Optically Variable Security Element Refractive Index Matching
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Solution Overview
Problem
Current optically variable security elements fail to provide high security against forgery while maintaining easy recognizability and verifiability, as they can be copied and their authenticity is difficult to verify, especially when viewed through.
Innovation Solution
An optically variable element with a transparent carrier layer, a partially transparent reflection layer forming semi-transparent micromirrors, and a transparent embedding layer, where the refractive indices of the carrier and embedding layers do not differ by more than 0.2, creating a 'see-through anti-watermark' effect that disappears when viewed through, and featuring a reflection layer with a high refractive index for color representation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a structured reflection layer forming micromirrors is used to create a visible motif from above, then the security element provides good recognizability and visual security features, but the motif becomes visible when viewed through, reducing security against forgery
Solution Approach 1:
The patent applies parameter changes by precisely controlling the refractive indices of the carrier layer (n1) and embedding layer (n2) such that their difference |n1 - n2| ≤ 0.2. This parameter optimization ensures that light passing through the structured reflection layer experiences minimal refraction, causing the motif to disappear when viewed through while maintaining visibility from above. This resolves the contradiction by changing the optical parameters of the layers to achieve both recognizability and security simultaneously.
2Illumination intensity
If the refractive indices of carrier and embedding layers differ significantly, then the motif is more visible from above due to enhanced refraction effects, but the motif becomes distorted and recognizable when viewed through, compromising security
Solution Approach 1:
The patent optimizes the refractive index parameter by constraining the difference between carrier layer refractive index (n1) and embedding layer refractive index (n2) to |n1 - n2| ≤ 0.2. This parameter control creates an optimal balance where sufficient refraction occurs to make the motif visible from above, while minimal refraction ensures the motif remains undistorted and unrecognizable when viewed through, thus maintaining security.
3Ease of manufacture
If the upper side of the embedding layer follows the relief of the micromirrors, then the three-dimensional structure enhances the optical effects from above, but it creates molding marks that facilitate unauthorized copying
Solution Approach 1:
The patent extracts the harmful molding marks by decoupling the upper surface of the embedding layer from the micmirror relief structure. Specifically, the upper side of the embedding layer is designed to be substantially planar while the lower side maintains the micmirror relief. This separation removes the copying vulnerability (molding marks on the surface) while preserving the internal optical structure that generates the desired visual effects, thus eliminating the harmful factor without sacrificing the beneficial optical properties.
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 element provides enhanced security against unauthorized copying and maintains visibility from above, while appearing as a transparent plane when viewed through, ensuring the motif is not recognizable, thus preventing undesired molding and easy verification of authenticity.
Implementation Method 1
the reflection layer is structured in this way in a motif area that it forms a multitude of semi-transparent micromirrors which, due to specular reflection of incident light, present a perceptible motif when the motif area is viewed from above
Implementation Method 2
the refractive indices of the support and embedding layers in the visible spectrum do not differ by more than 0.2 such that the motif that can be seen from above cannot be recognized when looking through the motif area
Data Source
Figure 1~3
Figure 4~5
Figure 6~7
AI summary
The invention relates to an optically variable element, in particular a security element, having a transparent carrier layer (5), a reflection layer (6), which is at least partially transparent and is formed on the carrier layer (5), and a transparent embedding layer (7), which is formed on the reflection layer (6), wherein the reflection layer (6) is structured in a motif region such that a multiplicity of partially transparent micromirrors (8) are formed, which, when the motif region is viewed directly from above, show a perceivable motif owing to the specular reflection of incident light, and wherein the refractive indices of the carrier layer (5) and the embedding layer (7) in the visible spectrum do not differ by more than 0.2 so that the motif, which is perceivable when viewed directly from above, cannot be seen when the motif region is viewed in transmitted view.