Driving voltages for advanced color electrophoretic displays and displays with improved driving voltages
AssigneeE Ink Corporation
InventorsStephen J. Telfer, Kosta Ladavac, Christopher L. Hoogeboom
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Abstract
Improved methods for driving a four particle electrophoretic medium including a scattering particle and at least two subtractive particles. Such methods allow displays such as a color electrophoretic display including a backplane having an array of thin film transistors, wherein each thin film transistor includes a layer of metal oxide semiconductor. The metal oxide transistors allow faster, higher voltage switching, and thus allow direct color switching of a four-particle electrophoretic medium without a need for top plane switching. As a result, the color electrophoretic display can be updated faster and the colors are reproduced more reliably.
Claims26
A color electrophoretic display comprising:
- a light-transmissive electrode at a viewing surface;
- a backplane including an array of thin film transistors coupled to pixel electrodes;
- and
- a four-particle color electrophoretic medium disposed between the light-transmissive electrode and the backplane, the four-particle color electrophoretic medium comprising:
- (a) a fluid;
- (b) a plurality of first and a plurality of second particles dispersed in the fluid, the first and second particles bearing charges of opposite polarity, the first particle being a light-scattering particle and the second particle having one of the subtractive primary colors;
- and
- (c) a plurality of third and a plurality of fourth particles dispersed in the fluid, the third and fourth particles bearing charges of opposite polarity, the third and fourth particles each having a subtractive primary color different from each other and from the second particles,
- wherein the thin film transistors each comprise a layer of a metal oxide semiconductor configured to switch control voltages greater than 25 Volts and less than −25 Volts while the light-transmissive electrode is held at constant voltage to enable driving the four-particle electrophoretic medium at five or more different addressing voltage levels to facilitate color optical state switching of pixels of the four-particle color electrophoretic medium among eight primary colors of red, green, blue, cyan, magenta, yellow, black, and white.
A method, comprising:
- providing a color electrophoretic display comprising a light-transmissive electrode at a viewing surface;
- a backplane including an array of thin film transistors coupled to pixel electrodes, each thin film transistor comprising a layer of a metal oxide semiconductor;
- and a four-particle color electrophoretic medium disposed between the light-transmissive electrode and the backplane, the four-particle color electrophoretic medium comprising:
- (a) a fluid;
- (b) a plurality of first and a plurality of second particles dispersed in the fluid, the first and second particles bearing charges of opposite polarity, the first particle being a light-scattering particle and the second particle having one of the subtractive primary colors;
- and (c) a plurality of third and a plurality of fourth particles dispersed in the fluid, the third and fourth particles bearing charges of opposite polarity, the third and fourth particles each having a subtractive primary color different from each other and from the second particles;
- and
- driving the color electrophoretic display by applying a set of at least five different addressing voltages, including voltages greater than 25 Volts and less than −25 Volts, to the pixel electrodes while holding the light-transmissive electrode at constant voltage to switch optical states of pixels of the four-particle color electrophoretic medium among eight primary colors of red, green, blue, cyan, magenta, yellow, black, and white.
Dependencies are inferred from the claim text.