Silver Nanoparticle Ink with Dual Polyol Stabilizers
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Solution Overview
Problem
Existing silver nanoparticle dispersions for electronic applications face challenges such as low conductivity, high viscosity, and poor stability, particularly due to low silver concentrations and inadequate stabilizers, which limit their use in high-concentration, low-viscosity, and water-reducible forms with excellent re-dissolution behavior.
Innovation Solution
A method involving silver nanoparticles dispersed in water with a water-soluble polymer containing carboxylic acid and sulfonic acid groups, allowing for high silver weight percentages up to 90% and low viscosity, along with a controlled synthesis process to achieve stable and conductive silver nanoparticle dispersions suitable for various printing techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If high concentrations of silver nanoparticles are used to achieve greater than 0.3 μm dry coverage, then the metal particle concentration in the ink must be greater than 15% by volume (greater than 65% by weight), but the viscosity of the ink increases significantly
Solution Approach 1:
The patent uses a dual stabilizer system comprising a short-chain polyol (e.g., glycerol, ethylene glycol) and a long-chain polyol (e.g., polyvinylpyrrolidone, polyethylene glycol). This combination changes the physical-chemical parameters of the dispersion medium to achieve low viscosity even at high silver concentrations (65-99% by weight). The short-chain polyol provides immediate viscosity control while the long-chain polyol ensures colloidal stability, resolving the contradiction between high concentration and low viscosity.
2Manufacturing precision
If multi-pass ink jet printing is used to generate conductive patterns with low aspect ratios, then the feature thickness can be reduced to less than 0.5 micron, but the electrical resistivity increases to greater than 0.2 ohms/square
Solution Approach 1:
The patent employs a sacrificial organic component (polyol stabilizer system) that can be completely removed through sintering at relatively low temperatures (150-300°C). This allows the formation of dense, continuous silver nanoparticle networks with excellent electrical conductivity (less than 0.2 ohms/square) even for thin features. The temporary presence of the organic stabilizer during deposition enables precise pattern formation, which is then removed to achieve high conductivity.
Solution Approach 2:
The patent utilizes the phase transition of the organic polyol stabilizer from liquid state during deposition to complete removal through sintering. This phase change allows the organic component to serve its stabilizing function during printing, then be eliminated to leave behind a pure metal network with optimal electrical properties, resolving the contradiction between thin feature formation and high conductivity.
3Ease of manufacture
If anionic polymer stabilizers with high molecular weight are used to stabilize silver nanoparticles, then the ink can be formulated for direct ink writing, but the electrical conductivity generated after annealing at high temperatures is limited
Solution Approach 1:
The patent segments the stabilizer function into two distinct components: a short-chain polyol that provides immediate viscosity control and can be easily removed, and a long-chain polyol that provides colloidal stability. This segmentation allows the short-chain component to be sacrificial (removed during sintering) while the long-chain component maintains stability during processing, enabling both ease of manufacture and high final conductivity.
Solution Approach 2:
The patent uses short-chain polyols (glycerol, ethylene glycol) as sacrificial stabilizers that can be completely removed through low-temperature sintering. These short-living organic components enable direct ink writing and pattern formation, then are eliminated to leave behind pure metal networks with excellent electrical conductivity, resolving the contradiction between manufacturability and final conductivity.
4Temperature
If carboxylic acid stabilizers are used to enable sintering at lower temperatures, then the dispersion can be sintered into conductive films at lower temperatures, but the dispersions are not water reducible and cannot be formulated into ink-jet inks
Solution Approach 1:
The patent creates a universal stabilizer system using polyols that can serve multiple functions: (1) provide colloidal stability for ink formulation, (2) enable low-temperature sintering, and (3) ensure water reducibility for ink-jet compatibility. The dual polyol system (short-chain and long-chain) achieves all three requirements simultaneously, making the dispersion adaptable to various deposition processes while maintaining low sintering temperatures.
Solution Approach 2:
The patent uses a composite stabilizer system combining short-chain and long-chain polyols, which together provide properties that neither component alone could achieve. This composite approach enables water reducibility, low-temperature sintering, and ink-jet compatibility simultaneously, resolving the contradiction between low sintering temperature and process versatility.
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 method provides highly conductive silver traces with improved stability and re-dissolution properties, enabling efficient deposition and sintering at lower temperatures, resulting in conductive articles with resistivity close to that of pure silver.
Implementation Method 1
silver nanoparticles dispersed in water with a water-soluble polymer having both carboxylic acid and sulfonic acid groups
Implementation Method 2
water-soluble polymer having both carboxylic acid and sulfonic acid groups
Implementation Method 3
converting the dried metal nanoparticle composition to improve the electrical conductivity of the dried metal nanoparticle composition
Implementation Method 4
improved electrical conductivity through sintering or halide exposure
Data Source
AI summary
A method of making a conductive article includes depositing on a substrate a metal nanoparticle composition having water, silver nanoparticles dispersed in the water and a water-soluble polymer having both carboxylic acid and sulfonic acid groups. The weight percentage of silver in the composition is greater than 10%. The metal nanoparticle composition is dried. The dried metal nanoparticle composition is converted to improve the electrical conductivity of the dried metal nanoparticle composition.