Electrophoretic Display Driving Method for Bright White and Ghosting Reduction
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Solution Overview
Problem
Current electro-optic display technologies face challenges in achieving bright and saturated white colors due to the dim white state and color gamut reduction, especially in displays like e-readers that require high black-white brightness and contrast, and suffer from issues like ghosting, edge artifacts, and color degradation over time.
Innovation Solution
The method involves applying pulse pairs and separation pulses to reset and precondition colored pigment particles in electrophoretic displays, which helps in reducing ghosting, improving color purity, and minimizing color degradation by ensuring accurate transition between optical states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If color filters are added on top of black/white sub-pixels to achieve color display, then color display capability is improved, but white state brightness deteriorates (white level becomes substantially less than half of black and white display)
Solution Approach 1:
The pixel is divided into multiple sub-pixels (red, green, blue, and white sub-pixels) that can be independently controlled. The white sub-pixel specifically contributes to bright white states while color sub-pixels provide color saturation, resolving the contradiction between color capability and white brightness.
Solution Approach 2:
Different sub-pixels have different local functions: color sub-pixels (red, green, blue) are optimized for color saturation while the white sub-pixel is optimized for brightness. This local specialization allows the display to achieve both color capability and high white state brightness simultaneously.
2Illumination intensity
If a fourth white sub-pixel is added to double the white level, then white state brightness is improved, but color saturation deteriorates (color gamut is reduced and colors become very light and unsaturated)
Solution Approach 1:
The display uses separate color sub-pixels (red, green, blue) and white sub-pixels that can be independently addressed. This segmentation allows the white sub-pixel to provide high brightness while color sub-pixels maintain full saturation by being controlled separately.
Solution Approach 2:
The display employs sequential coloring techniques where color and white sub-pixels are activated in specific sequences to create the perception of both saturated colors and bright white states, resolving the trade-off between white level and color saturation.
3Use of energy by moving object
If display operates in dark mode with colored pigment particles, then power consumption is reduced, but optical defects increase (ghosting, edge artifacts, and color degradation over time)
Solution Approach 1:
Reset pulses are applied before displaying content in dark mode to pre-position the colored pigment particles in their correct locations. This preliminary action prevents ghosting and edge artifacts by ensuring particles are properly oriented before the display sequence begins.
Solution Approach 2:
The display system monitors and adjusts the timing and intensity of reset pulses based on previous display states, preventing color degradation and maintaining image quality stability over time while operating in low-power dark mode.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enhances the display's ability to produce brighter, more saturated colors and reduces unwanted optical defects like ghosting and tinting, while maintaining long-term image quality.
Implementation Method 1
electrophoretic material having at least one type of colored pigment particle
Data Source
AI summary
A driving method for driving a display comprising an electrophoretic material having at least one type of colored pigment particle, the method includes applying at least one pulse pair to reset the at least one type of colored pigment particle, applying a separation pulse, and applying a second pulse pair to reset the at least one type of colored pigment particle.