Transparent Conductive Coatings with Delayed Sintering Additives
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Solution Overview
Problem
Existing methods for forming low resistance transparent conductive coatings require high-temperature sintering or costly and hazardous chemical processing steps, which are not suitable for flexible substrates in commercial roll-to-roll processing.
Innovation Solution
A process involving a water-in-oil emulsion with metal nanoparticles and a delayed sintering additive that reduces the standard reduction potential of metal ions, allowing for the formation of conductive traces without the need for separate chemical sintering, achieving sheet resistance below 100 ohm/sq through thermal treatment alone.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high-temperature sintering is used to achieve low sheet resistance, then electrical conductivity is improved, but the process becomes unsuitable for flexible polymeric substrates
Solution Approach 1:
The invention changes the chemical environment by introducing a water phase with specific pH conditions (pH < 3.0 before mixing, pH > 8.0 after mixing) that enables low-temperature sintering of metal nanoparticles. This parameter change in the chemical environment allows achieving low sheet resistance without high-temperature thermal treatment, making the process compatible with flexible polymeric substrates
Solution Approach 2:
The invention uses a composite emulsion system containing metal nanoparticles dispersed in an oil phase with a water phase, where the water phase contains additives that facilitate low-temperature sintering. This composite material approach enables the nanoparticles to sinter at lower temperatures while maintaining electrical conductivity, thus protecting the flexible substrate from thermal damage
2Reliability
If separate chemical sintering steps are used to achieve low sheet resistance, then electrical conductivity is improved, but process complexity and cost increase
Solution Approach 1:
The invention merges the sintering function into the coating formulation itself by incorporating a water phase with specific pH conditions and additives into the emulsion. This eliminates the need for separate chemical sintering steps, as the sintering occurs automatically during or after the coating and drying process, thereby reducing process complexity and cost
Solution Approach 2:
The invention performs preliminary chemical preparation by formulating the emulsion with a water phase that has specific pH conditions and contains additives capable of facilitating sintering. This preliminary action ensures that when the coating is applied and dried, the sintering process occurs automatically without requiring additional chemical treatment steps
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 process eliminates the need for chemical sintering, achieving low sheet resistance without hazardous chemicals and high-temperature processing, making it suitable for flexible substrates and scalable commercial production.
Implementation Method 1
an additive for delayed sintering of the nanoparticles that reduces the standard reduction potential of the metal ion of the metal forming the nanoparticles by an amount greater than 0.1V but less than the full reduction potential of the metal ion
Implementation Method 2
evaporating the liquid from the coating to form a dry coating comprising a network of electrically-conductive traces
Data Source
AI summary
A process is disclosed for the delayed sintering of metal nanoparticles in a self-assembled transparent conductive coating by incorporating a sintering additive into the water phase of the emulsion used to form the coating. The sintering additive reduces the standard reduction potential of the metal ion of the metal forming the nanoparticles by an amount greater than 0.1V but less than the full reduction potential of the metal ion. Emulsion compositions used in the process are also disclosed.