Electrophoretic Display Driving Voltage Control for Six-Color States
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Solution Overview
Problem
Conventional color electrophoretic display devices using color filters result in a dim white state and compromised color gamut, making them unsuitable for applications requiring high readability and contrast, such as e-readers and displays needing well-defined black-white brightness.
Innovation Solution
The use of an electrophoretic fluid with six types of particles (white, black, red, green, blue, cyan, and yellow) of different colors and charge potentials, dispersed in a dielectric solvent, allows for the creation of multiple high-quality color states by varying the driving voltage and electric field to control particle distribution within each pixel.
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 is reduced to about one third of desired level
Solution Approach 1:
The pixel is divided into three sub-pixels (red, green, blue) that can independently display black or colored states. By segmenting the pixel area and assigning specific color functions to each sub-pixel, the system achieves color display capability while maintaining the ability to display bright white when all sub-pixels show their respective colors.
Solution Approach 2:
The patent combines the black/white display function with color display function in a single electrophoretic display system. The electrophoretic fluid contains both colored particles and black/white particles, allowing the same pixel structure to achieve both color display and high brightness white state without requiring separate systems.
2Illumination intensity
If a fourth white sub-pixel is added to double the white level, then white state brightness is improved, but color saturation is reduced as colors become very light and unsaturated
Solution Approach 1:
The patent employs dynamic control of particle distribution through varying voltage amplitudes. By adjusting the voltage applied to the electrophoretic fluid, the system can dynamically switch between displaying high brightness white states and highly saturated color states, achieving both goals without compromise.
Solution Approach 2:
The system changes the electrical parameter (voltage amplitude) to control the display state. Different voltage levels cause different particle distributions, enabling the same physical structure to produce both bright white and saturated colors by simply changing the driving voltage parameter.
3Illumination intensity
If the area of color sub-pixels is reduced to one fourth each to accommodate a white sub-pixel, then white state brightness is improved, but color display quality deteriorates
Solution Approach 1:
Each sub-pixel is designed to be multi-functional, capable of displaying both black and colored states. The electrophoretic fluid in each sub-pixel contains both colored particles and black particles, allowing the same area to serve both color display and brightness functions without requiring additional dedicated white sub-pixels.
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 enables the display of six distinct color states without compromising brightness, providing non-compromised white and black states, as well as vibrant colors like red, green, and blue, enhancing the overall display performance and readability.
Implementation Method 1
an electrophoretic fluid with six types of particles (white, black, red, green, blue, cyan, and yellow) of different colors and charge potentials, dispersed in a dielectric solvent
Data Source
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AI summary
The present invention is directed to a color display device in which each pixel can display at least six high-quality color states, and an electrophoretic fluid for such an electrophoretic display. The different types of particles exhibit different levels of attraction force to display different color states.