Fine-Line Copper Mesh Touch Sensor for High Transparency and Durability
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Solution Overview
Problem
Current capacitive touch screens face issues with the fragility and high cost of Indium Tin Oxide (ITO) films, limited supply of Indium, and difficulties with alternative materials like PEDOT, which are not as optically clear or durable.
Innovation Solution
The use of fine-line printed metal electrodes, specifically copper or other high-conductivity metals, in a mesh pattern on a substrate, allowing for high transparency and robustness, with a self-test capability through loop-back testing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If ITO films are used for touch screen electrodes, then optical clarity is improved (92% transmission), but the films become fragile and expensive with limited suppliers
Solution Approach 1:
The patent changes the material parameter from ITO to copper, and changes the structural parameter from continuous film to fine-line mesh pattern. This transformation maintains optical clarity (98% transmission) while dramatically improving durability, as copper mesh is flexible and resistant to damage during production and use.
Solution Approach 2:
The patent creates a composite structure by combining copper metal lines with PET substrate. This composite approach allows the copper mesh to provide both electrical conductivity and mechanical flexibility, overcoming the fragility of ITO films while maintaining optical clarity.
2Reliability
If ITO films are used for touch screen electrodes, then capacitive touch functionality is achieved, but production costs increase and logistical problems arise due to limited suppliers
Solution Approach 1:
The patent replaces expensive ITO films with inexpensive copper mesh. Copper is abundant, cheap, and can be manufactured by many suppliers using printing processes, eliminating the logistical constraints and high costs associated with ITO supply chains.
Solution Approach 2:
The patent replaces the sputtering deposition process required for ITO with a printing process for copper mesh. This substitution simplifies manufacturing, reduces costs, and enables broader supplier base, as printing is a more accessible and flexible manufacturing method.
3Reliability
If metal density is increased to improve electrical conductivity, then touch sensitivity improves, but optical clarity deteriorates
Solution Approach 1:
The patent segments the continuous metal layer into fine-line mesh patterns with widths of 10 μm or less. This segmentation reduces metal density to less than 5% coverage while maintaining electrical conductivity through the interconnected mesh structure, and achieves superior optical clarity of 98%.
Solution Approach 2:
The patent applies metal lines only where electrically necessary, creating a mesh pattern that provides adequate conductivity at minimal density. The local placement of narrow copper lines maintains transparency in most areas while ensuring electrical functionality at electrode intersections and pathways.
4Ease of manufacture
If alternative materials like PEDOT are used to replace ITO, then cost is reduced, but optical clarity and environmental durability worsen
Solution Approach 1:
The patent uses copper, which is significantly cheaper and more abundant than ITO or PEDOT. Copper mesh can be manufactured at low cost using printing processes, providing both cost reduction and superior performance in optical clarity and environmental durability.
Solution Approach 2:
The patent changes from organic conductive polymers like PEDOT to inorganic copper metal, fundamentally altering the material properties. This change provides superior optical clarity, environmental stability, and flexibility while maintaining low cost and ease of manufacture through printing processes.
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 solution provides a cost-effective, durable, and highly transparent touch screen with enhanced optical clarity and reliability, overcoming the limitations of ITO and PEDOT, while reducing production costs and logistical challenges.
Implementation Method 1
fine-line printed metal deposited additively via a printing process onto a PET layer... highly conductive using copper... The narrow width of these tracks allows the film to be highly transparent, since the electric field used in capacitive touch screens can be made to propagate with very low metal densities
Implementation Method 2
fine-line printed metal deposited additively via a printing process onto a PET layer
Data Source
AI summary
A two-dimensional touch sensor comprising a plurality of electrodes arranged in a mesh pattern on a substrate. Each electrode is formed by interconnected metal traces, the metal being intrinsically opaque, but the metal traces being sufficiently narrow to be practically invisible. The metal traces have a width less than or equal to 10 μm and occupy less than or equal to 5% of the area of each electrode. The electrodes can be deposited additively via a printing process, for example using copper as the metal. The narrow width of the tracks allows the film to be highly transparent, since the electric field used in capacitive touch screens can be made to propagate with very low metal densities.