Iridescent and metallic structural colors originating from 3D photonic crystals (3DPCs) based on Bragg's law of diffraction have attracted considerable attention in recent years. The distinctive optical properties of the material promise tremendous potential in anticounterfeiting fields. However, the poor durability and device‐assisted detection of 3DPCs still limit the material's practical application. To overcome these inherent limitations, a novel iridescent flexible polyvinylidene fluoride (PVDF) plastic film with a 3D inverse opal (3DIO) structure is prepared for the anticounterfeiting of banknotes. The excellent durability of the plastic film is due to the intrinsic robust properties of PVDF resin. Patterns can be easily printed on the plastic films by pressing method. The patterned colored PVDF film changes into six distinct color states when the viewing angle increases from 5° to 45°, and the color switching requires no external stimuli, which makes the plastic films a higher security‐level material. Given their excellent mechanical properties, the colored films can serve as an ideal candidate for anticounterfeiting materials.

中文翻译：

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具有3D反蛋白石结构的图案和虹彩塑料，用于防伪钞票

近年来，源自基于布拉格衍射定律的3D光子晶体（3DPC）的彩虹色和金属结构色引起了相当大的关注。这种材料独特的光学性能在防伪领域具有巨大的潜力。但是，较差的耐用性和3DPC的设备辅助检测仍然限制了该材料的实际应用。为了克服这些固有的局限性，准备了一种具有3D反蛋白石（3DIO）结构的新型虹彩柔性聚偏二氟乙烯（PVDF）塑料薄膜，用于钞票的防伪。塑料薄膜的出色耐久性是归因于PVDF树脂的固有坚固性。通过压制方法可以很容易地将图案印刷在塑料薄膜上。当视角从5°增至45°时，图案化的有色PVDF膜会变为六种不同的颜色状态，并且颜色切换不需要外部刺激，这使塑料膜成为具有更高安全级别的材料。鉴于其优异的机械性能，彩色膜可以用作防伪材料的理想选择。