DE10116315A1 - Color coding for marking objects - Google Patents

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

The invention relates to a color coding for identifying counter stands, especially documents of value, as well as an on the objects Applicable security element with such a color coding.

Under the name "document of value" are within the scope of the invention Banknotes, checks, shares, tokens, ID cards, credit cards, passports and also other documents as well as labels, seals, packaging or understand other elements for product assurance.

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

From WO 99/38703, for example, a document of value is known, which ches complex, green colored particles with a grain size of less than 1 µm contains a low concentration, luminescent in the IR range Contain substance. 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 between 100 kg and 30 kg per ton of printing ink. The examination of such documents of value is on elaborate and requires the use of a particularly intensive stimulus light source, such as a flash, as well as an IR sensor.

DE-A-199 23 959 describes a document of value with similarly complex Color particles formed by crystal formation from several molecular sieves are produced, the luminescent dye in the molecular sieves  is installed. By the presence or absence of an or If several particles are encoded, the value document is encoded.

In EP-A-226 367 several are identified for identification purposes different luminescent color particles in paper in an amount of for example, 4,000 g per ton of paper. The particle size is like this chosen that the particles do not disappear in the background, but are individually recognizable during the test. Since the test takes place in the dark, Because of the luminescence of the particles, a particle size of 30 to is sufficient 500 µm, preferably 100 to 230 µm. The particles are in the safe storage paper or the paper is coated with it.

In contrast, EP-A-219 743 proposes much smaller lumines decorative color particles with a size of 10 to 35 µm and a Konzen tration of 1 to 15 g per ton of paper. The color particles consist of transparent material in which the luminescent substances are stored are. Because of their extensive transparency and their small size the particles are not visible to the naked eye when exposed to UV radiation however, they glow in the dark and are thus individually recognizable.

In another context, namely for the purpose of copying protection, it is proposed in EP-B-673 319 to use interference pigments a particle size of 5 to 30 microns on a colored background to press. If the interference pigments are on a complementary color pigment printed substrate can be applied, wrong colors arise when copying up to the invisibility of the copied Interference pigments.  

The color codes proposed in the prior art are by the The complexity of the color particles used is complex and corresponding expensive to manufacture. In addition, testing them is complex since it at least one dark room for testing and possibly still additional, expensive and possibly maintenance-sensitive help medium such as a UV light source and the like. Beyond that the possibilities of combining different color codes producing different colored color particles, very limited.

The object of the present invention is a color coding for counter would be available, in particular for securities, which numerous variation possibilities opened at low costs and which inconspicuous, that is, not easily recognizable with the naked eye, but is still detectable without much effort.

According to the invention, this is done by color coding with the features of claim 1 solved. In subordinate claims are a corresponding value document and security element specified. In of it dependent claims are special configurations and Developments of the invention specified.

The invention is based on a narrow with the color particles used Related combination of features, namely on the one hand the "particle size" and on the other hand the "particle concentration". The parties According to the invention, the kel size is selected such that the individual particles also are no longer perceptible to the naked eye. The particle con concentration is chosen so that it is not seen by the human eye as a coloring exercise of the product.  

Such a color coding can be created with simple color particles the. It is imperceptible to the naked eye, falls as a genuineness or Identification feature is therefore not based, but is nevertheless with the simplest technical aids, such as a magnifying glass or a simple microscope, recognizable. In addition, by combining different colors Particles with easily distinguishable from each other for the human eye Color tones an enormous variety of color coding can be achieved.

In terms of "particle concentration" not as coloring of the product is understood "and the particle size" with the naked eye is not perceivable ", are relative terms that in a certain sense Dimensions are also subjective. A specific definition of these terms is on due to the individual color sensation and the individual visual acuity of the human eye not possible and only roughly empirically determine.

The color sensation of the human eye depends not only on the concrete Hue as such but essentially also from the color saturation and the Color brightness of the hue or from the contrast to the background. Je ge ringer the color saturation ("glow of color") and the contrast, the more less for a given particle concentration than coloring the Perceived product. The same applies to visual acuity or that Resolving power of the human eye. Because during contrast colors may still be perceptible for a given particle size bar or dissolvable, less contrasting colors in the the same particle size can no longer be perceived. Also is too keep in mind that the visual acuity with age and also with the visual distance decreases. During the "near point" at which the human eye sees the 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 poor is more than that of a 20 year old.

Taking into account the aforementioned unavoidable terms Preferred areas of particle size are between 1 µm and 100 microns, especially 10 microns to 30 microns, and preferred areas of perfume kel concentration, in the event that the particles are mixed into a Paper pulp, between 10 g and 1000 g per ton of paper produced, in particular about 100 g per ton of paper produced, depending on the color, Color saturation and color brightness of the particles as well as beyond depending on the particle material. Because the required particle con concentration (based on the mass of paper) also depends on whether at for example the dyes in a transparent resin or polymer matrix are stored or whether colored metal oxide particles are used.

The color particles can be mixed with the product in many different ways get connected. For example, the particles of a printing ink, preferably in a concentration of 0.1 wt .-% based on the pressure color can be mixed, which is preferably white or transparent, the but can also be colored, provided that the color particles against can be clearly distinguished from the human eye by this coloring can. But also mixing the particles into a plastic or Paper pulp is possible. The particles can also be on or in one Plastic carrier material are provided, which for example is at least partially embedded in a paper pulp. The plastic Carrier material can be in the form of a security thread, one Mottled fiber or a planchette.  

However, the plastic or paper backing material can also be on anyone any other object, for example in the context of product security measures to be attached. The carrier material is in this Case preferably designed as a label. If the carrier material Be is part of the object to be secured, as is the case with Auf tear threads is the case, of course, any other shape possible.

The color coding preferably comprises more than just one color. To in In this case, ensure that the different colors match the Magnifying glass or microscope easily with the human eye from each other to distinguish, it makes sense to use color particles with the basic colors Yellow, red, blue and possibly additional color particles with the da to use between lying hues orange, violet, green. As offer further colors that are easily distinguishable from the aforementioned colors the mixed color brown and also black. Leave in addition some hues simply because of different brightnesses distinguish, for example light blue and dark blue.

Particles in the aforementioned colors can be easily and inexpensively Create way. Also easy to manufacture, but inherently worth it colored particles made of valuable substances are fuller and therefore more expensive zen such as gold, ultra man, malachite green, garnet and the like chen. For high quality value documents, the use of such can be more valuable Particles make sense to reduce their attractiveness to counterfeiting without thereby producing the color coding or checking the color labeling becomes more complicated.  

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 available 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 each
84 versions of three colors each
126 versions of four colors each
126 versions of five colors each
84 versions of six colors each
36 versions of seven colors each
9 versions of eight colors each
1 version every nine colors.

Using simple, easily distinguishable color particles there is already an enormous number of different color codes produce. Adding just one more color already results double the number of variants, i.e. 1023.

Conversely, the foregoing suggests that it is for reasons The easier to distinguish is to avoid particles of the same To use hues that are only insignificant in color brightness or Distinguish color saturation. On the other hand, no shades should ver that are so close together in the spectrum that they can be used are not easily distinguishable from 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 O 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.

To achieve the advantages of the invention, it is a question of for the color particles used, scatter around simple, angle-independent end color particles, either based on selective absorption or more diffuse Scatter based. In addition, the color particles reflect in the visual Spectral range to the human eye without additional appara tive effort, apart from a simple technical aid, such as with a magnifying glass or a microscope. The magnification The factor of these aids depends on the size of the equipment set particles, d. H. the smaller the particles, the stronger the Magnification factor. With particle sizes of about 50 µm and more a magnifying glass with 8x magnification (8 ×) is usually sufficient. at Particle sizes of less than about 50 microns, especially in the range of 10 µm, a microscope with 100x magnification is recommended (100 x).

However, this does not rule out that other color effects are additionally featured can be seen. A particular embodiment of the invention provides hence the colored particles with any machine readable Features are combined, for example luminescent sub punches that are not visible to the naked eye in daylight. This Luminescent substances can be provided separately, but are preferably together with the dyes in the resin or polymer embedded matrix. Such particles can then be seen both with the eye can also be detected with sensors, especially if the lumines ornamental substances only outside the visual spectral range luminesce, for example fluoresce in the UV or IR spectral range. This combination is particularly advantageous if, in addition to a label proof of authenticity should also be possible.  

Easily available luminescent dyes, but also specially developed for safety-related applications Luminescent substances are used. The first mentioned luminescence substances are preferred to the number of variants for the Increase color coding. Fluorescent substances such as. B. Distilbene derivatives with blue fluorescence or flavin or flavone dyes with yellow-green fluorescence. The especially for safety-related Applications developed luminescent substances are, for example wise around host lattice doped with rare earth elements.

Although basically a single machine feature for the real proof would suffice, preferably so many machines Features such as color particles can be read. This has the advantage that the full code is both eye and is recognizable with sensors. In this respect, one is particularly preferred Embodiment in which each of the different color particles Luminescent substance is admixed that lumi in approximately the same color nesces like the color particle in which the luminescent substance is embedded. Luminescent substances that are in the visible can also be used Show body color spectral range, i.e. without the human eye additional source of excitation appear in color, but with excitation additional fluoresce.

As mentioned at the beginning, there are different options for the products to be provided with the color coding, for example by storing the Particles in the volume of the product or by applying it on the top surface, for example by printing with Flexoprint or through Spraying on using a device according to EP 0 659 935 B1. The flexo Printing inks preferably consist of a colorless varnish with addition  such a small amount of particles that the printed color is not in itself looks colorful. In the case of flexographic printing, the surface can be customized Choose other patterns that are imperceptible to the naked eye are, but especially when the particles with fluorescent substances or other machine-readable features are combined by sensors are detectable.

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 strip the color particles or not to apply in strips and to create an additional strip, which only contains machine features that cannot be seen with the naked eye are cash. This opens up further coding possibilities.

Some exemplary embodiments of the invention are given below:

example 1

A paper sheet was formed, the substance suspension of which before the sheet formation with finely ground iron oxide Fe ₂ O ₃ (red, particle size approx. 100 µm) and additionally with finely ground chromium oxide (green, particle size approx. 100 µm) in an amount of each about 200 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 in it were easily recognizable with a magnifying glass of 8 × (8 ×). 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 identical to that in Example 1. The paper stock suspension was about 200 g of color particles per ton produced paper added. In this case the color particles were but made of a melamine resin, which is used to produce red Color particles mixed with a red organic dye and for generation green color particles have been mixed with a green organic dye was. The melamine resin is e.g. B. Maprenal VMF 3921w / 85WA (manufacturer: Vianova AG), the 5% by weight red or green dye, based on the amount of dry resin added. After the end hardening of the melamine resin thus dyed resulted in a brittle, light meal hard resin from which the color particles (particle size approx. 20 µm) by Mah len and added to the pulp suspension. The particles were with a microscope with a 100-fold magnification (100 ×) recognizable and easily distinguishable without the paper noticing showed clear coloring.

Example 3

A paper sheet of 90 g / m ^{2 was} formed, the stock 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 produced from Maprenal VMF 3921w / 85WA melamine resin (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. The mixture of Maprenal and Nylosan Rhodamin B300 or Blankophor BA is then 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 8300 has a red body color in the visible spectral range. The particles were recognizable with a microscope at 100 × magnification (100 ×) and easily distinguishable without the paper showing any perceptible coloring.

Example 4

In a pulp suspension, e.g. B. a suspension of 100 g of pine sulfate pulp in 5 l of water
10 mg ultraman (blue, particle size approx. 40 µm)
20 mg iron oxide Fe ₂ O ₃ (red, particle size approx. 30 µm)
20 mg of Blankophor BA resin particles, as produced in Example 3 (colorless, fluorescent blue when excited in UV, particle size 25 µm) and
10 mg of mica (shiny metallic, 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, there is also one in the visible spectrum blue fluorescence.

Claims (26)

1. Color coding for marking objects, comprising in visual spectral range reflecting, angle-independent scattering colored particles that are so small that they are mere human Are imperceptible to the eye, but with a magnifying glass or a microphone Skop are recognizable, and which existed in such a low concentration that the color coding from the naked human eye is not a color exercise of the object. 2. Color coding according to claim 1, wherein the color coding different colored particles easily distinguishable to the human eye. 3. Color coding according to claim 2, wherein the colors of the particles out choose from the group of basic colors red, yellow, blue and / or in between colors orange, green, violet. 4. Color coding according to claim 2 or 3, wherein the color coding is colored Particles with approximately the same color but easily distinguishable Color brightness includes. 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 are made 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 in which paper is stored. 10. Color coding according to claim 9, wherein about 100 g of colored particles per Ton of paper in which paper is stored. 11. Color coding according to one of claims 1 to 7, wherein the particles the surface of an object to be marked is applied. 12. Color coding according to claim 11, wherein the colored particles only in Partial areas of the surface of the object to be marked are upset. 13. Color coding according to claim 12, wherein the partial areas are strip-shaped are trained. 14. Color coding according to one of claims 1 to 13, wherein additionally machine-readable features are available. 15. Color coding according to claim 14, wherein one of the number different number of different machine-readable colored particles Features 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 separate from the colored particles. 18. Color coding according to claim 17, wherein the machine-readable Features are present in a strip separate from the colored particles. 19. Color coding according to one of claims 14 to 18, wherein the maschi Readable features are formed by luminescent substances. 20. Color coding according to claim 19, wherein the luminescent substances in fluoresce in a color corresponding approximately to the colored particles. 21. Color coding according to claim 19 or 20, wherein the luminescent Luminescent substances 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 selected from the group of the following substances: gold, ultraman, Malachite green, garnet. 24. Security element for application or storage on or in a Subject, wherein the security element is a color coding according to a of claims 1 to 23. 25. Document of value comprising a color coding according to one of the claims che 1 to 23 or a security element according to claim 24.   26. Value document according to claim 25, consisting of paper.