US 5,011,739 A · Moisture stable biasable transfer members and method for making same

Abstract

The invention provides rolls, belts and other biasable members having at least one layer or coating of an elastomeric resilient crosslinked polyurethane formed by reacting (a) a polyisocyanate prepolymer comprising the reaction product of an aliphatic polyisocyanate and a polyether polyol, specifically a polyalkylene glycol in which the alkylene group contains 2 to 3 carbon atoms, and (b) a hardening mixture comprising a polyether polyol of (a) and, as a conductivity control agent, from 0.01 to 3.0 weight percent based on the total weight of (b) of a complex of an oligoethylene glycol selected from the group consisting of di-, tri- and tetraethylene glycol with an ionizable alkali metal salt selected from the group consisting of sodium iodide, lithium iodide and sodium thiocyanate. The resistivity of the elastomeric resilient polyurethane coating on the biasable member is controlled or adjusted to within a desired level of resistivity due to the inclusion of the conductivity control agent in the crosslinked polyurethane elastomer. Additionally, the inclusion of the conductivity control agent in the crosslinked polyurethane elastomer reduces the sensitivity of the resistivity of the polyurethane coating on the biasable member to changes in relative humidity. Further, since the conductivity control agent is copolymerized with the polyisocyanate prepolymers and polyols used to make the elastomeric polyurethane coatings of the biasable members of the invention, the conductivity control agent is bonded covalently to the backbone and/or the crosslinking portion of the polyurethane elastomer where it forms a permanently fixed part of the crosslinked polymer and will not migrate therefrom resulting in a continuous change in the resistivity of the polyurethane coating over time and possible adverse affects on materials that may come into contact with the migrating agent. The utility of such biasable members is in the transfer of toner images from a photoconductor to a final support sheet where the member, for example, a bias transfer roll, electrically cooperates with a photoconductor to establish a directional force field therebetween.

Claims29

Dependent claims

A member for electrically cooperating with a photoconductive surface to attract charged toner particles from the surface towards the member comprising a conductive substrate capable of supporting a uniform bias potential thereon and at least one coating comprising a resilient crosslinked elastomeric polyurethane formed by reacting:

(a) a polyisocyanate prepolymer comprising the reaction product of:
(i) an aliphatic polyisocyanate, and
(ii) a polyether polyol selected from the group consisting of a polyalkylene glycol having 2 to 3 carbon atoms in the alkylene group;
and
(b) a hardening mixture comprising:
(i) a polyether polyol selected from the group consisting of a polyalkylene glycol having 2 or 3 carbon atoms in the alkylene group and,
(ii) as a conductivity control agent for controlling the resistivity of the elastomeric polyurethane, from 0.01 to 3.0 weight percent based on the total weight of (b) of a complex of an oligoether glycol selected from the group consisting of di-tri- and tetraethylene glycol with an ionizable alkali metal salt selected from the group consisting of sodium iodide, lithium iodide and sodium thiocyanate,
the coating being in electrical contact with the conductive substrate and having an electrical resistivity such that the coating is capable of transmitting a bias potential from the substrate to the outer periphery of the coating.

5 more elements

A method of preventing changes in the resistivity of members for electrically cooperating with a photoconductive surface to attract charged toner particles from the surface towards the members caused by changes in relative humidity comprising applying at least one coating of a resilient elastomeric polyurethane formed by reacting:

(a) a polyisocyanate prepolymer comprising the reaction product of:
(i) an aliphatic polyisocyanate, and
(ii) a polyether polyol selected from the group consisting of a polyalkylene glycol having 2 to 3 carbon atoms in the alkylene group;
and
(b) a hardening mixture comprising:
(i) a polyether polyol selected from the group consisting of a polyalkylene glycol having 2 to 3 carbon atoms in the alkylene group and,
(ii) as a conductivity control agent for controlling the resistivity of the elastomeric polyurethane, from 0.01 to 3.0 weight percent based on the total weight of (b) of a complex of an oligoethylene glycol selected from the group consisting of di-, tri- and tetraethylene glycol with an ionizable alkali metal salt selected from the group consisting of sodium iodide, lithium iodide and sodium thiocyanate,
to a cylindrical core of electrically conductive material for electrically cooperating with the photoconductive surface when brought into contact therewith whereby the elastomer is capable of transmitting a bias potential from the core of electrically conductive material to the outer periphery thereof and significant reductions in the sensitivity of the resistivity to changes in relative humidity occur.

5 more elements

Dependencies are inferred from the claim text.

Moisture stable biasable transfer members and method for making same

Life of this patent

Moisture stable biasable transfer members and method for making same

Life of this patent

Abstract

Claims29