Conductive roller and inspection method therefor
View Patent ↗To provide a conductive roller which does not cause defective images with, for example, black lines, which would otherwise be caused by current leakage due to aggregation of carbon black particles or a similar phenomenon, and a method for inspecting the roller. The 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 which has ion conductivity and which contains carbon black micropowder, characterized in that said rubber elastic layer satisfies the relationship represented by the following formula: |θ max /θ min |≦5, [F1] wherein θ max represents the maximum value of phase difference θ as measured upon application of an AC voltage of 1.0 V within a frequency range of 100 mHz to 10 kHz, and θ min represents the minimum value of phase difference θ as measured under the same conditions.
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 which has ion conductivity and which contains carbon black micropowder, and a surface layer formed on a surface of the rubber elastic layer, the surface layer being selected from the group consisting of a protective layer and a high-resistance layer, characterized in that said rubber elastic layer before providing the protective layer or the high-resistance layer, and said rubber elastic layer with the protective layer or the high-resistance layer, respectively, both satisfy the relationship represented by the following formula:
|θ max /θ min ≦2.96, [F1]
wherein θ max represents the maximum value of phase difference θ as measured upon application of an AC voltage of 1.0 V within a frequency range of 100 mHz to 10 kHz, and θ min represents the minimum value of phase difference θ as measured under the same conditions.
2. A conductive roller according to claim 1 , wherein the minimum value θ min satisfies the following formula:
θ min ≧30(degrees). [F2]
3. A conductive roller according to claim 1 , wherein the rubber elastic layer is formed of an epichlorohydrin rubber.
4. A conductive roller according to claim 1 , wherein the rubber elastic layer contains an ion-conducting agent.
5. A conductive roller according to claim 1 , wherein the surface layer is a surface-treated layer which has been formed through treating the surface with a surface-treatment liquid containing an isocyanate; the rubber elastic layer having the surface-treated layer satisfies the relationship represented by the formula F1, wherein θ max represents the maximum value of phase difference θ as measured upon application of an AC voltage of 1.0 V within a frequency range of 100 mHz to 10 kHz, and θ min represents the minimum value of phase difference θ as measured under the same conditions; and, after removal of the surface-treated layer, the rubber elastic layer also satisfies the relationship represented by the formula F1, wherein θ max represents the maximum value of phase difference θ as measured upon application of an AC voltage of 1.0 V within a frequency range of 100 mHz to 10 kHz, and θ min represents the minimum value of phase difference θ as measured under the same conditions.
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 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 having ion conductivity and containing carbon black micropowder, and a surface layer formed on a surface of the rubber elastic layer, the surface layer being selected from the group consisting of a protective layer and a high-resistance layer, wherein the method comprises; measuring a phase difference θ with an impedance analyzer apparatus, and determining whether or not the rubber elastic layer before providing the protective layer or the high-resistance layer and said rubber elastic layer with the protective layer or the high-resistance layer, respectively, both satisfy the relationship represented by the following formula:
|θ max /θ min |≦2.96, [F3]
wherein θ max represents the maximum value of phase difference θ as measured upon application of an AC voltage of 1.0 V within a frequency range of 100 mHz to 10 kHz, and θ min represents the minimum value of phase difference θ as measured under the same conditions.
8. A method for inspecting a conductive roller according to claim 7 , wherein the method comprises determining whether or not the minimum value θ min of phase difference θ as measured upon application of an AC voltage of 1.0 V within a frequency range of 100 mHz to 10 kHz satisfies the following formula:
θ min ≧30(degrees). [F4]
9. A method for inspecting a conductive roller according to claim 7 , wherein the rubber elastic layer is formed of an epichlorohydrin rubber.
10. A method for inspecting a conductive roller according to claim 7 , wherein the surface layer is a surface-treated layer which has been formed through treating the surface with a surface-treatment liquid containing an isocyanate; and the method includes, after removal of the surface-treated layer, determining whether or not the rubber elastic layer satisfies the relationship represented by the formula F3, wherein θ max represents the maximum value of phase difference θ as measured upon application of an AC voltage of 1.0 V within a frequency range of 100 mHz to 10 kHz, and θ min represents the minimum value of phase difference θ as measured under the same conditions.
11. A method for inspecting a conductive roller according to claim 10 , which method includes determining whether or not the rubber elastic layer having the surface-treated layer satisfies the relationship represented by the formula F3, wherein θ max represents the maximum value of phase difference θ as measured upon application of an AC voltage of 1.0 V within a frequency range of 100 mHz to 10 kHz, and θ min represents the minimum value of phase difference θ as measured under the same conditions.
12. A method for inspecting a conductive roller according to claim 10 , wherein the surface-treatment liquid further contain carbon black, and/or at least one polymer species selected from among an acrylic fluoropolymer and an acrylic silicone polymer.