Optically Variable Security Element Facet Orientation
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Solution Overview
Problem
Conventional see-through security elements with viewing angle-dependent multicolored color changes in transmitted light suffer from limitations such as sensitivity to lighting conditions, complex production processes, and limited protection against imitation, particularly in achieving uniformity and scalability for industrial applications.
Innovation Solution
The development of an optically variable see-through security element featuring a flat, surface pattern with facets oriented uniformly in terms of inclination and azimuth angles, combined with a varying interference layer thickness that depends on the angle of inclination, to produce strong color differences and realistic true-color images when tilted.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If holographic gratings or transmission gratings are used to generate diffraction colors in transmitted light, then multicolored color change depending on viewing angle is achieved, but the appearance depends heavily on lighting conditions and requires complex positioning
Solution Approach 1:
The patent changes the fundamental optical parameter from diffraction-based color generation to interference-based color generation. By using thin-film interference with controlled layer thicknesses (especially the dielectric spacer layer), the security element achieves viewing-angle-dependent color changes that are independent of lighting conditions and positioning, resolving the contradiction between manufacturing simplicity and color appearance consistency
Solution Approach 2:
The patent applies different layer thicknesses in different spatial regions of the security element to create specific color effects at different viewing angles. By locally varying the dielectric spacer layer thickness, the system achieves position-dependent and angle-dependent color changes, allowing complex security patterns while maintaining consistent appearance under various lighting conditions
2Reliability
If thin-film systems with varied layer thicknesses are used to generate colors through interference, then viewing angle-dependent color changes are achieved, but adjusting layer thicknesses is technologically very complex and requires high uniformity in printed layers
Solution Approach 1:
The patent segments the thin-film system into distinct functional layers (absorber layers and dielectric spacer layer) with specific roles. By dividing the structure into these segments, the system achieves complex optical effects through simple geometric arrangements and thickness variations, reducing production complexity while maintaining high counterfeit protection
Solution Approach 2:
The patent systematically varies the dielectric spacer layer thickness as the primary control parameter to achieve different color effects. This single-parameter control approach simplifies the production process compared to coordinating multiple layer thicknesses, while still enabling complex viewing-angle-dependent color changes for counterfeit protection
3Reliability
If subwavelength structures are used to generate colors in reflected and transmitted light, then viewing angle-dependent color changes are achieved, but the structures are very complex to manufacture and difficult to produce on large-scale industrial scale
Solution Approach 1:
The patent replaces complex mechanical subwavelength structures with a simpler thin-film interference system using conventional deposition techniques. This substitution maintains the authenticity of viewing-angle-dependent color effects while enabling large-scale industrial production through established manufacturing processes, resolving the contradiction between color effect authenticity and industrial scalability
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 solution provides a high degree of protection against forgery, maintains consistent brightness distribution, and enables the creation of visually appealing, multicolored effects that are not dependent on lighting conditions, while being producible on an industrial scale.
Implementation Method 1
the facets are provided with an interference layer with a color change in transmitted light that depends on the viewing angle
Data Source
Figure 1~3
Figure 4a~4b
Figure 5a~5d
AI summary
The invention relates to an optically variable transparent security element (12) for safeguarding valuables, said security element comprising a planar, optically variable surface pattern that when looked through displays a coloured appearance having a multi-coloured colour change that is dependent on the viewing angle. According to the invention, the optically variable surface pattern contains a plurality of facets (32) which create a substantially optical effect under radiation, the orientation of each facet being characterised by an angle of inclination α with respect to the plane of the surface pattern, which angle of inclination is between 0° and 45°, and by an azimuth angle Θ in the plane (30) of the surface pattern. The facets (32) are provided with an interference layer (36) which has a colour change in transmitted light depending on the viewing angle, and the optically variable surface pattern contains at least two partial regions (16, 18) each having a plurality of facets (32) that are oriented in the same direction, wherein the facets (32) of the at least two partial regions (16, 18) differ from one another in the angle of inclination with respect to the plane and/or in the azimuth angle in the plane.