In-Cell Capacitive Touch Sensor Electrode Configuration
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Solution Overview
Problem
In liquid crystal display devices with embedded touch sensors, the interference between touch sensor operations and pixel drive operations leads to reduced accuracy and position resolution in contact detection, particularly due to the short blank periods available for touch detection.
Innovation Solution
The implementation of a capacitive touch sensor system with separate drive and detection electrodes, arranged orthogonally to the pixel and common electrodes, allows for independent operation and extended detection periods, enhancing detection accuracy and position resolution by applying a drive signal to the drive electrodes and monitoring voltage changes in detection electrodes during effective display periods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the common electrode is used as the drive electrode of the capacitive touch sensor, then the device complexity is reduced, but the touch sensor operation and pixel drive interfere with each other, reducing detection accuracy
Solution Approach 1:
The patent segments the electrode functions by introducing separate drive electrodes and detection electrodes for the touch sensor, distinct from the pixel electrodes and common electrode. This segmentation allows independent optimization of pixel drive and touch detection operations, eliminating interference between the two functions while maintaining clear functional boundaries in the electrode structure.
Solution Approach 2:
The patent extracts the touch sensor drive function from the common electrode by introducing dedicated drive electrodes that are electrically isolated from the pixel drive circuitry. This extraction enables the touch sensor operation to be performed independently during effective display periods without being constrained by the pixel drive timing, thereby improving detection accuracy.
2Reliability
If contact detection is performed during the blank period, then interference between touch sensor operation and pixel drive is avoided, but the short blank period reduces the time available for detection, lowering detection accuracy and position resolution
Solution Approach 1:
The patent enables continuous touch detection during the effective display period by using separate drive electrodes that do not interfere with pixel operation. This continuity allows the touch sensor to perform detection throughout the entire display period rather than being restricted to brief blank periods, significantly increasing the time available for accurate capacitance measurement and position resolution.
3Area of stationary object
If multiple contact points are detected in time division manner, then the coverage area is increased, but the time assigned to each point is reduced, decreasing detection accuracy
Solution Approach 1:
The patent implements a systematic periodic scanning approach where drive signals are sequentially applied to multiple drive electrodes during the effective display period. This periodic action allows comprehensive coverage of multiple contact points while maintaining sufficient measurement time for each point, as the extended detection window enables complete scanning cycles without sacrificing per-point detection accuracy.
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 configuration prevents interference between touch sensor and pixel drive operations, enabling more accurate and high-resolution contact detection across a larger area, even during the effective display period, thereby improving the overall performance of the liquid crystal display device.
Implementation Method 1
detect, based on the voltage change in the detection electrode caused by the supply, a change in capacitance in an opposing part between corresponding one of the plurality of first electrodes and corresponding one of the plurality of second electrodes
Implementation Method 2
control alignment of the liquid crystal by an electric field generated between the pixel electrode and a common electrode
Data Source
AI summary
To achieve improved detection accuracy and position resolution in an in-cell type capacitive touch sensor embedded in a liquid crystal panel of a liquid crystal display device, a drive electrode of a touch sensor is formed of a transparent conductive film laminated on a surface of a TFT substrate on a liquid crystal side below a pixel electrode, and disposed in a region between gate lines. A detection electrode is formed of a transparent conductive film laminated on an outward-directed surface of the TFT substrate. A drive signal is supplied to the drive electrode to cause a voltage change, and based on the voltage change in the detection electrode caused thereby, a capacitance change in an opposing part between the drive electrode and the detection electrode is detected, to thereby detect contact of an object to a display surface near the opposing part in a liquid crystal panel.