Dichroic Optical Structures for Anti-Counterfeiting Security
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Solution Overview
Problem
Current color-shifting security features used in documents like banknotes are prone to counterfeiting due to their susceptibility to reproduction by color copiers and photographic equipment, and they often require complex structures that can confuse the general public.
Innovation Solution
Development of thin interference optical structures that exhibit color shift in both reflection and transmission modes with viewing angle, utilizing a dichroic structure with metal layers and transparent layers of specific refractive indices, integrated into documents as coatings, threads, or inks, providing a secure and easily identifiable authentication method.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional color-shifting security features are used in documents, then color shifting effect is achieved, but they are susceptible to counterfeiting by color copiers and photographic equipment
Solution Approach 1:
The patent applies dichroic interference structures that exhibit angle-dependent color shifting in both reflection and transmission modes. The color observed changes based on the viewing angle relative to the document surface, creating a dynamic optical effect that cannot be captured by static copying equipment. This angle-dependent color change mechanism directly addresses the counterfeiting vulnerability by making the security feature observable only under specific viewing conditions.
Solution Approach 2:
The patent employs composite optical structures consisting of multiple layers including dielectric layers with specific refractive indices, metal layers, and transparent layers. These composite structures create complex interference patterns that produce the dichroic color-shifting effect. The combination of different materials with specific optical properties (refractive indices, thicknesses) creates a security feature that is difficult to replicate with simple pigment-based copying methods.
2Reliability
If complex security structures are implemented, then security reliability is improved, but ease of verification by the general public deteriorates
Solution Approach 1:
The dichroic security feature produces visually striking color changes that are immediately noticeable to the general public. When viewers change the angle at which they look at the document, the color shifts dramatically between complementary colors (e.g., red-green, blue-yellow). This simple visual observation requires no special equipment or technical knowledge, making verification easy while maintaining high security through the complexity of the underlying optical structure.
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 optical structures offer a secure and easily verifiable authentication method that is difficult to counterfeit, as they change color when viewed from different angles, enhancing security features in documents and preventing counterfeiting.
Implementation Method 1
thin interference optical structures, films, coatings and pigments for producing color in both reflection mode and transmission mode
Implementation Method 2
dichroic structure with metal layers and transparent layers of specific refractive indices, providing a secure and easily identifiable authentication method
Data Source
Figure 1~2B-2
Figure 3~4
Figure 5A~5B
AI summary
A document, product, or package, such as a banknote, passport or the like comprises structures having dichroic effects that change color with viewing angle in both transmission and reflection. Such structures can be useful as security features that counter the ability to effectively use counterfeit documents, products, packages, etc.