Embedded Foil Strip for Security Document Window Quality
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Solution Overview
Problem
Existing methods for embedding foil strips in paper substrates for security documents result in poor window quality due to unclear borders and residual fibers, making it difficult to create sharp, fiber-free areas for security elements.
Innovation Solution
A method involving a partially porous foil strip embedded in the paper substrate, where fibers are selectively removed from the window area using a fluid jet or suction, and a hydrophobic surface treatment to inhibit fiber deposition, ensuring sharp borders and fiber-free zones for improved security features.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a foil strip is embedded in paper substrate using conventional papermaking methods, then the security element is integrated into the document, but the window area quality deteriorates with residual fibers and unclear borders
Solution Approach 1:
The foil strip is pre-perforated with openings before being embedded in the paper substrate. These pre-made openings allow fibers to be selectively removed from the window area during papermaking, enabling clear border definition and fiber-free zones while maintaining secure embedding of the foil strip in non-window areas
Solution Approach 2:
Fibers are selectively removed from the window area through the pre-perforated openings in the foil strip during the papermaking process. This extraction of fibers from specific regions creates the desired fiber-free zones with sharp borders, while the foil strip remains embedded in areas where fibers are retained
2Reliability
If the foil strip is fully embedded in the paper substrate, then security against copying is improved, but the visibility and accessibility of security elements in window areas deteriorates
Solution Approach 1:
The foil strip exhibits different embedding characteristics in different regions: in window areas, the pre-perforated openings allow fiber removal creating accessible, visible security elements; in non-window areas, the foil strip remains fully embedded in the paper substrate providing security against copying. This spatial variation in embedding quality satisfies both security and accessibility requirements
3Ease of manufacture
If conventional embedding methods are used without pre-perforation, then the manufacturing process is simpler, but the border sharpness and fiber-free quality of window areas deteriorates
Solution Approach 1:
The foil strip is pre-perforated with openings before the embedding process. This preliminary action enables subsequent selective fiber removal to create sharp borders and clear window areas, significantly improving manufacturing precision compared to conventional methods without pre-perforation, while the overall process remains integrated into standard papermaking operations
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 method enhances the quality of window areas by creating sharp, fiber-free zones, allowing for more effective security features and increased flexibility in creating tactile and optical effects that are difficult to replicate.
Implementation Method 1
the local repulsion being induced by application of a fluid (in form of a jet through a nozzle), in particular compressed air and/or water
Implementation Method 2
The locally selective inhibition can be provided by a hydrophobic or super-hydrophobic layer/structure
Implementation Method 3
the water droplet/solid surface snap-in forces - measured e.g. using the micro balance in a tensiometer - become zero because the surface tension of the water, hence its internal cohesion, is stronger than the reference surface wettability
Implementation Method 4
The exposed or uncovered area can also be generated by removal of fibers by suction, in particular discontinuous suction
Data Source
AI summary
The invention relates to a valuable document (10) comprising fibrous material (20) and methods of manufacturing the valuable document (10). The fibrous material (20) comprises a registered elongate strip of foil (30) embedded in the thickness of the fibrous material (20), the elongate strip of foil (30) being at least partially perforated in order to be permeable for fibers (33) of the fibrous material (20), wherein the elongate strip of foil (30) is exposed in that it is uncovered or substantially uncovered by fibers (33) of the fibrous material (20) in an exposed area on at least one side of the valuable document so as to provide a window area (32) comprising a security element of the elongate strip of foil (30) which is in register with the window area (32).