Methods for driving electro-optic displays

Abstract

Methods are provided for of driving a bistable electro-optic display having at least first and second pixels separated by an inter-pixel gap. In one method, there is applied to the first pixel a drive pulse which drives the pixel to one extreme optical state, and there is applied to the second pixel, which is in this extreme optical state, a reinforcing pulse of the same polarity as the drive pulse. In a second method, a drive pulse applied to the first pixel drives that pixel away from one extreme optical state, and an inverse reinforcing pulse applied to the second pixel is of opposite polarity to the drive pulse. The drive methods reduce edge ghosting or blooming.

Description

REFERENCE TO RELATED APPLICATIONS [0001] This application claims benefit of copending Application Ser. No. 60 / 803,305, filed May 26, 2006, and of copending Application Ser. No. 60 / 804,491, filed Jun. 12, 2006. [0002] This application is a continuation-in-part of copending application Ser. No. 11 / 611,324, filed Dec. 15, 2006 (Publication No. 2007 / 0091418), which is itself a divisional of application Ser. No. 10 / 249,973, filed May 23, 2003 (now U.S. Pat. No. 7,193,625, issued Mar. 20, 2007), which claims benefit of Application Ser. No. 60 / 319,315, filed Jun. 13, 2002 and copending Application Ser. No. 60 / 319,321, filed Jun. 18, 2002. [0003] This application is also related to application Ser. No. 10 / 065,795, filed Nov. 20, 2002 (now U.S. Pat. No. 7,012,600, issued Mar. 14, 2006), which is itself is a continuation-in-part of application Ser. No. 09 / 561,424, filed Apr. 28, 2000 (now U.S. Pat. No. 6,531,997, issued Mar. 11, 2003), which is itself a continuation-in-part of copending appli...

AI Technical Summary

Benefits of technology

[0039] This first method of the present invention (which may hereinafter be referred to as the “reinforcing pulse method”) may be applied to a monochrome display in which each pixel is intended to display only first and second (typically white and black) optical states. In such monochrome displays, when the first pixel is undergoing a transition from its first to its second optical state (say from white to black), while the second pixel is in its second optical state (black) and is to remain in this second optical state, the first pixel is given a pulse of one polarity to effect the desired transition. During this pulse, or shortly thereafter, the second pixel is given a reinforcing pulse of the same polarity as the drive pulse given to the first pixel (i.e., a black-going pulse). Since the second pixel is already black, the reinforcing pulse does not effect a gross change in the black color of the second pixel. However, if the second pixel has been in its black state for some time, so that its color has “drifted” from a true black to a dark gray, the reinforcing pulse serves to drive the second pixel back to a true black, thus avoiding having a dark gray second pixel immediately adjacent a true black first pixel, a situation which is readily apparent to the human eye. The reinforcing pulse also serves to reduce or eliminate edge ghosting in the inter-pixel gap between the first and second pixels.

[0055] The inverse reinforcing pulse method of the present invention is intended to reduce to eliminate the problems caused by excessive blooming as described above. In the situation already mentioned where the first of a pair of adjacent white pixels is transitioning from white to black while the second pixel is remaining white, there is a tendency for the drive pulse applied to the first pixel to cause the resultant black area to extend more than half-way across the inter-pixel gap, causing the problems noted above. By applying an inverse reinforcing (white-going) pulse to the second pixel, the excessive black blooming is reduced or eliminated.

Problems solved by technology

As discussed in the various applications and patents mentioned in the “Reference to Related Applications” section above, waveforms used to drive pixels of electro-optic displays from one optical state to another may be quite complex and may include drive pulses of both polarities.

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