Guard Electrode Suppresses Capacitance Noise in Touch Display
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Solution Overview
Problem
Existing touch panels integrated with liquid crystal display apparatuses face challenges in improving detection performance due to changes in capacitance caused by the liquid crystal layer's permittivity, leading to noise and reduced sensitivity in detecting external objects.
Innovation Solution
A display apparatus design that includes a basement with a display functional layer, a first electrode for detecting objects, a guard electrode to suppress capacitance changes, and a detection controller to process capacitance signals, with the electrodes and guard electrode arranged in a configuration that prevents capacitive coupling with the liquid crystal layer, thereby enhancing detection performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a liquid crystal layer is placed between the capacitance lines/source wires and the detection surface to enable display function, then display capability is achieved, but capacitance changes occur due to permittivity variations which deteriorate detection performance
Solution Approach 1:
A guard electrode is introduced as an intermediary element between the first electrode and the liquid crystal layer. This guard electrode is supplied with a guard signal that suppresses capacitance changes, thereby mediating the interaction between the detection electrode and the liquid crystal layer to prevent harmful capacitive coupling while maintaining display functionality.
Solution Approach 2:
The detection structure is segmented into multiple functional layers: the first electrode for detection, the guard electrode for capacitance suppression, and the liquid crystal layer for display. This segmentation allows each layer to perform its specific function independently, with the guard electrode layer specifically designed to block harmful capacitive effects from the liquid crystal layer.
2Ease of operation
If capacitance detection is performed through the liquid crystal layer, then touch detection function is enabled, but noise increases due to capacitance changes from permittivity variations
Solution Approach 1:
The guard electrode serves as a protective intermediary that blocks noise and capacitance fluctuations from the liquid crystal layer from reaching the first electrode. By supplying a guard signal to this intermediary layer, the system maintains clean detection signals while preserving touch detection functionality.
Solution Approach 2:
The guard electrode applies a preliminary counteracting effect by supplying a guard signal that preemptively suppresses capacitance changes before they can affect the detection electrode. This preliminary anti-action prevents noise generation rather than attempting to filter it afterward.
3Measurement precision
If the first electrode is positioned close to the liquid crystal layer to improve detection sensitivity, then detection capability increases, but capacitance coupling with the liquid crystal layer increases causing more noise
Solution Approach 1:
The guard electrode is positioned between the first electrode and the liquid crystal layer, allowing the first electrode to remain close to the liquid crystal layer for high detection sensitivity while the guard electrode mediates to prevent harmful capacitance coupling. The guard signal suppresses any capacitive effects that might otherwise interfere with detection.
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 effectively suppresses noise and improves detection sensitivity by preventing changes in capacitance due to the liquid crystal layer's permittivity changes, leading to enhanced touch detection capabilities.
Implementation Method 1
a first electrode that is arranged between the basement and the display functional layer and detects an object in contact with or in proximity to the first surface
Implementation Method 2
a guard electrode arranged between the first electrode and the basement and supplied with a guard signal, the guard signal suppressing a change in capacitance generated between the first electrode and the guard electrode
Implementation Method 3
a detection electrode that is arranged between the first electrode and the basement and outputs a detection signal based on a change in capacitance generated between the first electrode and the detection electrode
Data Source
AI summary
A display apparatus includes a basement, a display functional layer, a first electrode, a guard electrode, and a detection controller. The basement has a first surface and a second surface opposite to the first surface. The display functional layer is arranged on the side of the second surface of the basement. The first electrode is arranged between the basement and the display functional layer and detects an object in contact with or in proximity to the first surface. The guard electrode is arranged between the first electrode and the basement and supplied with a guard signal. The guard signal suppresses a change in capacitance generated between the first electrode and the guard electrode. The detection controller is a controller to which a signal based on a change in capacitance of the first electrode is output from the first electrode.