Bifunctional Pigment Flakes With Asymmetric Optical Modulation
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Solution Overview
Problem
Conventional interference effect pigments fail to balance diffraction efficiency with total reflectance, leading to poor color-shifting performance when different colors appear on opposite sides, and existing magnetizable pigments have low total reflectance at normal observation angles.
Innovation Solution
A bifunctional pigment flake with a multilayer optical structure featuring a first surface with a high modulation corresponding to a diffraction grating and a second surface with a reduced modulation, achieved by controlling the thickness of intermediate layers to balance diffraction and interference colors across different angles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a diffraction grating structure is applied to the pigment flake surface, then diffraction efficiency is improved, but total reflectance deteriorates
Solution Approach 1:
The patent applies different surface modulations to different surfaces of the pigment flake. The first surface has a high modulation diffraction grating structure to maximize diffraction efficiency, while the second surface has a reduced modulation to maintain total reflectance. This local differentiation resolves the contradiction by optimizing each surface for its specific function.
Solution Approach 2:
The patent creates an asymmetric structure where the first surface modulation is significantly larger than the second surface modulation. This asymmetry allows the pigment flake to exhibit different optical properties from each surface, with the first surface optimized for diffraction and the second surface contributing to overall reflectance.
2Ease of manufacture
If symmetric optical stacks are used on both sides of the substrate, then manufacturing simplicity is improved, but color-shifting performance deteriorates
Solution Approach 1:
The patent employs asymmetric optical stacks on the two sides of the substrate. The first optical stack is designed with specific layer thicknesses and materials to optimize diffraction colors at high angles, while the second optical stack is configured differently to optimize interference colors at low angles. This asymmetric design enables the pigment flake to display different colors from opposite sides, significantly enhancing color-shifting performance.
Solution Approach 2:
The patent utilizes the angular dimension by designing the optical stacks to respond differently to light incident at different angles. The first optical stack is optimized for high-angle incidence to produce diffraction colors, while the second optical stack is optimized for low-angle incidence to produce interference colors, thereby exploiting the angular dimension to achieve superior color-shifting effects.
3Illumination intensity
If the second surface modulation is reduced, then interference color performance is improved, but diffraction efficiency deteriorates
Solution Approach 1:
The patent optimizes each surface for its primary function: the first surface with high modulation is dedicated to diffraction, while the second surface with reduced modulation is dedicated to interference. This local optimization ensures that each surface contributes maximally to its intended optical effect without compromising the other.
Solution Approach 2:
The patent segments the optical functions between two surfaces, with the first surface handling diffraction and the second surface handling interference. This functional segmentation allows independent optimization of each surface's modulation depth, enabling the first surface to achieve high diffraction efficiency while the second surface maintains adequate total reflectance for interference color performance.
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 bifunctional pigment flake achieves balanced diffraction efficiency and total reflectance, exhibiting distinct diffraction and interference colors at varying angles, enhancing color-shifting performance and security applications.
Implementation Method 1
a first surface with a first modulation that corresponds to a relief of a diffraction grating... exhibit diffraction colors for a first range of angles
Implementation Method 2
The combination of optical materials with different refraction indices and different thicknesses creates interference structures... exhibit an interference color for a second range of angles
Data Source
Figure 1A~1B
Figure 2
Figure 3
AI summary
A pigment flake may comprise a multilayer optical structure. The multilayer optical structure may have a first surface with a first modulation that corresponds to a relief of a diffraction grating. The multilayer optical structure may have a second surface having a second modulation, with the second surface being opposite from the first surface and the second modulation being smaller than the first modulation such that the second surface is comparatively flatter than the first surface. The multilayer optical structure may exhibit diffraction colors for a first range of angles of the multilayer optical structure with respect to an angle of incident light, and may exhibit an interference color for a second range of angles of the multilayer optical structure with respect to the angle of the incident light.