Conductive roller and inspection method therefor

1. A conductive roller comprising a metallic core and at least one rubber elastic layer provided on the outer peripheral surface of the core, the rubber elastic layer being formed from a conductive rubber to which conductivity has been imparted by carbon powder, wherein the conductive roller satisfies the relationship represented by formula (1):

Zr/Zc ≧5  (1),

wherein Zr (Ω) represents a resistance component and Zc (Ω) represents a capacitive reactance component, the resistance component Zr (Ω) and the capacitive resistance Zc (Ω) being calculated respectively from impedance Z (Ω) and phase difference θ, when the impedance Z (Ω) is measured upon application of an AC voltage of 0.2 V at a frequency of 1 Hz to the rubber elastic layer.

2. A conductive roller according to claim 1 , wherein the relationship between resistance component Zr (Ω) and capacitive reactance Zc (Ω) satisfies formula (1), when the impedance Z (Ω) is measured upon application of an AC voltage of 0.2 V at a frequency of 1 Hz to the rubber elastic layer and under any of L/L conditions (10° C., 30% RH), N/N conditions (25° C., 50% RH), and H/H conditions (35° C., 85% RH).

3. A conductive roller according to claim 1 , wherein the rubber elastic layer is formed of a polyurethane rubber having conductivity, and the polyurethane is an ether-based polyurethane.

4. A conductive roller according to claim 3 , wherein the rubber elastic layer has, on a surface thereof, a surface-treated layer which has been formed through treating the surface with a surface-treatment liquid containing an isocyanate, and, the relationship between resistance component Zr (Ω) and capacitive reactance Zc (Ω) satisfies formula (2):

25 ≧Zr/Zc≧ 5  (2),

when the impedance Z (Ω) is measured upon application of an AC voltage of 0.2 V at a frequency of 1 Hz to the rubber elastic layer after removal of the surface-treated layer.

5. A conductive roller according to claim 4 , wherein the relationship between resistance component Zr (Ω) and capacitive reactance Zc (Ω) satisfies formula (2) when the impedance Z (Ω) is measured upon application of an AC voltage of 0.2 V at a frequency of 1 Hz to the rubber elastic layer having the surface-treated layer.

6. A conductive roller according to claim 5 , wherein the surface treatment liquid further contains carbon black, and/or at least one polymer species selected from among an acrylic fluoropolymer and an acrylic silicone polymer.

7. A conductive roller according to claim 4 , wherein the surface treatment liquid further contains carbon black, and/or at least one polymer species selected from among an acrylic fluoropolymer and an acrylic silicone polymer.

8. A method for inspecting a conductive roller having a metallic core and at least one rubber elastic layer provided on the outer peripheral surface of the core, the rubber elastic layer being formed from a conductive rubber to which conductivity has been imparted by carbon powder, wherein the method comprises determining whether or not the relationship between resistance component Zr (Ω) and capacitive reactance Zc (Ω), the resistance component Zr (Ω) and the capacitive reactance Zc (Ω) being calculated respectively from impedance Z (Ω) and phase difference θ satisfies formula (1):

Zr/Zc≧ 5  (1),

when the impedance Z (Ω)is measured upon application of an AC voltage of 0.2 V at a frequency of 1 Hz to the rubber elastic layer.

9. A method for inspecting a conductive roller according to claim 8 , wherein the method comprises determining whether or not the relationship between resistance component Zr (Ω) and capacitive reactance Zc (Ω) satisfies formula (1), when the impedance Z (Ω) is measured upon application of an AC voltage of 0.2 V at a frequency of 1 Hz and under any of L/L conditions (10° C., 30% RH), N/N conditions (25° C., 50% RH), and H/H conditions (35° C., 85% RH), to the rubber elastic layer.

10. A method for inspecting a conductive roller according to claim 8 , wherein the rubber elastic layer is formed of a polyurethane rubber having conductivity and formed of an ether-based polyurethane, and has, on a surface thereof, a surface-treated layer which has been formed through treating the surface with a surface-treatment liquid containing an isocyanate, and, the method comprises determining whether or not the relationship between resistance component Zr (Ω) and capacitive reactance Zc (Ω) satisfies formula (2):

25 ≧Zr/Zc≧ 5  (2),

when the impedance Z (Ω) is measured upon application of an AC voltage of 0.2 V at a frequency of 1 Hz to the rubber elastic layer after removal of the surface-treated layer.

11. A method for inspecting a conductive roller according to claim 10 , wherein the method comprises determining whether or not the relationship between resistance component Zr (Ω) and capacitive reactance Zc (Ω) satisfies formula (2), when the impedance Z (Ω) is measured upon application of an AC voltage of 0.2 V at a frequency of 1 Hz to the rubber elastic layer having the surface-treated layer.

12. A method for inspecting a conductive roller according to claim 11 , wherein the surface treatment liquid further contains carbon black, and/or at least one polymer species selected from among an acrylic fluoropolymer and an acrylic silicone polymer.

13. A method for inspecting a conductive roller according to claim 10 , wherein the surface treatment liquid further contains carbon black, and/or at least one polymer species selected from among an acrylic fluoropolymer and an acrylic silicone polymer.