Electrostatic charge image developer, process cartridge and image forming apparatus

1. An electrostatic charge image developer, comprising:

a toner containing an external additive; and

a carrier comprising a resin-coated layer formed on a surface of a core material,

wherein a resin that forms the resin-coated layer contains a copolymer of a monomer containing (i) a cycloalkyl group and (ii) a styrene monomer or dimethylamino methacrylate,

an average shape factor SF1 of the toner being from about 125 to about 135,

a number of particles having a shape factor SF1 of less than 125 being from about 5% to about 30% by number with respect to a total number of toner particles,

a number of particles having a shape factor SF1 of greater than 135 being from about 5% to about 30% by number with respect to the total number of toner particles,

a scratch line width in a scratch strength test of the resin used in the resin-coated layer being from about 80 μm to about 200 μm, and

a scratch depth being from about 60 μm to about 150 μm.

2. The electrostatic charge image developer of claim 1 , wherein the resin that forms the resin-coated layer is a resin obtained by polymerizing a monomer containing a styrene monomer.

3. The electrostatic charge image developer of claim 1 , wherein a glass transition temperature of the resin that forms the resin-coated layer is from about 70° C. to about 150° C.

4. The electrostatic charge image developer of claim 1 , wherein the cycloalkyl group has a 3- to 10-membered ring structure.

5. The electrostatic charge image developer of claim 1 , wherein the cycloalkyl group contains any one of a cyclohexyl group, an adamantyl group, a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, a cyclononyl group, a cyclodecyl group, an isobornyl group, a norbornyl group and a bornyl group.

6. The electrostatic charge image developer of claim 1 , wherein the resin that forms the resin-coated layer is formed by copolymerizing dimethylamino methacrylate in the range of from about 0.5 parts by weight to about 5 parts by weight.

7. The electrostatic charge image developer of claim 1 , wherein an average film thickness of the resin-coated layer is about 70 nm or more.

8. The electrostatic charge image developer of claim 1 , wherein a volume resistivity of the carrier is from about 1×10 7 Ω·cm to about 1×10 15 Ω·cm.

9. The electrostatic charge image developer of claim 1 , wherein the metal oxide particles are monodispersed spherical silica.

10. The electrostatic charge image developer of claim 1 , wherein a standard deviation of the particle diameters of the metal oxide particles is about D50×0.22 or less.

11. The electrostatic charge image developer of claim 1 , wherein a Wadell's sphericity of the metal oxide particles is about 0.6 or more.

12. The electrostatic charge image developer of claim 1 , wherein, after leaving a developer in an environment having a temperature of 22° C. and a relative humidity of 50% for 170 hours, a surface charge density distribution D shown by Formula (1) below of the toner is about 5 dB or more

D [dB]=10×log( m 2 /σ 2 )  Formula (1):

in the Formula (1), m expresses an average value of surface charge density of the toner, and σ expresses the standard deviation of the surface charge density of the toner.

13. The electrostatic charge image developer of claim 1 , wherein the toner contains a crystalline polyester resin.

14. The electrostatic charge image developer of claim 13 , wherein an acid component of the crystalline polyester resin comprises about 95% by mole or more of straight chain dicarboxylic acid having 6 to 10 carbon atoms.

15. The electrostatic charge image developer of claim 13 , wherein an alcohol component of the crystalline polyester resin comprises about 95% by mole or more of straight chain dialcohol having 6 to 10 carbon atoms.

16. The electrostatic charge image developer of claim 13 , wherein a content of the crystalline polyester resin in the toner is from about 3% by weight to about 20% by weight.

17. The electrostatic charge image developer of claim 1 , wherein a volume average particle size distribution index GSDv of the toner is about 1.30 or less.

18. The electrostatic charge image developer of claim 1 , wherein the external additive comprises metal oxide particles having a volume average primary particle diameter of from 70 nm to 200 nm.

19. The electrostatic charge image developer of claim 1 , wherein the resin that forms the resin-coated layer is derived from cyclohexyl (meth)acrylate.