MXPA05014025A - Printing machine - Google Patents

Abstract

A printing machine including at least one transfer system (5) for transferring a substrate (1) onto a printing cylinder (6), at least one cylindrical or planar screen (7, 8) with a scraper, which screen engages the printing cylinder (6) and prints the substrate using an ink that contains pigments of which the orientation can be adjusted by means of a magnetic field, and a discharge system (9) for removing the substrate (1). The printing cylinder comprises at least one magnetic element on the printing surface thereof, which magnetic element is positioned in a location corresponding to said printing of the substrate by said screen (7, 8).

Description

PRINTER MACHINE The present invention relates to a sheet or web printing machine, a printing method and a security element for paper-values. In the field of paper-securities, in particular bank notes, there is a growing need for security elements as protection against counterfeiting. In recent years, computers, scanners and photocopiers have experienced remarkable technical improvements and it is now possible to buy the most excellent devices at reasonable prices. As these devices become more excellent, it becomes necessary to develop new security elements, themselves more excellent, for paper-values, such as bank notes, checks, credit cards, passports or documents. of identity and other similar documents in order to protect these documents against forgery and prevent them from being copied by current computers, scanners and photocopiers. The known security elements for combating counterfeiting are, for example, formed by combinations of overlapping lines and / or patterns with colors, only visible under certain conditions, for example, UV light or in transparency. The interest of such security elements is that they are easy to print or place on the document before being protected and can be controlled by simple devices, as at first glance, but they are impossible to reproduce with current printers, scanners or photocopiers. By way of example, U.S. Pat. 6,050,606, incorporated for reference in the present application, describes a security element for securities, for example for banknotes. This security element is formed by a background having at least two juxtaposed regions, each region comprising appropriate geometric designs, said regions having a different color density. The security element further comprises a pattern corresponding to the region of which the color density is the lowest that is printed in superposition on said region in a color chosen so as to compensate for the difference in color density between said two regions. Thus, the security element will appear uniform and without reason to the naked eye, but the reason clearly stands out when a photocopy of said element. U.S. Pat. 5,443,579, incorporated for reference in the present application, describes another method of printing a latent image on a substrate. According to this patent, the printing of lines in relief with the lines without relief is combined. Thus, a latent color image is created that can not be reproduced with a photocopier or other photomechanical methods. U.S. Pat. 5,853, 197 and USA 5,487,567, incorporated for reference in the present application, show security elements that are not easily visible to the naked eye, but which, in rematch, become clearly apparent when a reproduction of the element by photocopy or scanning. Another specific technique uses watermarks in which the substrate, for example paper, is marked with lines or a motif that are visible only in transparency. Another development of this technique refers to pseudo-watermarks formed by the creation of a window in the substrate, a technique used in particular with paper substrates that are not normally transparent, said window being transparent to it. The US patent UU 6,082,778, of which the content is incorporated for reference in the present application, describes an identity card protected against unauthorized copying by photocopiers. In this patent, the idea is to create a safety element by combining the protective effect provided by a thin metal film with the physical properties, in particular optical properties, of an additional layer from which the combination of effects prevents the reproduction of the card . Under a transparent layer of coverage, there is a metal layer above a layer having specific oal properties. In a first embodiment, the metal layer is locally demetallised, thus exposing the layer with specific oal properties, that is, making it visible in the demetallised zone. The difference in contrast between the layers returns to the marks formed by demetallization that are easy to recognize with the naked eye. In a particular embodiment, the layer having specific oal properties has a dark color, for example, black. The combination of the direct reflection of the metallized zone and of a layer having a strong absorn (black layer) prevents the detection of the contrast difference so that the information formed by the demetallization will disappear completely in a copy of this security element. In another embodiment, the layer having specific oal properties contains fluorescent or phosphorescent substances that, irradiated by the light of a photocopier, do not emit light of a wavelength in the visible spectrum, so that the area does not reproduce anymore. According to other techniques known in the state of the art, a laser is used to either mark the substrate directly, or to mark a layer applied on said substrate and thus create security elements impossible to reproduce by photocopier or scanner. Other safety elements using oally variable elements ("OVD" ®) in the form of metallized patches (called "sheets") or holograms, and also of reflections or other similar reasons, all being, on the one hand, very difficult indeed impossible to copy with current devices but, on the other hand, very easy to control visually by appropriate means or at a glance. It is also known to use specific oally variable inks to print particular motifs or geometric shapes on the paper-stock substrate. These inks, known in the state of the art, contain pigments of variable oal effect and change color depending on the angle by which they are seen. By way of example, US 2002/0160194 A1, US 2002/0182383 A1 and EP 1239307 disclose such inks and their contents and are incorporated for reference in the present application because they describe the principle and composition of such inks. When such inks are used, it has been perceived that the pigments have variable oal effect containing a complementary magnetic layer that can be oriented by the application of a magnetic field and thus create particular effects. This particular technique is described in the publications US 6, 103,361, US 5,630,877, WO 03/000801 and US 5,364,689, and incorporated for reference in the present application. However, one of the problems encountered with oally variable ink printing resides in the fact that it is frequently used to print the value of paper-value (for example, banknotes), this value being indicated generally in a parallel to the length of the ticket. In addition, it is always sought to create a visible oal effect when the paper-value is rotated around an axis parallel to the length of said paper-value (high-low movement) before an axis parallel to the length (left-right movement). ), the first movement being more natural for a user. As a rule, the sheets comprising impressions of paper-values installed in matrix form move in the direction of the length of said impressions so that the integration of immobile magnets in a conventional printing machine imposes a movement parallel to the length of the prints. impressions for the creation of a visible effect (left-right movement mentioned above). The creation of an effect in the desired direction (high-low movement mentioned above) imposes a change of direction of movement of sheets if one wishes to obtain the particular effect in the desired direction (high-low motion mentioned above). A) Yes, the existing machines must be modified in an important way what has little economic interest and increases the time needed for printing. Thus, an object of the invention is to improve the known methods and devices. Another object of the invention is to propose a printing machine and a method employed by this machine that increases the security of printing. More particularly, the object of the invention is to propose a printing system, notably for papers, which can be incorporated into existing machines in a simple manner. Another object of the invention is to provide a particular printing method for paper-values. A further object of the invention is to propose an improved security element.

The invention is defined by the features of the claims. It will be better understood by the description of several modes of execution thereof and in reference the appended figures in which Figure 1 shows a schematic representation of a screen printing machine. Figure 2 shows an embodiment of a printing cylinder according to the invention. Figures 3A and 3B show two variants of the embodiment of Figure 2. Figure 4 shows a schematic diagram of the effect obtained by the invention. Figures 4A and 4B show schematically a first orientation configuration of magnetic pigments of variable optical effect. Figures 5A and 5B show schematically a second orientation configuration of magnetic pigments of variable optical effect. Figures 6A and 6B schematically show a third orientation configuration of magnetic pigments of variable optical effect. A classic sheet-by-sheet printing machine is described with reference to Figure 1. This known machine has been described in detail in U.S. Pat. UU 6, 109, 172 and its content is incorporated for reference in the present application with respect to the principle of operation of a screen printing machine. The machine comprises a reservoir 1 containing sheets to be printed, a marker 2 for the successive transfer of sheets along the path 3 towards a margin cylinder 4, a transfer cylinder 5 for bringing the successive sheets onto a printing cylinder 6, two sieve cylinders 7 and 8 with scrapers and cooperating with the printing cylinder 6 and a chain gripper system 9 which, once printing has been carried out, transport the sheets to the outlet tanks 10. The machine comprising two sieve cylinders 7 and 8 with the scrapers 55, 56 is capable of producing two-color screen printing on the successive sheets. In the printing cylinder 6, the sheets pass the first screen-holding cylinder 7 where a screen printing in a first color is effected, then the second screen-holding cylinder 8 passes where they receive a screen printing in a second color. . This second printing can be done in an area different from that printed by the first sieve cylinder 7 or in the same area. In the latter case, it is necessary to add an ink drying system placed by the first sieve cylinder 7, for example UV lamps or other equivalent system. FIG. 2 shows a printing cylinder 6 in section according to the present invention in the configuration of FIG. 1, that is to say surrounded by a feed cylinder, two sieve cylinders 7 and 8, a discharge system 9, for example a chain of tweezers, and a drying system 10, such as, for example, UV lamps. According to the invention, the printing cylinder 6 comprises a plurality of magnets 12, 13 and 14 arranged according to a distribution corresponding to the impressions in the substrate sheets, each set of magnets being separated by the notches 15, 16, 17 in the cylinder 6, in which the sheet retaining clips in the cylinder 6 are arranged. These magnets can be fixed by any appropriate means in the cylinder, notably by adhesion, screwing or other equivalent means. According to a first variant of the invention, the magnetic elements 59 (for example, magnets) are not placed directly on the printing cylinder 6 but on a discharge cylinder 57. According to a second variant of the invention, the magnetic elements 60 ( for example, magnets) are placed in an intermediate cylinder 58, which is located between the discharge cylinder and the UV lamps 10, in the direction of displacement of the substrate. According to another variant, the magnets are placed simultaneously in the printing cylinder 6 and / or in the discharge cylinder 57 and / or in the intermediate cylinder 58. The interest of two variants is that they allow to maintain a classic printing cylinder without risk of creating ripples or gaps in the impressions due to an uneven surface of the printing cylinder 6. In Figures 3A and 3B, two partial views of a printing cylinder with two variants of magnets have been shown schematically. In the first variant (FIG. 3A), the printing cylinder 6 comprises at least one notch 18 in which the gripper system 19 is retaining the substrate 1 that is printed. The cylinder further comprises a second groove 20 in which the magnets 21, 22 are placed according to a distribution corresponding to that of the impressions in the substrate (not shown). The magnets 21, 22 are covered by a plate 24 of non-magnetic material, for example aluminum or stainless steel. In this variant, the magnets 21, 22 are permanent magnets. In the variant of Figure 3B, identical elements are referred to in the same manner as in Figure 3A, and the difference is constituted by the means used as magnets. In this variant, the windings 25, 26 are used. The principles set forth with reference to FIGS. 3A and 3B for the printing cylinder 6 are applied in the same manner in the variants of the invention indicated above, when they are the discharge cylinder 57 and / or the intermediate cylinder 58 that support the magnetic elements. The principle used in the present invention is shown schematically in Figure 4. In this figure, a substrate 27, for example, a sheet of paper, on which an optically variable ink impression has been deposited, has been represented.

The printing cylinder 6 comprises as shown a permanent magnet 28 creating the magnetic field lines 29, 30 represented in this figure. In addition, the optically variable ink containing magnetic pigments has variable optical effect, the magnetic field lines 29, 30 will orient these pigments according to the directions indicated in this figure 4. In a central zone 31, the pigments will be aligned vertically when in the lateral zones 32 and 33, the pigments will take a more horizontal configuration, as shown. Thus, depending on the angle according to which the impression will be considered, the apparent color of the impression will change and a change of orientation will have a dynamic re at the printing level with color changes followed in the printing. One of the advantages of the system according to the invention is that since the sheet is static with respect to the magnets, the aforementioned problem mentioned in the usual direction of sheet movement with respect to the direction in which the optical effect is to be created is avoided. . It is now possible to believe this effect without changing directions of movement of successive sheets, certainly on the same sheet, to create the security elements with the optical effects in different directions (perpendicular or not) without influence on the direction of movement of successive sheets nor do you need to make successive impressions with the optically variable ink. Figures 4A and 4B show a first optical effect that can be obtained with the machine according to the invention. In Figure 4A, an ink print 40 containing magnetic pigments of variable optical effect forms the number "100". In order to correctly represent the effect obtained, this impression 40 has its upper part lighter and its lower part darker. The print 41 of FIG. 4A represents the same impression as the print 40 but having undergone a rotation about the X axis so as to vary the angle of consideration of the print. In this position, the lower part is kept which is lighter and the upper part is darker. To obtain this effect, the pigments are oriented by means of a magnet as in the section AA shown in FIG. 4B, that is to say approximately 45 ° in the left part 42 and approximately 135 ° in the right part 43. Thus, for the rotations in two directions around the X axis, a certain variation of colors of two portions of the impression is obtained reing in a dynamic optical effect, impossible to copy with the classic means such as scanners or photocopiers. A second optical effect that can be created with the invention is described with reference to Figures 5A and 5B. The print 44 forms the figure "100" and comprises a lighter area on its upper part. By rotating the print around the X axis, the clear area moves in the print, as shown in prints 45 and 46 to pass in the central part of the print (print 45) and in the lower part of that (print) 46).

This optical effect is obtained by the orientation of pigments as shown in Figure 5B which corresponds to section B-B of Figure 5A. As shown (from left to right), the pigments have an almost vertical orientation (zone 47), then progressively reach a horizontal orientation (zone 48) and finally return to a practically vertical orientation (zone 49). Thus, by rotations in two directions around the X axis, the visual effect of a shift of a clear area to the interior of the impression is obtained reing in a dynamic optical effect, impossible to copy by the photocopier or scanner. A third optical effect is represented in Figures 6A and 6B. This effect is obtained by two superimposed impressions created with the same optically variable ink. When the print is viewed perpendicularly (print 50), the print is bright and the background is matte. If the print is rotated regardless of which direction, then it has an inversion of bright and matt areas (impression 51). Furthermore, if the orientation is changed laterally (printing 52), a color variation is also obtained. These optical effects are obtained by the impressions represented in the section CC of Figure 6B in which there is a first layer 53 with pigments oriented in a first direction and a second layer 54, with pigments oriented in a second direction, the two directions being different. These layers are successively placed on the substrate and the first layer 53 must be dried before the second layer is not placed, in order to maintain the orientation of pigments in said first layer. The invention is not limited to the described embodiments, but variations are possible within the framework of the claimed protection. For example, the screen can be carried by a cylinder (as in the machine of figures 1 and 2) it can also be flat. Different types of ink are equally possible, at the moment they contain magnetically orientable pigments.

Claims (19)

1. CLAIMS 1. Printing machine for a substrate (1) in the form of a sheet or continuous band, said substrate intended to receive at least one impression, comprising at least one transfer system (5) to carry the substrate (1) over a printing cylinder (6), at least one screen (7, 8) of cylindrical or flat shape provided with a scraper (55, 56), the screen cooperating with the printing cylinder (6) and intended for printing the substrate by screen printing with an ink containing pigments orientable by a magnetic field and a discharge system (9) to carry the substrate (1) after the printing operation, characterized in that said printing cylinder comprises at least one magnetic element (12, 13, 14) on its printing surface, said magnetic element being placed in a place corresponding to said printing on said substrate made by said screen (7, 8). The printing machine according to claim 1, wherein the substrate (1) receives a plurality of impressions arranged in matrix form and the printing cylinder comprises a plurality of magnetic elements (12, 13, 14) arranged in a matrix form correspondent. 3. Printing machine for a substrate (1) in the form of a sheet or continuous band, said substrate intended to receive at least one impression, comprising at least one transfer system (5) to bring the substrate (1) on a printing cylinder (6), at least one screen (7, 8) of cylindrical or flat shape provided with a scraper (55, 56), the screen cooperating with the printing cylinder (6) and intended to print the substrate by screen printing with an ink containing pigments orientable by a magnetic field and a discharge system (9) to carry the substrate (1) after the printing operation, characterized in that the discharge system comprises a cylinder (57, 58) having at least a magnetic element (59, 60) on its surface, said magnetic element being placed in a corresponding place to said printing on said substrate made by said screen (7, 8). The printing machine according to claim 3, wherein said cylinder is a discharge cylinder (57). The printing machine according to claim 3, wherein said cylinder is an intermediate cylinder (58). Printing machine according to any one of the preceding claims, in which the magnetic element (s) (12, 13, 14, 59, 60) create a magnetic field in a predetermined direction. The printing machine according to claim 6, in which the magnetic element (s) are oriented in a direction parallel and / or perpendicular in the direction of displacement of the substrate. 8. Cylinder (6, 57, 58) for printing or transferring a substrate (1) in the form of a sheet or web, said substrate being used to receive at least one screen printing with an ink containing orientable pigments for a magnetic field, characterized in that it comprises at least one magnetic element (12, 13, 14, 59, 60) on its surface to orient the pigments of said ink, and in that said at least one magnetic element (12, 13, 14, 59, 60) is covered by a plate (24) of non-magnetic material. 9. Cylinder according to claim 8, characterized in that said plate (24) is made of aluminum or stainless steel. 10. Cylinder according to claim 8, characterized in that it comprises a plurality of magnetic elements (12, 13, 14) arranged in a matrix form. Printing machine according to one of claims 1 or 3, characterized in that the printing cylinder (6) or the discharge system cylinder (57, 58) is a cylinder as defined in claim 8, 9 or 10. 12. A method of printing by screen printing a substrate in the form of a sheet or band in which an impression is formed by means of an ink containing magnetic pigments, said impression being formed by passing said substrate in contact with a printing cylinder ( 6) with which at least one sieve cooperates (7), 8) of cylindrical or flat shape provided with a scraper (55, 56) for the screen printing of said ink, characterized in that said printing is subjected to a magnetic field before drying in order to orient said pigments. The printing method according to claim 12, wherein the magnetic field orients the pigments in a predetermined direction. The printing method according to claim 13, wherein the pigments are oriented parallel and / or perpendicularly in the direction of substrate displacement. The printing method according to any of claims 12 to 14, in which a first printing of variable optical effect ink is formed on the substrate, said printing is subjected to a first magnetic field orienting the pigments in a first direction, said first impression is dried, in the form of a second printing of variable optical effect ink on the first printing, said second printing is subjected to a second magnetic field orienting the pigments in a second direction, and said second printing is dried. 16. The printing method according to claim 15, wherein the first direction and the second direction differ. The printing method according to any of claims 12 to 16, wherein said printing comprises a plurality of individual impressions arranged in matrix form. 18. Printing method according to any of claims 12 to 17, characterized in that said magnetic field necessary for the orientation of said pigments is produced by means of a cylinder carrying at least one magnetic element on its surface. 19. Printing method according to claim 17, characterized in that for each of said individual impressions it produces a corresponding magnetic field.