Electrowetting Display Dark State Control via Segmented Three-Phase Line
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing electrowetting display devices face challenges in achieving high contrast ratios due to hysteresis and difficulty in controlling low transmission states, particularly in gray-scale displays.
Innovation Solution
The implementation of an electrowetting display device with a first and second immiscible fluid, where the position of the first fluid is controlled by voltage to create a three-phase line that can be completely within an inactive area for a dark state, allowing for improved contrast and reduced voltage requirements, and the use of a first fluid with lower absorption to enable the use of dyes beyond solubility limits and reduce backflow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the first fluid layer is made absorbing for radiation to improve contrast ratio, then the dark state contrast is improved, but the transmission in the dark state decreases and hysteresis control becomes more difficult
Solution Approach 1:
The display area is segmented into active and inactive areas, with the three-phase line positioned completely within the inactive area for dark states. This segmentation allows the absorbing properties to be localized to the inactive area while maintaining control over the active area transmission.
Solution Approach 2:
Different areas of the display have different optical properties - the inactive area is made absorbing for radiation while the active area maintains transmission characteristics. This local quality differentiation enables improved contrast without compromising overall controllability.
2Reliability
If a minimum area is kept in contact with the second fluid to reduce hysteresis, then hysteresis is reduced, but the dark state transmission increases and contrast ratio deteriorates
Solution Approach 1:
The contact area between fluids is segmented and confined to the inactive area only, while the active area maintains a three-phase line configuration. This allows hysteresis reduction through minimal contact area without compromising dark state transmission control.
Solution Approach 2:
Instead of maintaining minimum contact area across the entire display area, the contact is applied partially only in the inactive area, which is sufficient for hysteresis reduction but does not adversely affect the active area transmission.
3Speed
If the thickness of the first fluid layer is reduced to improve response time, then switching speed is improved, but the stability of gray-scale levels deteriorates
Solution Approach 1:
The first fluid layer thickness is optimized locally - thinner in regions requiring fast response and maintained at stable thickness in regions requiring gray-scale stability. The three-phase line configuration allows different thickness profiles in different areas.
Solution Approach 2:
Instead of uniformly reducing thickness across the entire fluid layer, the solution moves to controlling the vertical dimension selectively - maintaining appropriate thickness for stability while using the three-phase line geometry to achieve fast response in the horizontal dimension.
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 contrast by achieving darker dark states and more stable gray-scale levels, reducing the thickness of the first fluid layer, and allowing for better optical performance by optimizing the movement of the three-phase line between active and inactive areas.
Implementation Method 1
Application of a voltage causes the second fluid to adjoin the display area by displacing the first fluid. An increase of the voltage increases the area adjoined by the second fluid and produces a display effect.
Implementation Method 2
The minimum area of the display area is made absorbing for radiation to improve the contrast ratio of the picture element.
Data Source
AI summary
A display apparatus comprises an electrowetting picture element with a first support plate with a first support plate portion comprising a layer substantially non-transmissive for light and second support plate portion substantially non-absorbing for light. A display controller is configured to control a display effect of the electrowetting picture element between a dark and light display effect, and, responsive to input data corresponding to the dark display effect, output at least one signal to a driver corresponding to the dark display effect. The driver is configured to, responsive to the at least one signal output by the display controller, apply a first, non-zero, voltage to the electrowetting picture element to switch a first and a second fluid of the electrowetting picture element to a first configuration with the first fluid and the second fluid in contact with a first surface of the first support plate portion and the first fluid in contact with a second surface of the second support plate portion.