Siloxane Particle Films for Transparent Conductive Electrodes
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Solution Overview
Problem
There is a need for optically transparent and electrically conductive layers that can replace indium tin oxide (ITO) and aluminum tin oxide (ATO) layers, as ITO suffers from conductivity issues in larger displays and indium is scarce and expensive, while ATO is less stable.
Innovation Solution
A nanoparticle-siloxane composite electrode is developed, where conductive particles are deposited within or surrounded by a siloxane composite, achieving electrical percolation and high optical transmission, with the option to pattern the composite for specific applications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If ITO layers are used to make transparent electrically conductive coatings, then optical transparency is achieved, but electrical conductivity deteriorates in larger displays and material cost increases due to scarcity
Solution Approach 1:
The patent uses a composite material system consisting of conductive particles (metal, carbon, or conductive polymer) dispersed within an optically transparent polymer matrix. This composite structure allows the material to simultaneously achieve optical transparency from the polymer matrix and electrical conductivity from the conductive particle network, resolving the contradiction between transparency and conductivity in ITO layers.
Solution Approach 2:
The patent changes the physical and chemical parameters of the conductive phase by using particles with specific size ranges (0.1-10 micrometers), aspect ratios, and surface treatments. By optimizing particle concentration, size distribution, and morphology, the patent achieves percolation thresholds that provide adequate electrical conductivity while maintaining high optical transparency, thereby resolving the conductivity limitations of ITO in large displays.
2Reliability
If ITO deposition is performed using vacuum processes, then transparent electrically conductive coatings are formed, but manufacturing cost and processing time increase
Solution Approach 1:
The patent replaces the vacuum-based physical vapor deposition process with a solution-based coating process. The conductive particle-polymer composition can be applied using conventional coating techniques such as spin coating, dip coating, spray coating, or inkjet printing at atmospheric pressure. This substitution dramatically increases deposition speed and reduces manufacturing complexity while maintaining electrical conductivity through the percolating particle network.
3Quantity of substance
If ATO layers are used as replacements for ITO, then cost is reduced, but stability deteriorates
Solution Approach 1:
The patent creates a composite structure where chemically stable polymer matrices (such as epoxy, polyimide, or silicone resins) encapsulate the conductive particles. This composite architecture provides both cost advantage (using abundant materials) and enhanced stability (through the protective polymer matrix), overcoming the stability issues of ATO layers while maintaining low cost.
4Reliability
If conductive particle concentration is increased to improve electrical conductivity, then electrical percolation is achieved, but optical transmission deteriorates
Solution Approach 1:
The patent optimizes the particle concentration parameter to achieve the percolation threshold - the minimum concentration needed to form a continuous conductive network. By carefully controlling particle size (0.1-10 micrometers), aspect ratio, and spatial distribution, the patent achieves adequate electrical conductivity at the lowest possible particle loading, thereby minimizing optical absorption and scattering while maintaining electrical percolation.
Solution Approach 2:
The patent creates local conductive pathways through the random dispersion of conductive particles, where conductivity is achieved locally at the percolation threshold rather than uniformly throughout the material. This local quality approach allows the bulk material to remain highly transparent while specific particle clusters provide the necessary conductive paths, resolving the trade-off between conductivity and transparency.
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 siloxane particle composition provides improved optical and lifetime qualities, offering a viable replacement for ITO and ATO in various devices, including displays and photovoltaic cells, with potential uses in electronics and optoelectronics packaging.
Implementation Method 1
Conductive particles, which can be spherical, branched or wires, are deposited within or are surrounded with a siloxane composite. Low aspect ratio particles are arranged in lines or patterns to reach electrical percolation. Alternatively high aspect ratio particles are randomly dispersed within or underneath a siloxane material in sufficient concentration to reach electrical percolation threshold.
Implementation Method 2
The transparent and conductive film can be formed in one simultaneous coating step, or two consecutive coating steps. The coating can be also patterned according to various patterning processes disclosed herein.
Data Source
AI summary
A display has a plurality of pixels in a matrix, the pixels each comprising a liquid crystal layer and/or light emitting diode layer, a plurality of substrates, at least a first substrate being optically transmissive to visible light, an electrode formed on one of the substrates and having electrically conductive material that has an electrical resistivity of less than 200 Ω/sq and that comprises a siloxane material and particles having an average particle size of less than 10 microns.