Conductive Ink Formulation for Polymer Film Adhesion
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Solution Overview
Problem
Conductive inks face challenges in printing on polymer film substrates, including slow drying times, poor adhesion, and difficulties in forming continuous electrical circuits, which hinder production speed and efficiency, especially when subjected to electroplating processes.
Innovation Solution
A conductive ink formulation comprising silver, a solvent mixture, and a cross-link agent, such as 1,3,5-tris(6-isocyanatohexyl) biuret, that allows for quicker drying and improved adhesion, enabling faster production rates and effective electroplating compatibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional conductive ink formulations are used with screen printing methods, then good adhesion and print quality can be achieved, but the drying time becomes excessively long (3 to 20 minutes) which reduces production speed
Solution Approach 1:
The patent modifies the chemical composition parameters of the conductive ink by incorporating specific solvents (ethyl acetate, butyl acetate, isobutyl acetate, n-propyl acetate) and binders (polyvinyl butyral, polyvinyl formal) in optimized ratios. This parameter change enables the ink to achieve proper adhesion and film formation with significantly reduced drying time compared to conventional formulations
Solution Approach 2:
The patent creates a composite conductive ink formulation by combining silver particles with a carefully selected mixture of solvents and binders. This composite structure provides both the conductivity from silver particles and the adhesion properties from the polymer binders, while the solvent mixture ensures proper drying characteristics
2Reliability
If thicker layers of ink are used in screen printing to ensure good coverage and adhesion, then print quality improves, but the amount of ink required increases and drying time extends further
Solution Approach 1:
The patent optimizes the viscosity and composition parameters of the ink formulation to achieve uniform distribution and proper adhesion with thinner ink layers. The specific binder-to-solvent ratio and particle size distribution are tuned to ensure complete coverage and bonding without requiring excessive ink application
3Productivity
If rotogravure screen printing is used to increase production speed to approximately 50 feet per minute, then productivity improves, but the cost increases significantly and the ink forms disconnected diamond shapes rather than continuous lines
Solution Approach 1:
The patent modifies the ink's rheological parameters including viscosity, surface tension, and flow characteristics to ensure proper ink transfer and continuous line formation during high-speed rotogravure printing. The formulation ensures the ink maintains its continuity at printing speeds up to 50 feet per minute
Solution Approach 2:
The patent prepares the ink formulation in advance with optimized viscosity and flow properties specifically tailored for rotogravure printing. This preliminary optimization of ink characteristics ensures proper filling of the gravure cells and continuous line deposition at high printing speeds
4Ease of manufacture
If conventional conductive inks are used, then printing can be performed on polymer film substrates, but the ink separates from the film due to poor adhesion and requires extended curing time
Solution Approach 1:
The patent develops a composite ink system where polymer binders (polyvinyl butyral, polyvinyl formal) are specifically selected to bond with polymer film substrates. This composite formulation ensures strong adhesion between the conductive ink and the flexible substrate, preventing separation during handling and electroplating processes
Solution Approach 2:
The patent adjusts the molecular weight, functional groups, and composition ratios of the binder polymers to optimize adhesion to polymer films. The solvent mixture is also tuned to ensure proper wetting and penetration into the substrate surface for maximum bonding strength
5Adaptability or versatility
If screen printing methods are used with conventional inks, then electroplating can be performed, but the process becomes too slow for practical production due to extended drying and curing times
Solution Approach 1:
The patent modifies the drying kinetics parameters of the ink by adjusting the solvent evaporation rates and binder curing characteristics. This enables the ink to reach electroplating-ready state much faster than conventional formulations, allowing practical production speeds while maintaining electroplating compatibility
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 formulation achieves faster production speeds, better adhesion, and maintains conductivity, allowing for efficient printing of well-defined lines and patterns on polymer film substrates, including those intended for electroplating processes.
Implementation Method 1
A conductive ink formulation in accordance with an aspect of the invention includes a cross link agent
Data Source
AI summary
A conductive ink formulation comprising silver, at least one first solvent, and a cross link wherein the cross link agent is present in an amount of about 1.5 wt % to about 6 wt % based on total weight of the formulation. The conductive ink formulation is suitable for printing on polymer film substrates, in particular with a gravure printing method. The polymer film substrates may be then applied to other substrates, for example glass substrates, by any suitable process such as lamination.