EP2167317A1

EP2167317A1 - Printing device

Info

Publication number: EP2167317A1
Application number: EP08757299A
Authority: EP
Inventors: René Hauser; Wolfgang Bock
Original assignee: 3D AG
Current assignee: 3D AG
Priority date: 2007-07-09
Filing date: 2008-07-09
Publication date: 2010-03-31
Anticipated expiration: 2028-07-09
Also published as: AU2008274799A1; EP2167317B1; WO2009006749A1

Abstract

In a printing device with a printing forme for transferring a visually detectable information item onto a medium which is to be printed by means of a printing fluid, such as a printing ink, in which printing device a printing surface of the printing forme has a first structure which is intended to transfer the printing fluid in a predefined way to a printing substrate, and the first structure of which is provided here for transferring a first visually detectable information item onto the printing substrate, a possibility is to be provided, by which a substrate can be provided with a security element or a decorative element which is based on very small surface structures with the greatest possible flexibility in the colour selection, even independently of the embossability of said substrate. For this purpose, a second surface structure of the printing surface which is arranged in the region of the first structure is proposed, wherein the structuring of the second surface structure is smaller than the structuring of the first surface structure, and the second surface structure contains a detectable information item or a detectable information item can be produced with the second surface structure.

Description

print Setup

The invention relates to a printing device with a printing for transferring optically perceptible information on a medium to be printed by means of a

Printing Fluids, such as a printing ink, wherein a pressure surface of the

Printing form has a first structure, the predetermined transmission of the

Printing fluid is determined on a printing substrate, and the first structure of this

Transmission of a first optically perceptible information on the printing substrate is provided.

From the field of reproduction technology a variety of printing methods are known. All of these printing methods share the goal of duplicating visually perceptible information. In this case, in particular, optically directly perceptible information is to be generated, that is to say such information which can be recognized and evaluated by a viewer with the naked eye, ie without the aid of a device such as a microscope or an imaging sensor. In particular, information may be data in written form or graphic illustrations. In such printing method, a printing plate is always used, are transmitted with the predetermined information on the medium to be printed, such as paper or cardboard. As a rule, the printing form contains the information in identical or laterally reversed form. The information is transmitted from the printing form by means of the printing ink on the medium to be printed and displayed. These printing methods, which are known per se, are known, for example, as gravure printing, letterpress, planographic printing, throughprinting (screen printing), photoprinting, etc. Furthermore, the printing methods are distinguished according to whether the information is transmitted directly from the printing form to the medium to be printed or indirectly via an intermediate carrier to the medium to be printed. Examples of indirect printing methods in which the printing medium is first delivered from the printing form to the intermediate carrier and then from the intermediate carrier to the medium to be printed, are the flexographic printing or the gravure printing. All of these printing methods mentioned in a non-exhaustive list are suitable for the present invention. In many fields of technology, diffractive structures are used, ie structures which generate diffraction effects when light incidence of at least certain light frequencies occurs. Such structures are intended for a wide variety of purposes, in particular as decorative elements or as security elements. As decorative elements they are to achieve pleasing optical effects, for example as packaging films or as product labels with which the attention of customers can be directed to the corresponding products provided with such a decorative element. On the other hand, as security elements that are visible or invisible to the naked eye, they are intended to guarantee the authenticity of products, funds, substitutes, credit cards, and the like, because of their forgery potential, which is only possible with very high technical effort. In order to check the authenticity of the objects secured with such security elements, it is determined whether the respective security elements have certain properties or contain certain optically perceptible information.

To generate diffraction effects, for example, grating structures with lattice spacings in the range of about 200 nm to 1500 nm are required. Such diffractive active structures are generally produced in industrial mass production by first producing so-called master shims with the assistance of photolithographic or laser interferometric methods. From the master shims production shims are then prepared by means of galvanic processes, with which the lattice structures in suitable substrates, such as hot stamping foils, are impressed. The hot stamping foils can be designed, for example, as labels so that the diffraction-optically effective pattern can be applied to any desired backing.

Apart from diffractive structures, other superficial structures are also known, which are provided as a security feature, for example microfills or guilloches. In contrast to structures with a diffractive effect, the surface structures required to produce microfills and guilloches are at least 10 times larger than the longest wavelength in the visible light spectrum. This facilitates the production of such structures. In the prior art, the required high cost can be considered disadvantageous if a substrate is to be both printed with information and provided with a security feature. In addition, such processes can not satisfy the limited variability and flexibility in color design. In order to have a certain design appear in certain (primary color) colors, it is necessary to stock films with these colors. In addition, the applicability of the prior art methods is essentially limited to those substrates in the surface of which a lattice structure can be imprinted.

The invention is therefore based on the object to provide a way by which even the latter regardless of the embossability of a substrate with the greatest possible flexibility in the color selection can be provided with a security element or a decorative element based on the smallest surface structures, in particular diffractive acting structures.

This object is achieved according to the invention by a printing device of the type mentioned above, the printing surface - in addition to a first surface structure for the transmission of a first optically perceptible information - has a second surface structure, at least partially disposed in the region of the pressure surface in which the first surface structure wherein the structuring of the second surface structure is smaller or more finely structured than the structuring of the first surface structure and the second surface structure contains perceptible / detectable information or perceptible / detectable information can be generated with the second surface structure. The object is also achieved by a method according to claim 15 and by a printed substrate according to claim 12.

The invention thus provides for a multi-scale structuring of the printing surface which, in addition to larger structures, also includes these superposed smallest structures with predetermined geometrical properties. The second, smaller and thus finer surface structure may be suitable for use in conjunction with security elements and be produced on a substrate by printing with advantage. The second structure should be arranged at least partially in those areas of the printing surface, in which also the first structure located. According to the invention, these second structures may be contained in the surfaces of the printing medium, ie in the visible side of the finished printed substrate. Since it is generally the aim in conventional printing processes to obtain surfaces which are as smooth as possible, the invention provides for a measure which is diametrically opposed to the prior art. This does not change the fact that there are processes that include printing, but try to create a surface structure by embossing. This prior art surface structure, which differs from the surface structure according to the invention, is achieved in that the substrate to be printed is itself plastically deformed.

In the context of the invention, the first surface structure preferably generates optical information at least substantially without diffraction effects, the content of which is preferably detectable with the naked eye directly or only by automatic text recognition (OCR) or image processing. The information reproduced by the second surface structure, in particular its shape and color (s), can be detected or interpreted either by the naked eye or by machine.

Said diffractive second surface structure is advantageously produced on the substrate by means of a printing process, ie an application in which a printing medium, in particular a printing ink, is applied to a printable substrate. It is here - as in other embodiments of the invention - preferred that simultaneously with the application of the second surface structure having the said microstructures, there on the same surface portion of the substrate to be printed there also the optically perceptible first information is applied differs from the second information, but is preferably at least partially superimposed. The visually perceivable information of the first surface structure may be, for example, a relief, areas or lines that reproduce the perceptible information without optical diffraction. On the other hand, the optically perceivable information of the second surface structure preferably uses the effect of diffracting optically, in particular, different diffraction orders of light to reproduce the optical information contained therein. The latter can, for example various color effects and / or a tilt angle dependent reproduction of characters, graphics and the like included.

A particularly advantageous embodiment of the invention provides that the first and the second surface structure contained in a single printing form and are superimposed or combined. In contrast to other solutions, this ensures that the two pieces of information from the first and second surface structure are always precisely matched. This is true even if the substrate should warp during the printing process. Furthermore, with this embodiment according to the invention with only one printing plate, the entire printing can be carried out, which, despite the technically demanding, preferably diffractive, surface structure and in particular despite the accurate arrangement of the two information, keeps the expenditure in connection with the printing process within limits.

In another preferred embodiment, the second structure is provided for generating a perceptible with the naked eye and / or machine-readable information. By this example, embossed, very fine barcodes can be understood, which are perceived both with the naked eye as a diffraction effect, as well as contain a machine-readable information. Again, the information of the first structure should remain perceptible to the naked eye without significant interference. If, for example, the first information is a text printed with the first structure, then it should remain readable, although in its surface, for example, barcodes can be imprinted, which can be perceived as well as machine-readable both with the naked eye, for example as a color-changing pattern. For the latter purpose, a reading device known per se can preferably be guided over the printed substrate, wherein the reading device reads out the information of the second surface structure printed on the substrate preferably using printing inks.

In a preferred embodiment, an electrically conductive and ultraviolet radiation curable printing fluid from Conductive Ink Technology, Cambridge, is used. This will eg a line of eg 1 mm width and 50, for example mm length printed, which is visible to the naked eye and forms a first inventive pattern. This pattern has on its surface as a second pattern a one-dimensional barcode whose strip is formed by rectangular pits of different widths, the width of these pits being for example either 300 nm or 600 nm, and wherein the pits are, for example, 1 mm long and perpendicular to long axis projecting first pattern, and wherein the center of two successive wells has a constant distance of, for example 1200 nm. Such a barcode can be read out with a capacitive read head, as presented by JVC for reading out capacitive picture plates, the capacitor used here having a gap of, for example, 200 nm width, which detects the depressions.

It is also conceivable that the above first pattern is illuminated with a collimated laser beam, which diffracted by the second pattern described above in different angles - depending on the decency of the above barcode strip. It is conceivable that the first pattern was realized with a magnetic pressure fluid, so that the protruding strips are readable by a miniaturized read head.

Regardless of the mode of action (optical, electrical, magnetic etc.) of the second structure or its physical action principle for generating information, this can either (without) aids or (only) with technical aids, such as readers, receivers, devices for resistance measurement, etc., be noticeable. An example of structures whose information can only be perceived by auxiliary means are machine-readable barcode-like codings, e.g. the "Glyphs" proposed by Xerox Corporation for the Encoding of Paper Documents Insofar as such tools are required or even helpful, the corresponding printing device, the printed substrate, and the tools as a whole or parts thereof may be designed as a coordinated information system according to the invention.

The printing device provided for producing substrates printed according to the invention with optically perceptible information of the aforementioned second type can have a diffractive structure at least in a partial region of its surface exhibit. The latter is preferably arranged in an area or at the same location, which is also provided for receiving (loading) pressure medium. This at least one area, either alone or in combination with other areas of the printing device, should also serve to transfer non-diffractive optical information to the substrate. The non-diffractive optical information may result from the printing medium, in particular from its color (s) and geometric shape (s). The additional optical information due to the diffractive effect, however, results from the permanently applied to the printing medium, in particular imaged on her, grid structure. Since the surface of the printing medium provided with the diffractive structure forms a visible side of the printing medium applied to the substrate, both optical information can be perceived after the printing process.

In comparison with previous methods for producing diffractive structures, the invention makes it possible to produce such structures quickly and inexpensively. This is especially true when the diffractive structure is transformed into a non-diffractive optical

Information is integrated, which should also be generated independently of the diffractive structure, as may be the case for example in a packaging design.

By the invention it is possible, for example, to dispense with labels with diffractive security elements and still such on packaging

Provide security elements.

In principle, any printing method can be used in connection with the present invention in which a printing plate, for example in the manner of a printing plate, is used for printing with a printing medium, on the surface of which a grating structure having an optical diffraction effect or another predetermined superfine structure can be applied. In the printing process, the ink should wet all the structures of the printing surface of the printing plate and permanently retained after the impression on the substrate to be printed on its inherited from the printing surface structuring. Such a printing process is, for example, the gravure printing process and the high-pressure process, in particular flexographic printing. Even with the latter, it is expedient if the ink cures at least partially in the printing line. The second structure, in particular a diffractive second structure, may in particular include a security feature that is used to identify or to prove the authenticity of a product, payment means and the like. The printed security feature can here be visible to the naked eye or be designed as a hidden feature that can only be detected with the aid of technical aids, such as microscopes or profilometers.

Further preferred embodiments of the invention will become apparent from the claims, the description and the drawings.

The invention will be explained in more detail with reference to embodiments shown purely schematically in the figures, in which:

Fig. 1 is a perspective view of a erfindungsgemäässeπ

Printing means;

Fig. 2 shows an embodiment of a printed substrate produced with the printing device of Fig. 1;

Fig. 3 is a partial cross-sectional view of an inventive

Printing device in the region of a first and superimposed second surface structure;

Fig. 4 is a further partial cross-sectional view of an inventive

Printing device in the region of a first and superimposed second surface structure.

The purely schematically shown in Fig. 1 according to the invention printing device comprises a cylinder 1 of a gravure device whose surface - except for a part of the cylinder surface engaging pressure pattern - is smooth-surfaced and thus can be referred to as a smooth surface. The surface or the cylinder is preferably elastic. The rectangular printing pattern 4, which can be seen and evaluated by the naked eye, corresponds to a first optical information, for example, the rectangle shown in Fig. 1. The printing pattern has a multiplicity of smallest images which are introduced in the region of the printing pattern 4 on the surface of the cylinder 1 as recesses. Such surface structures are already known per se, and can-as they usually have size dimensions in the direction parallel to the directions of extension of the surface in the range of 10 μm to 150 μm-be referred to as micrometer-scale. Such recordings of the printing form are often referred to in screened gravure as wells. In other variants of intaglio printing, for example the so-called steel engraving, these images are usually executed as a graphic element, for example as a whole, one-to-one printable letters or lines.

The surfaces of the at least approximately concave-shaped receptacles (cups) themselves have a predetermined structuring 3, the elements 5 by at least one power of ten, preferably about three powers of ten, is smaller than the dimensions of the images 2. This second surface structure can therefore as "nanometer scale The term "second surface structure" should also be understood to mean higher and lower elements whose height differences may be in the range of 5 μm to 50 nm. In the exemplary embodiment are grid lines whose raised elements (lines) have a width of 0.05 microns - 5 microns and their recessed elements (valleys) may have a width of 0.05 microns - 5 microns. If their distances are in the range of the wavelengths of visible light (approximately 400-700 nm), perceptible effects are produced with incidental light by the naked eye. By a suitable choice of further, for example from the hologram embossing, known parameters of the structure, such as the azimuth angle, the properties of the achievable diffraction effects can be influenced.

The lattice structures of a single or, preferably, multiple shots 2 may provide perceptible information, such as readable characters such as letters or numbers, a graphic, and the like.

In Fig. 3 and in Fig. 4 are cross sections of a part of a printing plate, such as the printing cylinder 1 shown in FIG. 1. The section shown Fig. 3 shows a receptacle 2 in the printing surface of the printing form, which is part of the first surface structure. The receptacle 2 may be part of a gravure relief which is introduced in the printing surface and may be in the form of gravure printing cups. As shown schematically here, the surface of the receptacle 2 is not smooth-surfaced but is provided with its own predetermined surface structure 3 essentially over its entire recording surface. This microstructure of the second surface structure is thus provided within the gravure relief. The second surface structure 3 is provided as an effective diffractive optical or active structure, in particular, a frequency from a range of 20 lines / mm to 3000 lines / mm, preferably from 800 lines / mm to 2000 lines / mm, may have, with the height differences These structures preferably less than or equal to 2 microns, preferably less than or equal to 1 micron, and more preferably from a range between 200 nm and 600 nm, amount. The surface structure may be formed as a continuous or diskuntinierliche linear grid or cross lattice structure. Such nanometer-scale structures can be produced using different production methods, for example by holographic intereferometric lithography, in particular laser interferometry, e-beam lithography and / or by photolithographic methods.

FIG. 4 schematically shows a further possible embodiment of the first and second surface structures. In this embodiment, the first surface structure in its printing surface both a gravure relief (recording 2) and a high-pressure relief 9, which may be incorporated by engraving in the printing surface. Both the recessed structures and the raised structures are provided on their surface with second surface structures 3, which in turn are active diffraction optically due to their predetermined structuring.

In addition to the nanometer-scale surface structure of the images, areas between the images may also be provided with a nanometer-scale surface structure (3). The individual sections of the surface structured in this way yield one or more additional perceptible information. This additional perceptible optical information can either be one of the information described above, completely separate, further information or supplement this information. In the exemplary embodiment, the further information is additional independent information, namely a diffractive barcode designed as an additional security element. This or its information can be detected by machine, for example by a reading device, which preferably automatically checks whether certain properties are present in the security feature. The second optical information is superimposed on the first optical information, the rectangle of the embodiment.

The smooth surface of the printing cylinder (i.e., the surface of the printing cylinder which lies outside the photographs) - and thus also the second structure of the printing surface - is in this case such that a gravure doctor can slide on the printing surface. The printing surface and its structures can also be designed so that they are suitable for printing and possibly associated embossing operations.

FIG. 2 likewise shows in highly schematic form a substrate 8 printed with the printing device from FIG. 1, for example formed from a polymer film. This has a preferably multi-colored, first optically perceptible information which has been produced by printing a number of shots 2, wherein in Fig. 2, only a single shot is shown. Within the area of the first optical information, a nanoscale pattern 7 is imprinted as a second optical information by printing.

To produce the printed substrate with a printed image 6 of the receptacles 2 and the second surface structure, the printing device of FIG. 1 is used with a printing method according to the invention, which can take place as follows:

- The printing cylinder 1 is provided in an ink fountain with paint, which is preferably scraped off; - The substrate is passed between 1 and a further, not shown, so-called. Presseurzylinder, wherein the press cylinder presses the substrate along the print line on the printing cylinder;

Preferably, press cylinder and / or printing cylinder 1 are made transparent, so that UV light from the inside of the cylinder through their surfaces in the

Printing line can be irradiated, whereby a partial curing of the color is effected. This facilitates detachment of the ink from the printing form while maintaining the impression of the second surface structuring in the printing ink.

The ink used may be an ultraviolet-curable formulation provided with photoinitiators. The second surface structure is imaged in the printing ink of the printed substrate and is permanently contained in it due to the curing effect which prevents it from flowing away.

In another embodiment, a nanoscale structure may preferably also be incorporated in the smooth surface of FIG. 2, as shown in FIG. Such a structure is also printed on the substrate 8 according to the above method.

The surface structure of the printing device can be generated by selectively removing the printing plate provided with the first structure; but it can also be additive by the printing plate is provided with a soft stamp with the second structure.

LIST OF REFERENCE NUMBERS

pressure cylinder

Absorption nanometer-scale

texture region

print pattern

Element of 3

Printed image of 2

Printed image of 3

substratum

Pressure Relief

Claims

claims

1. Printing device with a printing for transferring an optically perceptible information on a medium to be printed by means of a

A printing fluid, such as a printing ink, wherein a printing surface of the printing plate has a first structure, which is intended for predetermined transmission of the printing fluid to a printing substrate, and whose first structure is provided for transmitting a first optically perceptible information to the printing substrate, characterized by a second surface structure of the pressure surface, which is arranged at least partially in the region of the first structure, wherein the structuring of the second surface structure is smaller than the structuring of the first surface structure and the second surface structure contains perceptible information or with the second surface structure perceptible information is generated.

2. Printing device according to claim 1, characterized in that the second surface structure has structuring elements whose size is in at least one at least approximately parallel to the printing surface extending direction of extension in the range of less than or equal to 10 microns.

3. Printing device according to claim 1 or 2, characterized in that the first and the second structure are provided in the same printing form and superimposed on each other.

4. Printing device according to claim at least one of the preceding

Claims, characterized in that the second surface structure is provided for generating an optical or optoelectronic information.

5. Printing device according to one of the preceding claims, characterized in that the second surface structure is provided for generating a magnetically active structure.

6. Printing device according to one of the preceding claims, characterized in that the second surface structure is provided for generating an optically perceptible information.

7. Printing device according to claim 6, characterized in that the Oberflächenstrukur is diffractive optical active and in particular a

Contains line structure in the form of a diffractive optical effective grid structure.

8. Printing device according to at least one of the preceding claims, characterized by a plurality of receptacles of the first surface structure for the temporary arrangement of the pressurized fluid on the printing form, wherein at least a part of the surface of at least some of

Recordings is provided with the second surface structure, which is intended to reproduce or generate the second information.

9. Printing device according to at least one of the preceding claims, characterized in that the printing form, in particular the printing surface, includes an elastic material.

10. Printing device according to at least one of the preceding claims, characterized by a means for curing the pressurized fluid.

11. Printing device according to claim 9, characterized in that the curing agent is arranged in or behind the printing form, whereby the curing agent, a radiation, in particular a UV, is introduced through the printing plate into the pressurized fluid

12. printed substrate on which a printing medium, in particular a printing ink, is applied for generating perceptible information, characterized in that on the substrate at least partially the printing medium reproduces a first optical information and the printing medium in the same section in which the first optical Information is provided with a surface structure representing a second optical information.

13. Printed substrate according to claim 12, characterized in that the surface structure is effective diffraction optically.

14. Printed substrate according to claim 12 or 13, characterized by the surface structure whose predetermined structuring surface elements have a size at least in a substantially parallel to the surface of the printing medium extending direction, which are less than or equal to 10 microns and the reproduction or production of the second optical information is provided.

15. A method for printing a substrate, wherein a printing medium, such as a printing ink, is applied to the substrate and under

Use of a printing device provided with a printing form optically perceptible first information is transmitted to a surface portion of the substrate, characterized in that the printing device in the printing medium at least partially a diffractive optical effective surface structure is generated, which is applied to the same surface portion, which also contains the first optically perceptible information.

16. The method according to claim 15, characterized in that predetermined surface elements are generated, which have a size at least in a direction substantially parallel to the surface of the pressure medium extending direction which are less than or equal to 10 microns and the

Playback or generation of a second information are provided

17. The method according to claim 15 or 16, characterized in that simultaneously with the application of the first information on the printing substrate and the second information is applied to the printing substrate.

18. The method according to at least one of claims 15 to 17, characterized in that the second information is applied at least in sections in a region of the printing substrate, in which the first information is applied.

19. The method according to at least one of the preceding claims 15 to 18, characterized in that on the pressure fluid in the printing form, a radiation is introduced to the curing thereof.