If philatelic lovers can encounter a stamp that has appreciated beyond imagination, just like the lottery winners in the lottery, it will arouse everyone's eager attention. Recently, a post-Cultural Revolution stamp that was “red in the mountains and rivers of the whole country†appeared in the Hong Kong auction market and was sold at a price of 368 Hong Kong dollars.
(Picture Note: The stamp "The National Mountains and Rivers Was Red" during the Cultural Revolution took a high price)
From the perspective of printing technology, postage stamps, like RMB, are a special kind of printed matter, and have little value in themselves. So, as an ordinary printed matter, how are stamps printed?
Stamp printing
The printing of stamps is mainly gravure printing, which is because gravure printing has better anti-counterfeiting. It is widely used in anti-counterfeiting printing. The characteristic of gravure printing is the large amount of ink used. Therefore, the thickness of the lines of the gravure printing and the change of the shades of the ink are rich. The graphics have a concave and convex feeling, the layers are diverse, the lines are clear, and they are easy to identify. Gravure is the earliest printing technology used in the field of anti-counterfeiting.
In terms of stamp printing, China's hand-carved gravure technology is world-class. The hand-carved knife style and superb artistic style are unmatched by other plate making methods. The portraits of banknotes in various countries at home and abroad have always been hand-carved, and hand-carved to express the characteristics of the characters in a unique style. The hand-engraved deep version prints the product with thick ink layer, good hand feel, and strong anti-counterfeiting. However, there are two problems with hand engraving. The first is low efficiency, which is not suitable for rapid production. In addition, because hand engraving must use a knife, the engraved pattern has a "V" shaped groove in the depth direction. This type of groove is not very good for ink storage. If the plate is wiped, the ink in the groove is easily wiped out, and the printed line ink layer is not full and thick. These are two problems that must be solved. In order to solve the problem of efficiency, when engraving a portrait abroad, the portrait is first enlarged by etching the enlarged image copperplate, and then the enlarged portrait copperplate is used as a template after manual carving; Engrave portraits that meet specifications. Sensible heat, engraving copper plate is easier and more efficient than directly engraving steel plate. As for solving the problem of groove "V" shape, the potential of corrosion gravure process needs to be tapped. The corrosion gravure process is to directly corrode the single-open graphic film on the copper plate coated with photosensitive material. The copper plate has low hardness, and other high-hardness plates can be pasted on the back of the copper plate. Or you can charge and plate a layer of red copper on the harder lining. After the single opening is corroded, the red copper plate is processed with a hot press on a 1mm thick plastic plate. The plastic plate is precision cut and high-frequency welded to make a large plastic plate. The large plastic plate is used. Re-coated copper plate, copper plate and then nickel relief plate, and finally nickel intaglio plate can be used on the machine. The intaglio plate produced by this etching process has a "U" shape groove, good ink storage performance, and the product line has a thick ink layer and strong hand feeling. In addition, the corrosion method can be used to make very small text and very thin lines. The size of the miniature text can now be 150-m. Such miniature gravure text can only be seen under the magnifying glass.
The gravure invisible image and text made by etching method has good refractive index and obvious color change. At the same time, this method of making gravure solves the problem of the amount of ink stored in the gravure pattern, and also solves the problem of low efficiency of manual engraving. However, the large-scale etching method also needs to adopt the processes of imposition, electroplating, and multiple copies to make the machine printing plate, which also has the problem of low efficiency. The technical problem of directly making gravure on the machine.
Application of Laser Holographic Anti-counterfeiting Technology in Stamp Printing
Laser holographic anti-counterfeiting technology is a high-tech anti-counterfeiting technology that appeared in the 1980s. It uses the basic laws of scattering, reflection, transmission, diffraction, interference, absorption, etc. generated when light interacts with substances to obtain a special visual effect. At present, the technical means of using optical anti-counterfeiting is a multi-layer dielectric film structure using a thin-film interference effect, a grating structure, and various types of laser holography using the concept of information light and light. The feature is the appearance of the molding process, which enables low-cost mass production of laser holograms, plus the hologram itself contains a wealth of information, and the holographic logo cannot be simply copied using ordinary photo-engraving and printing techniques. Therefore, molding The hologram is soon used in anti-counterfeiting security.
The application of laser holographic anti-counterfeiting technology to stamp printing was a matter of the late 1980s. The world's first stamp with a holographic anti-counterfeiting pattern was the 8-shilling stamp issued by Austria on October 18, 1988. The stamp was exhibited at the International Chamber of Commerce Export Products Exhibition and was very popular. In the center of the stamp, there are three holographic patterns, and then the shape of a sailboat composed of the letter A and MADEINAUSTRIA, etc., symbolizes the meaning of export. Later, on December 3, 1989, a 25-cent prepayment envelope issued by the US Postal Service (the hologram was attached to the square opening in the upper right corner of the envelope, produced by the American Banknote Holographic Company), whose hologram was that a spacecraft was on orbit space station.
Next, Finland, Hungary, Poland, Canada, Mongolia, Australia and many other countries have issued stamps of this anti-counterfeiting technology, making holographic anti-counterfeiting technology play a huge role in the production of stamp anti-counterfeiting. Our country also issued such stamps in 1996, first of all a souvenir cover for the "Hong Kong 98" exhibition. A small circular holographic pattern is affixed to the souvenir cover. The picture is a panda holding bamboo. The stamp is a picture of a green bamboo forest. Later, in order to celebrate the 22nd China Post Exhibition, a commemorative stamp with a holographic pattern was issued on July 18, 1996. The picture of the stamp is a statue of a person flying around the earth. Around the stamp is a pattern of air envelopes, airplanes, ships, trucks and so on. In addition, China's Xiangdao issued two postal postcards with holographic stamps on February 15, 1994. The holographic stamp on one postcard is a portrait of a Victorian female worker in 1685. The postcard on which the stamp is attached is the waterfront of Hong Kong in 1920. The holographic pattern on the other postcard is a picture of Queen Elizabeth II of England Avatar, the picture of this postcard is the waterfront of Hong Kong in 1933. [next]
AM cable and FM outlet
As a new anti-counterfeiting technology, changes in outlets are now attracting people's attention. It is gradually being used for anti-counterfeiting printing of tickets, with good results. The principle is to transform continuous tone images, text, graphics, etc. into tiny dot-dash lines with a certain direction, and change the angle to form a latent image. This pattern cannot be seen with the naked eye, but will appear after a digital scan. FM dot is to transform the image into tiny dots, depending on the density of dots to express the depth of the image density. If copying with a copier will produce moire. The United States has adopted this anti-counterfeiting method in some stamps. The direction of the offset dots of the whole stamp is regular, and only the latent image part changes the direction of the dots. Nothing can be seen with the naked eye, but it can be clearly seen on a postmark detector with a lenticular lens.
Perforation security
This is one of the common methods used in stamp anti-counterfeiting. We know that after the stamps are made, they have to go through the perforated holes. The earliest perforated stamps are for the convenience of tearing the stamps. Later, people gradually used the shape, arrangement, density of the perforations for the anti-counterfeiting of stamps In order to prevent the imitation of stamps and improve their collection value. Nowadays, the anti-counterfeiting technology of perforations has been greatly improved, thus becoming an important aspect of anti-counterfeiting of stamps.
In addition to the above, stamp anti-counterfeiting also includes pattern anti-counterfeiting, special printing ink anti-counterfeiting, secret memory anti-counterfeiting and so on. In short, most of the techniques and materials used in the security of tickets can be used in the security of stamps.
With the continuous development of anti-counterfeiting technology and materials, the anti-counterfeiting of stamps will develop to a higher level in the future. It can basically use the high-tech branch materials and technologies used in the anti-counterfeiting of tickets. Of course, the anti-counterfeiting of stamps is not as urgent as anti-counterfeiting such as banknotes. Important, because the anti-counterfeiting of stamps in terms of use value (ie, mailing) does not make much sense. This is mainly because their face value is relatively low, and counterfeiters spend more energy than gain. The real meaning of stamp anti-counterfeiting lies in the collection value of treasures. However, since the collection value is proportional to the age and the number of this variety, if the age is far, the paper quality of the stamp must be different from the new printing when counterfeiting , Counterfeit products are easy to be discovered and lose their value; and if a large number of counterfeiters print, they will lose the meaning of rare varieties, so they are easily discovered by people and lose their value. Therefore, in general, the anti-counterfeiting of stamps is not as important as the anti-counterfeiting of banknotes. But this does not mean that the anti-counterfeiting of stamps is not important. This can be explained by the case of rare stamp stamps in the world.
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