Stamp printing process and anti-counterfeiting technology
We are a big printing company in Shenzhen China . We offer all book publications, hardcover book printing, papercover book printing, hardcover notebook, sprial book printing, saddle stiching book printing, booklet printing,packaging box, calendars, all kinds of PVC, product brochures, notes, Children's book, stickers, all kinds of special paper color printing products, game cardand so on.
For more information please visit
http://www.joyful-printing.com. ENG only
http://www.joyful-printing.net
http://www.joyful-printing.org
email: info@joyful-printing.net
Stamps are a special kind of print that most of us will touch and use. In addition to its function as a valuable document, many stamps (especially rare stamps) are high-value works of art and collectibles. The stamps are rich in ornamental and scientific, and have the infinite charm of the world, the past and the present, and have a high collection value, and with the age, the collection volume continues to decrease and continue to appreciate. Therefore, the printing of stamps not only requires beautiful pictures, but also has a considerable amount of anti-counterfeiting technology. Nowadays, with the continuous development of anti-counterfeiting technology, the anti-counterfeiting technology content of stamp printing has also increased. Therefore, the printing of stamps is different from the printing of general books, advertisements, etc.
First, the printing technology of stamps
1. Plate making technology
At present, the printing of stamps is mainly based on gravure printing (partially printed with letterpress and offset printing). This is mainly to ensure its seriousness and accessibility. China's stamps generally use gravure printing. Gravure printing is a printing method that transfers a graphic below the layout onto a substrate. The printed lines printed by the gravure printing method have clear dots, clear layers, thick ink layers, good hand feeling and strong anti-counterfeiting. Therefore, they are mostly used for printing many banknotes, stamps, etc., and their quality is recognized.
There are many kinds of gravure production techniques. In addition to the hand-carving process, there are various engraving methods such as machine engraving, electronic engraving, and laser engraving. These engraving methods each have their own characteristics and uses.
(1) Photopolymerization intaglio. The plate material is composed of a base layer, a photosensitive layer and a protective layer. The first is to place the prepared color separation film on the plate for exposure, which is called color separation exposure. The image is transferred to the plate, and the polymerization reaction in the exposed area becomes an insoluble region. Then, the film was subjected to deep exposure without film to control the depth, and then rinsed with water, and the portion where no polymerization occurred was washed away by water. After rinsing, an intermediate exposure is performed to increase the hardness and printing durability of the plate. Finally, no film is added and exposed again to increase stability. This type of printing plate is used on a gravure press consisting of a plate cylinder, a doctor blade assembly and an impression cylinder. It is suitable for printing the base color of gold, silver, Xubu pearl powder or aluminum foil and plastic film.
(2) Hand-engraved gravure. First, the pattern to be printed is drawn into a sketch, and a pattern of rich points, patterns, or characters is engraved on the steel plate according to the sketch. The hand-engraved steel plate is called a small original. The small original is subjected to heat treatment to increase the hardness. The plate on the small original plate is pressed on the steel shaft surface by the plate machine, and the steel shaft is heat treated to increase the hardness, and the pattern on the shaft surface is pressed by the plate press. Turning the picture on the steel plate again, this process is called "over the plate." Thereafter, the image on the steel plate was pressed on a 1 mm thick plastic plate with a hot press. The plastic plate of the single picture is manually modified to make a large version of the plastic plated copper plate, with a copper plated nickel relief, and the nickel relief is turned into a nickel-gravure or iron intaglio printed on the machine for use on the machine. . Hand-engraved gravure is mainly used for printing securities (such as banknotes, stamps, etc.). However, the engraving gravure process in stamp printing has now adopted an electronic engraving process.
(3) Photographic corrosion intaglio. First, the color original is separated, and a monochrome negative image is made. After the revision, the negative image is placed on the continuous shooting machine to be photographed into a large Changyang color separation film, and the large Zhangyang picture is used to print on the printing plate. The plate is then etched with a ferric chloride solution and finally plated on the plate to increase the print durability.
Gravure stamps have been used in two platemaking processes, the traditional gravure process and the modern gravure process.
(1) Photographic etching gravure stamp making process. In the traditional gravure stamp making, the original is photo-separated, and the continuous negative shading of several colors is decomposed, and then manually corrected. The corrected negative image is retracted to the color by the connected camera. The stamps are of the same size and size, and are continuously photographed in tens of thousands or hundreds of copies of the full-page stamp.
When the plate is made, the grid for gravure printing (also called the network cable) is first exposed to carbon paper, and then the pattern of the stamp (positive image) is also dried onto the carbon paper of the existing grid, and then the carbon is applied. The film with the grid pattern on the paper is transferred to the prepared cylinder, and the surface of the cylinder is deeply corroded with a ferric chloride solution. In order to improve the printing durability of the printing cylinder, a layer of chrome is finally plated on the surface of the printing cylinder for printing on the machine. The traditional gravure plate making process is cumbersome, slow, long production cycle, poor product quality stability, and technically difficult to operate, difficult to master, and is currently not used in stamp printing. As the printing industry entered the era of electronic printing, the plate-making process of gravure stamps was also improved from traditional manual plate making to modern electronic plate making. After the transition from electronic subcontracting to copying the opaque film-electronic engraving, it entered the optical film platemaking stage of the electronic color separation high-end networking system and the electronic engraving workstation.
The stamp original is first separated by an electronic color separation machine, and the image information after color separation is transmitted to the computer for correction and editing. Stamp printing is different from ordinary printed matter. In addition to the use of the three primary colors, it often adds various spot colors. Therefore, it is necessary to correct the layout after the color separation. At the same time, because the stamp face is relatively small, the pattern is exquisite, and the required quality is very high, which brings great difficulty for printing, especially for high-speed printing. For this reason, special techniques for the printing interface of each color plate are also required for plate making. Processing to ensure print quality. In addition, text, border layout, placement, and the like need to be done in the computer. When the layout of a stamp is completed, the operator transmits the electronic data to the electronic engraving workstation. The electronic engraving workstation edits and layouts according to the data and the layout specifications of the full-page stamps and the layout requirements of the printed on the machine. It also needs to smooth the edges of the characters and lines and make the final minor corrections to the patterns. After that, the electronic engraving machine can engrave dozens or even hundreds of stamps of the same color and the same level on the electrolytic copper on the surface of the printing roller. The printing roller can be printed on the machine by chrome plating.
The plate making process of the modern gravure stamps is operated by the optical film, from the high-end electronic color separation system to the electronic engraving workstation. The plate making speed is improved, the production cycle is shortened, the plate overprinting precision is high, the plate making repeatability is good, and the quality is improved. Stable, conducive to the process of data, standardization and even standardized management.
(2) The plate making process of engraving gravure stamps. There are various methods for engraving gravure, such as mechanical over-plate method, electroplating plate method, and etching method. China uses the mechanical over-printing method. The method first shrinks the pattern of the stamp original to the flat steel plate according to the size of the stamp. The engraver uses the carving knife to manually pattern the pattern on the copper plate into different shapes, widths, and depths. And lines, in order to show the different levels in the picture. This engraved small steel plate is used as the original version of the engraved gravure (called the original steel plate), and it is used to copy the printing plate. The gravure stamp is printed on the rotary machine. Therefore, when making the printing plate, the original steel plate is first heat-treated to strengthen its hardness, and then placed on a special plate-making machine, and the flat steel plate is pressed by mechanical extrusion. The points of different shades and lines are transferred to another small steel shaft to obtain convex lines and pips; the small steel shaft is also heat-treated and placed on the plate machine, and the economic pressure is to apply the above pattern to the specification of the full-page stamp. One piece is transferred to a printing roller whose surface is coated with an electrolytic copper layer to obtain concave graphic points and lines; after chrome plating, the printing roller can be printed on the machine, and the plate making of the engraved gravure stamp is completed. Engraved gravure stamps have their own unique effects. The lines of the pattern are distinct, the ink layer is thick, and there is a slight bulge on the paper. The fine points and lines are clearly distinguishable. The color has not changed for a long time, which is conducive to the elimination of the forgery of stamps. Although the engraving and printing technology of engraving gravure is very difficult, its anti-counterfeiting performance is good, so most of the world's stamps and the like are printed by engraving gravure.
2. Stamp printing technology
The gravure stamps are printed on a special gravure rotary press with a four-color, five-color, six-color stamp press, a gravure stamp with one-color engraved gravure and a five- or four-color gravure overprint. These special stamp presses are equipped with counting codes, perforations and cutting devices. The stamps can be counted, punched, and cut into full-size stamps. The ink used for gravure printing is a solvent-based liquid ink. When printing, the printing plate is immersed in the ink fountain, and the ink of the non-image portion of the printing plate is scraped off by the doctor blade, and the graphic portion is the concave portion of the printing plate. The ink is stored. After the embossing cylinder is embossed, the ink is transferred to the paper, and then the multi-color overprint is printed on the paper. The printing ink used for engraving stamps is a viscous resin ink whose ink transfer form is similar to that of embossing, but since the graphic portion of the engraved gravure is concave, the ink on the non-image portion (planar) on the printing plate Then rely on a special ink-cleaning device to wipe off. At present, there are roughly four ways of engraving and printing: cloth wiping ink, trichloroethylene wiping ink, water wiping ink, and paper wiping ink. Using a cloth to wipe the ink, the printed engraved ink layer has better three-dimensionality and gloss, but the printing speed is slower; the printing speed of trichloroethylene ink is relatively fast, but the toxicity is large and harmful to the human body; the water wiping ink is a kind More advanced method of wiping ink, but also has problems in wastewater treatment and pollution; paper wiping is suitable for small paper printing, which is not suitable for large-scale stamp printing in China. China's engraving stamp printing presses are equipped with cloth wiping devices.
In addition to the single photo ticket or single engraving ticket mentioned above, the gravure stamp is also a kind of stamped and engraved stamp, which is called the shadow stamp. It is the favorite of philatelists. The printing of the shadow stamp is a combination of two different printing methods, a gravure and a gravure. Although engraving gravure is an ideal process for printing valuable securities, it is difficult to express rich colors and delicate layers. Gravure also has disadvantages. Because some stamp patterns are darker in color, the amount of ink required for printing is large, and gravure ink is a fluid with a very small viscosity, so irregular water marks are often present in deep adjustment, which destroys the stamp image. The delicate feeling, in addition, since the patterns of gravure printing are all composed of dots of different depths and different sizes, zigzag-shaped broken points appear at the edges of thin lines or characters, which affects the smooth and complete effect of printing. In order to make the stamps more perfect, the method of engraving gravure and gravure mixed overprinting is usually adopted, and the advantages of the two printing methods are exerted to obtain more ideal printing effects, such as the famous "Huangshan scenery" and "Lushan scenery". "Zodiac" stamps and stamps such as "China Ancient Tower", "Lushan" and "Rare Bird" issued in recent years are all printed in this way.
Combining two printing methods with completely different performances, the printing precision is very difficult in the process, especially the printing pressure required by them is completely different, the ink performance is different, and the printing suitability of the paper is also required. Therefore, the mechanical error in printing is large, and the scrap rate is higher than other printing methods. When designing the printing process of such stamps, it is necessary to fully understand and exert the characteristics of these two printing methods, and to gain strength and avoid weaknesses in order to obtain better printing results. This overprinted version of the stamps is generally based on the engraving version, to make the sketch of the picture pattern, and then lined with the gravure color of the gravure. Therefore, the main lines and ideas of the engraving plate should be heavy and realistic, and the contour image and main level of the pattern should be made; the color of the gravure can be shallow and imaginary, supplemented by the details of the color and the level, so that even if there is mechanical error It also does not affect the clarity and completeness of the theme landscape. The stamps printed on the stamps are solemn and straightforward. The theme is outstanding, the three-dimensional effect is strong, and the colors are magnificent. It has a very unique artistic effect, especially worthy of collection by collectors. At present, international stamps are mostly printed with engraving and offset printing. The modern offset printing technology greatly enhances the performance of color and level. The text and lines of offset printing are clear and clean, the background color of the large-area is even and thick, the color of the pattern is elegant and harmonious, and the lines and ideas of the engraving and engraving are reflected. More perfect.
3. Printing medium color application
The stamps are small prints, but the print volume is very large. Not only do a plate have dozens or even hundreds of patterns, but the color and level of each pattern are exactly the same; and the stamps of the same pattern are printed repeatedly. Tens of millions of pieces, the printing cycle sometimes lasts for several months. Such long-term, high-volume printing of the same product, but also to meet the high quality needs of philatelists and consumers, not only in the entire version of the stamp must be accurate, but also to ensure the color of the front and back printing The level is consistent. This requires the design of the pre-press process to take into account its characteristics, to ensure the repeatability of printing. For this reason, in addition to the use of conventional yellow, magenta, cyan, and black inks in stamp printing, the application of spot color inks is also essential. According to the characteristics of the original, different spot colors are used for printing, and the printed stamps can achieve satisfactory artistic effects and high qualification rates. Therefore, spot colors are often used in stamp printing, and they are mainly used in the following aspects.
(1) Background color. In the printing of stamps, there are two different manifestations of the background color. One is the background color that often appears in the stamp picture as the background of the theme pattern. Although it is not the theme of the picture, it plays a very important role in the whole picture. The important setting effect directly affects the artistic effect of the stamp picture. In order to make the color of the finished stamps after printing in large quantities basically the same, there is no obvious color shift phenomenon, which can perfectly reproduce the artistic concept of the designer. This background color is generally printed by color. When the background color of the original background is relatively dark or the area of the stamp is relatively large (such as a sheetfed sheet), it is also designed to print two deep and light spot colors with similar hue, so that the printed stamp has the bottom of the picture. The color matches the original, and the ink layer is thick, flat, not flowered, and does not leak white spots, which can truly reproduce the artistic effect of the original. There is also a background color that is used in the prepress process design. In order to facilitate the printing control of the hue and to compensate for the color difference between the printed matter and the draft, the background color of the stamp pattern is artificially added, and it is also printed by spot color. This is because the manuscripts of stamp patterns often use some Chinese paintings, gouache paintings, and oil paintings. Some of the art works are very beautifully designed, the colors are very rich, and the layers change vividly. If you use this kind of manuscript to copy the stamp, if you simply use the three primary colors and the black superimposition to reproduce the picture, the pattern color of the stamp picture will be monotonous and thinner than the original, which often gives people the feeling of lack of color, which is not as good as the original color. Rich and thick, the changes between colors are also blunt and uncoordinated. The scenes of the picture are also dull and rough, and the artistic effect of reproduction is not ideal. On the other hand, from the printing point of view, if the stamp image completely relies on the superposition of the three primary colors to produce a color change, it is more difficult to make the ticket face color consistent in high-volume printing. In this case, in order to perfectly reproduce the artistic charm of the original and obtain a high-quality stamp product, the process design is based on the main color of the original image, and one or two spot colors are set as the background color of the pattern portion. Paving, which is the complement of color, such as: deep, light gray, deep, light yellow, purple, etc., plus three primary colors. In this large-volume printing, the main color of the ticket surface is fixed, and the ink color can be easily aligned to ensure the printing quality. At the same time, the artistic effect of the stamp picture is greatly improved, and the color tone is basically the same as the original. Moreover, the smudge effect of the original color is better reproduced, the color is rich and soft, the color changes naturally and harmoniously, and the whole picture is flat and delicate.
(2) The skin color of the character. The skin color of the character, especially the skin color of the face, is an important part of the character pattern and the main rendering part of the art design. This is also crucial in the printing of other books and advertisements. It is even more prominent in the stamp of the stamp. Due to the small size of the stamp, the skin color of the face is smaller. If the three primary colors are used for overlay printing, it will bring some difficulty to the overprint and ink color control. For example, after mass printing, the facial skin color of the finished stamp often shows color cast, some are reddish, some are yellowish, and the overprint is not accurate, and the contour of the face will be deformed. In particular, the stamps of the character theme, if the subject's facial color is inconsistent, or the outline is unclear, will affect the character's image, directly affecting the artistic effect of the stamp, and of course greatly affect the quality of the stamp. Therefore, in the process design, according to the skin color hue of the original, a spot color is generally used as the main color of the skin color, and then the three primary colors are added to the level, so that the color of the printed portion of the stamp has little change, the overprint is accurate, and the contour of the face is clear. The level transition is natural and soft.
(3) Neutral gray. Neutral gray is a mark for checking the balance of the three primary colors in printing. Therefore, the reproduction of neutral gray in printing has certain technical difficulty, especially the neutral gray of light color, its color change is more visually sensitive, and the ratio of three primary colors With a slight deviation, the hue will be far apart. In the high-speed operation of large-volume stamp printing, if the neutral color is reproduced by the three primary colors, the technical difficulty and labor intensity will be high, and the final product yield is very low; the neutral gray color on the ticket surface will be Color cast. If the standards for quality inspection of finished products are not properly mastered, it will bring confusion to the philatelic market. In order to avoid the above phenomenon, in the process design, the neutral gray part of the ticket surface is generally printed with a spot color gray. Such pre- and post-printed stamp products will not have any discrepancies in the hue, which can greatly improve the yield of finished products, shorten the production cycle and save raw materials.
Second, the anti-counterfeiting technology of stamps
1. Printing anti-counterfeiting technology
As mentioned above, the printing of stamps is mainly based on gravure printing, which is because the gravure printing has better anti-counterfeiting. It is widely used in anti-counterfeiting printing. Gravure printing is characterized by a large amount of ink. Therefore, the thickness of the gravure printing line and the shade of the ink are varied. The graphic has a concave and convex feeling, various layers, clear lines, and easy identification, which brings great difficulty to counterfeiting. Gravure is the first printing technology used in the field of anti-counterfeiting.
In terms of stamp printing, China's hand-engraved gravure technology is world-class. The hand-carved knife style and artistic style are unmatched by other plate making methods. The portraits of Chinese and foreign banknotes have always been hand-carved, and hand-carved to express the characteristics of the characters. The hand-carved deep-printed product has a thick ink layer, good hand feeling and strong anti-counterfeiting. However, there are two problems in hand-carving. Firstly, it is inefficient and not suitable for rapid production. In addition, because the hand-engraving must use a knives, the engraved stencil is a "V" shaped groove in the depth direction. The ink storage property of the groove of this shape is not so good. If the concave method is used, the ink in the groove is easily wiped out, and the ink layer of the printed line is not sufficiently thick and thick. This is two issues that must be solved. In solving the problem of efficiency, when carving portraits abroad, the portrait is enlarged and the image is enlarged and corroded. After the manual carving, the enlarged portrait copper plate is used as a template; using this template as a mold, the shrinking machine is used to shrink on the steel plate. Engraving portraits that meet specifications. Sensible heat, engraving copper plate is easier and more efficient than directly engraving steel plate. As for solving the "V" shape of the groove, it is necessary to exploit the potential of the etching gravure process. The etching gravure process directly etches a single-open graphic film on a copper plate coated with a photosensitive material. The hardness of the copper plate is low, and other high-hardness plates can be pasted on the back of the copper plate. Or charge a layer of copper on a harder lining. The copper plate which has been treated with improved strength after being single-opened is pressed on a 1mm-thick plastic plate by a hot press, and the plastic plate is made into a large plastic plate by precision cutting and high-frequency welding, and a large plastic plate is used. The copper plate is flipped, the copper plate is re-turned to the nickel relief plate, and the nickel intaglio plate is finally available for use on the machine. The intaglio plate made by this etching process has a U-shaped groove, and has good ink-storing performance, and the printed product line has a thick ink layer and strong hand feeling. And the corrosion method can make small text and very thin lines, now the size of the miniature text can be done. 150-m, such a small gravureal miniature text can only be seen under the magnifying glass and is clearly visible.
The gravure invisible image made by the etching method has good refractive index and obvious color change. At the same time, the gravure method of this method solves the problem of the ink storage amount of the gravure pattern, and also solves the problem of low efficiency of hand engraving. However, in the large version of the corrosive method, it is necessary to use the process of imposition, electroplating and multiple piracy to make the printing plate. This also has the problem of inefficiency. To solve this problem, people have been exploring whether to use the etching method. The technical problem of directly making a gravure on the machine.
2. Application of laser holographic anti-counterfeiting technology in stamp printing
Laser holographic anti-counterfeiting technology is a high-tech anti-counterfeiting technology that emerged in the 1980s. It uses the basic laws of scattering, reflection, transmission, diffraction, interference, and absorption generated by the action of light and matter to obtain a special visual effect. At present, the technical means of using optical anti-counterfeiting are multi-layer dielectric film structures utilizing thin film interference effects, grating structures, and various types of laser holography techniques utilizing the concept of information light. It is characterized by the emergence of the molding process, which enables low-cost mass production of laser holograms, and the hologram itself contains a wealth of information, and the holographic logo cannot be copied simply by ordinary photolithography and printing techniques. Holograms are quickly gaining application in anti-counterfeiting security.
The application of laser holographic anti-counterfeiting technology to stamp printing was in the late 1980s. The world's first stamp with a holographic anti-counterfeiting pattern was an 8-soul 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. The stamp has three holographic patterns in the center, and is reproduced by the A letter and MADE.
The shape of the sailboat made up of IN AUSTRIA symbolizes the meaning of export. Later in 1989 On December 3rd, the 25-cent prepaid envelope issued by the US Postal Service (a hologram in the square opening in the upper right corner of the envelope, made by the American Banknote Hologram Company), whose hologram is a spacecraft is on the orbital 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 anti-counterfeiting of stamps. China also issued such stamps in 1996. First, a souvenir cover was issued for the "Hong Kong 98" exhibition. The commemorative cover is adorned with a small round holographic pattern. The picture is a panda holding a bamboo. The stamp is a picture of a green bamboo forest. Later, on July 18, 1996, a commemorative stamp with a holographic pattern was issued to celebrate the 22nd China Stamp Exhibition. The picture of the stamp is a statue of a person flying around the earth, surrounded by airmail envelopes, planes, ships, trucks and other patterns. In addition, China's Xiangdao in 1994 2 On the 15th of the month, two postal postcards with holographic stamps were issued. The hologram stamp on a postcard is a 1685 Victorian female worker's head. The picture of the postcard with this stamp is On the Hong Kong waterfront in 1920, the holographic pattern on another postcard was the head of Queen Elizabeth II of England. The picture of this postcard is the 1933 Hong Kong waterfront.
3. AM network cable and FM network
The change of outlets is now attracting people's attention as a new anti-counterfeiting technology. It is gradually being used for security printing of tickets and has a good effect. The principle is to convert a continuous tone image, a character, a figure, and the like into a minute dot-dash line having a certain directivity, and form a latent image by changing the angle thereof. This pattern is not visible to the naked eye, but it will appear as soon as it is digitized. The FM network point is to transform the image into tiny dots, depending on the intensity of the dots to express the depth of the image density. If you copy with a copier, it will produce a moiré. The United States has adopted this type of anti-counterfeiting method in some stamps. The direction of the offset printing dot of the stamp is regular, and the direction of the dot is changed only in the latent image portion. It can't be seen with the naked eye, but it can be clearly seen on the postmark detector with lenticular lens.
4. Perforation security
This is one of the common footwork used in stamp security. We know that the stamps have to go through the perforated holes after the production. The earliest stamping holes on the stamps are for the convenience of tearing the stamps. Later, people gradually used the shape, arrangement, and density of the perforations for the anti-counterfeiting of stamps. In order to prevent the imitation of stamps, increase the value of their collection. Nowadays, the anti-counterfeiting technology of the perforation has been greatly improved, which has become an important aspect of stamp anti-counterfeiting.
In addition to the above, stamp anti-counterfeiting is also anti-counterfeiting, anti-counterfeiting of special printing inks, anti-counterfeiting and so on. In short, most of the techniques and materials used in ticket anti-counterfeiting can be used in stamp security.
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 materials and technology used in ticket security. Of course, the anti-counterfeiting of stamps is not as urgent as anti-counterfeiting such as banknotes. Important, because the anti-counterfeiting of stamps on the value of use (ie mailing) does not make much sense, mainly because its face value is relatively low, and the counterfeiters spend more energy than they lose. The true 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 the varieties, if the age is far, the paper quality of the stamps will be different from the new ones when the fakes are printed. The counterfeit products are easy to be discovered and lose their value. If the counterfeiters print in large quantities, they will lose the meaning of rare species, so they are also easily found and lose their value. Therefore, in general, stamp anti-counterfeiting is not important for anti-counterfeiting such as banknotes. But this does not mean that stamp anti-counterfeiting is not important. This can be explained by the case of rare stamps in the world.