Surface Relief Security Features for Tactile Multi-Tonal Images
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Solution Overview
Problem
Existing security features on documents such as banknotes and passports, particularly those using intaglio printing on polymer substrates, face limitations in tactility and durability due to thermal instability, leading to difficulties in registration and ink transfer, and are prone to counterfeiting.
Innovation Solution
A security device featuring surface relief structures formed from cured materials on a flat substrate, with varying raised elements that create a multi-tonal image, enhancing tactility and durability while allowing precise registration and avoiding issues like set-off and long drying times.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If intaglio printing is used on polymer substrates, then tactile security features are provided, but thermal instability limits the embossing depth and profile height
Solution Approach 1:
The patent replaces the thermal embossing process with a mechanical casting process. A casting tool with a relief structure is pressed against the substrate, and curable material is forced into the recesses of the casting tool, creating raised elements without requiring thermal deformation of the polymer substrate. This mechanical approach overcomes the thermal stability limitations of polymer substrates.
Solution Approach 2:
The patent changes the fundamental parameter of the forming process from thermal (intaglio embossing) to mechanical/c chemical (casting and curing). By using a casting tool that physically displaces curable material rather than thermally deforming the substrate, the process achieves greater profile heights without being constrained by the substrate's thermal stability.
2Manufacturing precision
If intaglio printing is used, then high resolution images are achieved, but registration difficulties occur due to substrate deformation
Solution Approach 1:
The patent replaces the embossing-based intaglio process with a casting process that does not deform the substrate. The casting tool is pressed against the flat substrate, and curable material is deposited into the relief structure without causing permanent substrate deformation. This maintains substrate flatness and enables accurate registration of subsequent print processes.
3Strength
If conventional intaglio printing is used, then tactile images are formed, but set-off and long drying times occur
Solution Approach 1:
The patent changes the material state from liquid ink that requires drying to curable material that undergoes a chemical transformation. The curable material is applied in a liquid or paste state, then cured through UV irradiation or other curing mechanisms, eliminating the long drying times and set-off problems associated with conventional intaglio inks.
Solution Approach 2:
The patent utilizes a phase transition from liquid to solid through curing rather than evaporation. The curable material transitions from a liquid or paste state to a solid state through photopolymerization or other curing mechanisms, avoiding the evaporation-based drying process that causes set-off and extended drying times in conventional intaglio printing.
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 provides enhanced security through improved tactility, precise registration, and resistance to counterfeiting by utilizing cured materials on a flat substrate, overcoming limitations of intaglio printing on polymer substrates.
Implementation Method 1
The at least one curable material comprises a machine-readable substance... irradiating the curable material with UV radiation so as to cure the curable material
Data Source
AI summary
A security device is provided, comprising one or more surface relief structure(s), each formed of one or more cured material(s), the surface relief structure(s) being disposed on a substantially flat substrate and defining a plurality of raised elements spaced from one another, the raised elements corresponding to elements of an image, whereby the plurality of raised elements varies across the surface relief structure(s) so as to exhibit a multi-tonal version of the image. Methods of manufacturing such devices are also disclosed.