Image forming apparatus

1. An image forming apparatus comprising an electrophotographic photoreceptor having a photosensitive layer on an electroconductive substrate, and a toner for developing an electrostatic charge image, wherein the photosensitive layer of the electrophotographic photoreceptor comprises an azo compound; the toner for developing an electrostatic charge image is a toner for developing an electrostatic charge image comprising toner matrix particles formed in an aqueous medium; the toner has a volume median diameter (Dv50) of from 4.0 μm to 7.0 μm; and a relationship between the volume median diameter (Dv50) and a percentage in number (Dns) of toner particles having a particle diameter of from 2.00 μm to 3.56 μm satisfies formula (1):

Dns≦ 0.233EXP(17.3 /Dv 50)  (1)

where Dv50 is the volume median diameter (μm) of the toner, and Dns is the percentage in number of toner particles having a particle diameter of from 2.00 μm to 3.56 μm, wherein an exposure light of an exposure means for forming an electrostatic latent image is a monochromatic light having an exposure wavelength of from 380 to 500 nm, wherein in the toner for developing an electrostatic charge image, the percentage in number (Dns) of toner particles having a particle diameter of from 2.00 μm to 3.56 μm is from 1.83 to 5.87%.

2. The image forming apparatus according to claim 1 , wherein in the toner for developing an electrostatic charge image, the relationship between the volume median diameter (Dv50) and the percentage in number (Dns) of toner particles having a particle diameter of from 2.00 μm to 3.56 μm satisfies formula (2):

0.0517EXP(22.4 /Dv 50)≦ Dns   (2).

3. The image forming apparatus according to claim 1 , wherein the volume median diameter (Dv50) of the toner for developing an electrostatic charge image, is at least 5.4 μm.

4. The image forming apparatus according to claim 1 , wherein in the toner for developing an electrostatic charge image, the percentage in number (Dns) of toner particles having a particle diameter of from 2.00 μm to 3.56 μm is at most 6%.

5. The image forming apparatus according to claim 1 , wherein the toner matrix particles are toner matrix particles produced by radical polymerization in an aqueous medium in the production of the toner for developing an electrostatic charge image.

6. The image forming apparatus according to claim 5 , wherein the toner matrix particles are toner matrix particles produced by an emulsion polymerization agglomeration method.

7. The image forming apparatus according to claim 1 , wherein the toner matrix particles have fine resin particles fixed or deposited on core particles.

8. The image forming apparatus according to claim 7 , wherein the fine resin particles comprise wax.

9. The image forming apparatus according to claim 7 , wherein the core particles comprise at least polymer primary particles, and a proportion of the total amount of polar monomers in 100 mass % of all polymerizable monomers of a binder resin as the fine resin particles, is smaller than a proportion of the total amount of polar monomers in 100 mass % of all polymerizable monomers of a binder resin as polymer primary particles in the core particles.

10. The image forming apparatus according to claim 8 , wherein the core particles comprise at least polymer primary particles, and a proportion of the total amount of polar monomers in 100 mass % of all polymerizable monomers of a binder resin as the fine resin particles, is smaller than a proportion of the total amount of polar monomers in 100 mass % of all polymerizable monomers of a binder resin as the polymer primary particles in the core particles.

11. The image forming apparatus according to claim 1 , wherein the toner for developing an electrostatic charge image, comprises from 4 to 20 parts by weight of a wax component per 100 parts by weight of the toner.

12. The image forming apparatus according to claim 1 , wherein the developing process speed of a latent image support is at least 100 mm/sec.

13. The image forming apparatus according to claim 1 , which further satisfies the formula (3):

Guaranteed lifetime number of copies (sheets) of developing machine having developer packed×print ratio≧500 (sheets)  (3).

14. The image forming apparatus according to claim 1 , wherein a resolution of the latent image support is at least 600 dpi.

15. The image forming apparatus according to claim 1 , wherein the toner for developing an electrostatic charge image is obtained by a method wherein the method does not comprise removing particles of at most a volume median diameter (Dv50) from the toner for developing an electrostatic charge image or the toner matrix particles.

16. The image forming apparatus according to claim 1 , wherein the toner for developing an electrostatic charge image, has a standard deviation in static electrification of from 1.0 to 2.0.

17. The image forming apparatus according to claim 9 , wherein a volume average diameter (Mv) of the polymer primary particles obtained by emulsion polymerization is at least 0.02 μm.

18. The image forming apparatus according to claim 10 , wherein a volume average diameter (Mv) of the polymer primary particles obtained by emulsion polymerization is at least 0.02 μm.

19. The image forming apparatus according to claim 9 , wherein an acid value of the binder resin is in a range of from 3 to 50 mgKOH/g.

20. The image forming apparatus according to claim 10 , wherein an acid value of the binder resin is in a range of from 3 to 50 mgKOH/g.