EP2005258A1

EP2005258A1 - Storage medium comprising a security feature and method for producing a storage medium comprising a security feature

Info

Publication number: EP2005258A1
Application number: EP07723879A
Authority: EP
Inventors: Stefan BORGSMÜLLER; Steffen Noehte; Kay Schulte-Wieking
Original assignee: Tesa Scribos GmbH
Current assignee: Scribos GmbH
Priority date: 2006-04-04
Filing date: 2007-04-02
Publication date: 2008-12-24
Also published as: CN101405663A; US20090016208A1; CN101405663B; US8248908B2; WO2007115720A1; DE102006032538A1

Abstract

The invention relates to a storage medium comprising a security feature, having a substrate (1, 4, 10), at least one functional layer (2, 5, 11), at least one feature which is written into the functional layer (2, 5, 11) and is visible when reflected and at least one feature which is written into the functional layer (2, 5, 11) and is visible when transmitted, at least one feature being individualized and at least one feature having a diffractive structure. The invention solves the technical problem of providing a larger variety of combinations of different security features. The invention also relates to a method for producing a storage medium comprising a security feature.

Description

A storage medium comprising: a security feature and a method of manufacturing a storage medium having a security feature

safety feature

The invention relates to a storage medium with a security feature and to a method for producing a storage medium with a security feature.

Security features known from the prior art can be formed, for example, from computer-generated holograms which consist of one or more layers of dot matrices which, when illuminated with a preferably coherent light beam, lead to a reconstruction of the information encoded in the hologram. The point distribution can be calculated as an amplitude hologram, phase hologram or as a kinoform, Fourier or Fresnel hologram. For the production of computer-generated holograms, these are first calculated and then written with a suitable writing device by point-wise introduction of energy into a storage medium. The resolution of the resulting dot matrix can be in the range below 1 μm. Thus, holograms with a high resolution can be written in a small space, the information of which can only be read out by illuminating with a light beam and reconstructing the diffraction image. The size of the holograms can be between less than 1 mm ² and several 1 cm ² . A structuring of the type described above can also be referred to as microstructuring. The computer-generated holograms described above can be combined with directly visible information (microprint, microimages, encoded information).

Furthermore, a plurality of writing devices for writing computer-generated holograms are known from the prior art, which write in planar storage media the optical structures of the holgrams. For example, reference is made to the publications WO 02/079881, WO 02/079883, WO 02/084404, WO 02/084405 and WO 03/012549. Such writing devices are also referred to as laser lithographs or as lithographic systems.

Likewise, a plurality of reading devices are known, which are suitable for illuminating the hologram surface by means of a light beam and a suitable optical system to make the reconstruction visible or electronically representable and evaluable by means of recording means. By way of example, reference is made to the publications DE 101 37 832, WO 02/084588 and WO 2005/111913.

Visible light diffractive structures are therefore widely known and are - as already stated - used as security features, as their counterfeiting means a considerable technical effort, since they are constructed of structures whose structure sizes are in the range of optical wavelengths. Such structures are usually realized as reflective structures. However, they can also be realized as a transmittively observable / readable structure. The invention is based on the technical problem of specifying a method for producing a storage medium with a security feature as well as a storage medium with a security feature, wherein a greater variety of combinations of different security features is made possible.

The technical problem is solved by a storage medium with a security feature, with a substrate, with at least one functional layer, with at least one feature inscribed in the functional layer and observable in reflection, and with at least one feature inscribed in the functional layer and observable in transmission, wherein at least one Feature is individualized and wherein at least one feature has a diffractive structure.

The above-mentioned technical problem is also solved by a method for producing a storage medium having a security feature in which at least one feature observable in reflection, ie a structure and / or information content that is reflectively diffractive or reflectively observable by brightness modulation, can be observed in at least one functional layer of the storage medium Storage medium is written, in which in the at least one functional layer of the storage medium at least one observable in transmission feature, ie a transmissive diffractive or transmissive observable by brightness modulation structure and / or information content is written, wherein at least one feature is customized and wherein at least one feature is inscribed as a diffractive structure.

It is preferred that the features are inscribed as microstructures in the storage medium. Thus, it is stated for the first time that different microstructures observable in reflection and transmission are contained in a functional layer of a storage medium or can be inscribed with the same production process.

Diffractive structures can be simple grid arrangements, complex grid arrangements or holograms. The inventive method thus allows several different ways of storing and reading information in one and the same material. It can be stored by each individual storage a separate individual information. As individual information, for example, any information is understood that refers to one or more properties of the object on which the storage medium is to be attached as a security feature. Examples of such properties are serial numbers or manufacturing data.

The shape of the stored information of the different memory types may be e.g. consist of one or more types, and may e.g. digital data, text, numbers, serial numbers, images, faces, logos or patterns.

In a storage medium produced according to the invention, the areas which are distinguished by their type of Distinguish information storage, located at different locations, but these areas can also overlap partially or completely, so that in the latter case, different information is stored in one and the same place and can be read by different reading modes from this.

Typical ways of reading the information stored in different ways may be e.g. be:

Observation of shiny metallic structures in reflection with the naked eye, whereby different degrees of brightness can be observed Observation of diffractive structures in reflection with the naked eye, whereby different brightnesses and / or colors can be detected

T Reading holographic structures in reflection with a suitable device

Reading out diffractive or holographic structures in transmission with a suitable device or the naked eye by means of a suitable light source Reading out structures in transmission resulting from brightness modulation (grayscale images) with coherent but especially with non-coherent light, for example with normal daylight, with a lamp , with a light bulb etc.

With the method according to the invention can be produced objects that can serve as a security feature and one compared to known diffractive

Security features provide increased security against counterfeiting, since different types of memory are realized in the same storage medium and even to a and the same place, which, due to the increased complexity of the production of such objects, represents a strong technical hurdle for counterfeiting attempts.

The combination of memory types that require reading a special device, in combination with easy-to-check information content is a combination of memory types that realizes several levels of security in the same object and thus advantages over previously known security features shows, as these often only provide information at a security level. Such a combination of security levels is preferably that at least one feature is a level 1 security feature and at least one feature is a level 2 or level 3 security feature. A level-1 security feature is a feature that is visible to the naked eye and that can be verified without additional aids, here for example gray scale images that can be read in transmission with daylight. A level 2 security feature is a feature that is verifiable with simple or standard tools (e.g., a magnifying glass, a UV lamp, a bar code reader). A level 3 security feature is a feature that is verifiable only with specialized equipment. In particular, the storage of holographic digital data can be done as a level 2 security feature or as a level 3 security feature.

The invention further describes a storage medium suitable for producing such structures in a lithographic process utilizing laser radiation. In the following the invention will be explained in more detail with reference to various embodiments, reference being made to the accompanying drawings. The various examples describe different types of structures that can be created by a lithographic process. In the drawing show

1 shows a schematic structure of a storage medium,

FIG. 2 shows the storage medium shown in FIG. 1 with different inscribed structures, FIG.

3 shows the storage medium shown in FIG. 1 with various inscribed structures, FIG.

4 shows an exemplary embodiment of a combination of a hologram structure written in type 2 with a lattice structure in the form of a type Ib lettering in transmitted light against a light background,

FIG. 5 shows the combination shown in FIG. 4 in reflection, FIG.

FIG. 6 shows an exemplary embodiment of a combination of a hologram structure written according to type 2 and a digit or graphical elements in the form of different grating structures according to Typlb in transmitted light against a light background. FIG. FIG. 7 shows the combination shown in FIG. 6 in reflection, FIG.

FIG. 8 shows an exemplary embodiment of a combination of overlapping areas with different information contents in a transmittive observation against a light background, wherein a vertical dark bar can be seen on a light background, and FIG

Fig. 9 taken the combination shown in Fig. 6 in reflection, wherein a bright horizontal bar can be seen on a dark background.

The basic structure of the storage medium will be described as follows.

A storage medium shown in Fig. 1 consists in its simplest form of a polymer film 1, preferably a stretched polymer film which is at least partially transparent to visible light, and at least one functional layer 2, which absorbs the laser radiation during the lithographic writing process and is at least partially transparent. Between the film 1 and the functional layer 2, no further layers are preferably arranged. In addition, a further additional layer 3 can be present on the functional layer 2.

The lithographic writing is carried out in FIG. 1 from below through the film 1 onto the functional layer 2 or else from above onto the functional layer 2 through the optional additional layer 3. The additional layers 3 may be lacquers, protective layers, polymer layers, transparent glasses, crystalline layers, semiconductors, antireflection layers or further functional layers.

A lithographic process or writing process can be carried out through the film 1 onto the functional layer 2 or, alternatively, through additional layers 3 directly onto the functional layer 2. During the lithographic writing process, the functional layer 2 has inter alia the task of at least partially absorbing the laser radiation and convert it into heat and at least partially deliver it to the film 1.

Instead of a functional layer 2, it is also possible to provide two and more functional layers 2 arranged one above the other, which complement or reinforce each other in their function.

FIGS. 2 and 3 show various types of structures which can be produced in a lithographic process or writing process using, for example, laser radiation. The structure of the storage medium essentially corresponds to that of the storage medium shown in FIG. 1, consisting of the film 4 or 10, the at least one functional layer 5 or 11 and the optional additional layer 6 or 12.

If the information to be written is introduced into the storage medium by means of a lithographic system which uses focused laser radiation, then a focused laser beam is generated by a short laser pulse (or several consecutive pulses) a small structure in the storage medium which, along with many such written structures, gives the desired diffractive or holographic or directly visible overall structure.

The following differently generated and differently acting structures can be realized.

In FIG. 2, structure 7 represents a structure of type la +, structure 8 represents a structure of type lb +, and structure 9 represents a structure of type 2.

In FIG. 3, the structure 13 represents a structure of type Ia, the structure 8 represents a structure of type Ib, and the structure 9 represents a structure of type 3.

Depending on the temperature during the lithographic writing process in the

Functional layers or the film is present, the structures shown in Figs. 2 and 3 can be produced.

FIG. 2 shows, on the one hand, relief formations of a certain height on the basis of the structure 7 as an increase of the film surface of the type la + and on the basis of the structure 8 an increase of the film surface of the type 1b + with a greater height than in the structure 7 with the type la +. On the other hand, a removal of the at least one functional layer 5 by the example of the structure 9 corresponds to the type 2, which in the case that one of the functional layers 5 is a metal layer, a demetallization. FIG. 3 shows relief patterns on the basis of the structure 13 with type Ia and on the basis of the structure 14 with type Ib, similar to the types Ia + and Ib +, but in the form of a depression of the film surface. FIG. 3 also shows a structure formation in the form of the structure 3 with type 3, which changes the phase of the light when illuminated with a reading beam. The structure 15 may be formed, for example, in the form of a refractive index change of the film 10. A type 3 structure may also be a gas bubble formed by the exposure process.

Depending on the amount of energy absorbed during the writing process, which is converted into heat, as well as the amount of heat transferred to the film and the thermodynamic behavior of the film and the functional layer (s) may be formed in the film or demetallisations or structural changes of the Type 3 can be achieved.

As a suitable process parameter, the total energy of a single laser write pulse can serve this purpose in a lithographic process. With the same laser power different energies can be introduced into the storage medium with different lengths of laser pulses. Short pulses produce low energies, middle pulses medium energies and long pulses generate high energies. This allows both the type of exposure and the severity, i. Within certain limits, the size of the exposed point can be influenced.

Structures of the type Ia, ie low relief formations can be generated with low energies. Structures of the type Ib, ie strong relief formations can be generated with medium energies.

Type 2 structures, ie demetallizations, and type 3 structures can be generated at high energies.

By way of example, with suitable laser lithographs (diffraction-limited, 100-100 nm laser power in the visible or IR, UV range) with the same material and one and the same laser power types Ia, Ib and 2 can be generated with laser pulse lengths of 150ns, 300ns and 600ns.

As a further process parameter, the laser power can be used in a lithographic process. For equally long pulses with weak, medium or high laser power structures of type Ia, type Ib or type 2 and type 3 can be generated.

As a further process parameter, the number of individual pulses can be used in a lithographic process. For pulses of equal energy, e.g. a type Ia structure is generated with a pulse, a type Ib structure with a double pulse (2 pulses with a short pause), and a type 2 or type 3 structure with a triple pulse.

Further combinations of number of pulses, laser power, pulse duration, temporal laser pulse distance are possible.

In the following, the properties of generated structures of types Ia, Ib, 2, 3 are described in detail, it being within the scope of the invention, the properties the differently designed layers to combine.

Relief formations (structures of the types Ia, Ib) have an influence on the phase of the light during readout in reflection and are thus diffractive phase patterns. In transmission they do not act or hardly.

Phase changes in the film or bubbles (structures of type 3) lead to phase influence in reflection and transmission.

Demetallizations (structures of type 2) have an influence on the amplitude of the light both during reading in reflection and during reading in transmission and are thus diffractive amplitude patterns.

A memory material can be described lithographically with a structure according to type Ia with the following properties:

Functional layers are retained so that no change in optical density (OD) when viewed in transmission with e.g. White light occurs.

Lattice structures that are formed from relief formations, when viewed in reflection, lead to diffraction phenomena. Grids or complex grids can appear in different colors.

Holographic structures can be read in reflection with a suitable device. Relief formations in transmittive illumination lead to almost no diffraction or to diffraction effects with negligible diffraction efficiencies.

A memory material can be described lithographically with a structure according to type Ib with the following properties:

Lattice structures that are formed from relief formations, when viewed in reflection, lead to diffraction phenomena. Grids or complex grids can appear in different colors and are brighter than the same type Ia structures.

Holographic structures can be read in reflection with a suitable device and diffract more than type Ia structures.

Relief formations in transmittive illumination lead to almost no diffraction or to diffraction effects with negligible diffraction efficiencies.

A memory material can be described lithographically with a structure according to type 2 with the following properties:

Functional layers are not preserved, so that there is a change in the optical density (OD) when viewed in transmission with eg white light. This effect can be areal, so that in the case of a planar demetallization a maximum transmission results, or else lead to a desired gray value via a corresponding screening of metallised and demetallised surface.

Lattice structures formed from amplitude patterns, when viewed in reflection, lead to diffraction phenomena. Grids or complex grids can appear in different colors.

Grating structures formed from amplitude patterns, when viewed in transmission, give rise to diffraction phenomena.

Holographic structures can be read in reflection with a suitable device.

Holographic structures can be read out in transmission with a suitable device or the naked eye by means of a suitable light source.

A memory material can be described lithographically with a structure according to type 3 with the following properties:

Functional layers are not preserved, so that there is a change in the optical density (OD) when viewed in transmission with eg white light. This effect can take place in a planar manner, so that in terms of area, a maximum transmission results, or else lead to a desired gray value via a corresponding grid of metallised and demetallised area. When viewed in reflection, grating structures lead to diffraction phenomena. Grids or complex grids can appear in different colors.

Lattice structures lead to diffraction phenomena when viewed in transmission.

Holographic structures can be read in reflection with a suitable device.

The following describes the preferred combinations of various structures.

As described above, the various types of memories, i. Surfaces which have been described according to the types Ia, Ib or 2 or 3, contain different information.

For example, holographic structures can contain digital data, texts, numbers, serial numbers, images, faces, logos, patterns, encoded data, etc. in their reconstruction.

Identical data contents can be generated by diffractive structures as diffraction patterns. Likewise, such information contents can be generated by demetalization as gray value images, which are viewed in a transmissive arrangement. Different information contents can be combined with each other. It is thus known, for example, that pictorial information, for example a face, is combined with a hologram in such a way that the face can be seen when viewed in reflection with the naked eye, but the same structure is also present when reading in reflection with the aid of a corresponding reading device contains holographic information.

Such combinations can now be extended by the aspect of transmitive readout.

The illustration in FIG. 4 is taken in transmitted light against a light background. The non-demetallized areas appear dark. FIG. 4 shows by way of example that a hologram structure 17 written in type 2 can be combined with a lattice structure 18 in the form of a lettering according to type Ib. The hologram structure therefore appears bright in transmission, the lettering in transmission dark.

FIG. 5 shows a hologram 19 which has been written after type 2 and a text 20 as lattice structure according to type Ib. The illustration in FIG. 5 is taken in reflection. The non-demetallized areas containing gratings appear bright. Fig. 5 shows that, viewed in reflection, the lettering appears bright on the diffuse hologram background due to the diffraction.

Both in transmission and in reflection, the holographic information 17 or 19 can be read out with a corresponding reading device. FIG. 6 shows a similar combination as in FIG. 4. A hologram 21 is of type 2 and a number 22 or graphical elements 22 are inscribed as different lattice structures of type Ib. Fig. 6 shows a representation taken in transmitted light against a light background. The non-demetallized areas appear dark.

The regions 22 which can be identified as dark in FIG. 6 contain different grating structures. Here, however, holographic structures written by type Ib could also be located. Again, the hologram structure 21 appears bright in transmission, the graphical elements 22 dark in transmission.

FIG. 7 shows a type 2 hologram 23 and a number or graphic elements 24 as different lattice structures according to type Ib. The illustration of FIG. 7 is taken in reflection. The non-demetallized areas containing grids appear bright and colored, with the different colors shown as gray levels in the illustration. When viewed in reflection, it can be seen that the graphic elements 24 contain different diffraction gratings.

Here, too, the holographic information from 21 or 23 can be read out both in transmission and in reflection with a corresponding reading device.

FIG. 8 shows a functional example, which makes it clear that surfaces with different

Informational content can overlap. Thus, the example shown in FIG. 8 consists of 6 regions 25, 26, 27, 28, 29 and 30, wherein the areas 28 and 29 are generated identically, as well as the areas 26 and 30.

The region 25 contains holographic information, written in type 2. The regions 28 and 29 contain a type 2 lattice structure, i. these areas appear bright in transmissive observation in FIG.

The regions 26 and 30 contain the same holographic information as the region 25, however, the regions 26 and 30 are generated by type Ib. The region 27 contains a lattice structure written according to type Ib, i. these areas appear dark in transmissive observation in FIG.

As a result, in transmittive observation against a light background, a vertical dark bar on a light background can be seen.

Fig. 9 shows in reflective observation that the bright diffractive structure of the regions 33, 34 and 35 can be clearly seen, these being produced according to two different types. The hologram area 31, 32 and 36, however, can be recognized as a gray background. As a result, a bright horizontal bar can be seen in reflection.

Compared with the examples from FIGS. 4 to 7, the examples from FIGS. 8 and 9 in particular show that metallized and non-metallized as well as diffractive and non-diffractive regions can overlap. A visible in reflection information may consist of a grid orientation, which, however, was generated according to different types and thus in transmittive viewing does not have to show the same visible information.

Claims

PATENT APPLICATIONS

1. Storage medium with a security feature, with a substrate (1,4,10), with at least one functional layer (2,5,11), with at least one inscribed in the functional layer (2,5,11) and observable in reflection feature and with at least one feature inscribed in the functional layer (2, 5, 11) and observable in transmission, wherein at least one feature is individualized and wherein at least one feature has a diffractive structure.

2. Storage medium according to claim 1, characterized in that the features as microstructures in the functional layer (2,5,11) are inscribed.

3. Storage medium according to claim 1 or 2, characterized in that at least two features side by side in the functional layer (2,5,11) are inscribed.

4. Storage medium according to one of claims 1 to 3, characterized in that at least two features are at least partially overlapping in the functional layer (2,5,11) inscribed.

5. Storage medium according to one of claims 1 to 4, characterized in that at least one observable in reflection feature is formed as a relief structure in at least one reflective functional layer of the storage medium.

6. Storage medium according to one of claims 1 to 5, characterized in that at least one observable in reflection feature as a structure with different optical density, in particular as at least partially perforated reflective functional layer is formed.

7. Storage medium according to one of claims 1 to 6, characterized in that at least one observable in reflection feature is a reflective diffractive or reflective by brightness modulation observable structure.

8. Storage medium according to claim 7, characterized in that the reflective diffracting structure is observable by different brightnesses and / or colors.

9. Storage medium according to claim 7, characterized in that the reflectively observable by brightness modulation structure is a microimage, in particular a shiny metallic microimage.

10. Storage medium according to one of claims 1 to 9, characterized in that at least one observable feature in reflection as a reflective diffractive or reflective by brightness modulation observable information content is formed.

11. Storage medium according to claim 10, characterized in that the reflective diffracting information content is a computer-generated hologram.

12. Storage medium according to claim 10, characterized in that the reflectively observable by brightness modulation information content is a microwriting, a micro image or a barcode.

13. Storage medium according to one of claims 1 to 12, characterized in that at least one observable in transmission feature as a structure with different optical density, in particular as at least partially perforated reflective functional layer is formed.

14. Storage medium according to one of claims 1 to 13, characterized in that at least one observable in transmission feature is designed as a transmissive diffractive or transmissive observable by brightness modulation structure.

15. Storage medium according to claim 14, characterized in that the transmissive diffractive structure is a diffraction pattern.

16. The storage medium according to claim 14, characterized in that the structure which can be observed by brightness modulation is a microimage, in particular a halftone image.

17. Storage medium according to one of claims 1 to 16, characterized in that at least one feature observable in transmission is formed as a transmissively diffracting or transmissive observable by brightness modulation information content.

18. Storage medium according to claim 17, characterized in that the transmissively diffracting information content is a computer-generated hologram.

19. The storage medium according to claim 17, characterized in that the information content that can be observed transmissively by brightness modulation is a microprint or a barcode, in particular in the form of a gray value image.

20. Storage medium according to one of claims 1 to 19, characterized in that at least one feature is a level-1 security feature and that at least one Feature is a Level 2 or Level 3 security feature.

21. A method for producing a storage medium with a security feature according to one of claims 1 to 20, wherein in at least one functional layer of the

Storage medium at least one observable in reflection feature is written and in which in the at least one functional layer of the

Storage Medium is inscribed at least one observable in transmission feature, wherein at least one feature is individualized and wherein at least one feature is inscribed as a diffractive structure.

22. The method of claim 21, wherein the features are written as a microstructure in the functional layer.

23. The method of claim 21 or 22, wherein at least two features are written side by side in the functional layer.

24. The method according to any one of claims 21 to 23, wherein at least two features are written at least partially overlapping in the functional layer.

25. The method according to any one of claims 21 to 24, wherein the features are written by a lithographic process in the Funktionsgschicht.

26. The method of claim 25, wherein by changing at least one of the process parameters pulse duration of the laser pulses, energy of the laser pulses, number of laser pulses per structure to be written and temporal

Laser pulse distance differently effective structures (Typla, Typlb, type 2, type 3) are written in the at least one functional layer.