EP1383959A2

EP1383959A2 - Colour coding system for identifying objects

Info

Publication number: EP1383959A2
Application number: EP02712958A
Authority: EP
Inventors: Walter Schneider
Original assignee: Giesecke and Devrient GmbH
Current assignee: Giesecke and Devrient GmbH
Priority date: 2001-04-02
Filing date: 2002-03-26
Publication date: 2004-01-28
Anticipated expiration: 2022-03-26
Also published as: ATE372416T1; DE50210852D1; ES2289089T3; EP1383959B1; AU2002244755A1; WO2002078964A2; WO2002078964A3; DE10116315A1

Abstract

The invention relates to a colour coding system for identifying objects, especially valuable documents. Said system comprises coloured particles which reflect in the visual spectral region and disperse at any angle. Said particles are so small that they are not visible to the naked eye, but can be identified by means of a magnifying glass or a microscope. Furthermore, these particles are present in such a low concentration that the colour coding is not detected by the naked eye as being the colour of the product.

Description

Color coding for marking objects

The invention relates to a color coding for identifying objects, in particular documents of value, and a security element which can be applied to the objects and has such a color coding.

In the context of the invention, the term “value document” means banknotes, checks, shares, tokens, ID cards, credit cards, passports and also other documents as well as labels, seals, packaging or other elements for product security.

It is known to equip objects with color particles in order to be able to use these color particles to draw conclusions about the properties of these objects, for example their authenticity, origin or type. Such identification features should be protected against imitation as much as possible, which is why color particles that are difficult to imitate and as inconspicuous as possible are regularly used.

From WO 99/38703, for example, a document of value is known, which contains complex, green-colored particles with a grain size of less than 1 μm, which contain a low-concentration substance that is luminescent in the IR range. If the particles are stored in the paper volume, the concentration is between 500 g and 10,000 g per ton of paper. If the particles are printed on, their concentration is 100 kg to 30 kg per ton of printing ink. The checking of such documents of value is complex and requires the use of both a particularly intensive excitation light source, for example a flashing light, and an IR sensor.

DE-A-19923 959 describes a document of value with similarly complex color particles which are produced by crystal formation from several molecular sieves, the luminescent dye being incorporated into the molecular molecular sieves is installed. The presence or absence of one or more particles results in coding of the value document.

In EP-A-226367, several differently luminescent color particles are stored in paper in an amount of, for example, 4,000 g per ton of paper for identification purposes. The particle size is selected so that the particles do not disappear in the background, but are individually recognizable during the test. Since the test takes place in the dark, a particle size of 30 to 500 μm, preferably 100 to 230 μm, is sufficient because of the luminescence of the particles. The particles are embedded in the security paper or the paper is coated with it.

In contrast, EP-A-219743 proposes significantly smaller luminescent color particles with a size of 10 to 35 μm and a concentration of 1 to 15 g per ton of paper. The color particles consist of transparent material in which the luminescent substances are embedded. Due to their extensive transparency and their small size, the particles are not visible to the naked eye, but they shine in the dark when exposed to UV radiation and can thus be identified individually.

In another context, namely for the purpose of copy protection, it is proposed in EP-B-673319 to print interference pigments with a particle size of 5 to 30 μm on a colored background. If the interference pigments are applied to a background printed with a scattering, complementary color pigment, false colors arise when copying, up to the invisibility of the copied interference pigments. Due to the complexity of the color particles used, the color codes proposed in the prior art are complex and correspondingly expensive to produce. In addition, testing them is complex since at least one dark room is required for testing and, if necessary, additional, costly and, under certain circumstances, maintenance-related aids such as a UV light source and the like are required. In addition, the possibilities of producing different color codes by combining different colored color particles are very limited.

The object of the present invention is to provide a color coding for objects, in particular for securities, which opens up numerous variation possibilities at low cost and which is inconspicuous, that is to say is not readily recognizable to the naked eye, but can nevertheless be detected without great effort.

According to the invention, this is achieved by color coding with the features of patent claim 1. A corresponding document of value and security element are specified in secondary patent claims. Particular embodiments and developments of the invention are specified in dependent claims.

The invention is based on a combination of features closely related to the color particles used, namely on the one hand the "particle size" and on the other hand the "particle concentration". According to the invention, the particle size is selected such that the individual particles are no longer perceptible to the naked eye. The particle concentration is selected in such a way that it is not perceived by the human eye as coloring the product. Such color coding can be generated with simple color particles. It is imperceptible to the naked eye and is therefore not noticeable as an authenticity or identification feature, but is nevertheless recognizable with the simplest technical aids, such as a magnifying glass or a simple microscope. In addition, an enormous variety of color codes can be achieved by combining differently colored particles with color tones that are easily distinguishable from the human eye.

The terms, according to which the particle concentration "is not interpreted as coloring the product" and the particle size "is not perceptible to the naked eye", are relative terms, which are also somewhat subjective. A specific definition of these terms is not possible due to the individual color sensation and the individual visual acuity of the human eye and can only be roughly determined empirically.

The color perception of the human eye depends not only on the specific hue as such, but essentially also on the color saturation and the color brightness of the hue or on the contrast to the background. The lower the color saturation ("glow of color") and the contrast, the less this is perceived as a coloring of the product for a given particle concentration. The same applies to the visual acuity or the resolution of the human eye. Because while contrasting colors may still be perceptible or resolvable with a given particle size, less contrasting colors may no longer be perceptible with the same particle size. It should also be borne in mind that the visual acuity decreases with age and also with the visual distance. During the "near point", at which the human eye has the greatest resolving power, in 20-year-olds still around 10 cm in 30-year-olds it is already around 14 cm, so that the resolution of the human eye of a 30-year-old is correspondingly worse than that of a 20-year-old.

Taking into account the aforementioned unavoidable lack of definition, preferred ranges of the particle size are between 1 μm and 100 μm, in particular 10 μm to 30 μm, and preferred ranges of the particle concentration are between 10 in the event that the particles are mixed into a paper pulp g and 1000 g per ton of paper produced, in particular about 100 g per ton of paper produced, depending on the color tone, color saturation and color brightness of the particles and, moreover, also depending on the particle material. The required particle concentration (based on the paper pulp) also depends on whether, for example, the dyes are embedded in a transparent resin or polymer matrix or whether colored metal oxide particles are used.

The color particles can be connected to the product in a variety of ways. For example, the particles can be mixed with a printing ink, preferably in a concentration of 0.1% by weight, based on the printing ink, which is preferably white or transparent, but which can also be colored, provided that the color particles are in contrast to the latter Coloring can be clearly distinguished from the human eye. Mixing the particles into a plastic or paper mass is also possible. Likewise, the particles can be provided on or in a plastic carrier material which, for example, is at least partially embedded in a paper pulp. The plastic carrier material can have the form of a security thread, a mottled fiber or a planchette. However, the plastic or paper carrier material can also be attached to any other object, for example as part of product security measures. In this case, the carrier material is preferably designed as a label. If the backing material is part of the object to be secured, as is the case, for example, with tear threads, any other shape is of course also possible.

The color coding preferably comprises more than just one color. In order to ensure that the different colors can easily be distinguished from each other with the human eye using a magnifying glass or microscope, it makes sense to use color particles with the basic colors yellow, red, blue and, if necessary, additional color particles with the hues orange in between To use violet, green. The mixed color brown and, moreover, black are suitable as further colors that are easily distinguishable from the aforementioned colors. In addition, some hues can be easily distinguished based on different brightnesses, for example light blue and dark blue.

Particles in the aforementioned colors can be produced in a simple and inexpensive manner. Colored particles of valuable substances such as gold, ultramarine, malachite green, garnet and the like are also easy to produce, but are naturally more valuable and therefore more expensive. For high-quality documents of value, the use of such valuable particles can make sense in order to reduce their attractiveness to being counterfeited, without this complicating the production of the color coding or the checking of the color coding. For example, if you start from the nine aforementioned, easily and safely distinguishable shades, the following simple color scale results:

1. Black

2. Light blue

3. Dark blue

4 (Green

5. Violet

6. Red

7. Orange

8. Yellow

9. Brown.

Since particles with these colors are either only present or not available, different combinations can be used to create 2 ⁹ = 512 variants, of which one version ("no particles") is eliminated. The following 511 variants remain:

9 versions one color each

36 versions of two colors 84 versions of three colors 126 versions of four colors 126 versions of five colors 84 versions of six colors

36 versions each with seven colors 9 versions each with eight colors 1 version every nine colors. An enormous number of different color codes can thus already be generated using simple, easily distinguishable color particles. The addition of just one other color already results in twice the number of variants, i.e. 1023.

Conversely, it follows from the foregoing that, for the sake of being easier to distinguish, it should be avoided to use particles of the same hue which differ only insignificantly in terms of color brightness or color saturation. On the other hand, no shades should be used that are so close together in the spectrum that they cannot be easily distinguished by the human eye.

A particular advantage of the invention can be seen in the ease with which the particles can be produced, since they can easily be produced from an inexpensive material by grinding to the desired particle size. The particles can, for example, consist of ground, selectively absorbing metal oxides, for example iron oxide Fe ₂ 0 ₃ , which appears red to the viewer, or chromium oxide, which appears green to the viewer. However, the particles can also consist of a resin, in particular a melamine resin or polyurethane resin, to which organic substances with the desired hues (for example red or green) are added. After curing, the melamine resin or polyurethane resin is brittle and therefore easy to grind. Instead of a resin, polymer materials, in particular acrylic polymers, can also be used as the dye carrier insofar as these are brittle and can be ground. In the event that the particles are embedded in the product, for example by mixing them into the paper pulp during papermaking, it must be ensured that the particles are insoluble in the material, which is usually the case for organic dyes in melamine resin or polyurethane resin and acrylic polymers Case is. In order to achieve the advantages intended by the invention, the color particles used are simple color particles which scatter independently of the angle and are therefore based either on selective absorption or diffuse scattering. In addition, the color particles reflect in the visual spectral range to the human eye to be perceptible without additional equipment, apart from a simple technical aid, such as a magnifying glass or a microscope. The magnification factor of these aids depends on the size of the particles used, ie the smaller the particles, the stronger the magnification factor has to be. With particle sizes of around 50 μm and more, a magnifying glass with 8x magnification (8x) is usually sufficient. For particle sizes smaller than about 50 μm, especially in the range of 10 μm, a microscope with 100x magnification (100x) is recommended.

However, this does not rule out that other color effects can also be provided. A special embodiment of the invention therefore provides that the colored particles are combined with any machine-readable features, for example also luminescent substances that are not perceptible to the naked eye in daylight. These luminescent substances can be provided separately, but are preferably embedded together with the dyes in the resin or polymer matrix. Such particles can then be detected both with the eye and with sensors, in particular if the luminescent substances luminesce exclusively outside the visual spectral range, for example fluoresce in the UV or IR spectral range. This combination is particularly advantageous if, in addition to marking the products, proof of authenticity should also be possible. Easily available luminescent substances can be used as luminescent dyes, but also luminescent substances specially developed for safety-related applications. The first-mentioned luminescent substances are preferably used to increase the number of variants for color coding. Fluorescent substances such as, for example, are suitable

Distilbene derivatives with blue fluorescence or flavin or flavone dyes with yellow-green fluorescence. The luminescent substances specially developed for safety-related applications are, for example, host lattices doped with rare earth elements.

Although in principle a single machine feature would be sufficient for the proof of authenticity, as many machine-readable features as the number of color particles are preferably provided. This has the advantage that the complete code can be seen both with the eye and with sensors. To this extent, an embodiment is particularly preferred in which a luminescent substance is admixed to the different color particles, which luminesces in approximately the same color as the color particle in which the luminescent substance is incorporated. Luminescent substances which have body color in the visible spectral range, ie which appear colored to the human eye without an additional excitation source, but which also fluoresce when excited, can be used just as well.

As mentioned at the beginning, there are various options for providing the products with the color coding, for example by storing the

Particles in the volume of the product or by application to the surface, for example by printing using Flexoprint or by spraying using a device according to EP 0 659935 B1. The flexographic printing inks preferably consist of a colorless varnish with the addition such a small amount of particles that the printed color does not appear colored in itself. In the case of flexographic printing, any pattern can be selected on the surface which, although not visible to the naked eye, can be detected by sensors, especially if the particles are combined with fluorescent substances or other machine-readable features.

The color coding variants that can be achieved with the different color pigments can be further increased if the different color particles are present in separate, continuous strips on or in the product. In the case of two strips of variants above can be extended from 511 to 511 versions ^2/2 = 130,560 releases.

On the other hand, it is possible to apply the color particles in strips or not in strips, and to produce an additional strip which only contains machine eyes which are not visible to the naked eye. This opens up further coding possibilities.

Some exemplary embodiments of the invention are given below:

example 1

A paper sheet was formed, the suspension of which, prior to sheet formation, with finely ground iron oxide Fe ₂ 0 ₃ (red, particle size approx. 100 μm) and additionally with finely ground chromium oxide (green, particle size approx. 100 μm) in an amount of approx. 200 each g per ton of paper produced. The sheet was formed and dried on a paper sieve in the usual way. The red and green particles formed therein were 8-fold by means of a magnifying glass Magnification (8x) easily recognizable. Because of the small amount of colored particles, the paper sheet itself showed hardly any color deviation from white paper and is therefore not classified as discolored.

Example 2

The paper production was carried out in the same way as in Example 1. In this case, about 200 g of color particles per ton of paper produced were mixed into the paper stock suspension. In this case, however, the color particles were made from a melamine resin, which was used to produce red

Color particles were mixed with a red organic dye and a green organic dye had been mixed in to produce green color particles. The melamine resin is e.g. around Maprenal VMF 3921w / 85WA (manufacturer: Vianova AG), to which 5% by weight red or green dye, based on the dry amount of resin, are added. After the melamine resin thus colored had hardened, a brittle, easily grindable resin was formed, from which the color particles (particle size approx. 20 μm) were obtained by grinding and added to the paper stock suspension. The particles were recognizable with a microscope with a 100x magnification (100x) and easily distinguishable without the paper showing any perceptible coloring.

Example 3

A paper sheet of 90 g / m ^{2 was} formed, the suspension of which had been mixed with two different fluorescent particles (particle size approx. 20 μm) in an amount of approx. 200 g per ton of paper produced before the sheet formation. The sheet was formed and dried on a paper sieve in the usual way. The particles were made from melamine resin Maprenal VMF 3921 w / 85 WA (manufacturer Vianova AG), which contains 5% by weight of nylosan rhodamine B300, based on the dry resin quantity, to produce red color particles, and 5% by weight Blankophor BA to produce colorless particles, based on the amount of dry resin was added. Then the mixture is made

Maprenal and Nylosan Rhodamin B300 or Blankophor BA are each poured into a tray lined with polyester film and dried in an oven at 120 ° C. The film is removed and the hardened mass scraped off. The hardened mass is then crushed in a hammer mill and sieved through a sieve with a mesh size of 30 μm. The particle fraction passed through the sieve is added to the pulp suspension used for sheet formation. When excited under UV light, Blankophor BA fluoresces blue in the visible spectral range and Nylosan Rhodamin B 300 fluoresces red in the visible spectral range. In addition, Nylosan Rhodamine B300 has a red body color in the visible spectral range. The particles were recognizable with a microscope with a 100x magnification (100x) and easily distinguishable without the paper showing any perceptible coloring.

Example 4

In a pulp suspension, e.g. a suspension of 100 g pine sulfate pulp in 51 water

10 mg ultramarine (blue, particle size approx. 40 μm)

20 mg iron oxide Fe ₂ 0 ₃ (red, particle size approx. 30 μm)

20 mg Blankophor B A resin particles as produced in Example 3 (colorless, fluorescent blue when excited in UV, particle size 25 μm) and 10 mg mica (metallic gloss, particle size approx. 40 μm) added.

Sheets of 90 g / m ^{2 are} formed from this mixture on a paper sieve in the usual way. Under a microscope with 100x magnification, blue, red and shiny metallic particles can be recognized and easily distinguished without the paper showing any perceptible coloring.

When irradiated with UV light, a blue fluorescence occurring in the visible spectral range can also be seen.

Claims

Patent claims

1. Color coding for the identification of objects, comprising, in the visual spectral range, reflecting, angle-independent scattering colored particles that are so small that they are not perceptible to the naked human eye, but can be seen with a magnifying glass or a microscope, and that in such a way low concentration that the color coding is not perceived by the naked human eye as the color of the object.

2. Color coding according to claim 1, wherein the color coding comprises differently colored, easily distinguishable particles for the human eye.

3. Color coding according to claim 2, wherein the colors of the particles are selected from the group of primary colors red, yellow, blue and / or colors between them orange, green, violet.

4. Color coding according to claim 2 or 3, wherein the color coding comprises colored particles with approximately the same hue, but easily distinguishable color brightness.

5. Color coding according to one of claims 1 to 4, wherein the colored particles consist of finely ground iron oxide and / or chromium oxide.

6. Color coding according to one of claims 1 to 4, wherein the colored particles consist of colored melamine resin or polyurethane resin.

7. Color coding according to one of claims 1 to 4, wherein the colored particles consist of colored acrylic polymer.

8. Color coding according to one of claims 1 to 7, wherein the colored particles are embedded in the paper pulp.

9. Color coding according to claim 8, wherein 10 g to 1000 g of color particles per ton of paper are embedded in the paper.

10. Color coding according to claim 9, wherein about 100 g of colored particles per ton of paper are embedded in the paper.

11. Color coding according to one of claims 1 to 7, wherein the particles are applied to the surface of an object to be labeled.

12. Color coding according to claim 11, wherein the colored particles are applied only in partial areas of the surface of the object to be identified.

13. Color coding according to claim 12, wherein the partial areas are strip-shaped.

14. Color coding according to one of claims 1 to 13, wherein additionally machine-readable features are present.

15. Color coding according to claim 14, wherein a number of different machine-readable features corresponding to the number of differently colored particles is provided.

16. Color coding according to claim 14 or 15, wherein the machine-readable features are part of the colored particles.

17. Color coding according to claim 14 or 15, wherein the machine-readable features are present separately from the colored particles.

18. Color coding according to claim 17, wherein the machine-readable features are present in a strip separated from the colored particles.

19. Color coding according to one of claims 14 to 18, wherein the machine-readable features are formed by luminescent substances.

20. Color coding according to claim 19, wherein the luminescent substances fluoresce in a color approximately corresponding to the colored particles.

21. Color coding according to claim 19 or 20, wherein the luminescent substances luminesce outside the visual spectral range.

22. Color coding according to one of claims 1 to 20, comprising colored particles consisting of valuable substances.

23. Color coding according to claim 22, wherein the valuable substances are selected from the group of the following substances: gold, ultramarine,

Malachite green, garnet.

24. Security element for application or storage on or in an object, the security element having a color coding according to one of claims 1 to 23.

25. Value document comprising a color coding according to one of claims 1 to 23, or a security element according to claim 24.

6. document of value according to claim 25, consisting of paper.