Claims
- 1. A carrier for an clectrostatographic developer, said carrier comprising:particles of a hard magnetic ferrite material as the core and having a coating of a thermoplastic polymer resin selected from the group consisting of poly(vinylidene fluoride), poly(vinylidene fluoride-co-tetrafluoroethylene), and a mixture of poly(vinylidene fluoride) and poly(methyl methacrylate), said particles in turn having an outermost layer comprising a conductive charge control agent selected from the group consisting of lauramidopropyl trimethylammonium methylsulfate, cetyl pyridinium chloride, and dioctadecyl dimethyl ammonium chloride; wherein said outerrnost layer is formnnd by a process consisting essentially of the steps of coating said resin coating with a solution in a solvent of said conductive charge control agent, and then removing said solvent.
- 2. The carrier according to claim 1 wherein the amount of conductive charge control agent ranges from about 50 to 500 ppm by weight of the combined hard magnetic ferrite material and polymer resin coating.
- 3. The carrier according to claim 2 wherein the amount of conductive charge control agent is between about 200 ppm and 350 ppm by weight of the combined hard magnetic ferrite material and polymer resin coating.
- 4. The carrier of claim 1 wherein the hard magnetic ferrite material has crystalline structure that exhibits a coercivity of at least 300 Oersteds when magnetically saturated and an induced magnetic moment of at least EMU/g when in an applied magnetic field of 1000 Oersteds and having a number average particle diameter of from 10.0 to 38.0 micrometers.
- 5. The carrier of claim 1 wherein said hard ferrite magnetic material has a coercivity of about 1000 to 3000 Oersteds when magnetically saturated and an induced magnetic moment of about 30 to 70 EMU/g in an applied field of 1000 Oersteds.
- 6. The carrier of claim 1 wherein said hard maignetic ferrite material comprises a strontium ferrite material.
- 7. The carrier of claim 1 wherein said solvent in said solution of said charge control agent is selected from the group consisting of methanol, isopropyl alcohol, and water.
- 8. The carrier of claim 7 wherein said solvent is removed from said outermost layer by evaporation.
- 9. The carrier of claim 1 wherein said polymer resin coating is polyvinylidene fluoride, or a mixture of polyvinylidene fluoride and poly(methylmethacrylate).
- 10. An electrcostatographic two-component dry developer composition for use in the development of electrostatic latent images which comprises a mixture of charged toner and oppositely charged carrier according to claim 1.
- 11. The electrcostatographic developer of claim 10 comprising from about 75 to about 99 weight percent of the carrier and from about 1 to about weight per cent of the toner.
CROSS-REFERENCE TO RELATED APPLICATIONS
This is a continuation-in-part application of Ser. No. 08/649,384 filed May 17, 1996, now abandoned, entitled “Hard Carrier Particles Coated With a Polymer Resin and a Conductive Material” and claims priority from Provisional Application Serial No. 60/005,511, filed Sep. 28, 1995.
US Referenced Citations (23)
Foreign Referenced Citations (2)
Number |
Date |
Country |
1-134467 |
May 1989 |
JP |
2-210365 |
Aug 1990 |
JP |
Non-Patent Literature Citations (5)
Entry |
Grant, R. et al Grant & Hackh's Chemical Dictionary, 5th edition, McGraw-Hill Book Co, NY (1987), p. 541, 1987.* |
Diamond, A.S. ed. Handbook of Imaging Materials, Marcel Dekker, Inc., New York (1991), pp 169, 182, and 183, 1991.* |
Patent & Trademark Office English-Language Translation of Japanese Patent 2-210365 (Pub 8/90).* |
Patent & Trademark English-Language Translation of JP 1-134467 (Pub 5/89).* |
Plastics Additives Technical Bulletin, Aug. 1966, American Cyanamid Company. |
Provisional Applications (1)
|
Number |
Date |
Country |
|
60/005511 |
Sep 1995 |
US |
Continuation in Parts (1)
|
Number |
Date |
Country |
Parent |
08/649384 |
May 1996 |
US |
Child |
09/096985 |
|
US |