Smart Card Antenna Insert Flatness via Laminated Cover Layers
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Solution Overview
Problem
Smart card antennas often exhibit surface irregularities due to the presence of through holes, leading to imperfect flatness, which is detrimental to the visual appearance, especially when the outer faces are transparent, and fails to meet the standards for card thickness and flatness.
Innovation Solution
The use of a laminated structure for the cover layers with a proximal sheet having lower fluidity than the distal sheet, bonded together during lamination, ensures improved flatness and visual appearance by minimizing material flow through holes in the central layer, using polycarbonate sheets with different visco-elastic properties and mineral filler content.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If through holes are present in the central layer to allow cover layers to adhere, then the antenna structure is formed, but surface irregularities occur leading to poor flatness
Solution Approach 1:
The cover layer is segmented into two separate sheets (proximal sheet and distal sheet) with different fluidity characteristics. The proximal sheet has lower fluidity to maintain surface flatness and prevent material flow through holes, while the distal sheet has higher fluidity to ensure proper adhesion through the holes. This segmentation allows each sheet to perform its specific function independently, resolving the contradiction between maintaining flatness and ensuring structural integrity.
2Manufacturing precision
If cover layers are used to compensate for thickness irregularities, then flatness is improved, but material flows through holes causing surface irregularities
Solution Approach 1:
Different regions of the cover layer structure are assigned different material properties. The proximal sheet is positioned close to the central layer with lower fluidity to locally control material flow and maintain surface flatness. The distal sheet is positioned farther away with higher fluidity to locally ensure adhesion through the holes. This local differentiation of material properties resolves the contradiction between preventing material flow and ensuring proper bonding.
3Illumination intensity
If transparent structural layers are used, then visual appearance is improved, but surface irregularities become more visible
Solution Approach 1:
The cover layer is divided into two sheets with different optical and rheological properties. The proximal sheet with lower fluidity is positioned adjacent to the central layer to prevent material protrusion through holes, thereby maintaining surface smoothness that remains invisible even when the structural layers are transparent. The distal sheet with higher fluidity ensures proper adhesion. This segmentation allows the transparent card to maintain both visual appeal and surface regularity.
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 achieves a smart card with enhanced geometric characteristics, including improved flatness and compliance with thickness standards, while maintaining the security features and visual appeal, especially when the card faces are transparent.
Implementation Method 1
the two sheets being superimposed and laminated
Implementation Method 2
the proximal sheet has, during the lamination phase, a lower fluidity than that of the distal sheet
Data Source
Figure 1
Figure 2~3
AI summary
The invention relates to an insert forming an antenna (20) for a smart card, comprising: an antenna-forming central layer (21) comprising a substrate (22) and at least one conductor (24) extending along at least one surface of the substrate (22); at least one covering layer (30) covering at least one side of the central layer (21) and capable of compensating for the surface irregularities of the surface of the central layer (21). The covering layer(s) (30) comprise a proximal sheet (32) located close to the central layer (21) and a distal sheet (34) located away from the central layer (21), the two sheets being stacked and laminated and the proximal sheet (32) has, during the lamination phase, a lower fluidity than that of the distal sheet (34).