Silver Particle Dispersion for Flexographic Printing
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Solution Overview
Problem
Conductive ink solutions with fine silver particles face challenges in maintaining wire resistance and substrate compatibility due to the formation of thin web-shaped films during flexographic printing, leading to short circuits and reduced productivity.
Innovation Solution
A fine silver particle dispersing solution is developed, containing fine silver particles coated with an organic acid or derivative, ammonia, nitric acid, and a shape retaining agent, which prevents the formation of thin films and maintains wire resistance by using a water-based medium and specific additives like polyether-modified polydimethylsiloxane and silicone antifoaming agents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If fine silver particles are coated with a surfactant having a high molecular weight and a long chain to prevent aggregation, then the stability of fine silver particles is improved, but the heat treatment temperature must be increased and the treatment time extended, deteriorating productivity and limiting substrate choices
Solution Approach 1:
The patent changes the molecular weight parameter of the coating substance from high to low, and changes the chain length parameter from long to short. This allows the surfactant to be removed at lower temperatures (not higher than 200°C) and shorter times, improving productivity while maintaining particle stability during storage
Solution Approach 2:
The patent applies different properties to different stages: uses low molecular weight/short chain surfactants for the heat treatment stage to enable easy removal, while maintaining adequate coating coverage for storage stability. This local optimization resolves the contradiction between stability and productivity
2Stability of the object's composition
If organic solvent is used as the dispersing medium of the conductive ink, then the dispersibility of fine metal particles is improved, but environmental pollution occurs and additional ventilation equipment is required
Solution Approach 1:
The patent replaces persistent organic solvents with water as the dispersing medium. Water is environmentally friendly, non-toxic, and does not require special ventilation equipment, thereby eliminating environmental pollution while maintaining particle dispersibility
Solution Approach 2:
The patent changes the dispersing medium from organic solvent to water-based solution, fundamentally altering the chemical composition parameter to eliminate harmful environmental effects while preserving the functional requirement of particle dispersibility
3Ease of operation
If a conductive ink containing metal particles with particle diameter of about a few micrometers is used, then the material is easier to handle, but fine wires or conductive circuits cannot be formed and sintering requires high temperature
Solution Approach 1:
The patent changes the particle diameter parameter from micrometers to nanometers (1-100 nm). This enables the formation of fine wires and conductive circuits while the water-based formulation and surfactant system maintain ease of handling and printing
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 solution enables the formation of wires with stable resistance and prevents short circuits, allowing for efficient flexographic printing on various substrates without the need for high-temperature heat treatment, thus improving productivity and environmental safety.
Implementation Method 1
fine silver particles dispersed in a water-based dispersion medium
Implementation Method 2
fine silver particles coated with an organic acid or a derivative thereof... by preventing the fine metal particles from being sintered and/or aggregated with each other
Implementation Method 3
ammonia added to the water-based dispersion medium; nitric acid added to the water-based dispersion medium
Implementation Method 4
a shape retaining agent added to the water-based dispersion medium... prevents the formation of thin films
Implementation Method 5
specific additives like polyether-modified polydimethylsiloxane and silicone antifoaming agents
Implementation Method 6
it is also possible to sinter metal particles with each other even if they are burned at a low temperature of not higher than 200 °C
Data Source
Figure 1A~1B
Figure 2
AI summary
In a fine silver particle dispersing solution wherein 30 to 75 % by weight of fine silver particles, which are coated with an organic acid having a carbon number of 5 to 8 or a derivative thereof and which have an average particle diameter of 1 to 100 nm, are dispersed in a water-based dispersion medium which is a solvent containing water as a main component, the fine silver particle dispersing solution containing ammonia and nitric acid, there is added 0.15 to 0.6 % by weight of a surface regulating agent, which preferably contains a polyether-modified polydimethylsiloxane and a polyoxyethylene alkyl ether or a polyether, or 0.005 to 0.6 % by weight of an antifoaming agent which is preferably a silicone antifoaming agent.