Developing roller for image forming apparatus

1. An electrophotographic image forming apparatus comprising:

a main body;

a photoreceptor configured to form an electrostatic latent image; and

a developing roller that develops the electrostatic latent image by supplying a toner to the electrostatic latent image;

wherein:

a surface layer of the developing roller includes a plurality of protruding beads and has a surface roughness based on:

a thickness of the surface layer,

a particle size of the plurality of protruding beads, and

an amount of the plurality of protruding beads,

such that the surface layer has the surface roughness corresponding to a glossiness of the surface layer of the developing roller in a range of 4 to 15, in which a number average distance between the protruding beads is in a range of 200 μm to 400 μm,

where the glossiness is measured as a relative ratio with respect to 100 which is a glossiness of a surface of glass having a refractive index of 1.567, with the incident angle of incident light at 60 degrees.

2. The electrophotographic image forming apparatus of claim 1 , further comprising:

a toner reserving unit; and

a supplying roller that supplies the toner from the toner reserving unit to the developing roller,

wherein the photoreceptor, the developing roller, and the supplying roller are provided in the form of an imaging cartridge.

3. The electrophotographic image forming apparatus of claim 2 , wherein the supplying roller comprises a resin foam; and a conductive agent contained in the resin foam.

4. The electrophotographic image forming apparatus of claim 3 , wherein the resin foam is polyurethane foam, ethylene-propylene-diene rubber foam, or silicon rubber foam.

5. The electrophotographic image forming apparatus of claim 1 , wherein the developing roller further comprises a shaft; an electroconductive elastic layer provided on an outer circumference of the shaft

wherein the surface layer covers the electroconductive elastic layer.

6. The electrophotographic image forming apparatus of claim 5 , wherein the electroconductive elastic layer comprises an elastomer matrix; and electroconductive particles dispersed in the elastomer matrix.

7. The electrophotographic image forming apparatus of claim 6 , wherein the elastomer matrix is silicon rubber, polyurethane, or ethylene-propylene-diene rubber.

8. The electrophotographic image forming apparatus of claim 5 , wherein the surface layer comprises beads that are selected from an acryl-based resin such as polyacrylate or polymethacrylate; a polyamide-based resin such as nylon; a polyolefin-based resin such as polyethylene or polypropylene; a silicon-based resin, a phenol-based resin; a polyurethane-based resin; a styrene-based resin; a benzoguanamine resin; a polyfluoride vinylidene-based resin; a metal oxide powder such as silica, alumina, titanium oxide, or an iron oxide; a boron nitride; a silicon carbide; or a combination thereof.

9. The electrophotographic image forming apparatus of claim 1 , wherein the toner is a dry toner having a sphericity in a range of 0.960 to 1.0.

10. The electrophotographic image forming apparatus of claim 1 , wherein a thickness of the surface layer is in a range of 1 μm to 100 μm.

11. The electrophotographic image forming apparatus of claim 1 , wherein a resistance of the surface layer is in a range of 10 5 Ω cm to 10 11 Ω cm.

12. The electrophotographic image forming apparatus of claim 1 , wherein a shape of the beads is a sphere.

13. The electrophotographic image forming apparatus of claim 1 , wherein a shape of the beads is a plate.

14. The electrophotographic image forming apparatus of claim 1 , further comprising a supplying roller that supplies the toner from the toner reserving unit to the developing roller,

wherein the supplying roller comprises a plurality of foam cells, and a number average size of the foam cells is in a range of 300 μm to 500 μm.

15. The electrophotographic image forming apparatus of claim 1 , wherein the developing roller is arranged to rotate at a rotation linear velocity of 120% to 150% of a rotation linear velocity of the photoreceptor.

16. An imaging cartridge attachable and detachable to a main body of an electrophotographic image forming apparatus comprising a toner reserving unit,

wherein the imaging cartridge comprises:

a photoreceptor configured to form an electrostatic latent image; and

a developing roller that develops the electrostatic latent image by supplying a toner to the electrostatic latent image; wherein:

a surface layer of the developing roller includes a plurality of protruding beads and has a surface roughness based on:

a thickness of the surface layer,

a particle size of the plurality of protruding beads, and

an amount of the plurality of protruding beads,

such that the surface layer has the surface roughness corresponding to a glossiness of a surface layer of the developing roller in a range of 4 to 15, in which a number average distance between the protruding beads is in a range of 200 μm to 400 μm,

where the glossiness is measured as a relative ratio with respect to 100 which is a glossiness of a surface of glass having a refractive index of 1.567, with the incident angle of incident light at 60 degrees.

17. The imaging cartridge of claim 16 , further comprising a supplying roller that supplies the toner from the toner reserving unit to the developing roller,

wherein the supplying roller comprises a plurality of foam cells, and a number average size of the foam cells is in a range of 300 μm to 500 μm.

18. The imaging cartridge of claim 16 , wherein the developing roller is arranged to rotate at a rotation linear velocity of 120% to 150% of a rotation linear velocity of the photoreceptor.