Security Device with Decoupled Color-Shifting and Reflective Relief
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Solution Overview
Problem
Existing security devices struggle to create an integrated appearance of decoupled color-shifting and reflective relief effects, making it difficult to replicate convincingly and thus vulnerable to sophisticated counterfeiting techniques.
Innovation Solution
A method involving a substrate with a relief structure, a reflection enhancing layer, an absorber layer, an optical spacer layer, and a reflector layer, where the reflection enhancing layer and absorber layer are formed of the same material, creating a color-shifting structure that is partially opaque or transmissive, thereby decoupling the reflective relief effect from the color-shifting effect, providing an integrated and complex visual appearance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If decoupled color-shifting and reflective relief effects are provided in a security device, then security against counterfeiting is improved, but the integrated appearance is compromised and the device becomes easier to replicate
Solution Approach 1:
The device is segmented into distinct functional regions: a reflective relief structure region and a color-shifting structure region. These regions are spatially separated but optically integrated through the substrate, allowing each effect to function independently while maintaining an integrated appearance that is difficult to replicate
Solution Approach 2:
The color-shifting structure is nested within the substrate beneath the reflective relief structure. The substrate acts as a container that holds both structures, allowing the color-shifting effect to be embedded in the substrate while the reflective relief structure sits on top, creating a nested configuration that maintains integration
2Reliability
If multiple optical effects are combined in a single device, then visual complexity is increased and security is improved, but the difficulty of replication is reduced
Solution Approach 1:
Different regions of the device have different optical properties: the reflective relief structure region provides geometric reflection, while the color-shifting structure region provides angle-dependent color changes. This local differentiation creates visual complexity that is difficult to replicate without understanding the specific local characteristics of each region
Solution Approach 2:
The device uses a composite structure combining a substrate with embedded reflective relief structures and overlaying color-shifting structures. This composite configuration integrates multiple optical effects in a way that creates visual complexity and increases the difficulty of replication
3Illumination intensity
If the color-shifting structure is made opaque to decouple effects, then the reflective relief effect is enhanced, but the color-shifting effect is lost
Solution Approach 1:
The color-shifting structure is positioned in a different spatial dimension (within the substrate) relative to the reflective relief structure (on the surface). This dimensional separation allows the color-shifting effect to remain visible through the substrate while the reflective relief structure provides enhanced surface reflection, resolving the conflict between opacity and visibility
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 results in a security device with a more integrated appearance that is difficult to reverse engineer or counterfeit, as the color-shifting structure is not visible through the reflective relief structure, enhancing security against advanced counterfeiting methods.
Implementation Method 1
A colour-shifting structure, which produces such an effect, typically comprises at least a reflector layer and an absorber layer separated by an optical spacer layer. Interference between light reflecting from the reflector layer and the absorber layer causes the structure to have a coloured appearance, when viewed in reflection, which changes upon tilting as the optical path length between these layers changes depending on the viewing angle.
Implementation Method 2
periodic grids or arrays of triangulated or faceted structures, sometimes referred as micro-mirrors with periodicities typically greater than 5 um and more typically 10 um such that the incident light is geometrically reflected off one of the faceted sides in accordance with the laws of geometrical reflection.
Implementation Method 3
the reflection enhancing layer and the absorber layer, together, are substantially opaque or transmit less than 40% of incident light, preferably less than 20% of incident light
Data Source
AI summary
A method of manufacturing a security device is provided. The method comprises providing a substrate, the substrate having opposing first and second surfaces and a relief structure formed in the first surface of the substrate. A reflection enhancing layer is applied over the first surface of the substrate such that the reflection enhancing layer at least partially overlaps the relief structure and such that a first region of the first surface of the substrate does not have the reflection enhancing layer. An absorber layer is applied over the reflection enhancing layer such that the absorber layer at least partially overlaps the reflection enhancing layer and the relief structure where the reflection enhancing layer and the relief structure overlap each other, and such that the absorber layer at least partially overlaps the first region of the first surface of the substrate. An optical spacer layer is applied over the absorber layer such that the optical spacer layer at least partially overlaps the absorber layer, reflection enhancing layer and the relief structure where the absorber layer, reflection enhancing layer and the relief structure overlap each other, and such that the optical spacer layer at least partially overlaps the absorber layer and the first region where the absorber layer and the first region overlap each other. A reflector layer, formed of an at least partially reflective material, is applied over the optical spacer layer such that the reflector layer at least partially overlaps the optical spacer layer, the absorber layer, the reflection enhancing layer and the relief structure where the optical spacer layer, the absorber layer, the reflection enhancing layer and the relief structure overlap each other, and such that the reflector layer at least partially overlaps the optical spacer layer, the absorber layer and the first region where the optical spacer layer, the absorber layer and the first region overlap each other. The reflection enhancing layer and the absorber layer are formed of the same material. The absorber layer, the optical spacer layer and the reflector layer, together, form a colour-shifting structure. The reflection enhancing layer and the absorber layer, together, are substantially opaque or transmit less than 40% of incident light, preferably less than 20% of incident light.