Security Element with Colour Shift and Fluorescent Features
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Solution Overview
Problem
Existing security elements with color shift effects face challenges in visibility when embedded in documents, as light-absorbing backgrounds are conspicuous and fluorescent features on the visible side impair the optically variable effect, and there is a need for a solution that allows both optimal detection of the color shift effect and the inclusion of fluorescent features on the same side.
Innovation Solution
A security element with a layer structure featuring a light-absorbing metallic layer on one side and a reflective metallic layer on the other, using pigments like cholesteric liquid crystals or iridescent pigments, where gaps are visible in transmitted light and fluorescent colors are transparent in visible light but visible under UV, allowing for a clear optically variable effect and additional security through fluorescent features.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a light-absorbing background is used to optimally detect the color-shifting effect, then the color shift effect is enhanced, but the security element becomes immediately apparent as a dark area on the reverse side
Solution Approach 1:
A white or light-colored intermediate layer is introduced between the light-absorbing background and the optically variable coating. This intermediary layer masks the dark background when viewed from the reverse side, preventing the security element from being immediately apparent, while still allowing the color shift effect to be optimally detected when viewed from the front.
2Adaptability or versatility
If fluorescent features are added to the visible side, then additional security features are provided, but the opacity of fluorescent colors impairs the detectability of the optically variable effect
Solution Approach 1:
The fluorescent features are placed on the reverse side of the optically variable element, separating the two functions into different spatial dimensions. The optically variable effect is viewed from the front where it remains clearly detectable, while the fluorescent features are viewed from the reverse side under UV light, providing additional security without interfering with the primary optical effect.
3Adaptability or versatility
If fluorescent colors are used on the visible side, then additional security features are provided, but they significantly impair the detectability of the optically variable effect
Solution Approach 1:
The security element is segmented into distinct functional layers: the front side contains only the optically variable coating for clear detection of the color shift effect, while the reverse side contains the fluorescent features embedded in or on the light-absorbing background. This segmentation allows each security feature to be optimally detected without the other interfering.
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 clear visibility of the optically variable effect and fluorescent features without impairing the color shift effect, ensuring the security element is not recognizable from the reverse side in reflected light but visible from the front, with adjustable fluorescent colors and high transparency, enhancing security features.
Implementation Method 1
Color-shifting effects can be achieved through various methods, such as thin-film interference
Implementation Method 2
a coating of liquid crystals, either in the form of a pigmented layer or a polymerized film
Implementation Method 3
the pigments consist of cholesteric liquid crystals or a mixture of nematic and cholesteric liquid crystals
Implementation Method 4
a light-absorbing, preferably black, background is required
Implementation Method 5
this covering can be achieved, for example, with a metallic layer
Implementation Method 6
fluorescent features, which, however, are present on the side facing away from the side with the optically variable effect
Data Source
Figure 1~2
Figure 3~4
AI summary
The invention relates to a security element having a coating consisting of a material which has an optically variable effect, in particular a colour shift effect, and has recesses that can be recognised in transmitted light, wherein the security element comprises a support substrate, a partial layer with recesses, and a layer structure that generates a colour shift effect, characterised in that the security element, on the face which has the coating consisting of the material that has an optically variable effect, comprises one or more partial coatings consisting of a layer which has colours that are transparent in visible light and fluorescent in UV light.