Non-Conforming Dielectric Layer for Naked-Eye Color Shifting
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Solution Overview
Problem
Existing security devices rely on conforming coatings applied to stamped substrates, which require magnification to discern small structures, and lack efficient methods to create non-conforming dielectric layers with varying thickness for enhanced color shifting effects.
Innovation Solution
A method involving non-conforming dielectric layers with varying thickness applied to microstructured substrates, allowing for visible color shifting regions without magnification, and enabling the creation of flakes or foils with encoded patterns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conforming coatings are applied to stamped substrates, then the coating process is simple and reliable, but the structures require magnification to be discerned and color shifting effects are limited
Solution Approach 1:
The patent applies non-conforming dielectric layers with spatially varying thickness to create different optical paths in different regions. This local variation in layer thickness produces distinct color shifting effects in different areas without requiring magnification, while maintaining a relatively simple coating process using conventional vacuum deposition techniques.
Solution Approach 2:
The invention changes the thickness parameter of the dielectric spacer layer to create varying optical interference patterns. By controlling the thickness variation of the non-conforming dielectric layer, the patent achieves visible color shifting regions without magnification, resolving the contradiction between visibility and process complexity.
2Loss of information
If small structures are stamped on substrates, then encoded information can be created, but magnification is required to see the effects
Solution Approach 1:
The patent uses color shifting pigments and multi-layer thin films that change color based on viewing angle and light incidence. This color variation amplifies the visual impact of encoded information, making it visible to the naked eye without magnification while maintaining the encoded data integrity.
Solution Approach 2:
The invention adds the dimension of optical interference by varying dielectric layer thickness. This creates a third dimension of information encoding beyond simple physical structure size, allowing encoded information to be visible without magnification through color and thickness variations rather than relying solely on large physical features.
3Reliability
If decoupling layers are added to separate diffraction grating effects from color shifting effects, then optical control is improved, but device complexity increases
Solution Approach 1:
The patent combines the diffraction grating structure and color shifting thin films into an integrated Fabry-Perot cavity structure. The dielectric spacer layer serves dual functions as both the spacer for the Fabry-Perot resonance and the medium containing the color shifting pigments, eliminating the need for separate decoupling layers while maintaining reliable optical control.
Solution Approach 2:
The dielectric spacer layer performs multiple functions simultaneously: it provides the optical path difference for Fabry-Perot interference, contains the color shifting pigments, and maintains the cavity structure. This multi-functionality reduces overall device complexity while achieving reliable separation and control of optical effects.
4Manufacturing precision
If conventional vacuum deposition is used to create conforming layers, then manufacturing is straightforward, but non-conforming dielectric layers with varying thickness cannot be created
Solution Approach 1:
The patent creates a pre-structured substrate with varying thickness regions or masks before applying the dielectric layer. This preliminary structuring allows conventional vacuum deposition to create non-conforming layers with controlled thickness variations, maintaining manufacturing simplicity while achieving precise thickness control in different regions.
Solution Approach 2:
The invention uses a substrate or mask as an intermediary to transfer the desired thickness pattern to the dielectric layer. This intermediary allows conventional deposition equipment to create complex non-conforming layer structures without requiring complex process modifications, bridging the gap between simple manufacturing and precise thickness control.
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 distinct color shifting regions visible to the naked eye and allows for the production of flakes or foils with encoded information, enhancing security features by providing visible indicia and enabling removal from substrates.
Implementation Method 1
The provision of a dielectric layer with a varying thickness has been disclosed not only by Phillips in 7,630,109 but also much earlier in U.S. Pat. No. 5,877,89 in the name of Shaw et al.
Implementation Method 2
an embodiment of this invention uses non-conforming dielectric layer coated on a same side of a microstructured substrate as a reflective layer and absorbing layer. Therefore the Fabry-Perot structure is supported by the substrate.
Implementation Method 3
Color shifting pigments and colorants have been used in numerous applications, ranging from automobile paints to anti-counterfeiting inks for security documents and currency. Such pigments and colorants exhibit the property of changing color upon variation of the angle of incident light, or as the viewing angle of the observer is shifted.
Data Source
Figure 1
Figure 2A~2C
Figure 3A~3C
AI summary
A color shifting security device has a Fabry-Perot type structure wherein a dielectric layer is disposed between a reflector and an absorbing layer. The absorber and reflector layers may be conforming and the dielectric layer therebetween is non-conforming, filling the regions in the micro structured adjacent absorbing or reflecting layer, at least one of which has a microstructure therein or thereon. By having the dielectric layer not conform to the microstructure it is next to, its thickness varies in cross section, which allows for different colors to be seen where the thickness varies.