Asymmetrical Diffractive Relief Structure for Security Documents
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Solution Overview
Problem
Existing security documents are expensive to produce and require specialized skills, and current optically variable security features can be imitated, making them difficult to authenticate.
Innovation Solution
A security document with a transparent security element featuring an asymmetrical diffractive relief structure that provides different optical effects when viewed from the front and back, utilizing a blazed grating and reflective metallic layers to enhance contrast and authenticity, while being resistant to copying.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional optically variable security elements are used, then security features can be verified, but production costs are high and require specialized skills
Solution Approach 1:
The patent uses a diffractive relief structure that can be produced through molding or embossing techniques, creating a security feature that is difficult to copy but can be manufactured using relatively simple processes compared to traditional OVDs
Solution Approach 2:
The security element uses a transparent structural layer with a diffractive relief structure that can be produced inexpensively through standard manufacturing techniques, replacing expensive and complex traditional security elements
2Reliability
If optically variable elements are used for security, then authentication is improved, but these features can be imitated by color copiers and scanners
Solution Approach 1:
The patent employs an asymmetrical diffractive relief structure with sawtooth-shaped periods where the two flanks differ significantly in slope. This asymmetry creates different optical effects when viewed from the front versus the back, making the security feature difficult to replicate with standard copying equipment
Solution Approach 2:
The security element features localized optical properties through the diffractive relief structure, where specific areas have different optical characteristics that can be verified by bringing verification elements into congruence, creating a complex authentication pattern that is difficult to copy
3Adaptability or versatility
If transparent security elements are used, then different optical effects are visible from front and back, but the structure must maintain transparency throughout
Solution Approach 1:
The asymmetrical diffractive relief structure allows the same transparent element to display different optical effects when viewed from the front versus the back, achieving versatility without requiring multiple different components
Solution Approach 2:
The transparent structural layer with diffractive relief structure serves multiple functions: it provides the security feature, creates verification patterns, and maintains transparency, allowing a single element to perform multiple security functions
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 allows for a cost-effective security document that provides a unique, authenticatable optical effect resistant to imitation, ensuring the security element is visible from one side and not the other, even under varying lighting conditions.
Implementation Method 1
the asymmetrical relief structure has a different visual appearance when viewed from the front and the back. When viewing the security document, the asymmetrical relief structure arranged in the first area of the security element is visible from one side and invisible from the other side as a result of diffraction of the incident light.
Data Source
Figure 1a~1b
Figure 2
Figure 3a~3b
AI summary
The invention relates to a security document with a transparent security element (12) with a structural layer arranged in a window or in a transparent section of the security document, a first section (12f) of the structural layer comprising an asymmetrical diffractive relief structure, the first section (12f) having an unexpectedly different optical effect when the security document is viewed from the front and from the back.