EP2250536A1

EP2250536A1 - Method for providing matrices for embossing polymeric films and the like, particularly for imprinting microscopic identification strings and images, matrix according to the method, and polymeric film embossed by means of the matrix

Info

Publication number: EP2250536A1
Application number: EP08872273A
Authority: EP
Inventors: Francesco Cino Matacotta; Gianluca Massaccesi; Fabio Biscarini; Massimiliano Cavallini
Original assignee: Scriba Nanotecnologie Srl
Current assignee: Scriba Nanotecnologie Srl
Priority date: 2008-02-11
Filing date: 2008-11-12
Publication date: 2010-11-17
Also published as: ITBO20080089A1; WO2009100784A1

Abstract

A method (1) for providing matrices (2) for embossing polymeric films (3) and the like, particularly for imprinting microscopic identification strings and images (4), consisting of the following steps: A) providing a uniform background diffraction grating (5) on a flat plate (6) by means of a standard holographic technique; B) subjecting the flat plate (6) to at least one pulsed and localized energy beam by means of a procedure comprised among ablation, vaporization and melting of portion of material that constitutes the plate (6) in the neighborhood of the at least one point of incidence of the beam; C) repeating the exposure (B) to pulsed and localized energy beams according to a sequence of consecutive dots arranged in the configuration of the image of the element to be imprinted (4).

Description

METHOD FOR PROVIDING MATRICES FOR EMBOSSING POLYMERIC FILMS AND THE LIKE, PARTICULARLY FOR IMPRINTING MICROSCOPIC IDENTIFICATION STRINGS AND IMAGES, MATRIX ACCORDING TO THE METHOD, AND POLYMERIC FILM EMBOSSED BY MEANS OF THE MATRIX Technical Field

The present invention relates to a method for providing matrices for embossing polymeric films and the like, particularly for imprinting microscopic identification strings and images: such coding strings and images are normally imprinted on polymeric films for holographic or microscopic identification of the codes or of the information that they represent.

The present invention also relates to the matrix according to the method and to the polymeric film embossed by means of such matrix. Background Art

Security holograms provided with the so-called "dot-matrix" technique on polymeric films are one of the universally widespread tools for ensuring the authenticity of goods and documents. The dot-matrix technique consists in providing a matrix of diffraction gratings with a size on the order of tens of microns, written in succession with focused laser beams. Automated control of the orientation of the gratings allows to obtain various kinetic effects, such as expansions and contractions, rotations or fading. The holograms thus produced are characterized by a corrugated surface, which is constituted by a set of spots, each of which produces, in preset ways, the diffraction of incident light.

Dot-matrix security holograms are characterized by extremely simple production and therefore low manufacturing and application costs. Security is ensured on three levels: the first level is constituted by the graphics and by the optical characteristics that are perceived with the naked eye, which cannot be replicated perfectly and, in the case of unsophisticated imitations, can be recognized by a careful observer; the second level is represented by hidden features (microscopic graphic patterns, fluorescent details, et cetera) in the graphics, which are not visible to the naked eye but are revealed by simple tools (magnifying lenses, UV lamps, et cetera); finally, the third level consists of the unique microscopic structure of the holographic pattern, for which authenticity can always be established by laboratory comparison with the original print master.

To ensure that it. is impossible to transfer authentic holograms from one object to another, holograms are almost always applied with tamper evident solutions that tend to destroy the hologram itself in response to any attempt at tampering.

Of these three levels, the first one is obviously the weakest, since the end user is unlikely to be able to perceive the difference between the appearance of the original hologram and the counterfeit one. The presence of second-level security characteristics makes hologram counterfeiting much more difficult and expensive; of course, the presence of these characteristics forces the organization that uses them to have some kind of control network along the distribution of the goods or documents.

In practice, the provision of holographic images of this type is more complex and expensive, since the imprinting of microscopic images requires the adoption of particular operating technologies.

More specifically, when adopting technologies for the application of (microscopic) images to diffraction surfaces, according to a configuration disclosed in Italian patent application No. MI2007A002060 in the name of this same Applicant, the use of complex apparatuses on the part of particularly specialized and capable personnel becomes necessary. Moreover, this type of production is rather slow and not suitable for large production runs. Disclosure of the Invention The aim of the present invention is to provide a method for manufacturing matrices for embossing polymeric films and the like, particularly for imprinting microscopic identification strings and images, that is simple to perform and suitable for large production runs.

Within this aim, an object of the present invention is to provide a matrix that is suitable for the faithful transfer of the identification strings and images provided on its surface onto polymeric films by means of simple industrial processes.

Another object of the present invention is to provide a polymeric film that is embossed by means of the matrix according to the method that has a low cost and high quality and fidelity of the identification strings and images that are present on its surface.

Another object of the present invention is to provide a method for providing matrices for embossing polymeric films and the like, a matrix according to the method, and an embossed polymeric film that have a low cost, are relatively simple to provide in practice, and are safe in application.

This aim and these and other objects, which will become better apparent hereinafter, are achieved by the present method for providing matrices for embossing polymeric films and the like, particularly for imprinting microscopic identification strings and images, which consists of the following steps: A) providing a uniform background diffraction grating on a flat plate by means of a standard holographic technique; B) subjecting the flat plate to at least one pulsed and localized energy beam by means of a procedure comprised among ablation, vaporization and melting of portion of material that constitutes the plate in the neighborhood of the at least one point of incidence of the beam; C) repeating the exposure to pulsed and localized energy beams according to a sequence of consecutive dots arranged in the configuration of the image of the element to be imprinted. Brief description of the drawings

Further characteristics and advantages of the invention will become better apparent from the following detailed description of a preferred but not exclusive embodiment of a method for providing matrices for embossing polymeric films and the like, particularly for imprinting microscopic identification strings and images, of the matrix according to the method, and of the polymeric film embossed by means of the matrix, illustrated by way of non-limiting example in the accompanying drawings, wherein:

Figure 1 is a block diagram of the method according to the invention;

Figure 2 is a plan view of a matrix obtained by means of the method according to the invention;

Figure 3 is a schematic perspective view of the imprinting of a graphic element on polymeric film on the part of a matrix obtained by means of the method according to the invention. Ways of carrying out the invention

With reference to the figures, the reference numeral 1 generally designates a method for providing matrices for embossing polymeric films and the like, particularly for imprinting microscopic identification strings and images.

The method 1 consists of a sequence of steps, in which a first step A provides a uniform background diffraction grating 5 on a flat plate 6 by means of a standard holographic technique. The uniform diffraction grating 5 generally can be described as a surface that is corrugated so that the fraction of the surface that produces light diffraction is greater than 80% of the total surface, and so that the characteristic diffraction angle for each wavelength of the incident light does not vary by more than 10% for distances of 50 microns between points of incidence; the possibility to apply the method 1 according to the invention also to applications in which the characteristics of the grating are not comprised within the above-mentioned intervals is in any case not excluded.

From a functional standpoint, it is evident that the plate 6 is conveniently constituted, at least partly, by metallic material or by a metallic alloy, in order to make the method 1 according to the invention particularly effective and simple in terms of execution.

In particular, the flat plate 6 can be constituted by a nickel lamina whose thickness can vary between 10 and 1000 microns (preferably in the range comprised between 50 and 500 microns).

Purely by way of example, the possibility to provide the uniform grating 5 by means of the interference technique on a flat plate is noted.

It is also noted that the expression "uniform grating" 5 is understood to mean that the optical properties thereof do not vary significantly for a length at least equal to the spacing between diffracting and reflecting regions that are intended to be provided with the method 1.

Subsequently it is necessary to perform a second step B, which entails subjecting the flat plate 6 to at least one pulsed and localized energy beam for the ablation and/or vaporization and/or melting of a portion of material that constitutes the plate 6 in the neighborhood of the point of incidence of such beam.

Ablation and/or vaporization and/or melting, if the energy beam is constituted by a pulsed micro laser beam, can be identified physically as the region of the material that is transformed as a consequence of the interaction of such material with the beam.

According to an embodiment of particular interest in practice and in application, the pulsed and localized energy beam is a pulsed laser beam with a beam diameter of substantially less than 50 microns: more specifically, optimum results are obtained with beams having a diameter comprised between 1 and 10 microns.

During the step B for subjecting the flat plate 6 to at least one pulsed and localized energy beam, it is convenient to perform an adjustment which optionally provides for presetting the duration of the pulse, the number of pulses and the energy of each individual pulse. These adjustments and presets are performed as a function of the material that constitutes the plate 6 and of the desired matter ablation parameters.

A last third step C of the method 1 imposes the repetition of the exposure (described in step B) to pulsed and localized energy beams according to a sequence of consecutive dots arranged along the configuration of an element to be imprinted 4.

The result obtained by applying the method 1 to a flat plate 6 is a matrix 2 that comprises the flat plate 6 provided, on at least one of its surfaces, with a uniform background diffraction grating 5 and has, on the grating 5, regions that lack roughness and are contoured and distributed like the element to be imprinted 4 with the matrix 2 on a respective polymeric

The plate 6 is substantially made of metallic material, either in the pure state or as an alloy (although the alternative use of composite materials, ceramic materials, glass materials, silicon wafers and multilayer combinations of different materials is predictable): for example, it has been found that excellent results are achieved with nickel laminas, having thicknesses comprised between 10 and 1000 microns, such thicknesses being preferably chosen within the range from 50 to 500 microns.

By observing the matrix 2 according to the invention, it is straightforward to verify that the regions without embossing are constituted by a plurality of substantially contiguous areas.

Such regions face each other and are arranged so as to provide a contour that corresponds to the element to be imprinted 4.

The embossed polymeric film 3 obtained by means of the matrix 2 also comprises, in at least one of its portions, a surface embossing, which is complementary to the one that constitutes the uniform background of the flat plate 6, and at least one neighborhood without embossing, which is complementary to the corresponding regions of the flat plate 6 that represent the element to be imprinted 4. The film 3 is obtained by transferring the surface characteristics of the matrix 2 on one film 3 that is not processed, according to the method known as "roll to roll" embossing. The film 3, at the end of the transfer process, has the same optical characteristics as the matrix 2 by means of which such transfer was applied. As an alternative, the film 3 is obtained by transferring the surface characteristics of the matrix 2 onto one unprocessed film 3 according to the method known as flat embossing. In this case also, the film 3 has the same optical characteristics as the corresponding matrix 2.

It has thus been shown that the invention achieves the proposed aim and objects.

The invention thus conceived is susceptible of numerous modifications and variations, all of which are within the scope of the appended claims.

All the details may further be replaced with other technically equivalent ones.

In the exemplary embodiments shown, individual characteristics, given in relation to specific examples, may actually be interchanged with other different characteristics that exist in other exemplary embodiments.

Moreover, it is noted that anything found to be already known during the patenting process is understood not to be claimed and to be the subject of a disclaimer.

In practice, the materials used, as well as the shapes and dimensions, may be any according to requirements without thereby abandoning the scope of the protection of the appended claims. The disclosures in Italian Patent Application No. BO2008A000089 from which this application claims priority are incorporated herein by reference.

Where technical features mentioned in any claim are followed by reference signs, those reference signs have been included for the sole purpose of increasing the intelligibility of the claims and accordingly such reference signs do not have any limiting effect on the interpretation of each element identified by way of example by such reference signs.

Claims

1. A method (1) for providing matrices (2) for embossing polymeric films (3) and the like, particularly for imprinting microscopic identification strings and images (4), which consists of the following steps: A) providing a uniform background diffraction grating (5) on a flat plate (6) by means of a standard holographic technique;

B) subjecting the flat plate (6) to at least one pulsed and localized energy beam by means of a procedure comprised among ablation, vaporization and melting of portion of material that constitutes the plate (6) in the neighborhood of the at least one point of incidence of the beam;

C) repeating the exposure (B) to pulsed and localized energy beams according to a sequence of consecutive dots arranged in the configuration of the image of the element to be imprinted (4).

2. The method according to claim 1, characterized in that said flat plate (6) is at least partly made of metallic material.

3. The method according to claim 2, characterized in that said flat plate 6 is constituted by a lamina made of nickel, with a thickness that can vary between 10 and 1000 microns.

4. The method according to claim 1, characterized in that said pulsed and localized energy beam is a pulsed laser beam with a beam diameter of substantially less than 50 microns.

5. The method according to claim 1, characterized in that said step (B) for subjecting the flat plate (6) to at least one pulsed and localized energy beam to ablate a portion of the material that constitutes the plate (6) in the neighborhood of the point of incidence of the beam is performed by adjusting, and optionally presetting, the duration of the pulse, the number of pulses and the energy of each individual pulse as a function of the material that constitutes the plate (6) and of the desired matter ablation parameters.

6. A matrix (2) according to the method of claim 1, characterized in that it comprises a flat plate (6) which is provided, on at least one of its surfaces, with a uniform background grating (5), and has, on said grating (5), regions that do not have said grating (5) and are shaped and distributed like at least one element to be imprinted (4) with said matrix (2) on a respective polymeric film (3).

7. The matrix according to claim 6, characterized in that said plate (6) is substantially made of metallic material, such as nickel, with thicknesses comprised between 10 and 1000 microns.

8. The matrix according to claim 7, characterized in that said nickel plate (6) has thicknesses preferably comprised between 50 and 500 microns.

9. The matrix according to claim 6, characterized in that said regions without grating (5) are constituted by a plurality of substantially contiguous areas.

10. The matrix according to claim 6, characterized in that said regions without grating (5) are arranged so as to represent a code chosen among linear codes, two-dimensional codes .and the like.

1 1. An embossed polymeric film (3) obtained by means of the matrix (2) according to claim 6, characterized in that it comprises, in at least one of its portions, a surface embossing, which is complementary to the one that constitutes the uniform background (5) of said flat plate (6), and at least one neighborhood without embossing, which is complementary to the corresponding regions of said flat plate (6).

12. The film according to claim 1 1 , characterized in that it is obtained by transferring the surface characteristics of said matrix (2) on an unprocessed film (3) according to the method known as "roll to roll" embossing, said film (3) having, at the end of the imprinting-transfer process, the same optical characteristics as said matrix (2).

13. The film according to claim 10, characterized in that it is obtained by transferring the surface characteristics of said matrix (2) onto an unprocessed film according to the method known as flat embossing, said film (3) having, at the end of the imprinting-transfer process, the same optical characteristics as said matrix (2).