Electrostatic image developing processes and compositions
View Patent ↗Compositions and methods for electrographic image development, wherein the image development process employs a two-component developer that includes toner particles having a radius R T and magnetic carrier particles having a radius R C , wherein R C is preferably less than about 5R T and is more preferably less than or equal to about 3R T .
1. A two-component developer for use in electrographic printing comprising substantially spherical toner particles and substantially spherical magnetic carrier particles, the carrier particles having a dielectric constant ∈ C of at least about 6, the toner particles having a radius R T and the carrier particles having a radius R C , wherein R C is between about 1.5R T and about 10R T .
2. The developer of claim 1 , wherein R C is between about 2R T and about 5R T .
3. The developer of claim 1 , wherein the carrier particles have a dielectric constant ∈ C greater than about 10.
4. The developer of claim 3 , wherein R C is between about 2R T and about 5R T .
5. The developer of claim 1 , wherein the carrier particles have a dielectric constant ∈ C greater than about 100.
6. The developer of claim 5 , wherein R C is between about 2R T to about 5R T .
7. The developer of claim 1 , wherein the carrier particles have a dielectric constant ∈ C greater than about 298.
8. The developer of claim 7 , wherein R C is between about 2R T to about 5R T .
9. The developer of claim 1 , the carrier particles having a size distribution according to the Schulz distribution with z greater than about 6.
10. The developer of claim 1 , the carrier particles having a size distribution according to the Schulz distribution with z greater than about 10.
11. The developer of claim 1 , the carrier particles having a size distribution according to the Schulz distribution with z greater than about 50.
12. The developer of claim 1 , the carrier particles having a size distribution according to the Schulz distribution with z greater than about 100.
13. The developer of claim 1 , the toner particles having a size distribution according to the Schulz distribution with z greater than about 20.
14. The developer of claim 1 , the toner particles having a size distribution according to the Schulz distribution with z greater than about 30.
15. The developer of claim 1 , the toner particles having a size distribution according to the Schulz distribution with z greater than about 50.
16. The developer of claim 1 , the toner particles having a size distribution according to the Schulz distribution with z greater than about 100.
17. A method for producing electrographic images comprising the steps of:
(a) providing an electrographic printer comprising an imaging member, a toning shell located adjacent the imaging member and defining an external electric field of image development therebetween, and a two-component developer, comprising substantially spherical toner particles and substantially spherical magnetic carrier particles,
the carrier particles having a dielectric constant ∈ C of at least about 6,
the toner particles having a radius R T and the carrier particles having a radius R C , wherein R C is between about 1.5R T and about 10R T ; and
(b) causing developer to move through the external electric field, interacting with an electrostatic image carried on the imaging member.
18. The method of claim 17 , wherein R C is between about 2R T and about 5R T .
19. The method of claim 17 , wherein the carrier particles have a dielectric constant ∈ C greater than about 10.
20. The method of claim 19 , wherein R C is between about 2R T and about 5R T .
21. The method of claim 17 , wherein the carrier particles have a dielectric constant ∈ C greater than about 100.
22. The method of claim 21 , wherein R C is between about 2R T to about 5R T .
23. The method of claim 17 , wherein the carrier particles have a dielectric constant ∈ C greater than about 298.
24. The method of claim 23 , wherein R C is between about 2R T to about 5R T .
25. The method of claim 17 , wherein the external electric field of image development is less than the electric field produced by a uniformly-charged toner particle of charge q and radius R T .