Selective Curing of Oriented Effect Pigments for Fine Resolution Security Printing
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Solution Overview
Problem
Existing methods for producing security features with magnetically orientable effect pigments, such as banknotes, face limitations in achieving fine resolutions and effective nesting of microscopic surfaces, leading to coarse image information and inability to implement complex effects like flip effects or superimposed patterns due to coarse line widths and limited curing capabilities.
Innovation Solution
The method employs a combination of advanced light modulation techniques using 2D or 1D digital micromirror devices (DMD), Liquid Crystal on Silicon (LCoS), or diffractive optical elements (DOE) for selective curing of magnetically orientable effect pigments, allowing for higher resolutions and precise alignment of magnetic particles to achieve complex optical effects, enabling finer line widths and seamless combination of different effects on a single surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional laser curing methods are used, then the curing process can be completed, but the resolution is limited to coarse line widths of 1.59 mm to 9.5 mm, preventing fine detail reproduction
Solution Approach 1:
The patent segments the curing process into multiple discrete laser lines that can be independently controlled and positioned. By dividing the overall curing task into multiple fine-line segments, the system achieves high resolution (below 1.6mm) while maintaining manageable device complexity through systematic control of individual line elements.
Solution Approach 2:
The patent transitions from conventional point-by-point or area-based curing to line-based curing, adding a dimensional aspect to the process. This line-dimension approach enables finer resolution control and more precise positioning of cured features, achieving sub-1.6mm line widths that were not possible with traditional methods.
2Manufacturing precision
If coarse line widths are used for curing, then the process can be completed with existing technology, but fine motifs and intricate patterns cannot be realized
Solution Approach 1:
The patent segments complex motifs into multiple fine laser lines that can be precisely positioned and controlled. This segmentation allows intricate patterns and fine details to be reproduced by assembling many small, precisely-controlled line elements, achieving high motif detail resolution while maintaining systematic manufacturing simplicity.
Solution Approach 2:
The patent changes the key parameter of line width from conventional coarse dimensions (1.59-9.5mm) to fine dimensions (below 1.6mm). This parameter change enables the reproduction of fine motifs and intricate patterns while maintaining ease of manufacture through the systematic line-based curing approach.
3Adaptability or versatility
If single-step curing is used, then the process is simple, but complex optical effects and multiple image information layers cannot be achieved
Solution Approach 1:
The patent segments the curing process into multiple selective curing steps, each targeting specific areas or features. This segmentation enables the creation of complex optical effects and multiple image information layers by controlling different regions independently, while the line-based approach maintains reasonable productivity through efficient laser utilization.
Solution Approach 2:
The patent applies preliminary magnetic field application to orient effect pigments before curing, and uses selective curing steps to prepare different areas for specific optical effects. These preliminary actions enable complex optical effects to be achieved systematically, with each step building toward the final versatile security feature.
4Area of stationary object
If line-based curing with limited laser sources is used, then the system remains manageable, but large areas with varying intensity distributions cannot be cured effectively
Solution Approach 1:
The patent segments large curing areas into multiple manageable laser lines that can be systematically positioned and controlled. This segmentation allows extensive area coverage to be achieved with a limited number of laser sources, as each line can be independently directed to its target location without requiring a complex array of simultaneous laser sources.
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 approach enables resolutions below 1.6mm, allowing for intricate patterns and seamless combination of multiple effects on a single surface, enhancing the security features' visual appeal and authenticity verification without visible grids, enabling flip effects and movement effects to be visible from different angles.
Implementation Method 1
The printing ink printed onto a substrate is selectively cured with a light source modulated by 2D or 1D digital micromirror devices, Liquid Crystal on Silicon or diffractive optical elements
Implementation Method 2
An external magnetic field is then applied, causing the pigments to align, typically parallel to the field lines due to their shape anisotropy
Implementation Method 3
causing the pigments to align, typically parallel to the field lines due to their shape anisotropy
Implementation Method 4
In this state, the ink matrix surrounding the effect pigments is cured either by UV radiation or by the application of heat, thus immobilizing the pigments in their aligned state
Data Source
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AI summary
The invention relates to a method for producing a security document, in particular a banknote, comprising: a) providing a security document substrate; b) printing the security document substrate with a printing ink based on magnetically orientable effect pigments or OVMI pigments; c) while the printed ink is still liquid, orienting or aligning the magnetically orientable effect pigments by means of a first magnetic field; d) selectively curing the color matrix surrounding the magnetically oriented effect pigments by UV radiation or by laser radiation in a first region of the printed ink, such that the effect pigments are immobilized in the aligned state, wherein the curing is carried out with a resolution or line width of less than 1.59 mm, preferably less than 800 µm.