Developing roller
Provided are a developing roller which includes a shaft, and a base layer and a surface layer sequentially formed on an outer peripheral portion of the shaft in a radial direction, where 1) a low-resilience layer is disposed between the base layer and the surface layer, 2) the low-resilience layer has a loss tangent tan δ value that is larger than a loss tangent tan δ value of any of the base layer and the surface layer when measured under conditions of a temperature of 23° C., an amplitude of ±20 μm, and a frequency of 6 Hz, and 3) the developing roller has an Asker C hardness and thickness value of 500 or less, which is defined by the following formula (1): Asker C hardness and thickness value of the developing roller=Asker C hardness of the developing roller×(thickness of the developing roller+6) (1).
1. A developing roller comprising a shaft, and a base layer and a surface layer sequentially formed on an outer peripheral portion of the shaft in a radial direction, wherein
1) a low-resilience layer is disposed between the base layer and the surface layer,
2) the low-resilience layer has a loss tangent tan δ value that is larger than a loss tangent tan δ value of any of the base layer and the surface layer when measured under conditions of a temperature of 23° C., an amplitude of ±20 μm, and a frequency of 6 Hz, and
3) the developing roller has an Asker C hardness and thickness value of 500 or less, which is defined by the following formula (1):
Asker C hardness and thickness value of developing roller=Asker C hardness of developing roller×(thickness of developing roller+6) (1)
where the Asker C hardness of developing roller is a value measured under a load of 1 kg, and
the thickness of developing roller is a distance from a surface of the shaft of the developing roller to a surface of the surface layer in the radial direction of the shaft in unit of mm.
2. The developing roller according to claim 1 , wherein the developing roller has a CIT creep rate of 5.0% or more.
3. The developing roller according to claim 1 , wherein the low-resilience layer contains an aqueous urethane resin.
4. The developing roller according to claim 1 , wherein the surface layer contains urethane resin particles.
5. The developing roller according to claim 1 , wherein the low-resilience layer has a thickness of 40 μm or more.
6. An image forming apparatus using the developing roller according to claim 1 .
7. The developing roller according to claim 2 , wherein the low-resilience layer contains an aqueous urethane resin.
8. The developing roller according to claim 2 , wherein the surface layer contains urethane resin particles.
9. The developing roller according to claim 2 , wherein the low-resilience layer has a thickness of 40 μm or more.
10. An image forming apparatus using the developing roller according to claim 2 .
11. The developing roller according to claim 3 , wherein the surface layer contains urethane resin particles.
12. The developing roller according to claim 3 , wherein the low-resilience layer has a thickness of 40 μm or more.
13. An image forming apparatus using the developing roller according to claim 3 .
14. The developing roller according to claim 4 , wherein the low-resilience layer has a thickness of 40 μm or more.
15. An image forming apparatus using the developing roller according to claim 4 .
16. An image forming apparatus using the developing roller according to claim 5 .
17. The developing roller according to claim 7 , wherein the surface layer contains urethane resin particles.
18. The developing roller according to claim 7 , wherein the low-resilience layer has a thickness of 40 μm or more.
19. An image forming apparatus using the developing roller according to claim 7 .
20. The developing roller according to claim 8 , wherein the low-resilience layer has a thickness of 40 μm or more.