Bifunctional Pigment Flake With Asymmetric Optical Surfaces

The patent applies asymmetry by creating unequal optical stacks on opposite sides of the substrate. The first optical stack has a first set of layers with specific thicknesses and refractive indices, while the second optical stack has a second set of layers with different thicknesses and/or refractive indices. This asymmetric configuration prevents color blending between opposite sides and enables distinct color-shifting effects when viewed from different angles, resolving the contradiction between manufacturing simplicity and color-shifting performance.

The patent applies parameter changes by systematically adjusting multiple parameters including layer thicknesses, refractive indices, and material compositions in the optical stacks. By optimizing these parameters, the patent achieves a balanced configuration where both diffraction efficiency and total reflectance are maximized simultaneously. This resolves the contradiction by showing that proper parameter selection can achieve both enhanced diffraction colors and maintained reflectance.

The patent transforms the symmetric structure of conventional pigments into an asymmetric design where the optical stacks on opposite sides have different optical properties. This asymmetric configuration eliminates the color blending problem that occurs in symmetric structures, as each side produces distinct interference patterns. The solution maintains reasonable structural simplicity while dramatically improving color-shifting appearance through the asymmetric layer design.