Liquid Crystal Capacitor Voltage Control for Touch Sensing Interference
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Solution Overview
Problem
Capacitive touch sensing in liquid crystal displays (LCDs) is prone to interference from noise produced by liquid crystal capacitors, leading to incorrect touch detection due to varying capacitance values, which are difficult to stabilize, especially in portable applications.
Innovation Solution
A multi-touch system and method that includes a touch LCD panel with a thin film transistor (TFT) layer, sensing electrode layer, and common voltage layer, where the touch display control subsystem sets liquid crystal capacitors to a predetermined voltage during touch sensing to reduce noise interference, allowing for more stable touch detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If liquid crystal capacitors are used for display purposes with varying voltages, then display functionality is achieved, but touch sensing accuracy deteriorates due to capacitance variations
Solution Approach 1:
The patent divides the display panel into multiple regions with different liquid crystal capacitor configurations. Specifically, it segments the pixel structure to include both display capacitors and touch sensing capacitors, allowing independent optimization of each function. The touch sensing electrodes are separated from the display electrodes, enabling distinct control of capacitance values for display versus sensing purposes.
Solution Approach 2:
The patent applies different capacitance characteristics to different regions of the display panel. Touch sensing regions are designed with fixed capacitance values through specific liquid crystal material selection and electrode configuration, while display regions maintain variable capacitance for grayscale control. This local differentiation allows the touch sensing area to have stable electrical characteristics while the display area maintains full functionality.
2Adaptability or versatility
If capacitive touch sensing is implemented on LCD panel, then touch detection capability is added, but noise interference from liquid crystal capacitors increases
Solution Approach 1:
The patent extracts the touch sensing function from the display function by creating separate electrode systems. Touch sensing electrodes are distinct from display electrodes, and touch sensing capacitors are separated from display capacitors. This extraction removes the noise source (display capacitor variations) from the sensing path, allowing clean touch detection without interference from liquid crystal capacitor fluctuations.
Solution Approach 2:
The patent introduces intermediary structures between the display system and touch sensing system. Insulating layers and specific electrode configurations act as mediators that block noise transmission from display capacitors to touch sensing circuits. These intermediary elements allow both functions to coexist while preventing harmful electromagnetic coupling.
3Object-affected harmful factors
If insulating sheet or air gap is added between touch panel and display panel, then noise interference is reduced, but panel thickness and cost increase
Solution Approach 1:
The patent merges the touch panel and display panel into a single integrated structure with shared substrates and overlapping electrode layers. By combining both functions in one compact unit with precise layer positioning, the need for additional insulating sheets or air gaps is eliminated. The integrated design achieves noise isolation through spatial arrangement rather than physical separation, maintaining thin profile while reducing interference.
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 stabilizes touch sensing by fixing the capacitance of liquid crystal capacitors, reducing noise interference and improving detection accuracy, thereby prolonging the lifetime of touch sensing technology in portable applications.
Implementation Method 1
the capacitance changes of liquid crystal capacitors CLC in liquid crystal displays (LCDs) are used to achieve a display on the panels. The change of a liquid crystal capacitor is varied with different voltages
Implementation Method 2
liquid crystal capacitors CLC in liquid crystal displays (LCDs)
Implementation Method 3
The touch sensing detects a capacitance change between the finger capacitance Cp and the touch panel or LCD panel
Data Source
AI summary
A multi-touch system for controlling liquid crystal capacitors to reduce touch sensing interferences includes K gate driving lines, which are divided into N groups each corresponding to a common voltage conductive line. When a display driving signal is applied to an i-th group of gate driving lines for performing a display driving, the liquid crystal capacitor corresponding to the i-th group is set to a predetermined voltage, where i=1 to N. Finally, a touch driving signal is applied to an i-th common voltage conductive line corresponding to the i-th group for sensing touch points, so as to reduce touch sensing affections caused by noises of the liquid crystal display.