Covert Security Coating with Varying Thickness Dielectric
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Solution Overview
Problem
Existing security holograms are vulnerable to counterfeiting due to ease of reproduction and difficulty in authenticating their complex features, and they require direct specular illumination to be visible, limiting their effectiveness under diffuse light conditions.
Innovation Solution
A multilayer thin film filter with an organic dielectric layer of varying thickness, sandwiched between an absorber and reflector layer, is fabricated within a vacuum chamber to create a Chromagram-type device with covert security features only visible under magnification, allowing for in-line production of diffraction gratings or holograms without breaking the vacuum.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional holograms are used for security, then they provide visual security features, but they are vulnerable to counterfeiting due to ease of reproduction
Solution Approach 1:
The patent applies local quality by creating regions of uniform dielectric thickness that produce specific colors, with these regions arranged in patterns that are only visible under magnification. This local variation in thickness (and thus color) creates covert security features that are difficult to replicate while maintaining manufacturing feasibility through embossing techniques.
Solution Approach 2:
The patent utilizes color changes by employing a dielectric layer with varying thickness to produce different optical path lengths, which result in different reflected colors. These color variations are embedded in the coating structure itself, creating authentication features that are inherently difficult to counterfeit while using standard vacuum coating processes.
2Reliability
If complex security features are added to holograms, then authentication capability is improved, but difficulty in authenticating the features increases
Solution Approach 1:
The patent segments the security features into two distinct categories: visible features for general authentication and covert features (only visible under magnification) for advanced verification. This segmentation allows different authentication levels - casual users can verify basic features while experts can access additional covert features, thereby improving overall authentication capability without uniformly increasing complexity for all users.
Solution Approach 2:
The patent adds another dimension to authentication by incorporating covert features that require magnification to see. This creates a multi-layered authentication system where the same physical structure provides both visible and hidden information, effectively adding a 'magnification dimension' to the authentication process that enhances reliability without proportionally increasing detection difficulty.
3Reliability
If traditional holograms are used, then they provide security features, but they require direct specular illumination to be visible
Solution Approach 1:
The patent changes the optical parameters by using a dielectric layer with specific thickness variations that produce color shifts through interference effects. These thickness variations create regions that reflect different wavelengths of light, providing visible security features under various lighting conditions rather than requiring direct specular illumination, thereby improving reliability across different environments.
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 enhances security by providing covert color shifts and diffractive effects that are difficult to replicate, and ensures visibility under various lighting conditions, improving authentication and deterring counterfeiting.
Implementation Method 1
a dielectric layer of varying thickness... provide a grating or hologram... to produce a Chromagram type of device... diffractive effects... color shifts
Implementation Method 2
coating and or stamping a dielectric substrate to provide a grating or hologram preferably within a vacuum roll coating chamber while in a vacuum
Implementation Method 3
a diffraction grating or hologram etched or embossed into the substrate... iridescent visual effect created by a diffraction grating... ambient light is diffracted into its color components
Data Source
AI summary
A multilayer thin film filter is disclosed an organic dielectric layer serving as a spacer layer in a Fabry-Perot structure. The dielectric has embossed regions of varying thicknesses wherein the thickness within a region is substantially uniform. Each different region of a different thickness produces a different color (shift). The size of one of the embossed adjacent regions is such that the color of said one region is uniform and cannot be seen by a human eye as different in color from the uniform color of an adjacent region thereto, and wherein the color within a region can be seen with magnification of at least 10:1. This serves as a covert color coding system useful as a security device.