Optical anti-counterfeiting element

Abstract

The invention provides an optical anti-counterfeiting element capable of overcoming the defect of few color types of the current optical anti-counterfeiting element. The optical anti-counterfeiting element comprises a substrate (2), a sub-wavelength embossment structure (5) and a coating (6) with a multi-layer structure, wherein the substrate (2) comprises a first surface (3) and a second surface (4); the sub-wavelength embossment (5) is formed on all or a part of the first surface (3); and the coating (6)with the multi-layer structure is formed on all or a part of the sub-wavelength embossment structure (5) and comprise a dielectric layer formed by dielectric material with refractive index less than 1.8.

Description

Technical field [0001] The invention relates to the field of optical anti-counterfeiting, in particular to an optical anti-counterfeiting element. Background technique [0002] Today, optically variable (optically variable) technology is widely used for public anti-counterfeiting of high-security securities such as banknotes. This technology has features such as dynamic images and color changes that can be observed with the naked eye, and cannot use electronic cameras, scanners, printers, etc. Equipment imitates or duplicates. [0003] The Chinese Patent Publication Nos. 1360544, 1423598 and 1617805 disclose optical anti-counterfeiting elements that have a variety of different structures and simultaneously have the characteristics of interference light change and holography. Their common feature is that the metal reflective layer in the usual holography is replaced by an optical interference film, or the interference optically variable image and hologram are located on both sides ...

AI Technical Summary

Problems solved by technology

The period of the holographic grating is on the order of microns, which is larger than the wavelength of visible light. Therefore, the combination of holography and interference optical change has an optical effect of the simple superposition of the two effects, and no new effect is produced, and the two effects interact with each other. , which weakens the interfering light-variable feature, which is not conducive to identification, so it is only suitable for small-area use of optical-variable anti-counterfeiting components as one of the features, and is not suitable for large-area use

[0004] The application with the publication number CN101699323A discloses another optical anti-counterfeiting element with a grating layer structure. The grating layer is a single-layer dielectric film with a two-dimensional surface relief grating. The anti-counterfeiting element has an obvious optical change effect when observed under a polarizer. However, because it adopts a single-layer dielectric film structure, the light-changing effect is single, only red and green changes, and it is not easy to integrate with holographic and interference light-changing features.

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