Two particle electophoretic systems, electronic displays including two particle electophoretic systems, and methods for producing the two particle electophoretic systems
View Patent ↗An electrophoretic display includes a transparent polymeric film including at least one cavity including a first particle species and a second particle species. Application of an electrical field causes the first particle species and the second particle species to separate from one another, and align on opposite sides of the cavity. Subsequent electric field applications cause migration of the first and second particle species, affecting a color state of the display. The electrophoretic display may be fabricated from multiple display cells arranged on a substrate.
1. An electrophoretic display comprising:
at least one thin media sheet;
at least one pair of electrodes; and
a source of electrical charge;
wherein said thin media sheet comprises a polymeric material having therein at least one cavity; and
wherein the at least one cavity contains at least a first species of charged particles and a second species of charged particles, and said first species of charged particles has a charge opposite to the charge of said second species of charged particles;
wherein said first species of charged particles comprises a first hardenable material, a first charge additive, and a first colorant; and said second species of charged particles comprises a second hardenable material, a second charge additive, and a second colorant; and
wherein said first hardenable material and said second hardenable material are individually chosen from the group consisting of glass, silicon resins, and mixtures thereof.
2. The electrophoretic display according to claim 1 , wherein said polymeric material is at least one polymer chosen from the group consisting of elastomeric materials.
3. The electrophoretic display according to claim 2 , wherein said polymeric material is a silicone.
4. The electrophoretic display according to claim 1 , wherein said at least one cavity has a shape chosen from the group consisting of spherical shapes, discoid shapes and cylindrical shapes.
5. The electrophoretic display according to claim 1 , wherein said first charge additive is at least one positive charge additive and wherein said second charge additive is at least one negative charge additive.
6. The electrophoretic display according to claim 1 , wherein said first colorant and said second colorant are different and are each chosen from the group consisting of white and black colorants.
7. A process for preparing a thin media sheet for use in an electrophoretic display, comprising:
preparing a first species of charged particles;
preparing a second species of charged particles;
preparing composite particles including a sacrificial material and said first species and said second species of charged particles;
encapsulating at least one of said composite particles in a transparent polymeric material;
forming said transparent polymeric material including said at least one encapsulated composite particle into a film; and
removing said sacrificial material from said film to form at least one cavity in said thin media sheet, said cavity including said first species and said second species of charged particles;
wherein said first and said second species of charged particles have opposite charges and differ from each other in at least one of the physical characteristic of color fluorescence, phosphorescence and retroreflectivity.
8. The process according to claim 7 , wherein said preparing a first species of charged particles and said preparing a first species of charged particles each comprise the steps of
mixing a hardenable material, a charge additive and a colorant; and
forming charged particles.
9. The process according to claim 8 , wherein said hardenable material is chosen from the group consisting of glass, silicon, resins, high-temperature melting waxes, UV curable resins, thermocurable resins, hot-melt resins, and mixtures thereof.
10. The process according to claim 8 , wherein said hardenable material is chosen from the group consisting of linear polyethylene waxes having a molecular weight of about 2000.
11. The process according to claim 7 , wherein said preparing composite particles including a sacrificial material and said first species and said second species of charged particles comprises
melting said sacrificial material;
incorporating said first and said second species of charged particles into said sacrificial material; and
forming said mixture into composite particles.
12. The process according to claim 11 , wherein said composite particles have a shape chosen from spherical shapes, discoid shapes and cylindrical shapes.
13. The process according to claim 11 , wherein said forming said mixture into composite particles comprises forming cylindrically shaped composite particles by extrusion or injection molding.
14. The process according to claim 7 , wherein said removing said sacrificial material comprises diffusing said sacrificial material through said film.
15. The process according to claim 7 , wherein said sacrificial material is chosen from the group consisting of linear polyethylene waxes having a molecular weight of about 400.
16. The process according to claim 7 , wherein said transparent polymeric material is at least one polymer chosen from the group consisting of elastomeric materials.