Electrowetting display device and driving method thereof

• US 9,494,788 B2
• Filed: 07/27/2012
• Issued: 11/15/2016
• Est. Priority Date: 02/17/2012
• Status: Expired due to Fees

• Current Assignee: Amazon Technologies, Inc. (Amazon.com, Inc.)
• Original Assignee: Amazon Technologies, Inc. (Amazon.com, Inc.)
• Inventors: Hua, Chang Ku, Lee, So-Hyun, Shin, Sang Min, Kim, Woo Song, Choi, Uk Chul, Park, Mun-Soo
• Primary Examiner(s): Kumar, Srilakshmi K
• Assistant Examiner(s): Reed, Stephen T
• Application Number:
  US13/560,861
• Publication Number:
  US 20130215095A1
• Time in Patent Office: 1,572 Days
• Field of Search: None
• US Class Current: 1/1
• CPC Class Codes: G02B 26/005 based on electrowetting
• CPC Class Codes: G06F 3/038 Control and interface arrangements therefor, e.g. drivers or device-embedded control circuitry
• CPC Class Codes: G09G 2300/08 Active matrix structure, i.e. with use of active elements, inclusive of non-linear two terminal elements, in the pixels together with light emitting or modulating elements
• CPC Class Codes: G09G 3/348 based on the deformation of a fluid drop, e.g. electrowetting

Abstract

A display device includes a first electrode, a second electrode, a third electrode, a lyophobic layer, a first liquid, and a second liquid, where the lyophobic layer is lyophobic to the second liquid. A method of driving the display device includes: providing a first potential difference between the first electrode and the third electrode to thereby cause the first liquid to begin moving toward the second electrode; providing a second potential difference between the second electrode and the third electrode while reducing the first potential difference to thereby cause the first liquid to move toward the first electrode; and removing the second potential difference to thereby cause the first liquid to slow down in its movement toward the first electrode or to stop in its movement toward the first electrode.

Claims

1. A method of driving a display device, where the display device comprises a first electrode having a respective first surface disposed in a first area, a second electrode having a respective second surface disposed in a second area, the second electrode being spaced apart from the first electrode, a lyophobic layer provided over the respective first and second surfaces of the first and second electrodes, a first partition wall on the lyophobic layer and a second partition wall on the lyophobic layer, a third electrode spaced apart from above, and facing the lyophobic layer, the method comprising:

providing a first body of a first liquid as a first layer having a first thickness on the lyophobic layer, wherein the first layer extends from the first partition wall to the second partition wall;

providing a second body of a second liquid as a second layer between the first layer and the third electrode, wherein the second layer extends from the first partition wall to the second partition wall, the second body of the second liquid being immiscible with the first body of the first liquid and the lyophobic layer being lyophobic with respect to the second liquid; and

providing a first potential difference between the first electrode and the third electrode, causing the first liquid to coalesce over the second electrode in the second area, wherein the first liquid coalesces to have a second thickness that is greater than the first thickness;

while reducing the first potential difference, providing a potential difference waveform between the second electrode and the third electrode, wherein the potential difference waveform includes two or more pulses, causing at least part of the first liquid to start spreading movement towards the first area; and

at least partly after reducing the first potential difference, ceasing to provide the potential difference waveform, causing the at least part of the first liquid to slow down in the spreading movement toward the first area or to stop the spreading movement toward the first area.

2. The method of claim 1, wherein the first liquid entirely covers the second area.

3. The method of claim 1, wherein the providing of the potential difference waveform comprises:

applying a substantially constant voltage signal to the third electrode.

4. The method of claim 1, wherein there is substantially no potential difference between the second electrode and the third electrode during the providing of the first potential difference.

5. The method of claim 4, wherein:

a first voltage signal applied to the first electrode has a first value in the providing of the first potential difference and has a second value different from the first value in the providing of the potential difference waveform;

a second voltage signal applied to the second electrode has a third value different from the first value and the second value in the providing of the first potential difference,

the second voltage signal applied to the second electrode either (i) has a fourth value or (ii) swings between the fourth value and the first value in the providing of the potential difference waveform; and

a second voltage signal applied to the third electrode maintains the third value during the providing of the first voltage difference, and during the providing of the potential difference waveform.

6. The method of claim 1, wherein the first liquid is disposed in a first state when there is substantially no potential difference between the first electrode, the second electrode and the third electrode, and wherein the first liquid is disposed in a second state when the first potential difference is provided.

7. The method of claim 5, wherein the first value has a polarity different from a polarity of the second value.

8. The method of claim 1, wherein the first liquid forms as a coalesced single body of the first liquid during the providing of the potential difference waveform.

9. A method of driving a display device, where the display device has a first electrode, a second electrode spaced apart from the first electrode, a lyophobic layer disposed on the first and second electrodes, a third electrode spaced apart from and facing the lyophobic layer, a first liquid (i) disposed in a space between the lyophobic layer and the third electrode and (ii) having a first thickness, and a second liquid disposed in the space, the second liquid being immiscible with the first liquid, the lyophobic layer being lyophobic relative to the second liquid, the method comprising:

providing a potential difference between the first electrode and the third electrode to move the first liquid to be over the second electrode such that the first liquid has a second thickness greater than the first thickness, and to display a first grayscale level; and

while reducing the potential difference, providing a potential difference waveform between the second electrode and the third electrode, wherein the potential difference waveform includes two or more pulses, and to thereby transition from displaying the first grayscale level to displaying a target grayscale level different from the first grayscale level;

after reducing the potential difference, ceasing to provide the potential difference waveform before completing the transition; and

at least partly in response to ceasing to provide the potential difference waveform before completing the transition, causing the target grayscale level to be displayed.

10. The method of claim 9, wherein the first liquid covers an entire area of the second electrode.

11. The method of claim 9, wherein the providing of the potential difference waveform comprises:

applying a substantially constant voltage to the third electrode.

12. The method of claim 9, wherein there is substantially no potential difference between the second electrode and the third electrode during the providing of the potential difference.

13. A method of driving a display device including a first electrode, a second electrode spaced apart from the first electrode, a lyophobic layer on the first and second electrodes, a first partition wall on the lyophobic layer and a second partition wall on the lyophobic layer, and a third electrode facing the lyophobic layer, the method comprising:

providing a first body of a first liquid as a first layer having a first thickness on the lyophobic layer, wherein the first layer extends from the first partition wall to the second partition wall;

providing a second body of a second liquid as a second layer between the first layer and the third electrode, wherein the second layer extends from the first partition wall to the second partition wall, the second body of the second liquid being immiscible with the first body of the first liquid and the lyophobic layer being lyophobic with respect to the second liquid;

providing an electric field that is stronger in a first region between the first electrode and the third electrode than in a second region between the second electrode and the third electrode to thereby cause the first liquid to coalesce over the second electrode in the second region while the second liquid is caused to move into the first region, wherein the first liquid coalesces to have a second thickness that is greater than the first thickness;

providing an electric field in the second region that is stronger than a field, if any, present in the first region to thereby cause a movement of the first liquid toward the first region; and

providing a pulsed electric field weaker in the second region than in the first region before the movement of the first liquid toward the first region stops, thereby slowing down or stopping the movement of the first liquid toward the first region.

14. The method of claim 13, wherein the first liquid is a nonpolar liquid including a nonpolar dye.

15. A method of driving a display device including a first electrode, a second electrode spaced apart from the first electrode, a lyophobic layer on the first and second electrodes, a third electrode facing the lyophobic layer, a first liquid (i) in a space between the lyophobic layer and the third electrode and (ii) having a first thickness, and a second liquid in the space, the second liquid being immiscible with the first liquid, the lyophobic layer being lyophobic to the second liquid, the method comprising:

providing a potential difference between the first electrode and the third electrode to move the first liquid over the second electrode such that the first liquid has a second thickness greater than the first thickness, and to display a first grayscale level; and

while reducing the potential difference, providing a potential difference waveform between the second electrode and the third electrode during a duration, wherein the potential difference waveform includes two or more pulses that are applied during the duration; and

after reducing the potential difference, ceasing to provide the potential difference waveform to thereby display a target grayscale level different from the first grayscale level,

wherein a time span for reducing the potential difference is shorter than a time span for the transition from the first grayscale level to the target grayscale level.

16. The method of claim 15, wherein the number of voltage pulses included in the potential difference waveform that are applied during the duration is in a range from two to five.