Security Layer
LOOKING FOR THE FORM AND CONTENT
The correctly selected threads dramatically increase the printed products security
Threads play a very important part in the security complex of any product. And if before the threads were viewed only as a possibility of enhancement of the paper security features, today it is a separate trend in the security technologies.
How the threads started
The first threads appeared quite long ago. The idea was simple — to try to embed into the paper something to enhance its security and be a bright visual feature. The first variants of threads were quite plain — metallized foil about 1 mm wide or transparent band with a text. They were implemented into the paper mass and were seen only in transmitted light. The first threads were narrow — the specialists learned how to implement wide threads into the paper only recently. Such threads were used on the Russian banknotes in circulation before the modification of 2004. Because their withdrawal from circulation is taking place gradually, such banknotes still exist.
The so-called window threads appeared afterwards — the thread is viewed not only in transmitted light, but also on the banknote itself in the shape of repeated rectangular sections.
“The window thread technology is certainly interesting, but as practice showed, it is not hard to imitate the plain window thread. The counterfeiters often took two-layer paper and having printed a dark strip with black ink on one side, glued it, and then laminated the foil with relatively high accuracy or made overprints with metallized ink imitating the sections of thread on the surface.
Just like on the original paper, a dark strip was seen in the transmitted light, and pieces of foil were on the surface.” — Alexander Mochalov, Head of Department of New Product Development of Goznak, commented. — “Authenticating the window thread, it is necessary to observe that the metallized sections of foil on the surface accurately register with the parts of thread within the paper seen only in transmitted light. It is technologically difficult to provide the accurate register of the printed image and the foil sections, because these are two independent production processes.
Due to the fact that the banknotes are in most cases given only a cursory glance, the counterfeiters’ expectation that the person not viewing the security features attentively will accept the banknote as the original, proved true quite often.”
As a result, the window thread in its first variant did not live long. The specialists sophisticated it in order to make it more difficult to imitate.
The first thing done with this aim was thread demetallization in the shape of a text or an image, and it could be either negative or positive. It is a complicated technology difficult to imitate. Further color threads, luminescent inks for text printing were applied; there were also thread variants with the background printed with luminescent ink and with negative text. As a result, the text and the thread luminescent in the UV-light were seen in transmitted light.
Security by “Chameleon”
“Goznak, like other world manufacturers of security printed products, used different variants of window thread in its products. But the search for new alternative kinds of threads was continued. And the alternative should have been developed by Goznak and secured by patents. Thus a few kinds of principally new kinds of threads were developed for the visual and cash kinds of control, one of which (“Skate”) is introduced on the 5000‑ruble banknote”, tells Alexander Mochalov.
“Skate” is a window thread with a text. When viewing the thread at different visual angles, one may notice that the text is changed from negative to positive. The effect is achieved by combining the printing levels and metallized sections with the holographic image. From the visual point of view, the effect is very interesting, and it is hard to imitate. In addition to the main visual effect, the thread is luminescent under the UV-light. The thread acquired its name because it is double-faced, and its front and reverse sides look different.
Another development by Goznak, “Chameleon” thread, is used in the federal special and customs stamps. This thread also has UV-luminescence, a text is also applied to it, but it is fully within the paper.
One more Goznak’s development has a great security potential — winged or figured thread. It is a thread with a complicated edge shape partially embedded into paper. The central part of the thread remains on the surface, and its complicated profile is fully viewed in transmitted light.
There are a few modifications of the figured thread. The simpliest of them is metallized foil of a complicated shape, which gave the name to the whole feature — “winged thread”. The shape of “wings” may be various, for the high-tech equipment for the thread production allows it. That is one of the advantages of the winged thread — it is possible to create a lot of different shapes for various customers or products.
The technology determines everything
“The more the variability of the feature, the easier it is to change it regularly in the product, and it creates additional difficulties for the counterfeiters”, Alexander Mochalov explains. “The area of the wings and the thread width at this stage are limited by the technological abilities”.
During the process of embedding the figured thread into the paper the specialists had to overcome technical and technological difficulties. They were connected with both the large area of the thread surface and with the process of implementing the thread during the sheet formation. It was necessary to create such a traverse in which the thread would not wamble or kink — any thread twist means that the thread is “broken” within the paper and there is an imperfection on the spot. Besides, the wings should be sunk into the paper. “We had a few variants of how exactly the wings should be sunk into the paper. Either the thread should be practically on the paper surface, or the thread should be almost sunk into the paper, or only the wing edges should be on the surface. We tried a lot of variants to find the technologically stable optimal variant. We managed to embed the thread in the production volume in such a way that after the wear and tear resistance trials the banknote is practically worn to holes, but the thread remains within the paper without even loosing its glitter,” Alexander Mochalov continues. “After all the technological matters were settled, we started working directly with the thread. As a result, it became not only original well-identified thread embedded into the paper, but it also received a lot of additional security features.
For example, after the first experiments it turned out that quite simple thread imitations are possible; thus, by imprinting figured images on one of the layers of the two-layer paper followed with foil lamination. There were also attempts at imitating the characteristic repeated creases in the central part of the thread, which appear during the thread embedding into the paper. Without looking at the thread in transmitted light or checking the borders of the visible on the surface and the image of the embedded thread, the imitation was similar enough, and that complicated the non-specialist authentication.
Therefore we developed a few variants of the visual thread authentication control. One of the variants, a very successful one in my opinion, is demonstrated on the promotional banknotes of 2007. Color strips are applied across the thread visible in both transmitted light and on the surface. It is practically impossible to imitate this feature by printing the color strips on the paper and foil so that they coincided; besides, they would not be seen on the metallized foil in transmitted light. If such strips also have luminescence under the UV-light or have other machine-readable features, the imitation possibility vanishes. To my mind, it is the most interesting variant, the thread is easily identified and its authenticity is determined with high degree of probability”.
The products on which Goznak tested the technology of the winged thread implementation were mostly manufactured for the State Traffic Safety Inspectorate. The winged thread is embedded into the Calibration Sticker starting with 2007. Different variants of the additionally secured thread were used in the Calibration Stickers. Metallized thread with the color-shifting effect (i. e. it changes color at various visual angles) was implemented into the Calibration Sticker of 2010.
New abilities
The threads will experience changes in the future.
“The thread will become more complicated in the nearest future; it will bear new machine-readable features”, Alexander Mochalov is sure. “We have learned to work with the thread, to apply various layers, both holographic and printed, to demetallize it. It allows combining different features and receiving various effects. The thread itself becomes a separate security feature. And in combination with other types of paper security, the modern thread has a strong set of security features for visual, expert and cashdesk control levels.”
The example of the development carried out by the specialists of Goznak shows an additional thread ability. It is various figured windows creation. “Due to the fact that we have learned to implement quite wide threads — 6 or 7 mm — into the paper, we are now able to develop figured windows on the thread”, Alexander Mochalov explained. “The idea is interesting, because counterfeiters imitate the thread either with foil lamination or with overprinting. The characteristic peculiarity of the window is that thread sections are smoothly covered with the paper grains; the windows should be of complicated shapes. The smooth increase of the paper grain density well observed even without the magnifying glass is an excellent protection against imitations. It is impossible to imitate such a paper window by the counterfeiters’ methods.”
Bogdan Vinogradov
