Security Element With Height-Modulated Multilayer Color Filter
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Solution Overview
Problem
Existing security elements fail to effectively cover a large area of the color space in both reflection and transmission, limiting their ability to provide robust authenticity verification and anti-reproduction protection.
Innovation Solution
A security element with a height-modulated carrier and a multilayer structure comprising a metallic or semi-metallic first and third layer, and a dielectric second layer, allowing for periodic modulation and lateral variation in grating period and profile, along with the option of incorporating metallic nanoparticles, to achieve polarization-dependent color filter effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If Z-grid structures are used for color generation, then fine structured multicolored motifs can be produced in transmission, but the color contrast in reflection is only slightly pronounced and only a relatively small area of the color space can be reproduced
Solution Approach 1:
The patent combines metallic or semi-metallic layers with dielectric layers to form a composite multilayer structure. This composite approach enables the structure to exhibit both plasmonic effects (from metal) and high refractive index contrast (from dielectric), achieving broad color space coverage in both reflection and transmission while maintaining fine structured motif production capability
Solution Approach 2:
The patent varies structural parameters including layer thicknesses, grating periods, and profiles to optimize color generation across different wavelengths. By adjusting these parameters, the structure achieves enhanced color contrast in reflection while maintaining transmission properties, thereby expanding the reproducible color space
2Ease of manufacture
If interference filters or thin metal layers with plasma resonance effects are used, then color-influencing effects can be achieved, but the ability to cover a large area of the color space in both reflection and transmission is limited
Solution Approach 1:
The patent employs a composite structure combining metallic/semi-metallic layers with high-refractive-index dielectric layers. This composite design leverages plasma resonance effects from the metal while the dielectric layers enhance light interaction through refractive index contrast, enabling broad color space coverage in both reflection and transmission modes
Solution Approach 2:
The patent applies different material properties and structural characteristics to different layers within the multilayer structure. Each layer is optimized with specific thickness and material composition to contribute differently to the overall color generation mechanism, enabling comprehensive color space coverage across reflection and transmission
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 enables a broad coverage of the color space in both reflection and transmission, providing enhanced authenticity verification and making it difficult to reproduce, with the ability to produce finely structured, multicolored motifs that are resistant to copying.
Implementation Method 1
a multilayer structure acting as a color filter, which is formed on the height-modulated upper side... the first and third layers each being formed of a metallic material or a semi-metal... a second layer formed thereon and made of dielectric material
Implementation Method 2
metallically obliquely vapour-deposited sub-wavelength grids, so-called Z-grids... metallic grids under the excitation of surface plasmon polaritons
Implementation Method 3
The height modulation of the upper side and of the multi-layer structure can be periodic in a first direction... the grating period is smaller than the longest wavelength of the range of electromagnetic radiation
Data Source
Figure 1~2
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Figure 6~7
AI summary
The invention provides a security element (1) for security papers, documents of value or the like, having a substrate (3) the upper face (6) of which is height-modulated, and has a multilayer structure (7) which acts as a color filter, said structure being formed on the height-modulated upper face (6) and is likewise height-modulated as a result, and comprising a first layer (8), a second layer (9) of dielectric material formed thereon and a third layer (10) formed on the second layer (9), wherein the first and third layer (8,10) are each formed from a dielectric material having a higher refractive index than that of the second layer (9), or in each case from a metal or semi-metal material.