Holographic Printing Efficient Anti-Counterfeiting

Holographic printing

The Hologram was proposed by Gabor in 1948 to improve the electron microscope image quality. Its significance is a complete record. Gabor's experiment solved the basic problem in the invention of holography, namely the recording and reproduction of the wavefront, but due to the lack of a bright coherent light source (laser), the image quality of the hologram was poor. In 1962, with the advent of lasers, the concept of carrier frequency was introduced on the basis of Gabor holography. Off-axis holography was invented, which effectively overcomes the problem of poor imaging quality of holograms at the time - twinning images, three-dimensional objects became At the time, holographic research was hot, but this imaging science far exceeded the development of the economy at that time. The cost of making and observing such holograms was very expensive. Holography basically became an impractical one with high expenses. Synonymous with fantasy.

Benton invented rainbow holography in 1969, setting off a new culmination of holographic three-dimensional display featuring a white light display. The rainbow hologram is a plane hologram that can realize white light display. Compared with Denisuk's reflection hologram, it has hologram processing in addition to the bright stereo image observed under ordinary incandescent lamps. Simple process, easy to copy and so on. Combining rainbow holography with the maturing and developing hologram compression molding technology at that time, it has formed a holographic printing industry that is currently popular in the world, producing holographic credit cards, holographic trademarks, holographic banknotes, holographic cartoons, holographic decorative materials, and even holographic garments. New applications such as security, anti-counterfeiting and decorative holograms. Therefore, it can be said that the invention of rainbow holography has taken a gratifying first step towards the social acceptance of holograms out of the laboratory.

Holographic printing is an anti-counterfeiting printing technology developed using laser holographic imaging technology. A three-dimensional model is illuminated from different angles with a laser beam and reference light separated from the laser beam. The light reflected by the model passes through a slit to form interference fringes containing the model holographic information. This interference fringe was recorded on a photographic film, turned into a nickel plate, and pressed on an aluminized film to reproduce the model holographic pattern under normal light. This is the principle of holographic printing.

Holographic plate light source

According to the characteristics of holography, the feature of holographic platemaking is to record the true image of a three-dimensional object through the interference of reference and object light. However, in the holographic recording process, the light scattered and reflected from the surface of different parts of the three-dimensional object has different optical paths to the holographic plate due to different depths of the object. When it interferes with the reference light wave, the optical path difference between the two will be different. Changes in a wide range. Therefore, it is required to record the light source with a longer coherence length, ie better temporal coherence; and in order to be able to record objects with a large spatial distribution range, it is required that the illumination light beams be coherent among the light in the larger cross section. That is, the required beam has good spatial coherence; in addition, in order to meet the temporal and spatial coherence required for holographic recording, the beam is often split slightly after beam splitting in the holographic recording system, and used as a reference light wave and object illumination. Light waves, which require the light source's energy to have a higher concentration in space. At present, only lasers can meet these requirements, and other common light sources cannot meet these conditions. So far, holograms for recording three-dimensional objects can only use laser light, and recording holograms with white light is also limited to two-dimensional objects.

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Holographic plated lasers

Laser selection

Holograms for recording three-dimensional objects in general using holographic plates can be used with He-Ne lasers. For shooting large depth of field objects, a long coherence length He-Ne laser can be used. When using dichromate gelatin as a recording medium, it is preferable to use an Ar+ laser with an output wavelength of 400 nm. For the photoresist, a He-Cd laser with an output wavelength of 441 nm or an Ar+ laser with an output wavelength of 457.9 nm should be used. . If you are shooting a hologram of a moving object, you need a pulsed laser.

Although the colors of objects in nature are varied and varied, according to the visual theory of color, there are three kinds of cones that are sensitive to the red, green, and blue (R, G, B) colors. We call these three colors primary colors. Studies have shown that the various colors in the natural world can in principle be mixed with different proportions of the three primary colors. This different proportion is reflected in the photographic material, and it is a different gray scale. Color offset printing is the conversion of different grayscale recording media into a printing plate made up of dots of varying sizes and uneven density, and then overprinted with four primary colors or multicolors to reproduce the manuscript's level and tone. Although the color holographic printing has a very different way from the color printing in reproducing the original color, the former uses the yellow, magenta, cyan, and black inks to reproduce the original by color subtracting, while the latter uses the red, green, and blue primary colors. An additive color method reproduces the color of the original, but the principle of decomposing the original in the three primary colors and reproducing the color of the original in the three primary colors is the same except that they differ greatly in the specific process technology in the copying process. Therefore, a white laser should be used when recording a true color hologram of an object. Studies have shown that the three primary colors can correspond to three pure spectra. For this reason, the International Commission on Illumination has developed three primary colors. The 1931 CIE-RGB true three-primary color system specifies that the wavelength of the red primary color = 700.0 nm, the wavelength of the green primary color = 546.1 nm, and the wavelength of the blue primary color = 435.8 nm. The 1964 CIERGB system provides that the primary colors of red, green, and blue are 645.2nm, 526.3nm, and 444.4nm. Hologram recording requires the use of lasers. The output wavelength of existing lasers is generally inconsistent with the wavelengths of the three primary colors. Therefore, it is only possible to use relatively close wavelengths. For example, a K+ white laser or an Ar+-Cd laser can be used as a three-primary laser source. According to the current status of the laser industry, laser output suitable for holographic plate making has the following sets of wavelengths for selection.

The principle of selection is mainly based on the sense of reality of color, and the area of ​​the triangles occupied by the three wavelengths in the xy chromaticity diagram (Fig. 2) should be maximized, taking into account other factors such as the output power of the laser. For example, in Table 2, the third group (solid triangles in Figure 2), the second group (dotted triangles), and the fifth group (dotted triangles in Figure 2), the second group dominates from the chromaticity diagram, and yellow More abundant; and from the output power point of view, because the 477.1nm wavelength power is much smaller than the 488.0nm power, the third group is more appropriate. In addition, the appropriate three-primary laser wavelengths should be selected according to the conditions of the laboratory.

When recording with a three-primary laser, three holograms are overlaid on a dry plate. If the hologram is still illuminated in the direction of the reference light with a three-primary laser, there are nine diffracted light waves that make up the original image. The three diffracted light waves of the holograms formed by the three wavelengths of red, green, and blue for the respective colors are in the same direction, and a true color virtual image with the same color as the object is generated. However, they generate diffracted light waves with different directions in six directions for holograms formed by light waves of different colors, resulting in color crosstalk of reproduced images. Therefore, one of the keys to true color holography is the elimination of color crosstalk. $Page break $

Holographic high-speed positioning anti-counterfeiting stamping foil

With the development of the situation, tobacco anti-counterfeit packaging has received increasing attention from the industry and consumers. Tobacco companies are constantly seeking new anti-counterfeiting technologies and anti-counterfeiting products with high technical content, strong confidentiality, and non-reproducibility. Laser holographic technology has played an important role in protecting famous brands and cracking down on counterfeiting and counterfeiting. In the ongoing competition with counterfeit molecules, laser holographic anti-counterfeiting technology has also made considerable progress, rapid replacement, holographic high-speed positioning security stamping foil is one of them.

The development of holographic anti-counterfeiting technology in cigarette packaging anti-counterfeiting applications has undergone five processes: self-adhesive holographic anti-counterfeit identification, holographic compounding, holographic transfer, holographic hot stamping, and holographic positioning hollow positioning hot stamping.

At present, the holographic hot stamping process is the main method for applying holograms in large quantities, and it is even more so in the combination of security anti-counterfeiting and packaging printing. The hologram stamped on the substrate is very thin and integrated with the substrate. The hologram and the printing pattern and color on the substrate can be matched with each other to obtain a very good visual effect.

For holographic hot stamping, the medium for recording holograms is required to have a high resolution, usually capable of reaching 3000 line pairs/mm or more; it is also required that the imaging layer of the hologram hot stamp foil ensure that the information of the high resolution laser hologram is not lost. To ensure that the hologram after hot stamping still has a high diffraction efficiency.

According to different hot stamping processes, holographic hot stamping can be roughly divided into three types, namely, low-speed holographic hot stamping, fast holographic hot stamping and high-speed positioning holographic hot stamping. Among them, the high-speed positioning hologram hot stamping technology has the highest requirements and the greatest anti-counterfeiting efforts. It is necessary to ensure that the hologram is completely and accurately stamped at a specified position under high production efficiency, and the positioning accuracy cannot be lower than ±0.25 mm.

The production of fast positioning holographic hot stamping foil not only has certain requirements for the imaging layer, separation layer and hot melt adhesive, but also puts high requirements on the precision of the holographic hot stamping foil molding process and the separation process, so as to ensure the hot Imprint accurate positioning.

In the near future, we will eliminate the space for fake cigarettes completely by using this increasingly sophisticated anti-counterfeiting technology. $Page break $

Application of Laser Holographic Material in Wine Paper Packaging

Judging from the current market demand and trend, liquor and paper packaging mostly use laser holographic materials for bottle stickers and wine boxes. The use of this material for wine packaging has a good momentum of development.

Liquor containers Liquor containers are obviously disadvantaged in the use of expensive anti-counterfeiting materials because of their large size. They can use small-area laser holographic aluminum foils. There is currently no product using laser holographic paper. With the development of the famous wine brand strategy, there may be certain changes in the future.

The wine label as a trademark is characterized by its function and form, and the rich information it contains must be presented in a concise form in a relatively small space.

Therefore, the trademark design has a relatively wide selection of laser holographic materials. Laser holographic aluminum adhesive labels, laser holographic aluminum foils, laser holographic paper or other methods can be used to make laser holographic texts and patterns. Demonstrate the personality characteristics of the product, so that consumers can understand the most fundamental content of the product at a glance.

Wine box packaging Wine box packaging needs to show a relatively large visual space, and it is necessary to express the rich cultural connotation of white wine products through packaging. Judging from the current situation, most of the wine box packaging products use laser holographic aluminum foils for anti-counterfeiting and decoration. There are few products that use laser holographic paper as the printing carrier, which depends on the overall planning requirements of the liquor brands. It also depends on the overall structure of the color, pattern, and text of the wine box during the development and design phase.

Of course, with the further development of the liquor brand strategy, laser holographic papers with laser holographic patterns and texts will surely be used more in wine packaging boxes. According to the size of the output, the label can be processed by processing or compounding on the machine to achieve a one-time process of printing, hot stamping, embossing, and die-cutting, ensuring accurate registration of the laser holographic pattern, text, and printed pattern.

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