Layered structure with high dielectric constant for use with active matrix backplanes
Layered dielectric materials for use in controlling dielectric strength in microelectronic devices, especially as they relate to electrophoretic and electrowetting applications. Specifically, a combination of a first atomic layer deposition (ALD) step, a sputtering step, and a second ALD step result in a layer that is chemically robust and nearly pinhole free. The dielectric layer may be disposed on the transparent common electrode of an electrophoretic display or covering the pixelated backplane electrodes, or both.
1. An electrophoretic display including:
an electrophoretic medium comprising a non-polar fluid and a first set of light-scattering charged pigment particles and two additional sets of charged pigment particles dispersed in the non-polar fluid and movable through the non-polar fluid under influence of an electric field, said two additional sets of charged pigment particles having different optical characteristics from each other and from the first set of light-scattering charged pigment particles;
a light-transmissive electrode on one side of the electrophoretic medium;
a rear electrode on an opposite side of the electrophoretic medium; and
a dielectric layer having a dielectric constant greater than 5 between the electrophoretic medium and the light-transmissive electrode or between the electrophoretic medium and the rear electrode configured to reduce electrode electrochemical degradation and buildup of remnant voltages in the display.
2. The electrophoretic display of claim 1 , wherein the dielectric layer is between 10 nm thick and 100 nm thick.
3. The electrophoretic display of claim 1 , wherein the dielectric layer is between 25 nm thick and 75 nm thick.
4. The electrophoretic display of claim 1 , wherein the dielectric layer comprises aluminum oxide, hafnium oxide, tantalum oxide, or silicon nitride.
5. The electrophoretic display of claim 1 , wherein the electrophoretic medium further includes an additional set of charged pigment particles.
6. A method of driving an electrophoretic display with a DC-unbalanced waveform, comprising:
providing an electrophoretic display including:
an electrophoretic medium;
a light-transmissive electrode on one side of the electrophoretic medium;
a rear electrode on an opposite side of the electrophoretic medium; and
a dielectric layer having a dielectric constant greater than 5 between the electrophoretic medium and the light-transmissive electrode or between the electrophoretic medium and the rear electrode configured to reduce electrode electrochemical degradation and buildup of remnant voltages in the display;
providing a voltage source; and
driving the electrophoretic layer with a DC-unbalanced waveform generated by the voltage source that includes both a driving portion and a grounding portion.
7. The method of claim 6 , wherein the driving portion is done during a first period, the grounding portion is done during a second period, and the second period is as long as the first period or longer.
8. The method of claim 6 , wherein the dielectric layer is disposed between the electrophoretic medium and the light-transmissive electrode.
9. The method of claim 6 , wherein the dielectric layer is disposed between the electrophoretic medium and the rear electrode.
10. The method of claim 6 , wherein the dielectric layer is disposed between the electrophoretic medium and the light-transmissive electrode, and another dielectric layer is disposed between the electrophoretic medium and the rear electrode.
11. The method of claim 6 , wherein the electrophoretic medium comprises a non-polar fluid and a first set of light-scattering charged pigment particles and two additional sets of charged pigment particles dispersed in the non-polar fluid and movable through the non-polar fluid under influence of an electric field, said two additional sets of charged pigment particles having different optical characteristics from each other and from the first set of light-scattering charged pigment particles.
12. The electrophoretic display of claim 1 , wherein the dielectric layer is disposed between the electrophoretic medium and the light-transmissive electrode.
13. The electrophoretic display of claim 1 , wherein the dielectric layer is disposed between the electrophoretic medium and the rear electrode.
14. The electrophoretic display of claim 1 , wherein the dielectric layer is disposed between the electrophoretic medium and the light-transmissive electrode, and another dielectric layer is disposed between the electrophoretic medium and the rear electrode.
15. The electrophoretic display of claim 1 , wherein the dielectric layer reduces ion and electron transport to the light-transmissive electrode or the rear electrode to reduce electrode electrochemical degradation.
16. The electrophoretic display of claim 1 , wherein the dielectric layer functions as a capacitive element to reduce buildup of remnant voltages in the display.
17. An electrophoretic display including:
an electrophoretic medium comprising a non-polar fluid and a first set of light-scattering charged pigment particles and two additional sets of charged pigment particles dispersed in the non-polar fluid and movable through the non-polar fluid under influence of an electric field, said two additional sets of charged pigment particles having different optical characteristics from each other and from the first set of light-scattering charged pigment particles;
a light-transmissive electrode on one side of the electrophoretic medium;
a rear electrode on an opposite side of the electrophoretic medium; and
a dielectric layer between the electrophoretic medium and the light-transmissive electrode and another dielectric layer between the electrophoretic medium and the rear electrode configured to reduce electrode electrochemical degradation and buildup of remnant voltages in the display.
18. The electrophoretic display of claim 17 , wherein the dielectric layers are between 10 nm thick and 100 nm thick.
19. The electrophoretic display of claim 17 , wherein the dielectric layers are between 25 nm thick and 75 nm thick.
20. The electrophoretic display of claim 17 , wherein the dielectric layers comprise aluminum oxide, hafnium oxide, tantalum oxide, or silicon nitride.
21. The electrophoretic display of claim 17 , wherein the electrophoretic medium further includes an additional set of charged pigment particles.
22. The electrophoretic display of claim 17 , wherein the dielectric layers reduce ion and electron transport to the light-transmissive electrode and the rear electrode to reduce electrode electrochemical degradation.
23. The electrophoretic display of claim 17 , wherein the dielectric layers function as a capacitive elements to reduce buildup of remnant voltages in the display.
24. A method of driving an electrophoretic display with a DC-unbalanced waveform, comprising:
providing an electrophoretic display including:
an electrophoretic medium;
a light-transmissive electrode on one side of the electrophoretic medium;
a rear electrode on an opposite side of the electrophoretic medium; and
a dielectric layer between the electrophoretic medium and the light-transmissive electrode and another dielectric layer between the electrophoretic medium and the rear electrode configured to reduce electrode electrochemical degradation and buildup of remnant voltages in the display;
providing a voltage source; and
driving the electrophoretic layer with a DC-unbalanced waveform generated by the voltage source that includes both a driving portion and a grounding portion.
25. The method of claim 24 , wherein the driving portion is done during a first period, the grounding portion is done during a second period, and the second period is as long as the first period or longer.
26. The method of claim 24 , wherein the electrophoretic medium comprises a non-polar fluid and a first set of light-scattering charged pigment particles and two additional sets of charged pigment particles dispersed in the non-polar fluid and movable through the non-polar fluid under influence of an electric field, said two additional sets of charged pigment particles having different optical characteristics from each other and from the first set of light-scattering charged pigment particles.