EP2189286B1 - Printing machine and method - Google Patents

Abstract

The machine has a transfer cylinder for transferring a substrate onto a printing cylinder (6). One of two breaker plate cylinders (7, 8) prints the substrate by screen printing using an ink containing pigments. A chain clip system (9) removes the substrate after printing operation. The cylinder (6) has magnets positioned in a location corresponding to the printing by the cylinders (7,8) that are engaged with the cylinder (6). The breaker plate cylinders are engaged with the printing cylinder. An independent claim is also included for a printing method by screen printing of a substrate.

Description

The present invention relates to a sheet or web printing machine, a printing method and a security element for securities.

In the field of securities, especially banknotes, there is a growing need for security features as protection against counterfeiting. In recent years, computers, scanners and photocopiers have undergone significant technical improvements and it is possible to purchase high-performance devices at reasonable prices. As these devices have become very efficient, it has become necessary to develop new security elements, themselves also more efficient, for securities, such as banknotes, checks, credit cards, passports or documents. identity documents and other similar documents to protect these documents against counterfeiting and prevent them from being copied by current computers, scanners and photocopiers.

Security elements known to combat counterfeiting are, for example, formed by combinations of lines and / or patterns with colors, only visible under certain conditions, for example UV light or transparency. The advantage of such security elements is that they are easy to print or place on the document to be protected and they can be controlled by simple devices, even with the naked eye, but they are impossible to reproduce with the current printers, scanners and photocopiers.

For example, the patent US 6, 050, 606 describes a security element for securities, for example for banknotes. This security element is formed by a bottom having at least two juxtaposed regions, each region having clean geometric patterns, said regions having a different color density. The security element further comprises a pattern corresponding to the region of the lowest color density superimposed on said region in a color selected to compensate for the difference in color density between said two regions. Thus, the security element appears uniform and without a pattern to the naked eye, but the pattern is clear in a photocopy of said element.

The patent US 5,443,579 discloses another method of printing a latent image on a substrate. According to this patent, the printing of raised lines is combined with lines without relief. Thus, a latent color image is created which can not be reproduced with a photocopier or other photomechanical processes.

The patent application WO 01/76874 A2 describes a printing machine with several stencils and dryers around a common cylinder. Licences US 5,853,197 and US 5, 487, 567 show security features that are not easily visible to the naked eye, but which, on the other hand, become clearly apparent when copying or scanning the item.

Another specific technique uses watermarks in which the substrate, for example paper, is marked with lines or a pattern that are visible only in transparency. Another development of this technique concerns pseudo-watermarks formed by the creation of a window in the substrate, a technique used in particular with paper substrates which themselves are not normally transparent, said window being transparent.

The patent US 6,082, 778 describes an identity card protected against unauthorized copying by photocopiers. In this patent, the idea is to create a security element by combining the protective effect provided by a thin metal film with the physical properties, in particular optical properties, of an additional layer whose combination of effects prevents reproduction. from the menu. Under a transparent cover layer, there is a layer of metal over a layer having specific optical properties. In a first embodiment, the metal layer is demetallized locally exposing the layer with specific optical properties, that is to say making it visible in the demetallized zone. The difference in contrast between the layers makes the marks formed by demetallization easy to recognize with the naked eye. In a particular embodiment, the layer having specific optical properties has a dark color, for example black. The combination of the direct reflection of the metallized zone and a layer having a strong absorption (black layer) prevents the detection of the contrast difference so that the information formed by the demetallization disappears completely on a copy of this element of security.

In another embodiment, the layer having specific optical properties contains fluorescent or phosphorescent substances which, irradiated by the light of a photocopier, do not emit light of a wavelength in the visible spectrum, so that the zone is not reproduced either.

According to other techniques known in the state of the art, a laser is used either to mark the substrate directly, or to mark a layer applied to said substrate and thus create security elements impossible to reproduce by photocopying or scanning.

Other security elements use optically variable elements ("OVD" ®) in the form of metallized patches (called "foils") or holograms, and also moirés and other similar patterns, all of them on the one hand, very difficult or impossible to copy with current devices but, on the other hand, very easy to control visually by appropriate means or the naked eye.

It is also known to use specific inks such as optically variable inks to print particular patterns or geometric shapes on the paper-money substrate. These inks, known per se in the state of the art, contain pigments with variable optical effect and change color depending on the angle at which they are viewed. For example, publications US 2002/0160194 A1 , US 2002/0182383 A1 and EP 1 239 307 show such inks for this that they describe the principle and the composition of such inks.

When using such inks, it has been found that variable optical effect pigments containing an additional magnetic layer 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 .

However, one of the problems with optically variable ink printing is that it is often used to print the value of the paper (eg bank note), this value being indicated generally parallel to the length of the note. In addition, there is always a desire to create a visible optical effect when the value paper is rotated about an axis parallel to the length of said value paper (up-down motion) rather than an axis parallel to the width. (left-right movement), the first movement being more natural for a user.

In the usual way, the sheets comprising printed-image impressions arranged in matrix form move in the width direction of said prints so that the integration of immobile magnets in a conventional printing machine imposes a parallel movement on the printing machine. print width for creating a visible effect (left-right movement mentioned above). Creating an effect in the desired direction (up-down movement mentioned above) imposes a change of direction of leaf movement if one wishes to obtain the particular effect in the desired direction (up-down movement mentioned above). Thus, existing machines must be modified significantly which has little economic interest and increases the time required for printing.

Thus, an object of the invention is to improve known methods and devices.

The invention also aims to provide a printing machine and a method implemented by this machine that increases the security of printing.

More particularly, the object of the invention is to propose a printing system, particularly for securities, which can be incorporated into existing machines in a simple manner.

Another object of the invention is to provide a particular printing process for securities.

An additional object of the invention is to provide an improved security element.

The invention is defined by the features of the claims.

• la figure 1 montre une représentation schématique d'une machine d'impression sérigraphique,
• la figure 2 montre un mode d'exécution d'un cylindre d'impression selon l'invention,
• les figures 3A et 3B montrent deux variantes du mode d'exécution de la figure 2,
• la figure 4 montre un schéma de principe de l'effet obtenu par l'invention,
• les figures 4A et 4B montrent de façon schématique une première configuration d'orientation de pigments magnétiques à effet optique variable,
• les figures 5A et 5B montrent de façon schématique une deuxième configuration d'orientation de pigments magnétiques à effet optique variable,
• les figures 6A et 6B montrent de façon schématique une troisième configuration d'orientation de pigments magnétiques à effet optique variable,

It will be better understood by the description of several embodiments thereof and with reference to the appended figures in which

• the figure 1 shows a schematic representation of a screen printing machine,
• the figure 2 shows an embodiment of a printing cylinder according to the invention,
• the Figures 3A and 3B show two variants of the execution mode of the figure 2 ,
• the figure 4 shows a schematic diagram of the effect obtained by the invention,
• the Figures 4A and 4B show schematically a first orientation configuration of magnetic pigments with variable optical effect,
• the Figures 5A and 5B show schematically a second orientation configuration of magnetic pigments with variable optical effect,
• the Figures 6A and 6B show schematically a third orientation configuration of magnetic pigments with variable optical effect,

A conventional sheet-fed printing machine is first described with reference to the figure 1 . This known machine has been described in detail in the patent US 6, 109, 172 as regards the principle of operation of a screen printing machine. The machine comprises a magazine 1 containing sheets to be printed, a feeder 2 for the successive transfer of the sheets along the path 3 to a margin cylinder 4, a transfer cylinder 5 for feeding the successive sheets onto a printing cylinder 6, two screen rolls 7 and 8 with rakes and cooperating with the printing cylinder 6 and a chain clamp system 9 which carries a Once the print has been made, the sheets to the 10 outlets.

The machine having two screen rolls 7 and 8 with rakes 55, 56, it is capable of producing two-color screen printing on the successive sheets. On the printing cylinder 6, the sheets first pass the first screen cylinder 7 where a screen printing in a first color is performed, then they pass the second screen cylinder 8 where they receive a silk screen printing in a second color. This second printing can be done in a different area from that printed by the first screen cylinder 7 or in the same area. In the latter case, it is necessary to add a drying system of the ink deposited by the first screen cylinder 7, for example UV lamps or other equivalent system.

The figure 2 shows a printing cylinder 6 in section according to the present invention in the configuration of the figure 1 , that is surrounded by a feed cylinder, two screen rolls 7 and 8, a discharge system 9, for example a clip chain, and a drying system 10, such as UV lamps.

According to the invention, the impression cylinder 6 comprises a plurality of magnets 12, 13 and 14 placed in a distribution corresponding to the impressions on the sheets substrate, each set of magnets being separated by notches 15, 16, 17 in the impression cylinder 6, in which sheet-retaining clips on the cylinder 6 are arranged. These magnets can be fixed by any appropriate means on the cylinder, in particular by gluing, screwing or other equivalent means.

According to a first variant of the invention, the magnetic elements 59 (for example magnets) are not placed directly in the impression cylinder 6 but in 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 both in the impression cylinder 6 and / or in the discharge cylinder 57 and / or in the intermediate cylinder 58.

The advantage of both variants is that they maintain a conventional printing cylinder without the risk of creating bumps or dips in the print due to an uneven surface of the impression cylinder 6.

In the Figures 3A and 3B schematically, two partial views of a printing cylinder with two variants of magnets are shown schematically. In the first variant ( figure 3A ), the printing cylinder 6 has at least one notch 18 in which is the gripper system 19 holding the substrate 1 which is printed.

The cylinder further comprises a second notch 20 in which are placed magnets 21, 22 in a distribution corresponding to that of the impressions on 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 the figure 3B identical elements are referenced in the same way as in the figure 3A , and the difference is constituted by the means used as magnets. In this variant, windings 25, 26 are used.

The principles set out with reference to Figures 3A and 3B for the impression cylinder 6, of course, apply in the same way in the variants of the invention indicated above, when it is the discharge cylinder 57 and / or the intermediate cylinder 58 which support the magnetic elements.

The principle used in the present invention is schematically shown in FIG. figure 4 . In this figure there is shown a substrate 27, for example a sheet of paper, on which an optically variable ink printing has been deposited. The impression cylinder 6 comprises as shown a permanent magnet 28 which creates the magnetic field lines 29, 30 shown in this figure. In addition, the optically variable ink containing magnetic pigments with variable optical effect, the magnetic field lines 29, 30 will orient these pigments according to the directions indicated in this document. figure 4 . In a central zone 31, the pigments will be aligned vertically while in the lateral zones 32 and 33, the pigments will assume a more horizontal configuration, as shown. Thus, depending on the angle at which the print will be viewed, the apparent color of the print will change and a change of orientation will have a dynamic print result with color changes followed in the print. .

One of the advantages of the system according to the invention is that since the sheet is static with respect to the magnets, it avoids the problem mentioned above related to the usual direction of movement of the sheets relative to the direction in which one wants to create the optical effect. We can now create this effect without changing directions of movement of successive sheets, even on the same sheet, create security elements with optical effects in different directions (perpendicular or otherwise) without influence on the direction of movement of successive sheets or need to perform successive impressions with optically variable ink.

The Figures 4A and 4B show a first optical effect that can be obtained with the machine according to the invention. In the Figure 4A an ink imprint 40 containing magnetic pigments having a variable optical effect forms the number "100". In order to correctly represent the effect obtained, this impression 40 has its upper half lighter and its lower half darker.

Printing 41 of the Figure 4A is the same impression as the print 40 but has been rotated about the X axis so as to vary the angle of consideration of the print. In this position, it is now the lower half is lighter and the upper half is darker.

To obtain this effect, the pigments are oriented by means of a magnet as in the section AA shown in FIG. Figure 4B that is, approximately 45 ° in the left-hand portion 42 and approximately 135 ° in the right-hand portion 43.

Thus, by rotations in two directions around the X axis, a determined variation of the colors of the two halves of the printing is obtained which results in a dynamic optical effect, impossible to copy with conventional 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 number "100" and has a lighter area on its upper part. By rotating the printing around the X axis, the bright area then moves into the print, as shown in prints 45 and 46 to pass through the middle part of the print (print 45) and into the part bottom of it (print 46).

This optical effect is obtained by the orientation of the pigments as represented in FIG. Figure 5B which corresponds to the BB cup of the Figure 5A . As shown (from left to right), the pigments initially have an almost vertical orientation (zone 47), then gradually arrive at a horizontal orientation (zone 48) and finally resume a substantially vertical orientation (zone 49).

Thus, by rotations in two directions about the X axis, we obtain the visual effect of a displacement of a light area inside the printing which results in a dynamic optical effect, impossible to copy by photocopy or caning.

A third optical effect is represented in the 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 in any direction, then there is a reversal of the bright and dull areas (print 51). In addition, if one changes the orientation laterally (impression 52), one obtains in addition a variation of color.

These optical effects are obtained by the impressions represented in the section CC of the 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 deposited successively on the substrate and the first layer 53 must be dried before the second layer is deposited, in order to maintain the orientation of the pigments in said first layer.

The invention is not limited to the embodiments described but variations are possible within the scope of the claimed protection. For example, the sieve can be carried by a cylinder (as in the machine of figures 1 and 2 ) or can also be plane.

Different types of ink are also possible, as long as they contain magnetically steerable pigments.

Claims (10)

1. Printing machine for printing a substrate (1) in the form of a sheet or continuous web, said substrate being intended to receive at least one impression, said printing machine comprising at least :

   - a transfer system (5) for conveying the substrate (1) onto an impression cylinder (6),

   - first and second screens (7, 8) of cylindrical or flat shape equipped with a doctor blade (55, 56), the first and second screens (7, 8) cooperating with the impression cylinder (6) and being intended to perform a screen-printing operation on the substrate with an ink, and

   - an unloading system (9) for carrying the substrate (1) away after the printing operation,

   said second screen (8) applying a second impression in a same zone as a first impression applied by means of said first screen (7) and said printing machine comprising a drying system for drying the ink deposited by the first screen (7) before deposition of the ink by the second screen (8),
   characterized in that the ink contains pigments that can be orientated by a magnetic field,
   and in that said impression cylinder comprises at least one magnetic element (12, 13, 14) on the printing surface thereof so as to orientate said pigments that can be orientated contained in the ink before drying thereof.
2. Printing machine according to claim 1, characterized in that said drying system comprises UV lamps.
3. Printing machine for printing a substrate (1) in the form of a sheet or continuous web, said substrate being intended to receive at least one impression, said printing machine comprising at least :

   - a transfer system (5) for conveying the substrate (1) onto an impression cylinder (6),

   - first and second screens (7, 8) of cylindrical or flat shape equipped with a doctor blade (55, 56), the first and second screens (7, 8) cooperating with the impression cylinder (6) and being intended to perform a screen-printing operation on the substrate with an ink, and

   - an unloading system (9) for carrying the substrate (1) away after the printing operation,

   said second screen (8) applying a second impression in a same zone as a first impression applied by means of said first screen (7) and said printing machine comprising a drying system for drying the ink deposited by the first screen (7) before deposition of the ink by the second screen (8),
   characterized in that the ink contains pigments that can be orientated by a magnetic field,
   and in that said unloading system comprises a cylinder (57, 58) having at least one magnetic element (59, 60) on the surface thereof for orienting said pigments that can be orientated contained in the ink before drying thereof.
4. Printing machine according to claim 3, characterized in that said drying system comprises UV lamps.
5. Printing machine according to any of the preceding claims, wherein the machine is further adapted to apply a plurality of impressions arranged in the form of a matrix on said substrate (1).
6. Method of screen-printing a substrate in the form of a sheet or of a web in which first and second impressions are formed on said substrate using an ink with varying optical effect, with the following steps:

   a. said first impression is formed on the substrate ;

   b. said first impression is dried ; characterized in that

   c. said second impression is formed on the first impression;

   d. said second impression is dried,

   in that the ink with varying optical effect contains pigments that can be orientated by a magnetic field,
   and in that said first impression and said second impression are subjected to a magnetic field before drying thereof in order to orient said pigments.
7. Method of printing according to claim 6, characterized in that the drying of said first impression is carried out by UV.
8. Method of printing according to claim 6 or 7, characterized in that the pigments contained in the ink of the first impression are oriented in a direction different from the pigments contained in the ink of the second impression.
9. Method of printing according to any one of claims 6 to 8, characterized in that the magnetic field required to orient said pigments is produced using a cylinder having at least one magnetic element on the surface thereof.
10. Method of printing according to any one of claims 6 to 9, wherein the first and second impressions comprise a plurality of individual impressions arranged in matrix form.

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