Application of holographic anti-counterfeiting

Early laser holography can only be reproduced by laser, that is, if we want to observe laser holography, we can only use laser as a light source to illuminate the hologram at a certain angle to observe the image. In order to realize the commercialization of laser holography, it is necessary to realize white light reproduction, that is, laser holographic images can be observed under ordinary light sources. Two-step rainbow holography and one-step rainbow holography are the most commonly used laser holography techniques for white light reproduction in imprint holography.

Laser holography has been successfully applied to three-dimensional image display, interferometry and nondestructive testing, and its wider application is after the invention of molded laser holography. The early hologram replication was based on laser as light source and photosensitive material as carrier, which was complicated, costly and inefficient.

The special photosensitive material for molding laser holography is photoresist. After laser holographic exposure, this material can be processed to obtain the relief phase hologram, that is, the master for making the relief hologram. The surface of the master disk is covered with uneven interference fringes, the density of which can reach more than 0/000 per millimeter/kloc. The metallic nickel with a certain thickness is electroplated on the surface of the master to make a metallic master which can be used for batch reproduction (printing), and the metallic master replicates interference fringes on the holographic master. A holographic film material (PET, BOPP, etc.) formed by mounting a metal master on a molding machine and heating. ), the metal master will press on the film material with a certain pressure, so that the embossed hologram on the metal master will be imprinted on the molded holographic film material. This is a large-scale, high-speed and low-cost laser hologram replication method, which has brought a leap for the application of laser holography technology.

The more mature molded laser holographic technology came out in the United States in the early 1980s, and was introduced to China in the mid 1980s. The early molding laser holography technology was mainly used for image display (arts and crafts). Molded laser holography technology has developed rapidly after it was applied in the field of anti-counterfeiting.

In China, the first application of shaped laser technology in anti-counterfeiting field was in 1988. The reason why this technology can be used in the field of anti-counterfeiting is mainly because of its strong information carrying capacity, in addition to low price and convenient identification. Molded hologram can record the state of holographic shooting, the properties of optical elements used, the post-processing situation and the properties of photosensitive materials. Its complex optical properties cannot be effectively replicated. Because of its powerful information bearing capacity and microform technology, this is a very difficult ink printing method and a very simple die-pressing laser holography.

In China, the shaping laser holography technology has developed from the early two-step rainbow method, two-step rainbow mask method and grating shining method to low-frequency lithography and pixel lithography. In terms of materials, from permanent molding materials to disposable molding materials and hot stamping molding materials, regular dealumination, partial dealumination, halftone holography and perspective holography have been developed in the pre-treatment or post-treatment of materials. Combined with printing technology, fluorescent ink printing, laser label uncovering, laser label scraping and laser holographic hot stamping are developed. Combining the two materials, a double-layer hidden logo is developed, and other anti-counterfeiting technologies are combined to develop laser holographic telephone code recognition. Non-expert inspection of the authenticity of holographic anti-counterfeiting trademarks has also developed from simple visual inspection to card inspection, magnifying glass inspection, laser beam irradiation inspection and so on. The future trend is electronic identification inspection.

The laser holographic logo of early relief has low brightness, small observation range, not bright color and unclear pattern. The use of mask method improves the clarity of the pattern and facilitates the observation of the pattern. The application of grating illumination method improves brightness and bright colors; The application of pixel lithography technology realizes the automation of holographic photography, and each pixel unit has different parameters through point-by-point blasting, thus realizing the colorful dynamic changes of our design. The further development of two-step rainbow technology has realized film and three-dimensional motion. Although the molding laser holography technology is unforgeable, it is quite difficult for ordinary consumers to identify the authenticity. Early holographic anti-counterfeiting was mainly based on exclusivity. With the popularization of holographic technology, exclusivity no longer exists. In order to cope with the fierce competition and improve the identification ability of non-professionals, laser holographic technicians are constantly developing new technologies, such as first-line anti-counterfeiting technologies such as meteor spot and magic pattern technology, and second-line anti-counterfeiting technologies such as laser encryption and dual-card technology. The identification direction of molded laser holographic logo is: fast electronic semi-automatic/automatic identification.

The use of disposable molding materials solves the problem of secondary transfer of anti-counterfeiting trademarks and plays a great role in the promotion of molded laser holographic trademarks. The use of hot stamping molding materials realizes the integration of packaging anti-counterfeiting. Due to the technical problems of domestic holographic hot stamping materials, its popularization speed has been affected, but it will become the biggest application of molded laser holography. The invention of wide molding machine greatly improved the production efficiency. Pre-treatment and/or post-treatment of holographic molded materials can produce regular dealumination (regular exposure), partial dealumination, positioning dealumination, hollow molded holographic anti-counterfeiting marks, half-tone holograms and perspective holographic anti-counterfeiting marks. When the logo with regular dealumination or regular exposure is stuck on the adherend and uncovered, part of the aluminized layer falls off from the adherend, showing preset characters or patterns; Some dealuminated logo have horizontal strips to remove the aluminized layer and become transparent (also known as unidirectional positioning dealumination); The regular dealumination die removes the aluminized layer at the marked fixed position and becomes transparent (also called bidirectional positioning dealumination); The hollowed-out anticorrosive material is intaglio printed on the aluminum surface of the embossed holographic aluminized film. After etching, the aluminum layer on the aluminized film is regularly hollowed out, forming characters or graphics (non-positioning dealumination), which are mostly used for cigarette anti-counterfeiting cables. Leave 20-30 points of the aluminized layer of the molding material, and remove the remaining aluminized layer to make a halftone holographic product. For example, the laser holographic anti-counterfeiting technology used in ID cards is halftone holography. The printed characters covered by the perspective holographic marking film can be observed through the holographic film without affecting the observation of the laser holographic image.