Relief Structure Pattern Transfer for High-Resolution Security Printing
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Solution Overview
Problem
Current security devices for authenticating documents of value, such as banknotes, face limitations in resolution due to ink spreading and pressure-induced deformation during printing, making them susceptible to counterfeiting and difficult to distinguish from copies.
Innovation Solution
A method involving a surface relief structure with extended contact and reduced pressure transfer of curable material onto a substrate web, allowing for higher resolution patterns with minimal deformation and improved adhesion, using a curable material applied only to raised portions of the relief structure and cured during or after transfer, with optional additional curing steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional printing processes (intaglio, gravure, flexographic, lithographic) are used to manufacture pattern elements, then production efficiency and ease of manufacture are maintained, but ink spreading and pressure-induced deformation limit resolution to 15-50 μm line widths
Solution Approach 1:
The patent replaces conventional mechanical printing processes with a photopolymerization-based transfer method. A relief master is created through photolithographic patterning, and the pattern is transferred to the substrate via contact photopolymerization of a curable composition, eliminating the need for high-pressure mechanical printing while achieving superior resolution
Solution Approach 2:
The patent changes the physical state and chemical properties of the printing medium by using a curable composition that transitions from a liquid precursor to a solid polymer network upon photopolymerization. This parameter change enables high-resolution pattern transfer without ink spreading, as the composition cures in place rather than flowing under pressure
2Manufacturing precision
If high pressure is applied during pattern transfer to ensure complete ink transfer, then transfer completeness is improved, but pattern element deformation increases and resolution deteriorates
Solution Approach 1:
The patent utilizes the phase transition of the curable composition from liquid to solid through photopolymerization. The composition is applied in liquid form, allows complete transfer under minimal pressure, then cures to solid state to lock in the high-resolution pattern without deformation, ensuring both transfer completeness and dimensional accuracy
3Manufacturing precision
If curable material is cured while in contact with the relief structure, then adhesion to substrate is improved, but material retention in recesses increases and pattern fidelity decreases
Solution Approach 1:
The patent applies preliminary action by first transferring the curable composition from the relief master to the substrate under minimal pressure while in liquid form, ensuring complete transfer without deformation. Only after the pattern is fully transferred does photopolymerization occur, locking the pattern in place on the substrate without the risk of material being trapped in recesses during curing
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
This method achieves pattern elements with dimensions 30% or less increase relative to the actual width of elevations on the surface relief, enhancing security device resolution and durability, reducing the need for high-pressure contact and minimizing ink spreading, thereby improving the security and authenticity verification of documents.
Implementation Method 1
the curable material is irradiated with electromagnetic radiation, such that the curable material is at least partially cured
Data Source
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AI summary
A method of manufacturing a pattern on a substrate web is disclosed, comprising: providing a production tool having a surface relief structure of elevations and depressions, the elevations corresponding to the desired pattern to be applied to the substrate web. A curable material is applied to the elevations of the surface relief structure on the production tool. The applied curable material on the surface relief structure is brought into contact with a substrate web at a first location. The substrate web and surface relief structure are transported together in contact from the first location to a second location, the first and second locations being spaced from one another along the transport direction of the substrate web. The substrate web is separated from the surface relief structure at the second location whereupon the curable material forming the pattern is affixed to and carried by the substrate web. The curable material on the substrate web is cured by exposure to at least one curing energy source, either while the substrate web and surface relief structure are in contact between the first and second locations and/or after the substrate web has been separated from the surface relief structure at the second location.