Security Thread Microstructure for Anti-Counterfeiting
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Solution Overview
Problem
Current security threads and window elements for objects of value lack a robust, easily perceivable optical effect that is difficult to replicate, particularly in providing a high-resolution, color-impressive design that is authenticatable from both sides without being disturbed by light scattering or diffraction effects.
Innovation Solution
A multi-layer body with a transparent, embossed layer having a microstructure that is either sub-wavelength or microcavities with specific dimensions and an aspect ratio, metallized in sections to be light-absorbing from both sides, combined with cholesteric liquid crystal layers on either side, and optionally supported by transparent carrier films, arranged in a non-orthogonal lattice like hexagonal for optimal light absorption and minimal scattering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a metallized surface with regular or irregular structures in the wavelength range of light is used, then the security element provides anti-counterfeiting protection and appears deep black from almost all angles, but light scattering and diffraction effects disturb the optical effect and reduce perception quality
Solution Approach 1:
The patent changes the geometric parameters of the microstructure, specifically using sub-wavelength structures with dimensions smaller than the wavelength of visible light (e.g., 200-500 nm). This parameter change eliminates light scattering and diffraction effects while maintaining the deep black appearance and anti-counterfeiting properties of the metallized surface.
Solution Approach 2:
The patent applies different local qualities to different regions of the security element. The background areas use sub-wavelength structures for optimal light absorption without scattering, while specific security features or patterns may use different microstructure geometries or metallization patterns to create distinguishable optical characteristics for authentication.
2Illumination intensity
If a microstructure with high aspect ratio and specific aperture width is used, then light absorption is improved and the appearance becomes deeper black, but the manufacturing precision requirements increase
Solution Approach 1:
The patent uses copying techniques where a master template with the precise sub-wavelength microstructure pattern is created first, then used to replicate the pattern across the entire security element surface. This copying approach maintains high manufacturing precision for the critical sub-wavelength dimensions while enabling large-scale production.
Solution Approach 2:
The patent transitions from two-dimensional surface patterns to three-dimensional sub-wavelength structures with controlled depth and aperture. By adding the depth dimension and controlling the aspect ratio, the patent achieves superior light absorption while the self-similar repeating nature of the 3D structures simplifies manufacturing through techniques like embossing or molding.
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 a secure, high-resolution, color-impressive optical effect that is easily perceivable from both sides, resistant to light scattering and diffraction, enhancing authenticity checks and preventing counterfeiting while maintaining structural integrity.
Implementation Method 1
the microstructure is designed such that it is at least partially light-absorbing from both the front and the back
Implementation Method 2
Cholesteric liquid crystal layers are located on both sides of the transparent layer structure thus obtained. Since the microstructure is at least partially light-absorbing on both sides, both cholesteric liquid crystal layers are located at least partially against a dark background.
Data Source
Figure 1~4
Figure 5~7
Figure 8(a)~10(b)
AI summary
The invention relates to a security thread or window element for a valuable article. Said security thread or window element has a multi-layered body with a front side (V) and a rear side (R). Said body comprises: a transparent, embossed layer (2), the surface thereof being embossed with a microstructure (6), a metallisation (7) which is applied at least to parts of the surface of the embossed layer (2), a transparent cover layer (3) which is applied to the surface and over the metallisation (7), said cover layer leveling out the microstructure (6), a first liquid crystal layer (4.1) which is applied over the cover layer (3). Said microstructure (6) has either a sub-wave structure (10) or comprises micro-cavities (12) having an aperture width of between 0,5 μm - 3 μm and an aspect ratio of 0,5 and larger, and is designed such that it absorbs light at least in sections from the front side (V) as well as from the rear side (R). A second liquid crystal layer (4.2) is provided below the embossed layer (2).