Colored Thin-Film Element for Plastic Value Document Security
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Solution Overview
Problem
Current plastic substrate-based value documents lack effective security features against forgery, particularly in terms of optical variability and design flexibility in the transparent window areas.
Innovation Solution
Incorporating a colored thin-film element with a semi-transparent multilayer structure, such as an Al/SiO2/Al layer system, into the transparent window of plastic substrate documents, which changes color appearance when viewed in reflected versus transmitted light, combined with modulated opaque color-accepting layers to create unique foreground/background effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional opaque ink-accepting layers are used on plastic substrates, then printability is improved, but security against forgery deteriorates
Solution Approach 1:
The patent applies a colored thin-film element with angle-dependent color shift effect to the plastic substrate. This element changes its color appearance depending on the viewing angle, providing an optically variable security feature that is difficult to counterfeit while maintaining compatibility with conventional printing processes on opaque ink-accepting layers.
Solution Approach 2:
The invention combines multiple materials and layers including the plastic substrate, opaque ink-accepting layers, and a colored thin-film element with multilayer structure (e.g., Al/SiO2/Al). This composite structure integrates the printability of conventional opaque layers with the security properties of optically variable thin-film elements.
2Adaptability or versatility
If transparent windows are created by cutouts in opaque ink-accepting layers, then design flexibility is improved, but security features deteriorate
Solution Approach 1:
The colored thin-film element is specifically applied in the transparent window regions, providing angle-dependent color shift effects and optically variable properties in areas that would otherwise be simple transparent cutouts. This enhances security while preserving design flexibility.
Solution Approach 2:
The colored thin-film element is selectively positioned in the transparent window regions rather than uniformly across the entire document. This local application provides enhanced security features specifically where needed in the window areas while maintaining the overall design flexibility of the document.
3Reliability
If angle-dependent color shift effects are implemented, then security against forgery is improved, but device complexity deteriorates
Solution Approach 1:
The patent uses a thin-film element with a multilayer structure (such as Al/SiO2/Al) that can be applied as a flexible coating on the plastic substrate. This thin-film approach provides angle-dependent color shift effects without requiring complex mechanical structures, maintaining relative simplicity while achieving enhanced security.
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
Enhances security against forgery by providing angle-dependent color shifts and optically variable effects, offering improved visual attractiveness and security features not achievable with conventional paper banknotes.
Implementation Method 1
The color shift effect in such thin-film elements is based on viewing-angle-dependent interference effects caused by multiple reflections in the various sub-layers of the element
Implementation Method 2
The path difference of the light reflected by the various layers depends on the one hand on the optical thickness of a dielectric spacer layer
Data Source
Figure 1~3
Figure 4~6
Figure 7~9.
AI summary
The invention relates to a value document (1, 9, 17, 26), comprising a plastic substrate (6, 14, 181, 30) having a first surface and a second surface, an opaque first ink-receiving layer (7, 15, 182, 31) provided with a cut-out being arranged on the first surface of the plastic substrate (6, 14, 181, 30) and a second opaque ink-receiving layer (8, 16, 183, 32) provided with a cut-out being arranged on the second surface of the plastic substrate, the two cut-outs forming a window region (3, 11, 19, 28) of the value document (1, 9, 17, 26), the first surface of the plastic substrate (6, 14, 181, 30) having a first colour thin-layer element (4, 12, 20, 29), in the region of the opaque first ink-receiving layer (7, 15, 182, 31) provided with a cut-out.