermogravimetric analyzer, reaches 0.1%, is 15 minutes or more, and wherein a melting point of a wax contained in a shell layer of the core particle having a capsule structure is 70° C. or higher.

9. The electrostatic image developing toner according to claim 1 , wherein the toner base particle is obtained through a process comprising mixing a dispersion of core particles with an aqueous solution containing the water-soluble resin to adhere the water-soluble resin to the surface of the core particle, and further mixing therein a dispersion of particles to constitute the shell layer to adhere the particles to constitute the shell layer.

10. The electrostatic image developing toner according to claim 1 , wherein the toner base particle is obtained through a process comprising mixing a dispersion of core particles with an aqueous solution containing a water-soluble resin that has a charging property opposite to that of the core particles to adhere the water-soluble resin to the surface of the core particle and further mixing therein a dispersion of particles to constitute the shell layer that has a charging property opposite to that of the water-soluble resin to adhere the particles to constitute the shell layer.