Piezochromic Security Element Rapid Color Change
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing piezochromic systems used in security documents take a considerable time to revert to their original state after pressure application, resulting in a slow and undesirable color change process.
Innovation Solution
A reversibly piezochromic security element is developed using a collection of optically contrasting pigment particles in an elastic polymer film or coating layer, where the density and orientation of the particles change upon compression or elongation, leading to rapid and reversible color changes when pressure is applied or released.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If existing piezochromic systems are used in security documents, then color change effect is achieved, but the reversion time to original state is considerable and slow
Solution Approach 1:
The patent replaces chemical piezochromic systems with a mechanical system based on liquid crystal molecules aligned in an elastic polymer matrix. The color change is achieved through mechanical deformation (compression or elongation) that reorients the liquid crystal molecules, eliminating the slow chemical reversion process and enabling rapid reversible color change upon pressure release.
Solution Approach 2:
The patent changes the fundamental parameter from chemical composition change to physical orientation change. By using liquid crystal molecules whose optical properties depend on molecular orientation rather than chemical state, the system achieves rapid reversible color change through mechanical deformation without the time-consuming chemical reversion process.
2Reliability
If piezochromic materials are applied as printing ink for security protection, then forgery protection is provided, but the color change process is slow and takes a minute or two
Solution Approach 1:
The patent replaces the slow chemical mechanism with a fast mechanical-optical mechanism using liquid crystals in an elastic polymer. The security feature maintains reliability through the reversible color change effect while reducing the duration from minutes to seconds through the physical reorientation of liquid crystal molecules under mechanical stress.
3Ease of manufacture
If electron donating and electron accepting compounds are combined in a coating composition, then piezochromic effect is achieved, but the system requires considerable time to revert to original state
Solution Approach 1:
The patent substitutes the electron transfer mechanism with a mechanical reorientation mechanism. The coating composition uses liquid crystal molecules embedded in an elastic polymer matrix, where mechanical deformation directly reorients the molecules to produce color change, eliminating the time-consuming electron transfer and chemical reversion processes while maintaining ease of manufacture as a printable coating.
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 enables a fully reversible and rapid color change response to pressure, enhancing the security features of documents by providing a visible effect that is immediate and easily observable, making it suitable for use on value documents, banknotes, and other security items.
Implementation Method 1
upon compression or elongation of the elastic polymer, the density and/or the orientation of the pigment particles changes; this results in a visible color change
Implementation Method 2
Most preferred pigments for embodying this invention are the thin-film interference pigments, in particular the optically variable pigments
Implementation Method 3
the pigment particles need to be responsive to the chosen external fields. Fig. 1 schematically shows how the pigment particles in the coating can be oriented... the preferred pigment particles for embodying the invention are selected from the magnetic or magnetizable pigment particles
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
The invention discloses a reversibly piezochromic security element for the forgery-protection of value documents, the security element being characterized in that it comprises a collection of optically contrasting pigment particles in a film or a coating layer of an elastic polymer. In a particular embodiment, the particles are optically variable pigment flakes, oriented in a position which is substantially different from an alignment in the plane of the film or coating layer.