Flexible EL Display with Integrated Strain Gauges for Multi-Touch
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Solution Overview
Problem
Traditional touch screen displays integrated with electroluminescent (EL) displays face issues such as high cost, reduced sensitivity and image quality due to separate construction, parallax effects, and inability to accurately detect multiple touch points, especially when using passive matrix addressing and non-transparent touch screens.
Innovation Solution
A flexible EL display with integrated, force-activated multi-touch sensors embedded within a single substrate, utilizing chiplets with strain gauges to provide accurate touch detection without overlaying the image plane, allowing for high-density sensor arrays to differentiate between touch locations and bending of the display.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a separate touch screen substrate is positioned over the display substrate, then touch sensing capability is provided, but manufacturing cost increases and image quality deteriorates due to reduced transparency and parallax effects
Solution Approach 1:
The patent combines the touch sensor array and display elements into a single integrated substrate, eliminating the need for a separate touch screen overlay. This integration reduces manufacturing complexity and cost while maintaining both touch sensing capability and display quality, as the sensors and display elements share the same plane and substrate.
Solution Approach 2:
The patent transitions from a three-layer structure (display substrate, touch screen overlay, and air gap) to a two-dimensional integration where touch sensors and display elements coexist on the same substrate plane. This dimensional reorganization eliminates parallax effects and improves transparency while maintaining touch functionality.
2Measurement precision
If active addressing techniques with arrays of thin film transistors are used, then sensitivity and response time improve, but manufacturing cost increases significantly
Solution Approach 1:
The patent divides the substrate into discrete sensor regions corresponding to individual display elements, with each region having its own readout circuitry. This segmentation enables precise localization of touch events while using a scalable architecture that can be manufactured using standard thin-film fabrication processes, balancing performance and cost.
3Ease of operation
If reflective metal traces are included in the touch screen to convey electrical signals, then electrical signal transmission is enabled, but transparency is reduced and image quality deteriorates
Solution Approach 1:
The patent employs transparent conductive materials such as indium tin oxide (ITO) or other transparent conducting oxides to replace traditional reflective metal traces. These materials maintain electrical conductivity while allowing light to pass through, thereby preserving display transparency and image quality while enabling signal transmission.
4Adaptability or versatility
If the touch screen is placed over the display with a gap between substrates, then structural flexibility is provided, but light reflection between substrates increases and effective contrast is reduced
Solution Approach 1:
The patent merges the touch sensor layer and display layer into a single integrated structure, eliminating the air gap between substrates. This integration prevents light reflection and interference between separate layers, maintaining high contrast and image quality while preserving the flexibility of the underlying substrate.
5Device complexity
If piezo actuators are placed at corners or edges of substrate, then device complexity is reduced, but ability to detect multiple touch points deteriorates
Solution Approach 1:
The patent implements a segmented sensor array where each display element corresponds to a discrete sensor region with independent readout capability. This segmentation enables precise detection of multiple simultaneous touch points across the display surface, as each touched location can be independently identified and localized.
Solution Approach 2:
The patent transitions from corner/edge-based sensing (zero-dimensional points) to a two-dimensional array of sensor elements distributed across the entire substrate. This dimensional expansion enables accurate detection and differentiation of multiple touch locations simultaneously.
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 enables a cost-effective, high-sensitivity, and transparent touch interface that accurately detects multiple touch points without degrading image quality, reducing parallax, and providing force and pressure information, enhancing user interaction with flexible and accurate multitouch capabilities.
Implementation Method 1
a first plurality of distributed chiplets for sensing stress or strain associated with bending of the flexible substrate to provide respective displacement signals
Implementation Method 2
one or more electroluminescent (EL) display elements for emitting light in response to an electrical signal
Data Source
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AI summary
A display device including a touch sensitive EL display having a flexible substrate; one or more power busses and one or more EL elements disposed over the flexible substrate; and a plurality of distributed duplets arranged so that at least two chiplets are associated with each of a plurality of touch sensitive areas on the EL display and for sensing stress or strain associated with bending of the flexible substrate or the chiplet substrate to provide respective displacement signals corresponding to the touch sensitive areas; each chiplet connected to one or more of the power busses and one or more of the EL elements for modulating power from the power busses to the EL elements in response to a control signal; and a controller for providing control signals to the chiplets in response to an input image signal and for receiving displacement signals from the chiplets and producing touch signals.