Multilayer structures comprising reflective core layers

A multilayer thin film that reflects an omnidirectional structural color comprising:

• a reflective core layer comprising a metallic material;
• a protective layer encapsulating the reflective core layer;
• a second layer extending across at least a portion of the protective layer;
• a third layer extending across the second layer;
• and
• an outer layer extending across the third layer, wherein the outer layer is formed from a dielectric absorbing material or a dielectric material, wherein
• the multilayer thin film reflects a single narrow band of visible light having a color shift of the single narrow band of visible light is less than 30° measured in Lab color space when the multilayer thin film is exposed to broadband electromagnetic radiation and viewed from angles between 0° and 45° relative to a direction normal to an outer surface of the multilayer thin film, and
• the reflective core layer has a skin depth δ of greater than or equal to 1.0 μm in a frequency range from 20-40 GHz, as calculated by:
• δ
• =
• 2
• ⁢
• ρ
• (
• 2
• ⁢
• π
• ⁢
• f
• )
• ⁢
• (
• μ
• 0
• ⁢
• μ
• r
• )
• ≈
• 5
• ⁢
• 0
• ⁢
• 3
• ⁢
• ρ
• μ
• r
• ⁢
• f
• ,
• wherein
• δ is skin depth in m;
• ρ is resistivity in Ω·m;
• f is frequency of an electromagnetic radiation in Hz;
• μ0 is permeability;
• and μr is relative permeability of the metallic material.

A multilayer thin film that reflects an omnidirectional structural color comprising:

• a reflective core layer comprising NiCr metallic material;
• a second layer extending across the reflective core layer, wherein the second layer is a dielectric absorber or dielectric material;
• a third layer extending across the second layer, wherein the third layer comprises a semi-transparent absorbing layer;
• and
• an outer layer extending across the third layer, wherein the outer layer is formed from a dielectric material or a colorful dielectric material,
• wherein the multilayer thin film reflects a single narrow band of visible light that is less than 30° measured in Lab color space when the multilayer thin film is exposed to broadband electromagnetic radiation and viewed from angles between 0° and 45° relative to a direction normal to an outer surface of the multilayer thin film.