Electrophoretic Display Pixel with Restrictor and Low Viscosity Fluid
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Solution Overview
Problem
Existing electrophoretic display devices face challenges with slow switching times and bi-stable character, leading to inadequate pixel switching speed and homogenous pixel absorbance, particularly in the 'dark' state, which is not sufficient for many applications, and are plagued by issues like haze, unstable pigment storage, and electric breakdown.
Innovation Solution
The development of smaller pixel sizes (down to 0.1 milliseconds switching time) with a restrictor to enhance bi-stable time, using low viscosity fluids with charged particles smaller than 500 nm, and a dual-electrode system for improved particle distribution and control, along with a temperature-sensitive gel to maintain stability and reduce power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If electrophoretic display devices use conventional particle sizes and fluid viscosities, then particle movement is controllable, but switching times are slow (not sufficient for practical applications)
Solution Approach 1:
The patent applies parameter changes by reducing particle size from conventional micrometer scale to below 500 nm, and by using low viscosity fluids. These parameter changes enable faster particle movement (improving switching time) while the restrictor structure maintains bi-stable character by confining particles in storage areas when not in use.
Solution Approach 2:
The display cell is segmented into functional zones including aperture areas and storage areas. The restrictor structures divide the cell into regions that control particle movement, allowing particles to be quickly moved to aperture areas for display while being confined to storage areas when not displaying, thus maintaining bi-stability despite fast switching capability.
2Speed
If pixel size is reduced to improve switching speed, then switching time decreases, but homogenous pixel absorbance in the 'dark' state deteriorates
Solution Approach 1:
The patent applies local quality by creating different functional zones within the pixel structure. Aperture areas are optimized for light transmission and particle display, while storage areas are optimized for particle confinement. This local differentiation allows small pixel sizes with fast switching while maintaining homogeneous absorbance in the dark state through proper particle storage and retrieval mechanisms.
Solution Approach 2:
The restrictor structures act as intermediaries between the particle suspension medium and the aperture areas. They control particle movement and distribution, ensuring homogeneous particle distribution in storage areas and enabling uniform absorbance characteristics even in small pixels with fast switching times.
3Device complexity
If conventional electrophoretic display structures are used, then device simplicity is maintained, but haze and unstable pigment storage occur
Solution Approach 1:
The display cell is segmented into aperture areas and storage areas with restrictor structures. This segmentation provides stable pigment storage in dedicated storage areas while maintaining optical clarity in aperture areas, eliminating haze issues without significantly increasing overall device complexity.
Solution Approach 2:
The patent extracts the storage function from the display aperture area by creating separate storage areas with restrictors. This separation removes unstable pigment storage from the optical path, eliminating haze while maintaining the basic electrophoretic display structure.
4Device complexity
If electrophoretic display devices operate without restrictors, then device complexity is low, but bi-stable time is insufficient for practical use
Solution Approach 1:
The display cell is segmented into aperture areas and storage areas with restrictor structures. This segmentation provides stable pigment storage in dedicated storage areas while maintaining optical clarity in aperture areas, eliminating haze issues without significantly increasing overall device complexity.
Solution Approach 2:
The patent extracts the storage function from the display aperture area by creating separate storage areas with restrictors. This separation removes unstable pigment storage from the optical path, eliminating haze while maintaining the basic electrophoretic display structure.
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 solution significantly reduces switching times by a factor of 4-16, achieves bi-stable times of over 10 seconds, and allows for practical use in various applications, including sunlight readability and adaptability to changing light conditions, while minimizing power consumption and preventing electrical breakdown.
Implementation Method 1
charged pigment particles are moved to generate a required pigmentation of a pixel
Implementation Method 2
an electro-magnetic field, typically an electric field
Implementation Method 3
a temperature-sensitive gel to maintain stability
Data Source
Figure 1~3
AI summary
Electrophoretic display devices are a relatively new technique of pixilated display devices in which charged pigment particles are moved to generate a required pigmentation of a pixel. The invention relates to a pixel for an electrophoretic display device, to a display device, to a driver circuit for use in the electrophoretic display device and to use of the electrophoretic display device.