Decorative Element Microstructure Zeroth Order Color Generation
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Solution Overview
Problem
Current decorative elements in security documents lack the ability to generate memorable and eye-catching color effects that are recognizable when tilted, relying primarily on rainbow-shaped color gradients which are not visible in zeroth-order diffraction but only in higher orders, and there is a need for a more effective theoretical understanding of the interaction between diffractive microstructures and light.
Innovation Solution
A decorative element with a microstructure coated with a high-refractive index material, where the first distance between the base surface and element surfaces is optimized to generate color effects through constructive or destructive interference in the zeroth order of diffraction, combined with specific design parameters such as flank angles, area coverage, and spacing of basic elements to produce strong and consistent color impressions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If conventional diffraction gratings are used to generate color effects, then rainbow-shaped color gradients are produced in higher diffraction orders, but these color effects are not visible in the zeroth order of diffraction and require tilting the security document to a specific angle
Solution Approach 1:
The patent applies different structural characteristics to different regions of the microstructure. Specifically, it uses basic elements with varying densities, sizes, and spacing arrangements in different zones to generate different color effects. This local differentiation allows the zeroth order diffraction to display colors while maintaining the rainbow effects in higher orders, eliminating the need for tilting.
Solution Approach 2:
The microstructure is divided into multiple basic elements (such as cylinders, cones, or pyramids) with different geometric parameters arranged in specific patterns. By segmenting the diffraction surface into distinct functional zones with different element densities and configurations, the patent achieves simultaneous color generation in both zeroth and higher diffraction orders.
2Illumination intensity
If the microstructure uses standard diffraction grating designs, then the color gradient is generated through wavelength-dependent diffraction, but the color effects lack memorability and visual impact
Solution Approach 1:
The patent employs asymmetric basic elements with specific geometric configurations (such as cylinders with varying diameters, cones with different apex angles, or pyramids with varied base dimensions). These asymmetric structures create distinctive interference patterns that generate memorable color effects. The asymmetry in element geometry, combined with non-uniform spacing and density distributions, produces unique optical signatures that are easily recognizable and difficult to replicate.
3Illumination intensity
If the element surfaces are spaced far from the base surface, then stronger color effects are generated through interference, but the structural stability and manufacturing precision become more difficult to maintain
Solution Approach 1:
The patent optimizes the spacing parameters between element surfaces and the base surface to achieve the desired color effects while maintaining manufacturability. By carefully selecting and adjusting geometric parameters (such as element height, diameter, spacing, and density) within specific ranges, the patent achieves strong color effects without requiring excessive precision that would complicate manufacturing. The parameter optimization balances optical performance with fabrication feasibility.
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 generates vivid and memorable color effects that are visible in both zeroth and higher orders of diffraction, enhancing the visual appeal and security features of decorative elements, while providing a deeper understanding of light interactions through interference principles.
Implementation Method 1
interference of light reflected at the base surface and the element surfaces generates in incident light a first color in the zeroth order of diffraction or in scattered light
Implementation Method 2
The color gradient is generated due to the wavelength-dependent diffraction of light into the first and higher orders of diffraction
Implementation Method 3
the middle layer comprises a material with a higher refractive index than the surrounding layers
Data Source
Figure 1a~1c
Figure 1d
Figure 2a~2c
AI summary
A decorative element (2), more particularly in the form of a transfer film, a laminating film or a security thread, and a security document comprising a decorative element and a method for producing same are described. The decorative element (2) has a microstructure (4) that generates an optical effect in reflected light and/or in transmitted light. The microstructure (4) has in a first region (32) a base surface (40) and a plurality of base elements (41), which each have an element surface elevated or recessed relative to the base surface (40) and a flank arranged between the element surface and the base surface (40). The base surface (40) of the microstructure defines a base plane spanned by coordinate axes x and y. The element surfaces of the base elements (41) each run substantially parallel to the base plane. In at least one or a plurality of first zones of the first region (32), the element surfaces of the base elements (41) and the base surface (40) are spaced apart, in a direction running perpendicularly to the base plane (40) in the direction of a co-ordinate axis z, at a first distance, chosen such that more particularly as a result of interference of the light reflected at the base surface and the element surfaces in reflected light and/or more particularly as a result of interference of the light transmitted through the element surfaces and the base surface in transmitted light, a colour is generated in the one or the plurality of first zones, and wherein the base elements (41) are shaped and arranged in the first region (31, 32) in such a way that, by means of the base elements (41), the incident light is deflected by scattering and/or by diffraction from direct reflection or direct transmission or the zeroth order of diffraction in such a way that a second colour different from the first colour, more particularly a second colour complementary to the first colour, is generated upon viewing in direct reflection or direct transmission or in the zeroth order of diffraction.