Electrophoretic display with reduction of remnant voltages by selection of characteristics of inter-picture potential differences

• US 20070262949A1
• Filed: 06/25/2004
• Published: 11/15/2007
• Est. Priority Date: 07/03/2003
• Status: Abandoned Application

• Current Assignee: Adrea LLC (Warner Bros. Discovery, Inc.)
• Original Assignee: Adrea LLC (Warner Bros. Discovery, Inc.)
• Inventors: Johnson, Mark, Zhou, Guofu
• Application Number:
  US10/562,542
• Publication Number:
  US 20070262949A1
• Time in Patent Office: Days
• US Class Current: 345/107
• CPC Class Codes: G09G 2310/06 Details of flat display driving waveforms
• CPC Class Codes: G09G 2310/061 for resetting or blanking
• CPC Class Codes: G09G 2320/0204 Compensation of DC component across the pixels in flat panels
• 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

An electrophoretic display panel (1), comprising a plurality of picture elements (2), an electrophoretic medium (5) having charged particles (6), and first and second electrodes (3,4) associated with each picture element (2) for receiving a potential difference. As the display (1) is addressed, for each picture element (2), the product of voltage and duration of picture voltages is read from a controller (102). After one or more image update periods, there will be a history generated of the total energy seen by each picture element (2). DC balancing is achieved by introducing feedback loop into the controller (102) which attempts to reduce the number stored in the memory (104) to zero, for each picture element (2) by applying one or more high voltage short pulses with a polarity opposite to the number stored in the memory (104).

Claims

1. A display apparatus (1) comprising:

an electrophoretic medium (5) comprising charged particles (6) in a fluid;

a plurality of picture elements (2);

a first and second electrode (8,9) associated with each picture element (2) for receiving a potential difference; and

drive means (100) arranged to;

a) supply a sequence of picture potential differences to each of said picture elements (2), each of said picture potential differences having a picture value and an associated picture duration, the product of which represents a picture energy for enabling the particles to occupy one of the positions for displaying a picture; and

b) supply one or more inter-picture potential differences between at least two consecutive picture potential differences, said one or more inter-picture potential differences having an inter-picture value and an associated inter-picture duration, the product of which represents an inter-picture energy which is insufficient to substantially change the positions of the particles;

the apparatus (1) further comprising memory means (104) for receiving data representative of the picture energy and inter-picture energy of all potential differences applied to each picture element (2), and providing a running total thereof for each picture element (2), the drive means (100) being arranged to select the polarity of said one or more inter-picture potential differences such that the magnitude of said running total for a respective picture element (2) is reduced.

2. Apparatus (1) according to claim 1, wherein a time interval is provided between each inter-picture potential difference applied to a picture element (2).

3. Apparatus (1) according to claim 2, wherein said time interval is of the order of 0.5.

4. Apparatus (1) according to any one of the preceding claims, wherein the pulse time-period of each inter-picture potential difference is 2-8 ms.

5. Apparatus (1) according to any one of the preceding claims, wherein the value of said inter-picture potential differences is substantially the maximum voltage available on the drive means (100).

6. Apparatus (1) according to any one of the preceding claims, wherein one or more of said inter-picture potential differences have an inter-picture value below the threshold voltage of the ink materials used in said display apparatus.

7. Apparatus (1) according to any one of the preceding claims, wherein the number and polarity of said inter-picture potential differences are stored in the memory means (104).