A pure red optically variable anti-counterfeit pigment and preparation method thereof

Abstract

The invention provides an optically variable anti-counterfeiting pure red pigment. The anti-counterfeiting pigment comprises a central reflecting layer, a first dielectric layer, a first half-absorption layer, a second dielectric layer and a second half-absorption layer. The first dielectric layer and the first half-absorption layer are outwardly, sequentially, circularly and symmetrically arranged from the central reflecting layer. As the outermost layer of the anti-counterfeiting pigment, the second dielectric layer and the second half-absorption layer are symmetrically arranged on the two sides of the central reflecting layer. The rest can be done in the same manner. That means, along with the increasement of the total number of the layers, the layers are outwardly and symmetrically in radiation distribution from the central reflecting layer. According to the technical scheme of the invention, the pigment is of a N-layer symmetrical structure, and is constructed based on the multi-beam destructive interference condition for reflection beams within the wavelength range of blue and green light beams, wherein N=7, 9, 11, 13....,7+(2n). Meanwhile, the multi-beam constructive interference for reflection beams within the wavelength range of red light beams is ensured at the same time. Therefore, the pigment is displayed within the color range of pure red chromaticity.

Description

technical field [0001] The invention relates to the technical field of optical anti-counterfeiting and the technical field of high-grade color printing and coating, in particular to a pure red optically variable anti-counterfeiting pigment and a preparation method thereof. Background technique [0002] The optically variable pigment (OVP) and the optically variable ink (OVI) prepared based on the principle of thin film multi-beam interference are high-end anti-counterfeiting materials in the field of anti-counterfeiting. The products printed by them have color display that changes with the viewing angle of the human eye. This discoloration characteristic cannot be reproduced by usual color copying and electronic scanning. It has strong anti-counterfeiting performance and plays a great role in the anti-counterfeiting of financial security products such as currency and securities. In recent years, it has also been widely used in the anti-counterfeiting packaging of tobacco and...

AI Technical Summary

Problems solved by technology

However, this type of structure will cause serious color cast when constructing a pure red color display effect in the long-wave band. When the main wavelength is selected as the red band, it can be seen that the optically variable film using this type of five-layer symmetrical structure is usually An interference-enhanced reflection sub-peak will be formed in the blue band, so that the red and blue reflection peaks are superimposed, resulting in the usually displayed colors being purple or pink, Figure 4 It is the vertical observation chromaticity coordinates of the 5-layer symmetrical red light-changing structure of the prior art; image 3 The structure shown is a 5-layer symmetrical red light-variable structure, forming a double reflection peak structure, resulting in the final color being purple-red, and its chromaticity coordinates are x=0.407, y=0.2704

According to the description of color characteristics by the CIE-1931 standard colorimetry system, the chromaticity value of the corresponding color is represented by the chromaticity coordinates x, y. Under the conditions of the D65 standard lighting source and the CIE-1931 standard viewing body, for pure red color domain, its chromaticity coordinates should be located in the color block region constructed by x=0.58-0.74, y=0.18-0.4, obviously, the above-mentioned magenta display, although the chromaticity coordinate y=0.2704 is located in the pure red y chromaticity coordinate interval, However, x=0.407 shifts to the purple region, making the overall display purple-red. It can be seen that the optically variable anti-counterfeiting film constructed by the existing technology cannot realize a single main reflection peak in the pure red region, and cannot display In the traditional Chinese sense, the red area usually symbolizes the meaning of festive prosperity, especially on some high-end tobacco and alcohol packaging, pure red color is often used as a standing color for packaging

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