Security Element With Inverted Line Gratings and Metalized Relief
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Solution Overview
Problem
Existing security elements for documents of value, such as banknotes, struggle with color saturation issues when exposed to unpolarized light, and are difficult to replicate due to complex registration requirements in conventional printing processes.
Innovation Solution
A security element featuring a dielectric substrate with embedded high-index material line gratings in two planes, where the second grating bars are inverted relative to the first, creating sub-wavelength structures that produce angle-dependent color-filtering effects, combined with a metalized relief structure for enhanced contrast and design variability, allowing for embossing processes that simplify production and increase forgery resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional printing processes are used to produce security elements with line gratings, then production can be achieved, but registration requirements become complex and difficult to replicate
Solution Approach 1:
The patent replaces conventional printing processes with an embossing process to produce the line grating structure. The embossing process uses mechanical deformation to create the grating pattern directly in the substrate, eliminating the need for complex printing registration. This substitution of mechanical embossing for printing resolves the contradiction by simplifying the production process while maintaining manufacturing precision.
2Ease of manufacture
If sub-wavelength grating structures are used to achieve color-filtering properties, then angle-dependent color effects are produced, but color saturation drops significantly when incident light is unpolarized
Solution Approach 1:
The patent employs a composite structure combining high-index dielectric material line gratings with a metalized relief structure. The high-index dielectric material provides the sub-wavelength grating effect for angle-dependent color filtering, while the metalized relief structure enhances light interaction to maintain color saturation with unpolarized incident light. This composite approach resolves the contradiction by combining materials with complementary optical properties.
3Reliability
If the line grating structure is made with dimensions less than 300 nm to achieve sub-wavelength effects, then color-filtering properties are enhanced, but the structure becomes more difficult to manufacture with conventional processes
Solution Approach 1:
The patent uses an embossing process to directly create the sub-wavelength grating structure with dimensions less than 300 nm in the substrate. The embossing process employs mechanical deformation at controlled temperatures and pressures to form the precise nanoscale features without requiring conventional lithography or etching steps. This mechanical approach resolves the contradiction by making sub-wavelength structure fabrication more accessible and reliable.
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 achieves stable color effects under varying angles of incidence and provides high-contrast, optically variable designs that are difficult to replicate, enhancing security features and production simplicity.
Implementation Method 1
The underlying Guided-Mode-Resonance-Effect forms resonances in that a significant portion of the incident light is coupled through a dielectric grating into a waveguide layer and this light portion in turn interferes constructively or destructively with the incident light.
Implementation Method 2
this light portion in turn interferes constructively or destructively with the incident light
Implementation Method 3
Such color filter properties are known both for reflecting and for transmitting sub-wavelength structures. These structures have a strong polarizing effect on the reflection or transmission of an incident light beam.
Data Source
Figure 1
Figure 2A~2B
Figure 2C~3A
AI summary
The invention relates to a security element for the production of value documents, such as banknotes, checks or the like, which has a linear lattice having first and second lattice webs (3, 7), wherein the first and second lattice webs (3, 7) do not form a coherent film and the arrangement of the second lattice webs (7) is inverted with respect to that of the first lattice webs (3), in which different regions (17-19) are formed in the security element (S), which differ with regard, for example, to the orientation of the longitudinal direction of the linear lattice, wherein the various regions encode at least one motif. According to the invention, in plan view, a metallised relief structure (11) is arranged underneath the linear lattice, said relief structure having various sections (12-15) which differ with regard to the relief and the reflection of radiation, wherein the various sections (12-15) of the metallised relief structure (11) are assigned to the various regions (17-19) of the linear lattice and further structure the motif.