UV-Curable Thermoformable Dielectric for Capacitive Switches
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Solution Overview
Problem
Existing UV-curable dielectric compositions are not commonly used in thermoformable capacitive circuits, which require protection of conductive silver from moisture, and traditional dielectrics can cause cracking in polycarbonate substrates during thermoforming.
Innovation Solution
A polymer thick film UV-curable thermoformable dielectric composition comprising 20-60 wt % acrylated urethane oligomer, 5-30 wt % alkyl acrylate monomer, 1-15 wt % acrylated amine, and 5-35 wt % inorganic powder, designed to provide a protective and insulating layer that prevents moisture penetration and maintains substrate integrity during thermoforming.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional dielectric compositions are used in thermoformable capacitive circuits, then moisture protection of silver conductors is provided, but cracking occurs in polycarbonate substrates during thermoforming
Solution Approach 1:
The patent modifies the chemical composition parameters of the dielectric by incorporating specific flexible polymer components (polyurethane, polyester, polyether in 20-60 wt% range) and controlling plasticizer content (5-30 wt%), which changes the material's thermal and mechanical properties to prevent cracking during thermoforming while maintaining moisture protection
Solution Approach 2:
The patent creates a composite dielectric formulation combining multiple polymer types (acrylated polyurethane, polyester, polyether), plasticizers, and inorganic fillers (5-35 wt%) to achieve both flexibility for thermoforming and effective moisture barrier properties, resolving the contradiction between substrate integrity and moisture protection
2Productivity
If UV-curable dielectric compositions are used, then rapid curing and adhesion are achieved, but compatibility with thermoforming processes is poor
Solution Approach 1:
The patent adjusts the chemical composition by selecting specific oligomers with appropriate molecular weights and functional groups, and controlling the ratio of monomers to oligomers (40-80 wt% total), which enables the dielectric to cure rapidly under UV while remaining flexible enough for subsequent thermoforming operations
Solution Approach 2:
The patent creates different functional zones within the dielectric composition: the oligomer and monomer components provide UV curability and adhesion, while the plasticizer and flexible polymer components provide thermoforming compatibility, allowing each component to fulfill its specific function locally within the composite material
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 composition effectively protects silver layers from moisture, prevents cracking in polycarbonate substrates, and enables the formation of reliable crossover circuitry in 3-dimensional capacitive circuits with improved adhesion and electrical properties.
Implementation Method 1
UV-curable dielectric composition... acrylated urethane oligomer... alkyl acrylate monomer... acrylated amine
Implementation Method 2
5-35 wt % inorganic powder... maintains substrate integrity during thermoforming
Data Source
AI summary
This invention is directed to a polymer thick film UV-curable thermoformable dielectric composition. Dielectrics made from the composition can be used in various electronic applications to protect electrical elements and particularly to insulate and protect both the conductive thermoformable silver and the polycarbonate substrate below it in capacitive switch applications. The thermoformed capacitive switch circuit may be subsequently subjected to an injection molding process.