Mesh Extraction Electrode for Touch Panel Visibility and Capacitance
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Solution Overview
Problem
Conductive films used in touch panels, particularly those made of indium tin oxide (ITO), have high electrical resistance and are conspicuous when formed as extraction electrodes, leading to reduced visibility and accuracy in touch detection due to lower initial capacitance between electrodes.
Innovation Solution
A conductive film design featuring a base with first and second electrodes facing each other and an extraction electrode formed on the same surface, using a mesh pattern of thin metal wires that surrounds the second electrode, reducing visibility and increasing initial capacitance for improved detection accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an extraction electrode is formed by metal wires in a visible region, then electrical resistance is reduced, but the extraction electrode becomes conspicuous and visibility is reduced
Solution Approach 1:
The extraction electrode is divided into a mesh pattern consisting of multiple thin metal wire segments arranged in a grid structure. This segmentation reduces the visual conspicuousness of individual wire segments while maintaining overall electrical conductivity through the collective effect of multiple segments.
Solution Approach 2:
The mesh pattern creates local variations in the electrode structure, with thin metal wires distributed across the surface. This local quality approach allows the electrode to have different properties at different scales: locally appearing transparent due to thin wire distribution, but globally providing sufficient conductivity through the cumulative effect of all wire segments.
2Reliability
If electrodes are formed on both sides of a substrate, then initial capacitance between electrodes is increased, but manufacturing complexity and cost increase
Solution Approach 1:
The patent transitions from a three-dimensional arrangement (electrodes on both sides of the substrate) to a two-dimensional arrangement (all electrodes on one surface). This dimensional change allows the extraction electrode to be positioned on the same surface as the touch electrode, simplifying manufacturing while maintaining capacitance through optimized spatial arrangement on the single surface.
Solution Approach 2:
The patent merges the functions of touch detection and signal extraction onto a single surface. The touch electrode and extraction electrode are both formed on the same surface, eliminating the need for separate substrate layers and reducing manufacturing steps while maintaining the necessary electrical capacitance for touch detection.
3Illumination intensity
If thin metal wires are used to form the extraction electrode, then visibility is improved, but the proportion of conductive portion decreases and detection accuracy is reduced
Solution Approach 1:
The extraction electrode is segmented into multiple thin metal wires arranged in a mesh pattern. While individual wires are thin to maintain visibility, the collective arrangement of numerous wires provides sufficient conductive area. The mesh structure ensures that the total conductive portion proportion is adequate for maintaining detection accuracy while preserving visual transparency.
Solution Approach 2:
The mesh pattern creates a composite structure combining transparent spaces with conductive metal wire elements. This composite arrangement allows the electrode to exhibit both transparency (from the transparent spaces) and sufficient conductivity (from the metal wire network), resolving the contradiction between visibility and detection accuracy.
Data Source
AI summary
The touch sensor includes a base, first and second electrodes that are formed on a main surface of the transparent base so as to face each other, and an extraction electrode that is formed on the main surface of the transparent base and extends from the second electrode. The first electrode has a shape which surrounds a portion of the second electrode. At least the extraction electrode is formed in a mesh pattern including a plurality of grids which are formed by thin metal wires.