Electrophoretic display and driving method thereof

• US 8,179,387 B2
• Filed: 05/30/2007
• Issued: 05/15/2012
• Est. Priority Date: 12/13/2006
• Status: Active Grant

• Current Assignee: E Ink Holdings Incorporated
• Original Assignee: LG Display Co., Ltd.
• Inventors: Shin, Sung Woo, Yang, Hui Eun
• Primary Examiner(s): Beck, Alexander S
• Assistant Examiner(s): Hicks, Charles V
• Application Number:
  US11/806,209
• Publication Number:
  US 20080143700A1
• Time in Patent Office: 1,812 Days
• Field of Search: 345/107, 345208-210, 345214-215
• US Class Current: 345/208
• 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 2310/068 Application of pulses of alternating polarity prior to the drive pulse in electrophoretic displays
• 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

Abstract

A method of driving at least one cell of an electrophoretic display panel through a pixel electrode and a common electrode includes storing at least first data representative of an image currently displayed and second data representative of an image to be displayed; and applying a first AC data waveform and a first AC common waveform for initializing the at least one cell during a first number of frames, applying a second AC data waveform and a second AC common waveform for displaying the second data during a second number of frames, wherein the first number of frames depends on the first data and the second number of frames depends on the second data.

Claims

1. A display device, comprising:

an electrophoretic display panel including at least one cell with a micro capsule to display an image;

a data driver converting a digital data corresponding to the image into a data voltage;

a common voltage generator generating a AC common voltage which swings between a high potential common voltage and a low potential common voltage in response to a control data; and

a controller supplying the digital data to the data driver and comparing an entire image of an entire current frame with an entire image of an entire next frame to generate a digital video data which controls a drive waveform of the data voltage in accordance with the comparison result and the control data which controls a drive waveform of the AC common voltage for updating of the digital data in accordance with the comparison result,

wherein the AC common voltage is changed in accordance with the frame and in accordance with the gray level of the current frame image and the next frame image,

wherein the drive waveform of the data voltage includes a reset voltage waveform which is generated for a reset period inclusive of a plurality of frame periods to initialize the micro capsule, a first stabilization voltage waveform for separating electrically charged particles within the micro capsule for a first stabilization period inclusive of a plurality of frame periods, following the reset period, a second stabilization voltage waveform for separating the electrically charged particles within the micro capsule in a direction opposite to the first stabilization period for a second stabilization period inclusive of a plurality of frame periods, following the first stabilization period and an entry data voltage waveform for expressing a gray level in the cell for a data writing period inclusive of a plurality of frame periods, following the second stabilization period,

wherein the AC common voltage is inverted after being maintained to a low potential common voltage for the reset period, is inverted again after being maintained to a high potential common voltage for the first stabilization period, and then is maintained to the low potential common voltage for the second stabilization period,

wherein the AC common voltage is inverted between the second stabilization period and the data writing period, and maintained to the high potential common voltage for the data writing period,

wherein the reset voltage waveform supplies a white display voltage to a pixel electrode of all the cells for the frame periods which are included in the reset period in accordance with a state of the current frame image to primarily initialize a particle arrangement within the micro capsule,

wherein the first and second stabilization voltage waveforms alternately supply a white display voltage and a black display voltage for the first and second stabilization periods to separate the positively charged white particle and the negatively charged black particle within the micro capsule to the bistable state, and

wherein the first and second stabilization periods are the same, regardless of the gray level difference between the current frame image and the next frame image.

2. The display device of claim 1, wherein the controller includes:

a first frame memory to store the image of the current frame, a second frame memory to store the image of the next frame;

a lookup table to generate the digital video data and the control data in accordance with the comparison result;

a frame counter to count the number of frames; and

a data memory to store the digital data corresponding to the digital video data outputted from the lookup table.

3. The display device of claim 2, wherein the lookup table has a plurality of lookup tables which register information on the drive waveform of the AC common voltage and the drive waveform of the data voltage supplied to each cell for a plurality of frame periods in accordance with the image of the current frame and the image of the next frame for each frame.

4. The display device of claim 3, wherein the lookup table compares the image of the current frame with the image of the next frame by the unit of the cell for each fixed frames of which a number is indicated in accordance with the frame number information from the frame counter and selects the digital video data of 1 bit for each cell in accordance with the comparison result.

5. The display device of claim 4, wherein the digital video data selected by the lookup table includes a reset data for initializing the state of the current cell, a stabilization data for stabilizing a bistable state within the cell, and an entry data for expressing a gray scale.

6. The display device of claim 4, wherein the lookup table selects the control data of 1 bit indicating the drive waveform of the pre-set AC common voltage.

7. The display device of claim 1, wherein the digital video data is converted into the data voltage changed into any one of 2 number voltage levels by the data driver.

8. The display device of claim 1, wherein the control data is converted into the AC common voltage changed into any one of 2 number voltage levels by the common voltage generator.

9. A method of driving at least one cell of an electrophoretic display panel having a plurality of cells with a micro capsule driven in accordance with a data voltage and an AC common voltage applied to a pixel electrode and a common electrode respectively, the method comprising:

storing a first data corresponding to an entire image of an entire current frame and a second data corresponding to an entire image of an entire next frame;

comparing the first data with the second data by the unit of the cell using a lookup table;

outputting a control data which controls a drive waveform of the AC common voltage for updating of a digital data corresponding to an image displayed at the electrophoretic display panel in accordance with the comparison result and a digital video data of 1 bit which controls a drive waveform of a data voltage corresponding to the digital data in accordance with the comparison result;

generating the AC common voltage which swings between a high potential common voltage and a low potential common voltage in response to the control data; and

converting a digital data into the data voltage in response to the digital video data and supplying the data voltage to the pixel electrode,

wherein the AC common voltage is changed in accordance with the frame and in accordance with the gray level of the current frame image and the next frame image,

wherein the drive waveform of the data voltage includes a reset voltage waveform which is generated for a reset period inclusive of a plurality of frame periods to initialize the micro capsule, a first stabilization voltage waveform for separating electrically charged particles within the micro capsule for a first stabilization period inclusive of a plurality of frame periods, following the reset period, a second stabilization voltage waveform for separating the electrically charged particles within the micro capsule in a direction opposite to the first stabilization period for a second stabilization period inclusive of a plurality of frame periods, following the first stabilization period and an entry data voltage waveform for expressing a gray level in the cell for a data writing period inclusive of a plurality of frame periods, following the second stabilization period,

wherein the AC common voltage is inverted after being maintained to a low potential common voltage for the reset period, is inverted again after being maintained to a high potential common voltage for the first stabilization period, and then is maintained to the low potential common voltage for the second stabilization period,

wherein the AC common voltage is inverted between the second stabilization period and the data writing period, and maintained to the high potential common voltage for the data writing period,

wherein the reset voltage waveform supplies a white display voltage to a pixel electrode of all the cells for the frame periods which are included in the reset period in accordance with a state of the current frame image to primarily initialize a particle arrangement within the micro capsule,

wherein the first and second stabilization voltage waveforms alternately supply a white display voltage and a black display voltage for the first and second stabilization periods to separate the positively charged white particle and the negatively charged black particle within the micro capsule to the bistable state, and

wherein the first and second stabilization periods are the same, regardless of the gray level difference between the current frame image and the next frame image.

10. The method of claim 9, wherein the digital video data outputted by the lookup table includes:

a reset data for initializing the state of the current cell;

a stabilization data for stabilizing a bistable state within the cell; and

an entry data for expressing a gray scale.

11. The method of claim 9, wherein the digital video data is converted into the data voltage changed into any one of 2 number voltage levels.

12. The method of claim 9, wherein the control data is converted into the AC common voltage changed into any one of 2 number voltage levels