Methods for driving electro-optic displays

A method for driving an electro-optic display having at least one pixel capable of achieving any one of at least four different gray levels including two extreme optical states, the method comprising:

• displaying a first image on the display;
• and
• rewriting the display to display a second image thereon,
• the method permitting any pixel to undergo at least two transitions without touching an extreme optical state, but being such that during the rewriting of the display any pixel which has undergone a number of transitions exceeding a predetermined value, the predetermined value being at least two, without touching an extreme optical state, is driven to at least one extreme optical state before driving that pixel to its final optical state in the second image, wherein said predetermined value is not greater than N/2, where N is the total number of gray levels capable of being displayed by a pixel;
• and
• wherein, for at least one transition undergone by the at least one pixel from a gray level R2 to a gray level R1, there is applied to the pixel a sequence of three impulses of the form:
• (a) -TM(R1,R2)
• (b) IP(R1)-IP(R2);
• and
• (c) TM(R1,R2)
• where “IP(Rx)” represents the relevant value from an impulse potential matrix having one value for each gray level, and TM(R1,R2) represents the relevant value from a transition matrix having one value for each R1/R2 combination.