Liquid Crystal Display Touch Sensing via Segmented Capacitors
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Solution Overview
Problem
Conventional liquid crystal display devices with touch sensing capabilities face challenges in accurately detecting multiple touches and maintaining signal reliability due to increased parasitic capacitance and line resistance, leading to decreased signal-to-noise ratios and reduced touch recognition accuracy.
Innovation Solution
The implementation of touch sensing units with second storage capacitors and sensing capacitors connected in series between gate lines and a common electrode, along with switching transistors and a read-out line parallel to data lines, allows for improved capacitance sensing and reduced parasitic capacitance, enabling accurate touch detection and position determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If touch sensing units are integrated within the liquid crystal display panel, then the device volume is reduced and no external touch panel is needed, but parasitic capacitance and line resistance increase leading to decreased signal-to-noise ratio
Solution Approach 1:
The display panel is divided into pixel regions, with each pixel containing dedicated touch sensing units (sensing capacitor, storage capacitor, switching transistor). This segmentation allows independent touch detection at each pixel location, reducing the impact of parasitic capacitance by localizing the sensing function rather than using a few large sensing lines across the entire panel.
Solution Approach 2:
Touch sensing components are distributed locally at each pixel region rather than using centralized sensing lines. Each pixel has its own sensing capacitor connected to the common electrode, creating local sensing zones that reduce the overall parasitic capacitance affecting the signal-to-noise ratio while maintaining integrated design benefits.
2Adaptability or versatility
If multiple touches are detected using conventional capacitance sensing methods, then touch position recognition is attempted, but increased parasitic capacitance reduces detection accuracy
Solution Approach 1:
The panel is segmented into multiple pixel regions, each with independent touch sensing capability. This allows simultaneous detection of multiple touch positions by reading the capacitance state of individual pixel sensing units, enabling accurate multi-touch recognition despite the presence of parasitic capacitance in each local sensing circuit.
Solution Approach 2:
The switching transistor in each pixel region controls the connection between the sensing capacitor and read-out line based on the applied voltage signal. This feedback mechanism allows selective reading of touch capacitance at different pixel locations, enabling accurate determination of multiple touch positions by sequentially or simultaneously reading the state of each pixel's sensing capacitor.
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 enhances the ability to detect touches and determine touched positions with improved signal reliability and reduced noise interference, maintaining performance even in larger panel sizes without the need for external touch panels.
Implementation Method 1
A liquid crystal display device displays an image by adjusting the light transmittance of liquid crystals using an electric field
Implementation Method 2
liquid crystal display device, which recognizes a variation in liquid crystal capacitance according to a touch to be capable of sensing whether or not the device is touched and the position of a touched region
Data Source
AI summary
The liquid crystal display device is for recognizing a variation in liquid crystal capacitance according to a touch to be capable of sensing whether or not the device is touched and the position of a touched region and includes a first substrate and a second substrate being opposite to each other; a plurality of gate lines and a plurality of data lines crossing each other on the first substrate to define pixel regions; pixel transistors respectively disposed at the intersections of the plurality of gate lines and the plurality of data lines, and pixel electrodes respectively disposed in the pixel regions; a common electrode disposed on the entire surface of the second substrate; a liquid crystal layer filling a gap between the first and second substrates; liquid crystal capacitors between the pixel electrodes and the common electrode; first storage capacitors disposed between the pixel electrodes and first storage electrodes on the first substrate; second storage capacitors and sensing capacitors in series between the gate lines and the common electrode; a read out line being parallel with the data lines; and switching transistors, each of which is provided with a gate electrode connected to a node between the second storage capacitor and the sensing capacitor, a drain electrode connected to the read out line, and a source electrode connected to a power voltage line.