Display apparatus

• US 8,730,154 B2
• Filed: 08/06/2012
• Issued: 05/20/2014
• Est. Priority Date: 08/04/2011
• Status: Active Grant

• Current Assignee: Gamma Dynamics LLC
• Original Assignee: Gamma Dynamics LLC
• Inventors: Dean, Kenneth A., Heikenfeld, Jason C.
• Primary Examiner(s): Zhou, Hong
• Application Number:
  US13/567,976
• Publication Number:
  US 20130033476A1
• Time in Patent Office: 652 Days
• Field of Search: 345 48- 50, 345/87, 345/105, 345/107, 345/204, 345/690, 345208-211, 359/290, 359/296, 359/665
• US Class Current: 345/107
• CPC Class Codes: G09G 2300/0456 with a reflective area and a transmissive area combined in one pixel, such as in transflectance pixels
• CPC Class Codes: G09G 2300/0469 Details of the physics of pixel operation
• CPC Class Codes: G09G 2300/0866 by means of changes in the pixel supply voltage
• CPC Class Codes: G09G 2320/0252 Improving the response speed
• CPC Class Codes: G09G 3/344 based on particles moving in a fluid or in a gas, e.g. electrophoretic devices electrophoretic devices per se G02F1/167
• CPC Class Codes: G09G 3/3446 with more than two electrodes controlling the modulating element

Abstract

A device, an electrode configuration and a sequence for activating those electrodes for the purpose of switching device states quickly with minimum flicker during bi-stable image reset. The disclosure addresses the constraints of electrofluidic technology: 1) the polar fluid can be attracted to a position with voltage, but it cannot be repelled, and 2) because the polar fluid translates, changing its area against an electrode and thereby changing the capacitance, the time to discharge the capacitor formed by area contact with a polar fluid is significantly smaller than the time to charge a capacitor, which requires translation of the fluid. Setting the grayscale is based on discharging, not charging, when possible. In addition, the use of pixel-level partial reset states reduces the appearance of flicker further by minimizing the change in pixel state during data write/update.

Claims

1. A display apparatus comprising:

a plurality of electrofluidic display elements, each element including;

a volume of a polar fluid,

a volume of a non-polar fluid,

a first substrate,

a second substrate,

a conductive film between the first and second substrates that is porous to both the polar fluid and the non-polar fluid, the conductive film arranged relative to the first substrate to define a first channel and a second channel,

a first electrode layered with a first dielectric layer, arranged between the conductive film and the first substrate, the first electrode configured to receive a voltage and cause the polar fluid to occupy the first channel,

a second electrode including a second dielectric layer, the second electrode arranged between the conductive film and the second substrate, the second electrode configured to receive a voltage and cause the polar fluid to occupy the second channel,

a first capacitor comprising the first electrode, the first dielectric layer, and the conductive film, and

a second capacitor comprising the second electrode, the second dielectric layer, and the conductive film; and

,

driving circuitry including a plurality of switching circuits in electrical communication with the plurality of electrofluidic display elements, where the plurality of switching circuits are configured to supply a switched voltage to the first capacitor and the second capacitor for each of the plurality of electrofluidic display elements, and where a difference in capacitor voltages is configured to change a coverage area of the polar fluid occupying the first channel.

2. The display apparatus of claim 1, wherein the difference in capacitor voltages is maintained for a fixed time by the driving circuitry to facilitate change in the coverage area of the polar fluid occupying the first channel.

3. The display apparatus of claim 1, wherein a degree of initial difference in capacitor voltages set by the driving circuitry controls an amount of change to the coverage area of the polar fluid occupying the first channel.

4. The display apparatus of claim 1, wherein a charge balance between the first capacitor and the second capacitor controls the coverage area of the polar fluid occupying the first channel.

5. The display apparatus of claim 1, wherein the driving circuitry changes polarity of the voltage bias on the first and second capacitors regularly.

6. The display apparatus of claim 1, wherein a display frame rendered on the plurality of electrofluidic display elements includes an update rate faster than 300 milliseconds.

7. The display apparatus of claim 1, wherein the polar fluid has a stable position in an absence of applied voltage into at least one of the first channel and the second channel.

8. The display apparatus of claim 1, wherein the plurality of electrofluidic display elements are arranged in a matrix of rows and columns, with the second capacitor connected to an output of a thin film transistor.

9. The display apparatus of claim 1, wherein each of the plurality of electrofluidic display elements is configured to be in electrical communication with a storage capacitor.

10. The display apparatus of claim 1, wherein the first capacitor and the second capacitor are configured to have no voltage difference therebetween during a passive matrix drive where non-select lines are biased.

11. The display apparatus of claim 1, wherein a steady state condition for the polar fluid occurs when the voltage on the first capacitor is equivalent to the voltage on the second capacitor.

12. The display apparatus of claim 1, wherein the driving circuitry further includes:

a first subframe comprising a high logic state and an accompanying voltage signal to a viewer side electrode and a polar connection electrode, and a selectable first subframe logic state and a selectable accompanying voltage to a backside electrode of each of the plurality of electrofluidic display elements in a display channel to be updated, thereby providing a condition to have the polar fluid occupy a backside channel; and

,

a second subframe comprising a low logic state and an accompanying voltage for the viewer side electrode, a high logic state and an accompanying voltage for the polar connection electrode, and a selectable second subframe logic state and a selectable accompanying voltage to the backside electrode of each of the plurality of electrofluidic display elements in the display channel to be updated, provided by scanning row electrodes to turn a row of transistors to an on state while sending each pixel on the row of transistors a selectable voltage signal through column electrodes, thereby providing a condition to have the polar fluid occupy a viewer side channel.

13. The display apparatus of claim 12, wherein the selectable first subframe logic state is common to each of the plurality of electrofluidic display elements during a frame.

14. The display apparatus of claim 12, wherein the selectable first subframe logic state is individually selected for each of the plurality of electrofluidic display elements by scanning the row of transistors during a frame.

15. The display apparatus of claim 12, wherein scanning the row electrodes to the on state while sending each pixel on the row a selectable voltage signal through the column electrodes includes providing an appropriate charge to at least one of the plurality of electrofluidic display elements to create a display state, and moving to a next scanned row prior to completion of a movement of the polar fluid to an equilibrium condition.

16. The display apparatus of claim 12, wherein the channel of the display to be updated is the entire display.

17. The display apparatus of claim 12, wherein a time to set a pixel charge state in the second subframe is less than 5 milliseconds, and more preferably less than 0.5 milliseconds.

18. The display apparatus of claim 12, wherein a polarity of logic signals and electrode voltages are alternated between display update frames.

19. The display apparatus of claim 12, wherein the channel of the display to be updated is a fraction of the display and wherein the said driving electronics provide a first subframe comprising a low logic state and accompanying voltage signal to the viewer side electrode and the polar connection electrode, and a selectable voltage logic state and accompanying voltage to all the display elements in the display channel to be updated, thereby providing a condition to move polar fluid into the backside channel, and a second subframe comprising a low logic state and accompanying voltage for the viewer side electrode, a high logic state and accompanying voltage for the polar connection electrode, and display element variable logic state to the backside electrode provided by scanning the row electrode to turn the row of transistors to the on state while sending each pixel on the row a selectable voltage signal through the column electrodes, thereby providing a condition to move polar fluid into the viewer side channel.

20. The display apparatus of claim 12, wherein reset states are included in the display apparatus, and the driving circuitry switches the polar fluid to a nearest reset state to a desired optical performance rather than a complete switching of the pixel.

21. A display apparatus, the apparatus comprising:

a plurality of electrofluidic display elements, each element including;

a volume of a polar fluid,

a volume of a non-polar fluid,

a first substrate,

a second substrate,

a conductive film between the first substrate and the second substrate that is porous to both the polar fluid and the non-polar fluid, the conductive film arranged relative to the first substrate to define a first channel occupied by at least one of the polar fluid and the non-polar fluid,

a first electrode layered with a first dielectric layer, arranged between the conductive film and the first substrate, the first electrode configured to receive a voltage and cause the polar fluid to occupy the first channel, the conductive film arranged relative to the second substrate to define a second channel occupied by at least one of the polar fluid and the non-polar fluid,

a second electrode layered with a second dielectric layer, arranged between the conductive film and the second substrate, the second electrode configured to receive a voltage and cause the polar fluid to occupy the second channel,

a first capacitor comprising the first electrode, the first dielectric layer, and the conductive film,

a second capacitor comprising the second electrode, the second dielectric layer, and the conductive film,

a first spacer interposing the first electrode and the conductive film,

a second spacer interposing the second electrode and the conductive film,

wherein at least one of the first spacer and the second spacer is translucent and aligned with a translucent region of the conductive film; and

,

driving circuitry including a plurality of switching circuits in electrical communication with the first electrode, the second electrode, and a counter electrode, the driving circuitry configured to supply a switched voltage to the first capacitor and the second capacitor of a display element, where a difference in capacitor voltages changes a coverage area of the polar fluid occupying the first channel, and where the driving circuitry is in electrical communication with a light source located behind the first substrate, and where the switched voltages applied to the first capacitor and the second capacitor reposition the polar fluid within the first channel and the second channel and modify the transmitted light.