ES2436544T3 - Printing cylinder for gravure and gravure procedure - Google Patents

Abstract

There is described an impression cylinder (01) for intaglio printing of security documents, especially banknotes, comprising a cylinder body (10) carrying at least one blanket (20) on its circumference, and a packing (30) disposed between the cylinder body (10) and the blanket (20). The packing (30) exhibits at least one depression (40) whose location is selected to correspond to the location of at least a selected portion of a corresponding security element (50) having optical and/or structural properties to be preserved, which security element (50) is provided or exposed on a backside (60b) of a substrate (60) to be supported against the blanket (20) during intaglio printing, the said at least one depression (40) being designed to lead to a local reduction of the printing pressure at the location of the said at least selected portion of the corresponding security element (50).

Description

Printing cylinder for gravure and gravure procedure

Preamble-Technical Field

The present invention relates in general to a gravure printing cylinder, use thereof for hollow engraving and a corresponding gravure process.

Background of the invention

The term "intaglio", as used herein, refers to direct printing of plates using recorded print media (eg, engraved plates or cylinders) as commonly applied for the production of banknotes and security documents. The term "steel / copper etching" is also sometimes used to refer to this particular procedure. Banknotes, for example, are normally provided with hollow engraved patterns (such as portraits and other pictorial representations, latent images, image patterns, denominations, bank designation, etc.) that are easily recognizable by contact due to the contact stamping and tactile effect inherent to gravure. Gravure presses are known for hollow engraving, for example, of European patent applications numbers EP 0 091 709 A1, EP 0 406 157 A1, EP 0 563 007 A1, EP 0 873 866 A1, EP 1 602 482 A1 and International Application No. WO 03/047862 A1, all on behalf of the present applicant.

The gravure is characterized by high printing pressures applied between the gravure cylinder that performs the inked gravure means (usually a plate cylinder carrying one or more printing plates) and the printing cylinder, which carries or supports the substrate that It has to be printed (usually individual sheets). These high printing pressures lead to a characteristic printing of the substrate, which results in stamped structures corresponding to the recordings of the gravure media, whose stamped structures can be noticed by touch.

The gravure printing cylinder normally carries a blanket that is designed to have a rough or rough surface structure. Such a rough surface structure is necessary in the printing cylinder, since it ensures proper adhesion and support of the substrate to be printed on the circumference of the printing cylinder and therefore optimum print quality. Blankets that have a rough surface structure from suppliers such as I. T. G. GmbH Graphic Products (http://www.itg-graph.com/) are commercially available.

Blankets that have a smooth surface structure are also available, but are not typically used as blankets for gravure printing press cylinders, but rather as blankets for inking cylinders such as for the so-called Orlof cylinder (or collecting cylinder for ink) used in direct inking gravure presses of the type described in European patent applications Nos. EP 0 091 709 A1, EP 0406 157 A1, EP 0 563 007 A1, EP 0 873 866 A1, EP 1 602 482 A1 and International application No. WO 03/047862, already listed above. Such direct inking gravure presses as sold by the Applicant are known under the Super Orlof Intaglio® trademark.

An inherent effect of rough blankets used in gravure printing cylinders is that the surface structure of the blanket is printed on the back side of the substrate being printed (i.e., the opposite side to which the ink receives from the cylinder gravure) due to high printing pressures. Unfortunately, this may deteriorate the optical and / or structural properties of security elements that may have been printed, applied, embedded or otherwise arranged or exposed on the back face of the substrate before hollowing out optically variable elements, such as called optically variable devices (or OVD's) as supplied, for example, by OVD Kinegram AG (http://www.kinegram.com/) or as optical safety elements and devices, since the rugged structure of the blanket is also printed on the surface of the security elements. This can be a problem in the case of double-sided gravure, in which the substrates are fed twice into the gravure press in order to print both sides of the substrates.

A solution to this problem may be to apply optically variable devices or similar safety features between the gravure phases and applying the aforementioned security elements to the remaining face of the substrates that still need gravure. In this way, the safety elements are brought into contact with the smooth and hard surface of the gravure medium (for example the engraving plate) during the subsequent gravure phase.

However, this does not solve the problem in all cases, especially in cases where the security elements are already embedded in the substrate before gravure or in cases where the security elements are arranged on both sides of the substrate before of the hollow gradation. Performing gravure before applying security elements, such as OVD’s, can also create problems during the subsequent application process, such as a hot foil stamping process,

Typically used to apply OVD’s, since this process can interfere with the quality of the hollow patterns already applied on the substrate and affect the quality.

Another solution is described in European Patent Application No. EP 1 881 904 A2. This publication describes a intaglio blanket (and a method for printing security documents by means of intaglio), whose blanket has a first region that has a rough surface characteristic and a second region that has a surface characteristic that is different of the surface characteristic of the first region, whose second region is configured as a receiver for at least one section of an optically variable element. According to a first embodiment of EP 1 881 904 A2, the second region of the blanket is designed to have a rough surface that is less than the surface roughness of the first region. According to a second embodiment of EP 1 881 904 A2, the second region of the template is designed so as to have a previously defined depression. According to a third embodiment of EP 1 881 904 A2, the second region of the blanket is designed to have a previously defined modulus of elasticity that is less than the previously defined modulus of elasticity of the first region.

Although the solution described in European Patent Application No. EP 1 881 904 A2 theoretically solves the aforementioned problem, it nevertheless creates another problem due to the fact that the blanket per se has to be designed in a concrete way to present the necessary First and second regions of different surface characteristics. This significantly increases the complexity and manufacturing costs of the blanket, which negatively affects production and maintenance costs, since the blanket is no longer of a consumable quality.

As regards the first and third embodiments of EP 1 881 904 A2, the manufacture of the required blanket is difficult for the final consumer, namely the printing plant, which does not necessarily have the precise tools to produce said blanket. As for the second embodiment of EP 1 881 904 A2, it is inappropriate practice to machine the depressions required in the blanket directly, since this blanket is normally made of flexible fibrous material that is also relatively thin (usually 0.5 mm thick ).

There is therefore a need for a practical and low cost solution.

Summary of the invention

Therefore, a general objective of the invention is to provide an improved gravure printing cylinder that solves the problem of deterioration of the optical and / or structural properties of security elements resulting from the contact of the surface of the security elements with the surface of the printing cylinder during hollow engraving.

A further object of the invention is to provide an improved gravure process that similarly solves the aforementioned problem.

Still another object of the invention is to provide such a gravure printing cylinder that is more practical and economical in manufacturing and production, and that facilitates maintenance operations.

Still another object of the invention is to provide such a gravure printing device that allows the use of conventional blankets.

These objectives are achieved thanks to the gravure press defined in the claims.

Therefore, a printing cylinder is provided for hollow recording security documents, especially banknotes, comprising a cylinder body that carries at least one blanket in its circumference, and a fitting arranged between the cylinder body and the mantilla. The lining has at least one depression whose situation is selected to correspond to the situation of at least a selected part of a corresponding security element that has optical and / or structural properties to be preserved, whose security element is arranged in a rear face of a substrate to be supported against the blanket during hollow etching, said depression being at least one depression designed to lead to a local reduction of the printing pressure at the location of said at least a selected part of the corresponding security element.

The use of such a printing cylinder is also claimed to perform the gravure of security documents, especially banknotes.

A gravure printing process is also provided for printing security documents, especially banknotes, in which a back side of a substrate to be printed is brought into contact, during gravure, with a circumference of a printing cylinder that It carries at least one blanket and in which the at least one security element, which has optical and structural properties to be preserved, is arranged on the back face of the substrate and in which the printing cylinder is a printing cylinder as defined above.

Other advantageous embodiments of the invention form the subject of the dependent claims and are explained in the following.

Brief description of the drawings

Features and advantages of the present invention will appear more clearly upon reading the following detailed description of embodiments of the invention that have been presented only by way of non-limiting examples and are illustrated by the accompanying drawings, in which:

Figure 1 is a schematic and partially side view of a gravure unit of a gravure press showing in particular the cooperation of a printing cylinder and a gravure cylinder;

Figure 2 is a schematic side view of a hole or cylinder socket of the printing cylinder of Figure 1, showing an illustrative example of means for retaining a blanket and associated fitting on the circumference of the printing cylinder;

Figure 3 is a schematic cross-sectional view illustrating the cooperation between the printing cylinder and the rotogravure cylinder of Figure 1 in the area or print contact line with the blanket, the fitting and the substrate supported by the printing cylinder which are interposed between the two cylinders; Y

Figures 4A and 4B are possible variants of the fitting that could be used instead of the fitting shown in Figure 3.

Detailed description of embodiments of the invention

Within the scope of the present invention, the term "gravure cylinder" is to be understood to mean a cylinder used for gravure (especially for printing security documents such as banknotes) with at least one gravure means in its circumference. This comprises either a cylinder with hollow embossed patterns on its circumference or a plate cylinder that carries at least one gravure plate on its circumference. In the following description, the gravure cylinder is a plate cylinder that carries several gravure plates in its circumference.

The term "printing cylinder" means the cylinder that cooperates with the gravure cylinder and otherwise carries or supports the substrate to be printed.

Figure 1 schematically shows a partial side view of a gravure unit of a gravure press comprising a printing cylinder 01 that is in contact with a gravure cylinder 02 designed in this example as a plate cylinder 02, forming the point of contact between the printing cylinder 01 and the plate cylinder 02 a so-called contact zone or line PN or pressure. The printing cylinder 01 is a three-segment cylinder that in this example has three different blankets 20 in its circumference. Both ends of each blanket 20 are secured by appropriate means (shown in Figure 2) located in three corresponding alveoli 15 of the cylinder and distributed at regular intervals around the circumference of the printing cylinder 01. The interval between successive blankets 20 corresponds to the interval between successive substrates (in this case individual sheets) to be printed (not shown in Figure 1), whose substrates are being transferred to the printing cylinder 01 in an upstream part with respect to the pressure zone PN by means of a mechanism suitable for sheet transfer, in this particular example a transfer cylinder 04 which acts as a sheet feed. As shown by an arrow in Figure 1, the printing cylinder 01 rotates clockwise and carries the successive substrates from the transfer cylinder 04 through the pressure space PN, where the substrates are printed, and up to a sheet delivery system 05 by means of which the freshly printed substrates are removed from the printing cylinder 01 to be supplied through drying units to appropriate delivery piles (not shown).

In the illustrated example, the plate cylinder 02 is also designed as a three-segment cylinder and therefore has three different gravure plates in its circumference, whose gravure plates are similarly secured at both ends thereof by appropriate means of clamping plates located in three corresponding cylinder sockets, also shown in figure 1, but not referenced. As shown by means of an arrow in Figure 1, the plate cylinder 02 rotates counterclockwise.

Gravure plates supported by plate cylinder 02 are usually inked by means of an appropriate inking system that is not shown in Figure 1. Different types of inking systems are possible, including indirect inking systems such as those taught. in European patent applications Nos. EP 0 091 709 A1, EP 0 406 157 A1, EP 0 563 007 A1, EP 0 873 866 A1, EP 1 602 482 A1 and International application No. WO 03/047862 A1, whose publications were introduced in the preamble of this report.

Figure 1 further shows a cleaning roller assembly 03 in contact with the surface of the cylinder 02 of

plates. This cleaning roller assembly 03, which will not be described in detail herein, is used to clean the surface of the gravure plates that have been properly inked by means of the inking system upstream of the cleaning roller assembly 03. The cleaning roller assembly 03 removes excess ink outside the prints to ensure proper print quality before the gravure plates are brought into contact with the surface of the substrates to be printed. An illustrative example of a cleaning roller assembly 03 is described in International Application No. WO 2007/116353 A1 on behalf of the applicant applicant.

Figure 2 schematically shows an enlarged view of one of the cylinder sockets 15 of the printing cylinder 01 of Figure 1. As illustrated in Figure 2, a fixing system 25 is provided to ensure adequate support of the blankets 20 on the circumference of the printing cylinder 01. A fitting 30 is interposed between each blanket 20 and the cylinder body 10 of the printing cylinder 01, a leading end 20a of the blanket 20 and a leading end 30a of the fitting 30 being fixed and secured. by means of a clamping bar 26. A rotating shaft 27 is also provided to hold the rear end 20b of the blanket 20, the axis of which in this example comprises a groove in which the rear end 20b of the blanket 20 is inserted. rotation of the shaft 27 counterclockwise ensures proper tension of the blanket 20 on the printing cylinder 01. In this example, the rear end 30 b of the fitting 30 is not supported by the shaft 27, the length of the fitting 30 being selected such that it ends at the part where the socket 15 of the cylinder begins.

Figure 3 schematically shows a cross-sectional view (i.e., a view taken along a plane that intersects the printing pressure space along the contact line between cylinders 01. 02) illustrating the cooperation between the printing cylinder 01 and the rotogravure cylinder 02 of Figure 1 in the printing pressure line NP. The already described cylinder body 10 bearing the lining 30 and the blanket 20 and the gravure cylinder 02 itself is recognized (the gravure plates supported by the gravure cylinder 02 and associated engravings are not illustrated for reasons of simplicity).

Also shown in Figure 3 is a substrate 60 with a front face 60a that is in contact with the surface of the gravure cylinder 02 (i.e., the surface of the gravure plates) and a rear face 60b that is in contact with the surface of the blanket 20. As illustrated, a security element 50 is printed, which has optical and / or structural properties to be preserved, applied, embedded or otherwise arranged or exposed on the rear face 60b of the substrate 60 Such security element 50 may in particular be an optically variable device (or "OVD") or the like, which includes, for example, security elements embedded in the thickness of the substrate 60 and exposed ++ on at least the rear face 60b thereof. , such as security threads in windows.

In order to preserve the optical and / or structural properties of the security element 50 (or at least a selected part thereof), the fitting 30 is provided with at least one depression 40 on its surface, whose location or position is selected from so that it corresponds to the situation of at least a selected part of the corresponding security element 50.

Although only one security element 50 is illustrated in Figure 3, it should be appreciated that a plurality of such security elements 50 may be arranged on the rear side 60b of the substrate, typically in a matrix-like arrangement and which would be therefore a corresponding number of depressions 40 on the surface of the lining 30 in corresponding places.

In Figure 3, the lining 30 is shown as consisting of only a single lining sheet 31. However, it will be appreciated that the lining 30 may comprise more than one lining sheet (see, for example, the variants of Figures 4A and 4B).

The depression 40 has a selected depth (d) designed to lead to a local deformation of the blanket 20 and therefore a local reduction of the printing pressure applied by the printing cylinder 01 in place of the selected part of the corresponding element of security 50. In this way, the optical and / or structural properties of the selected part of the security element 50 can be preserved.

Tests performed by the Applicant have shown that a selected depth (d) of 100 microns or less, preferably 60 to 80 microns, is appropriate. This means that standard printing pressures are applied between the printing cylinder and the rotogravure cylinder. Greater depth may be necessary

(d) if it happens that the printing pressures were greater than normal values.

To ensure proper and optimum print quality and accuracy, a combined thickness (h) of the blanket 20 and the lining 30 must be kept constant outside the place of depression or depressions 40. This combined thickness (h) is preferably 2 mm. In that context, the thickness of the blanket 20 is preferably 0.5 mm, which means that the thickness of the lining 30 must be 1.5 mm.

As shown in the example of Figure 3, the depression 40 is disposed within the thickness portion of the lining sheet 31 which is thicker than the required depth (d) of the depression 40. This is

It also applies to the variant shown in Figure 4B, in which the lining 30 consists of two lining sheets 34, 35, the upper lining sheet 34 similarly having a thickness greater than the required depth (d) of the depression 40.

Depression 40 can be formed by any appropriate technique. A suitable and preferred technique may be to engrave the relevant garrison sheet by mechanical engraving using an engraving tool or by laser engraving provided that the relevant garrison sheet is made of, or comprises, an appropriate layer that can be laser engraved .

Alternatively, as illustrated in Figure 4A, depression 40 may be formed by practicing a through opening in a first lining sheet 32 having the same thickness as the required thickness (d) of depression 40, at least one second sheet being arranged trim 33 below the first trim sheet 32 in order to achieve the required trim height. More than one lining sheet may be provided under the first lining sheet 32, if necessary.

The variant of Figure 4B, which has already been briefly explained, is similar to that of the first embodiment of Figure 3 in that the depression 40 is formed within part of the thickness of the lining sheet 34 which has a thickness greater than the required depth (d) of depression 40. In this example, however, at least one additional lining sheet 35 is disposed below the first lining sheet 34.

As mentioned, the trim 30 may comprise at least two trim sheets as illustrated in Figures 4A and 4B, or even more than two if necessary or appropriate. In such a case, it is preferable that only the uppermost garrison sheet is provided with the necessary depression or depressions 40 and this only requires an appropriate design or mechanization of a single garrison sheet.

A fundamental advantage of the proposed solution with respect to the known solution is that a conventional blanket having a unique rough surface characteristic can be used. In addition, no special treatment or processing of the sheet as such is necessary, which means that commercial and normal available blankets can be used.

In addition, manufacturing and maintenance costs can be maintained at a very low level, since the lining material barely affects the total cost and can be chosen from lining materials that can be easily acquired, treated and replaced,

It will be clearly appreciated that the printing cylinder described above can be used to gravure security documents, especially banknotes.

It will also be appreciated that the above description is also directed to a gravure method for printing security documents, especially banknotes, in which a back side of a substrate to be printed is brought into contact during gravure with the circumference of a printing cylinder that carries at least one blanket, in which at least one security element having optical and / or structural properties to be preserved, and in which it is arranged or exposed on the rear face of the substrate The printing cylinder is a printing cylinder as described above.

In the above-described embodiments, several modifications and / or improvements can be made without departing from the scope of the invention as defined in the appended claims. For example, the invention is equally applicable to the printing of substrates formed of individual sheets or of successive parts of a continuous web.

List of references used in the figures and in the report

printing cylinder 02

gravure cylinder / plate cylinder 03

cleaning roller assembly 04

transfer cylinder (sheet feed) 05

sheet delivery system 10 print cylinder cylinder body 01 15 print cylinder cylinder socket 01 20 blanket 20a front end of the blanket 20 20b rear end of the blanket 20 25 support system to support the blanket 20 on the cylinder body 10 26 clamp bar to hold the front end 20a of the sheet 20 together with the end

front 30a of the lining 30 27 rotary axis to hold the rear end 20b of the blanket 20 and tension the blanket 20 30 fitting 30a front end of the fitting 30 30b rear end of the fitting 30 31 fitting sheet (figure 3) 32 blade of first (upper) fitting (figure 4a) 33 second (lower) fitting sheet (figure 4a) 34 first (upper) fitting sheet (figure 4b) 35 second (lower) fitting sheet (figure 4b) 40 depression in fitting 30 50 security element that has optical and / or structural properties to be preserved

(for example, optically variable element, hologram, etc.) 60 substrate (for example, sheet or band) 60a front face of the substrate 60 which is brought into contact with the gravure cylinder 02 60b rear face of the substrate 60 carrying the element optically variable that is brought into contact

with the blanket 20 of the printing cylinder 01 d depth of the depression 40 h combined thickness of the blanket 20 and the lining 30 outside the place of the depression 40

Claims (13)

1. A printing cylinder (01) for hollow recording security documents, especially banknotes, comprising a cylinder body (10) carrying at least one blanket (20) in its circumference, and a fitting (30) arranged between the cylinder body (10) and the blanket (20), characterized in that said lining (30) has at least one depression (40) whose position is selected to correspond to the position of at least a selected part of a corresponding security element (50) having optical and / or structural properties that must be preserved, whose security element (50) is arranged or exposed on a rear face (60b) of a substrate (60) to be supported against said blanket (20) during hollow etching, said at least one depression (40) being designed to lead to a local reduction of the printing pressure in the place of said minus a selected part of the corresponding security element (50).

2.

The printing cylinder (01) as defined in claim 1, wherein said at least one depression (40) has a depth (d) of 100 microns or less, preferably 60 to 80 microns.

3.

The printing cylinder (01) as defined in claim 1 or 2, wherein said at least one depression (40) is disposed within part of the thickness of a gasket sheet (31; 34) having greater thickness than a required depth (d) of said at least one depression (40).

Four.

The printing cylinder (01) as defined in claim 1 or 2, wherein said at least one depression (40) is arranged as a through opening in a first lining sheet (32) having the same thickness that a required depth (d) of said at least one depression (40) and in which at least a second lining sheet (33) is disposed below the first lining sheet (32).

5.

The printing cylinder (01) as defined in any of the preceding claims, wherein said fitting (30) comprises at least two trim sheets (32, 33; 34, 35).

6.

The printing cylinder (01) as defined in claim 5, wherein only the uppermost trim sheet (32; 34) is provided with said at least one depression (40).

7.

The printing cylinder (01) as defined in any of the preceding claims; wherein a combined thickness (h) of the blanket (20) and the lining (30) outside the position of said at least one depression (40) is 2 mm.

8.

The printing cylinder (01) as defined in claim 7, wherein a blanket thickness

(20) is 0.5 mm.

9.

The printing cylinder (01) as defined in any of the preceding claims, wherein said at least one depression (40) is performed by engraving or cutting.

10.

The printing cylinder (01) as defined in claim 9, wherein said lining (30) comprises or is made of a layer that can be etched, preferably a layer that can be etched by laser, which is etched to form said depression at least (40).

eleven.

The printing cylinder (01) as defined in any of the preceding claims, wherein said blanket (20) has a unique rough surface feature.

12.

Use of the printing cylinder (01) as defined in any of the preceding claims for hollow engraving of security documents, especially banknotes.

13.

A gravure procedure for printing security documents, especially banknotes, in which the back side (60b) of a substrate (60) to be printed is brought into contact during gravure with the circumference of a printing cylinder (01) which carries at least one blanket (20) and in which at least one safety element (50), which has optical and / or structural properties to be preserved, is arranged or exposed on the rear face (60b ) of said substrate (60) and wherein said printing cylinder (01) is a printing cylinder as defined in any of claims 1 to 11.