Silver-containing non-aqueous composition containing cellulosic polymers
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Solution Overview
Problem
Current methods for fabricating electrically-conductive silver patterns are time-consuming, expensive, and incompatible with temperature-sensitive substrates, particularly in high-speed manufacturing processes.
Innovation Solution
A non-aqueous silver precursor composition comprising reducible silver ions, a cellulosic polymer, and a nitrogenous base in a hydroxylic organic solvent, which facilitates the formation of silver nanoparticles through thermal reduction, enabling direct digital printing on polymeric substrates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If photolithographic and electroless techniques are used to fabricate silver patterns, then electrical conductivity is achieved, but the process becomes time-consuming and expensive
Solution Approach 1:
The patent replaces complex mechanical and chemical processes (photolithography, electroless plating) with a simple thermal reduction process. The silver precursor composition undergoes thermal decomposition to directly form conductive silver patterns, eliminating the need for multiple fabrication steps, photoresists, and extensive cleaning processes.
Solution Approach 2:
The patent changes the chemical parameters of the silver deposition process by using a thermal reduction mechanism instead of electroless plating. The silver precursor composition contains organic silver salts that decompose thermally to release metallic silver, allowing direct pattern formation through controlled heating rather than complex chemical reduction steps.
2Reliability
If high temperatures are used for calcination or sintering to increase electrical conductivity, then conductivity improves, but temperature-sensitive polymeric substrates are damaged
Solution Approach 1:
The patent changes the temperature parameter of the silver deposition process by using organic silver salts that decompose at low temperatures (below 100°C). This thermal decomposition mechanism replaces high-temperature calcination, allowing silver pattern formation on heat-sensitive polymeric substrates without damaging the substrate.
Solution Approach 2:
The patent uses transient organic silver salt complexes that decompose completely during the low-temperature thermal reduction process. These organic precursors serve as temporary carriers of silver ions, decomposing to release metallic silver and leaving no harmful residues, enabling low-temperature processing compatible with polymeric substrates.
3Temperature
If alkylamines are used as reducing agents for silver, then room temperature reduction is achieved, but long term stability of the composition is compromised
Solution Approach 1:
The patent changes the chemical structure of the reducing agent by using nitrogenous bases with higher pKa values (e.g., pyridine, piperidine, triethylamine) instead of alkylamines. These stronger bases provide sufficient reducing power at room temperature while forming more stable complexes with silver ions, thereby improving the long-term stability of the ink composition.
Solution Approach 2:
The patent creates a composite system combining silver salts with nitrogenous base ligands to form stable coordination complexes. These complexes remain stable during storage but can be reduced to metallic silver under appropriate conditions, providing both compositional stability and reducibility.
4Reliability
If high silver content is required for high electrical conductivity, then conductivity improves, but material cost and processing complexity increase
Solution Approach 1:
The patent changes the oxidation state parameter of silver by using silver(I) salts that can be directly reduced to metallic silver(0). This one-step reduction process is more efficient than multi-step methods, allowing high silver content formulations to achieve excellent conductivity without requiring additional processing steps or complex chemistry.
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 a simple, safe, and cost-effective way to generate high-weight fraction, fully dispersed silver nanoparticles with long-term stability, suitable for pattern formation in high-speed manufacturing processes.
Implementation Method 1
facilitates the formation of silver nanoparticles through thermal reduction
Implementation Method 2
through thermal reduction, enabling direct digital printing
Data Source
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AI summary
A non-aqueous silver precursor composition has (a) a cellulosic polymer; (b) reducible silver ions at a weight ratio to the cellulosic polymer of 5: 1 to 50:1; (c) an organic solvent having a boiling point of 100°C but less than 500°C; and (d) a nitrogenous base having a pKa (acetonitrile) of 15-25 at 25°C. The Hansen parameter (δTSolvent) of the cellulosic polymer is ≤ the Hansen parameter (δTSolvent) of the organic solvent. The nitrogenous base is present in an equimolar amount or molar excess to the reducible silver ions. Silver nanoparticles as silver nanoparticle cellulosic polymeric composite are prepared by mixing the (a) one or more cellulosic polymers, the (c) organic solvent, and a (d) nitrogenous base. Upon heating this premix solution to a temperature of at least 75°C, a solution of reducible silver ions is added. The resulting silver nanoparticle composite is cooled, isolated, and re- dispersed in an organic solvent.