Electro-optic displays with reduced remnant voltage

• US 8,558,783 B2
• Filed: 11/24/2004
• Issued: 10/15/2013
• Est. Priority Date: 11/20/2001
• Status: Active Grant

• Current Assignee: E Ink Corporation (E Ink Holdings Incorporated)
• Original Assignee: E Ink Corporation (E Ink Holdings Incorporated)
• Inventors: Wilcox, Russell J., Whitesides, Thomas H., Amundson, Karl R., Danner, Guy M., Webber, Richard M., Cao, Lan, Paolini, Richard J. Jr., Chebiyam, Rajesh, Honeyman, Charles H.
• Primary Examiner(s): Wang, Quan-Zhen
• Assistant Examiner(s): Chow, Yuk
• Application Number:
  US10/904,707
• Publication Number:
  US 20050179642A1
• Time in Patent Office: 3,247 Days
• Field of Search: 345/55, 345/84, 345/87, 345/107
• US Class Current: 345/107
• CPC Class Codes: G02B 26/00 Optical devices or arrangements for the control of light using movable or deformable optical elements control of light by modification of the optical properties of the media of the elements involved therein G02F1/00
• CPC Class Codes: G02B 26/026 based on the rotation of particles under the influence of an external field, e.g. gyricons, twisting ball displays based on orientable dipolar particles G02F1/172; based on electrophoresis G02F1/167
• CPC Class Codes: G02F 1/0018 Electro-optical materials
• CPC Class Codes: G02F 1/13306 Circuit arrangements or driving methods for the control of single liquid crystal cells G02F1/132, G02F1/133382 take precedence
• CPC Class Codes: G02F 1/167 by electrophoresis
• CPC Class Codes: G02F 2001/1678 characterised by the composition or particle type
• CPC Class Codes: G09G 2320/0257 Reduction of after-image effects
• CPC Class Codes: G09G 2340/16 Determination of a pixel data signal depending on the signal applied in the previous frame
• CPC Class Codes: G09G 3/34 by control of light from an independent source
• 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 3/36 using liquid crystals
• CPC Class Codes: G09G 3/3629 using liquid crystals having memory effects, e.g. ferroelectric liquid crystals

Abstract

The invention provides materials and methods (including driving methods) for reducing the effects of remnant voltages in electro-optic displays.

Claims

1. A method of driving a bistable electro-optic display having a plurality of pixels each of which is capable of displaying at least two gray levels, the method comprising applying to each pixel of the display a waveform determined by the initial and the final gray level of the pixel, wherein, for at least one transition from a specific initial gray level to a specific final gray level, a first waveform is used if the pixel has been in its initial gray level for less than a predetermined interval, and a second waveform, different from the first waveform, is used if the pixel has been in its initial gray level for more than the predetermined interval.

2. A method according to claim 1 wherein, for said at least one transition, first, second and third waveforms, all different from each other, are used, the first waveform being used if the pixel has been in its initial gray level for less than a first predetermined interval, the second waveform being used if the pixel has been in its initial gray level for more than the first predetermined interval but less than a second predetermined interval, and the third waveform being used if the pixel has been in its initial gray level for more than the second predetermined interval.

3. A method according to claim 2 wherein the first predetermined interval is in the range of from about 0.3 to about 3 seconds, and the second predetermined interval is in the range of from about 1.5 to about 15 seconds.

4. A method according to claim 1 comprising:

storing a look-up table containing data representing, for each possible transition between gray levels of a pixel, the one or more waveforms to be used for that transition;

storing initial state data representing at least an initial state of each pixel;

storing dwell time data representing the period for which each pixel has remained in its initial state;

receiving an input signal representing a desired final state of at least one pixel of the display; and

generating an output signal representing the waveform necessary to convert the initial state of said one pixel to the desired final state thereof, as determined from the look-up table, the output signal being dependent upon the initial state data, the dwell time date and the input signal.

5. A method according to claim 4 further comprising storing data representing at least one prior state of each pixel prior to said initial state thereof, and wherein said output signal is generated dependent upon both said at least one prior state and said initial state of said one pixel.

6. A method according to claim 4 further comprising receiving a temperature signal representing the temperature of at least one pixel of the display and generating said output signal dependent upon said temperature signal.

7. A method according to claim 4 further comprising generating a lifetime signal representing the operating time of said pixel and generating said output signal dependent upon said lifetime signal.

8. A device controller for controlling a bistable electro-optic display having a plurality of pixels, each of which is capable of displaying at least two gray levels, the controller comprising:

storage means arranged to store look-up table data representing, for each possible transition between gray levels of a pixel, one or more waveforms to be used for that transition, at least one transition having at least two different waveforms associated therewith, the storage means also being arranged to store initial state data representing at least an initial state of each pixel and dwell time data representing the period for which each pixel has remained in its initial state;

input means for receiving an input signal representing a desired final state of at least one pixel of the display;

calculation means for determining, from the input signal, the initial state data, the dwell time data and the look-up table, the waveform required to change the initial state of said one pixel to the desired final state; and

output means for generating an output signal representative of said waveform.

9. A controller according to claim 8 wherein the storage means is also arranged to store prior state data representing at least one prior state of each pixel prior to the initial state thereof, and the calculation means is arranged to determine said waveform dependent upon the input signal, the initial state date, the dwell time data, the prior state data and the look-up table.

10. A controller according to claim 8 wherein the input means is arranged to receive a temperature signal representing the temperature of at least one pixel of the display, and the calculation means is arranged to determine said waveform dependent upon the input signal, the initial state data, the dwell time data and the temperature signal.

11. A controller according to claim 8 further comprising lifetime signal generation means arranged to generate a lifetime signal representing the operating time of said pixel, the calculation means determining said waveform from the input signal, the initial state data, the dwell time data and the lifetime signal.

12. A method of driving a bistable electro-optic display having a plurality of pixels each of which is capable of displaying at least two gray levels, the method comprising applying to each pixel of the display a waveform determined by the initial and the final gray level of the pixel, wherein, for at least one transition from a specific initial gray level to a specific final gray level, at least first and second waveforms differing from each other are available, and the remnant voltage of a pixel undergoing said transition is determined prior to said transition, and the first or second waveform is used for said transition depending upon the determined remnant voltage.