Microstructured Security Elements Using Polarized Ultrashort Laser
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Solution Overview
Problem
There is a need for advanced security features in documents that are difficult to counterfeit and can be reliably verified, particularly those that are not immediately recognizable by human inspection and require complex manufacturing processes.
Innovation Solution
A security element with microstructured features created using polarized ultrashort pulsed laser light in transparent materials, which are only visible under polarized light and can store individualized information, allowing for verification through image comparison using unpolarized and polarized illumination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If polarized ultrashort pulsed laser light is used to create microstructuring in transparent material, then the security feature becomes difficult to counterfeit and verify, but the manufacturing process becomes more complex
Solution Approach 1:
The patent applies parameter changes by utilizing ultrashort pulsed laser light with specific parameters (pulse duration in subnanosecond range, typically 10-1000 femtoseconds) to create microstructuring in transparent material. This specific parameter regime enables the formation of microstructures that induce birefringence, making the security feature visible under polarized light while remaining invisible under normal conditions. The precise control of laser parameters allows for high manufacturing precision despite the complexity of the process.
2Reliability
If the security feature is made invisible to naked eye under normal inspection, then the security level increases, but the verification process requires special optical equipment
Solution Approach 1:
The patent employs optical property changes rather than color changes - specifically, it utilizes birefringence effects where microstructures alter the polarization state of transmitted light. When viewed under polarized light, the microstructured areas appear bright or colored against a dark background, while remaining invisible under non-polarized light. This provides a clear visual contrast for verification using relatively simple polarized light sources and polarizing filters.
3Loss of information
If microstructuring is created in transparent volume region, then the security feature cannot be immediately recognized, but it enables storage of individualized information
Solution Approach 1:
The patent creates a physical copy or imprint of information in the form of microstructures within the transparent material volume. The three-dimensional microstructured patterns replicate the desired information (text, images, or data) in a manner that is invisible under normal conditions but can be optically read out under polarized light. This allows information to be embedded deeply within the material rather than just on the surface.
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 provides a secure and easily verifiable microstructured security feature that is difficult to imitate, utilizing changes in polarization direction to differentiate microstructured areas from non-structured transparent material, enhancing authentication and data protection.
Implementation Method 1
The pulsed, polarized, ultra-short pulsed laser light creates anisotropies in the volume of the transparent material, which lead to effects such as birefringence or the like. As a result, when polarized light passes through, its direction of polarization is changed.
Implementation Method 2
Polarized ultrashort pulsed laser light can be used to produce microstructuring in transparent material... the microstructures produced by the polarized ultrashort pulse laser light are clearly perceptible compared to the unchanged transparent surroundings.
Implementation Method 3
If, on the other hand, the transparent area is irradiated with polarized light and the light emerging from the area is also viewed through a polarization filter acting as an analyzer, the microstructures produced by the polarized ultrashort pulse laser light are clearly perceptible compared to the unchanged transparent surroundings.
Data Source
Figure 1~2
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Figure 5~6
AI summary
The invention relates to a novel security element (1), for example in the form of a security document (2), with a microstructured security feature, wherein the security element (1) comprises: a security element body (50), wherein the security element body (50) comprises a transparent volume region (25) extending to an outer surface (5, 6) of the security element body (50), wherein microstructured marking elements (60, 61, 62) are formed in the interior of the volume region (25) by means of polarized ultrashort pulse laser light. The invention further relates to a method for its production and a verification method.