Conductive elastic roller and image forming apparatus comprising the same
There is provided a conductive elastic roller ( 1 ) comprising a shaft member ( 2 ) and one or more elastic layers ( 3 ) disposed on an outside of the shaft member ( 2 ) in a radial direction, wherein at least one of the elastic layers ( 3 ) is composed of an ultraviolet-curing type resin formed by curing a raw material for the elastic layer comprising a urethane acrylate oligomer (A), a photo-polymerization initiator (B) and a conductive agent (C) through ultraviolet irradiation, and the urethane acrylate oligomer (A) is a urethane acrylate oligomer synthesized by using as a polyol a polyether polyol (a1) having a proportion of primary hydroxyl groups in hydroxyl groups located at molecular ends of not less than 40% obtained by an addition polymerization of propylene oxide to a polyhydric alcohol alone, or the polyether polyol (a1) and another polyol (a2), and provides a conductive elastic roller ( 1 ) provided with an elastic layer having a low hardness, a small compression residual strain and an improved stain resistance to an adjoining member such as Organic Photoconductors or the like.
1. A conductive elastic roller comprising a shaft member and one or more elastic layers disposed on an outside of the shaft member in a radial direction, characterized in that at least one of the elastic layers is composed of an ultraviolet-curing type resin formed by curing a raw material for the elastic layer comprising a urethane acrylate oligomer (A), a photo-polymerization initiator (B) and a conductive agent (C) through ultraviolet irradiation, and the urethane acrylate oligomer (A) is a urethane acrylate oligomer synthesized by using as a polyol a polyether polyol (a1) having a proportion of primary hydroxyl groups in hydroxyl groups located at molecular ends of not less than 40% obtained by an addition polymerization of propylene oxide to a polyhydric alcohol alone, or the polyether polyol (a1) and another polyol (a2).
2. A conductive elastic roller according to claim 1 , wherein the polyether polyol (a1) has a molecular weight of 500-5,000, a functionality of 1.5-2.5 and a hydroxyl value of 20-230 mg KOH/g.
3. A conductive elastic roller according to claim 1 , wherein a mass ratio (a1/a2) of the polyether polyol (a1) to the other polyol (a2) is within a range of 100/0-30/70.
4. A conductive elastic roller according to claim 1 , wherein the raw material for the elastic layer further contains an acrylate monomer (H).
5. A conductive elastic roller according to claim 4 , wherein the acrylate monomer (H) is at least one selected from the group consisting of isomyristyl acrylate and β-acryloyloxyethyl hydrogen succinate.
6. A conductive elastic roller according to claim 1 , wherein the ultraviolet-curing type resin has an Asker C hardness of 40-60 degrees.
7. A conductive elastic roller according to claim 1 , which is a developing roller or a charging roller.
8. An image forming apparatus using a conductive elastic roller as claimed in claim 1 .