Flat-Panel Display Touch Sensor High-Impedance Segmentation
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Solution Overview
Problem
Existing flat-panel display devices with integrated surface-capacitive touch sensors face issues of increased thickness, higher costs, and decreased display quality due to the presence of the touch sensor on the display surface, along with low signal-to-noise ratios and leakage currents that affect position detection accuracy and display performance.
Innovation Solution
A flat-panel display device design where at least one electrode is placed at a high impedance during current detection, allowing for improved signal-to-noise ratios and reducing the need for a separate surface-capacitive touch sensor, thereby minimizing thickness and resource usage while maintaining display quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a separate surface-capacitive touch sensor is added to the flat-panel display device, then touch detection capability is improved, but device thickness increases and manufacturing cost rises
Solution Approach 1:
The patent combines the touch sensor functionality with the display device by integrating a transparent conductive film into the display structure itself. The display device includes a substrate, liquid crystal layer, and transparent opposing electrode, where the transparent opposing electrode serves dual purposes as both a display component and a touch sensor element. This merging eliminates the need for a separate touch sensor layer, thereby preventing thickness increase while maintaining touch detection capability.
Solution Approach 2:
The transparent opposing electrode in the display device is designed to perform multiple functions: it serves as the counter electrode for the liquid crystal display and simultaneously functions as the conductive film for capacitive touch sensing. By making this component multi-functional, the patent avoids adding extra layers for touch sensing, thus preventing thickness increase and reducing manufacturing complexity.
2Adaptability or versatility
If a separate surface-capacitive touch sensor is added to the flat-panel display device, then touch detection capability is improved, but manufacturing cost increases
Solution Approach 1:
The patent merges the touch sensor functionality with the display device by integrating a transparent conductive film into the display structure itself. The display device includes a substrate, liquid crystal layer, and transparent opposing electrode, where the transparent opposing electrode serves dual purposes as both a display component and a touch sensor element. This merging eliminates the need for a separate touch sensor layer, thereby preventing thickness increase while maintaining touch detection capability.
Solution Approach 2:
The transparent opposing electrode in the display device is designed to perform multiple functions: it serves as the counter electrode for the liquid crystal display and simultaneously functions as the conductive film for capacitive touch sensing. By making this component multi-functional, the patent avoids adding extra layers for touch sensing, thus preventing thickness increase and reducing manufacturing complexity.
3Device complexity
If the transparent opposing electrode is used for both display and touch sensing, then device complexity is reduced, but signal-to-noise ratio decreases due to leakage currents
Solution Approach 1:
The patent segments the operation into distinct time intervals: a display drive interval for normal display operation and a position detection interval for touch sensing. During the position detection interval, the transparent opposing electrode is electrically isolated from the liquid crystal layer by placing pixel switches in the off state and setting electrodes to high impedance. This temporal segmentation allows the same electrode to serve dual purposes while preventing signal interference and leakage currents that would otherwise degrade position detection accuracy.
Solution Approach 2:
The patent employs periodic switching between display drive and position detection modes. The pixel switches are turned on during display operation and turned off during touch detection, creating periodic intervals where the transparent opposing electrode functions exclusively as a touch sensor. This periodic action prevents continuous leakage currents and enables accurate position detection while maintaining display functionality.
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
The solution enhances the signal-to-noise ratio of position detection signals, reduces the cost of signal processing, and prevents leakage currents, resulting in a thinner, more cost-effective display device with improved detection accuracy and maintained display performance.
Implementation Method 1
If the touch sensor is touched by a finger, very small currents flow into the finger owing to a capacitance formed by the surface of the touch panel and the finger.
Implementation Method 2
at least one electrode for transmitting an electrical signal from the exterior to the interior of the display area from among the electrodes that apply the electrical signals to the display elements is placed at a high impedance
Data Source
AI summary
A combination flat-panel touch sensor/display device includes a display device substrate on which signal lines, scanning lines and storage capacitance lines for applying electrical signals to liquid crystal are formed. A surface of the flat-panel display device corresponding to a display area has a transparent conductive film serving as an impedance surface. The device further includes current detecting circuits for detecting currents that flow through the impedance surface. In an interval over which the current detecting circuits detect current, at least one of the signal lines, scanning lines and storage capacitance lines is placed at a high impedance. The device reduces thickness without decline in display characteristics.