Cylindrical body and method for producing same

1. A cylindrical body formed of a conductive member provided having a spiral spring portion, the cylindrical body comprising a Ni metal layer and a Ni—W alloy layer containing W at least on an end portion of the cylindrical body,

wherein at the end portion the Ni—W alloy layer protrudes outward from an end surface of the Ni metal layer by a distance of 1 μm or more of the cylindrical body.

2. The cylindrical body according to claim 1 , wherein the Ni—W alloy layer is disposed on an outer peripheral surface side of the Ni metal layer.

3. The cylindrical body according to claim 1 , wherein the Ni—W alloy layer is disposed on an inner peripheral surface side of the Ni metal layer.

4. A method for producing a cylindrical body comprising:

forming a gold plating layer on an outer peripheral surface of a core wire;

forming a Ni metal layer on an outer peripheral surface of the gold plating layer;

forming a Ni—W alloy layer containing W on an outer peripheral surface of the Ni metal layer;

forming a resist layer on an outer peripheral surface of the Ni—W alloy layer;

forming a spiral groove in the resist layer;

removing the Ni metal layer and the Ni—W alloy layer located in a formation portion of the spiral groove by etching using the resist layer as a masking material and eroding an end portion of the Ni metal layer such that an end portion of the Ni—W alloy layer protrudes outward from an end surface to an outer side of the Ni metal layer by a distance of 1 μm or more of the cylindrical body, depending on a difference in etching rate between the Ni metal layer and the Ni—W alloy layer;

removing the resist layer;

removing the gold plating layer located in the formation portion of the spiral groove; and

drawing the core wire.

5. A method for producing a cylindrical body comprising:

forming a gold plating layer on an outer peripheral surface of a core wire;

forming a Ni—W alloy layer containing W on an outer peripheral surface of the gold plating layer;

forming a Ni metal layer on an outer peripheral surface of the Ni—W alloy layer;

forming a resist layer on an outer peripheral surface of the Ni metal layer;

forming a spiral groove in the resist layer;

removing the Ni metal layer and the Ni—W alloy layer located in a formation portion of the spiral groove by etching using the resist layer as a masking material and eroding an end portion of the Ni metal layer such that an end portion of the Ni—W alloy layer protrudes outward from an end surface of the Ni metal layer by a distance of 1 μm or more of the cylindrical body, depending on a difference in etching rate between the Ni metal layer and the Ni—W alloy layer;

removing the resist layer;

removing the gold plating layer located in the formation portion of the spiral groove; and

drawing the core wire.

6. The cylindrical body according to claim 1 , wherein the Ni—W alloy layer protrudes outward from the end surface of the Ni metal layer at least by a distance equal to or smaller than 0.5 times of an outer diameter of the cylindrical body.

7. The method according to claim 4 , wherein the Ni—W alloy layer also protrudes outward from the end surface of the gold plating layer.

8. The method according to claim 5 , wherein the Ni—W alloy layer also protrudes outward from the end surface of the gold plating layer.