Electrostatic latent image developing toner

1. An electrostatic latent image developing toner comprising a plurality of toner particles each including a core and a shell layer disposed over a surface of the core, wherein

the shell layer contains first resin particles having a number average particle diameter of at least 60 nm and no greater than 100 nm, and second resin particles having a number average particle diameter of at least 10 nm and no greater than 50 nm,

a particle diameter difference obtained by subtracting the number average particle diameter of the second resin particles from the number average particle diameter of the first resin particles is at least +20 nm and no greater than +50 nm,

the first resin particles contain a charge control agent,

the first resin particles have a higher softening point than a softening point of the second resin particles,

a ratio of a mass of the first resin particles to a sum of the mass of the first resin particles and a mass of the second resin particles is at least 0.7 and no greater than 0.9, and

the first resin particles protrude further outward from a surface of the toner particle than the second resin particles.

2. The electrostatic latent image developing toner according to claim 1 , wherein

the core contains a polyester resin, and the first resin particles contain a styrene-acrylic acid-based resin.

3. The electrostatic latent image developing toner according to claim 2 , wherein

the styrene-acrylic acid-based resin is a polymer of a styrene-based monomer, an alkyl(meth)acrylate, and a (meth)acryloyl group-containing quaternary ammonium compound.

4. The electrostatic latent image developing toner according to claim 3 , wherein

the second resin particles contain a styrene-acrylic acid-based resin.

5. The electrostatic latent image developing toner according to claim 3 , wherein

the (meth)acryloyl group-containing quaternary ammonium compound is a quaternary ammonium compound represented by formula (A) shown below,

wherein in the formula (A), R 1 represents a hydrogen atom or a methyl group, R 21 , R 22 , and R 23 each represent, independently of one another, a hydrogen atom, an optionally substituted alkyl group, or an optionally substituted alkoxy group, R 2 represents an optionally substituted alkylene group, and X − represents an anion forming an ionic bond with N + in the formula (A).

6. The electrostatic latent image developing toner according to claim 1 , wherein

the second resin particles contain a polyester resin.

7. The electrostatic latent image developing toner according to claim 6 , wherein

the core contains a polyester resin, and the first resin particles contain an acrylic acid-based resin having a repeating unit derived from a (meth)acryloyl group-containing quaternary ammonium compound.

8. The electrostatic latent image developing toner according to claim 7 , wherein

the acrylic acid-based resin having a repeating unit derived from a (meth)acryloyl group-containing quaternary ammonium compound is a polymer of an alkyl (meth)acrylate and a quaternary ammonium compound represented by formula (A) shown below,

wherein in the formula (A), R 1 represents a hydrogen atom or a methyl group, R 21 , R 22 , and R 23 each represent, independently of one another, a hydrogen atom, an optionally substituted alkyl group, or an optionally substituted alkoxy group, R 2 represents an optionally substituted alkylene group, and X − represents an anion forming an ionic bond with N + in the formula (A).

9. The electrostatic latent image developing toner according to claim 1 , wherein

the first resin particles contain an acrylic acid-based resin having a repeating unit derived from a (meth)acryloyl group-containing quaternary ammonium compound, and the second resin particles contain an acrylic acid-based resin containing no charge control agent.

10. The electrostatic latent image developing toner according to claim 9 , wherein

the acrylic acid-based resin having a repeating unit derived from a (meth)acryloyl group-containing quaternary ammonium compound is a polymer of an alkyl (meth)acrylate and a quaternary ammonium compound represented by formula (A) shown below,

wherein in the formula (A), R 1 represents a hydrogen atom or a methyl group, R 21 , R 22 , and R 23 each represent, independently of one another, a hydrogen atom, an optionally substituted alkyl group, or an optionally substituted alkoxy group, R 2 represents an optionally substituted alkylene group, and X − represents an anion forming an ionic bond with N + in the formula (A).

11. The electrostatic latent image developing toner according to claim 1 , wherein

the second resin particles contain no charge control agent.

12. The electrostatic latent image developing toner according to claim 1 , wherein

a percentage of area of regions of the surface of the core that are covered with at least one of the first and second resin particles is at least 90% and no greater than 100%.

13. The electrostatic latent image developing toner according to claim 1 , wherein

a softening point difference obtained by subtracting the softening point of the second resin particles from the softening point of the first resin particles is at least +10° C.

14. The electrostatic latent image developing toner according to claim 1 , wherein

the first resin particles have a softening point of at least 120° C. and no greater than 130° C., and the second resin particles have a softening point of at least 100° C. and no greater than 110° C.

15. The electrostatic latent image developing toner according to claim 1 , wherein

the toner particles further include inorganic particles as an external additive.

16. The electrostatic latent image developing toner according to claim 1 , wherein

the first resin particles have a softening point of at least 55° C. and no greater than 63° C., and the second resin particles have a softening point of at least 55° C. and no greater than 63° C.