Common Electrode Segmentation in Touch Sensors for Noise Reduction

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Solution Overview

Problem

Existing touch sensors suffer from vertical-direction parasitic capacitance that interferes with the detection accuracy of finger or pen positions due to noise from display driving signals, which existing noise reduction techniques fail to address effectively.

Innovation Solution

A touch sensor design that includes a common electrode with conductor-area-reduction portions to minimize the area of the common electrode, reducing the vertical-direction parasitic capacitance without increasing the thickness of the glass substrate.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If the common electrode area is reduced to decrease vertical-direction parasitic capacitance, then detection accuracy is improved, but electrical connectivity and image quality may deteriorate

Engineering Contradiction:

Improvedetection accuracyVSAvoidelectrical connectivity

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The common electrode is segmented into multiple regions with different area ratios in different pixel regions. The first region has a larger area ratio to maintain electrical connectivity and reduce parasitic capacitance, while the second region has a smaller area ratio to improve detection accuracy. This segmentation allows different parts of the electrode to serve different functional purposes simultaneously.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the common electrode are assigned different area ratios based on their functional requirements. The first region (near pixel electrodes) uses a larger area ratio for electrical connectivity, while the second region (touch detection area) uses a smaller area ratio for detection accuracy. This local differentiation optimizes both electrical performance and touch sensitivity.

Inventive Principle:

Principle #3Local quality

2Object-affected harmful factors

If the common electrode area is reduced to reduce vertical-direction parasitic capacitance, then noise interference is reduced, but image quality may deteriorate

Engineering Contradiction:

Improvenoise interferenceVSAvoidimage quality

Core Design Contradiction:

Object-affected harmful factorsVSManufacturing precision

Solution Approach 1:

The common electrode is divided into regions with different area ratios, allowing the first region to maintain sufficient coverage for image quality while the second region reduces area to minimize noise interference. This segmented approach enables differential optimization of image quality and noise reduction in different spatial locations.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the common electrode have different area ratios tailored to local requirements. Regions requiring good image quality maintain larger electrode area, while regions requiring low noise have reduced electrode area. This local quality differentiation resolves the contradiction between image quality and noise interference.

Inventive Principle:

Principle #3Local quality

3Power

If display driving signal strength is increased to improve display performance, then vertical-direction parasitic capacitance noise increases, but detection accuracy deteriorates

Engineering Contradiction:

Improvedisplay driving signal strengthVSAvoiddetection accuracy

Core Design Contradiction:

PowerVSMeasurement precision

Solution Approach 1:

The patent converts the harmful effect of vertical-direction parasitic capacitance into a beneficial design feature by deliberately designing the common electrode area ratio to be between 10% and 50%. This controlled parasitic capacitance level allows display driving signals to maintain sufficient strength for display performance while limiting noise interference to acceptable levels, thus protecting touch detection accuracy.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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 design effectively reduces vertical-direction parasitic capacitance, maintaining detection accuracy by minimizing noise interference from display driving signals while preserving image quality and electrical connectivity.

Implementation Method 1

parasitic capacitance is also generated between the touch panel and the display panel. Hereinafter, the latter parasitic capacitance will be referred to as 'vertical-direction parasitic capacitance'

Methodology Applied

Scientific EffectParasitic capacitance: Parasitic Capacitance

Data Source

PatentUS12477924B2Touch sensor

Publication Date: 2025.11.18 WACOM CO LTD

AI summary

A touch sensor includes a display panel that includes a plurality of pixel electrodes each provided in a corresponding one of a plurality of pixels, and a common electrode shared by the plurality of pixels. The touch sensor also includes a touch panel that detects a position of at least either a finger or a pen. The display panel and the touch panel are superimposed on each other in a vertical direction. The common electrode includes a conductor-area-reduction portion that reduces an area of the common electrode.