EP0911787B1 - Laserlabels and their use - Google Patents

Description

Technical labels are used in many areas for high quality applications, as type plates for vehicles, machines, electrical and electronic devices, as control labels for process flows as well as guarantee and test badges. frequently these applications inherently involve the requirement for a more or less pronounced level of security against counterfeiting. This security against counterfeiting applies primarily for the period of attachment and the entire useful life on the part to be marked: removal or manipulation is only to be done with destruction or visible, irreversible change. In particularly sensitive fields of application a security level must also apply to the manufacture of the labels: too easy procurement and labeling of such labels and production Plagiarism would prevent unauthorized persons from unauthorized distribution of articles enable.

For the rational and variable production of high-quality labels, especially in technical-industrial applications, the laser marking of suitable base material is becoming increasingly popular. DE G 81 30 861.2 describes a multilayer label in which a different colored cover layer is removed by the laser beam and thus the color contrast to the next layer enables high quality and legibility inscriptions. This label is a type of engraving, which eliminates the possibility of manipulation as with traditional printing with colors and inks. In DE G 81 30 861.2 , the label film is so brittle due to the raw materials used and the manufacturing process that removal of the bonded labels from the adhesive substrates is only possible with destruction.

An additional security level is given in the single-layer laser label according to DE G 94 21 868: in addition to the advantageous properties of DE G 81 30 861.2 the inscription is not here by engraving in the top layer, but by a Color change in the plastic layer itself causes what is later manipulation largely prevented on the labels.

The only potential gap in the security chain is that such Single and multi-layer labels for laser marking are freely accessible - for accordingly High quality goods could thus be sourced from the labels and lettering to be regarded as possible and worthwhile even with expensive laser units.

In order to remedy this, the development goal was to develop the label pre-material for to design the later lettering in such a way that it is always authentic original material can be identified with little effort and non-destructively. For those already named laser labels is in principle a subsequent identification possible, but with unacceptable analytical effort and not non-destructive.

Known for particularly security-related goods such as banknotes, checks, checks and Personal identification cards etc. are various procedures to prevent counterfeiting to ensure. In addition to watermarks, printing with filigree patterns, application Holograms also occasionally turn into "invisible" markings used.

JP 08/328474 describes a textile clothing label which is printed on the top with a transparent, fluorescent color, the woven design and printed image being said to be approximately congruent. A similar superficial printing with UV-active, photochromatic inks is described in WO 8801288; however, an additional protective layer against oxygen and water is necessary to protect the chemicals in this colored layer.

In FR 2734655 , security marking for checks is achieved in that the printing under an only IR-transparent layer is invisible in the visible wavelength range, but is machine-readable / identifiable with special IR light.

In EP 727316 , concealed security against forgery is achieved in that two reactive components are present in an extra layer , especially on paper, which give rise to a color reaction under pressure - this is, however, irreversible.

The use of electrically conductive or magnetic inks for printing on the surface are described in JP 08/054825 and CN 1088239 . Systems of this type can only be used to a very limited extent for label applications on complex metal parts such as, for example, vehicle and machine parts.

The ink ribbons described in JP 07/164 760 with fluorescent particles that can be excited by IR are transferred by heat using thermal transfer printers. Although the prints contain a hidden tamper-evident designation, the printing is superficially applied with solvents, heat as well as mechanically removable or changeable.

DE 4231800 describes labels which, for security against counterfeiting , leave indelible traces on the adhesive substrates by means of sublimation dyes or corrosive substances - however, the traces can only be identified after the label has been removed, which is often undesirable or impossible.

In EP 453131 for highly secured papers such as passports, shares, bank notes etc. it is described that fluorescent, especially UV-fluorescent indicators are incorporated into an intermediate layer between two permanently bonded layers of paper, which are only detectable when light of suitable wavelength is transmitted through the laminate, but not through reflection in reflected light. This system is unsuitable for applications in which a transmission of light through the glued label is not possible, as well as for the completely opaque laser labels.

All of these methods are applied superficially or are superficially effective and therefore not or only to a limited extent usable for the known laser labels, because here for e.g. Nameplate applications optically high quality and extremely resistant Surface would change and deteriorate. Would be particularly annoying such a modification in the as a technical standard for type plates visible two-layer labels with a high-gloss black top layer and white base layer. Also include those known in the art Subsequent superficial anti-counterfeiting the potential, mechanical or manipulations using heat, chemicals, etc.

The object of the present invention was therefore to provide a largely "invisible" additional Install security level in the label stock, so that with as possible verification of originality is carried out quickly and non-destructively with little effort can be. This invention became an example of the laser-inscribable labels carried out, but is for the specialist readily for similar problem cases as printed labels, self-adhesive tapes, etc. available.

This task is solved by a laser label, as described in the claims is marked.

In particular, a way was found as a solution to the problem that allows it to be variable and a cost-effective customer-specific security marking at the label pre-material level to be installed: especially when using the standard label film DE G 81 30 861.1 or DE G 94 21 868 or similar is on the back of the slide in front of the Coating with adhesive, printing is carried out. Are used here special printing inks with thermochromic pigments or phosphors, in particular with fluorescent colors or in particular with electron beams, X-rays, IR or Long-afterglow color pigments that can be excited by UV radiation. After The material received is printed with self-adhesive as standard coated, dried and covered with release paper.

Different color pigments and - fabrics are used. The most common are long-afterglow (phosphorescent) or fluorescent pigments that are only or predominantly caused by UV radiation be excited and emit in the visible region of the spectrum (as Overview see e.g. Ullmann's Encyclopedia of Technical Chemistry, 4th edition, 1979, Verlag Chemie). However, IR-active luminescent pigments are also known. Examples of systems with UV fluorescence are xanthenes, coumarins, naphthalimides etc., some of which under the generic term 'organic phosphors' or 'optical brighteners' in the literature be performed. The addition of a few percent of the phosphors in question is sufficient, the integration into a solid polymer matrix is particularly favorable in Regarding luminosity and stability. For example, recipes can be used with RADGLO® pigments from Radiant Color N.V./Holland or Lumilux® CD pigments by Riedel-de-Haen. Inorganic phosphors are also suitable; as have long afterglow substances, especially with emission of light in the yellow area metal sulfides and oxides, usually in combination with suitable activators, as cheap proved. These are for example under the trade name Lumilux® N or as in terms of stability, luminosity and afterglow duration improved luminous pigments under the Trade names LumiNova® available from Nemoto / Japan.

In principle, luminescent materials are also suitable, which are caused by electron beams, X-rays etc. are excited as well as thermochromic pigments, which change with temperature change reversible coloring; is also the use of electrically conductive paints possible - however in these cases the identification is carried out on the glued In practice, label is cumbersome and more complex than visualization using light suitable wavelength.

When selecting the color pigments, care should be taken that they are used for the further manufacturing process the labels (e.g. adhesive coating) are sufficiently stable and secure not irreversible in the process conditions (possibly thermal drying, electron beam or UV curing, etc.) change. Advantageous for permanent use of the labels is that these mostly sensitive phosphors are embedded in a polymer matrix and are additionally protected by the color film.

This additional marking is from the front in the area of the laser marking not recognizable (except for a transparent or translucent layer), but just around the label on the edge. To make it clearly recognizable at the label edge ensure strong luminous color pigments in sufficient layer thickness printed - the additional security is nevertheless covered and therefore inconspicuous. This Security marking is protected from external access because of the pressure embedded between the label film and the adhesive layer: subsequent manipulations are not to be feared, as a replacement of the known laser labels only destruction of the paint film is possible.

Customized "fingerprints" of the labels can be realized by different Colors or patterns can be printed. Especially regular lines and Line patterns leave characteristic patterns of luminous dots on the label edges arise and are also particularly material and cost-saving. After Punching or laser cutting of the label and application on the adhesive substrates is at the edge of the label when choosing a suitable lighting source to recognize a pattern that is characteristic of colors and geometries.

The advantage of this security label is particularly logistical and cost-effective noticeable: it can affect commercially available printing inks and non-specific label film material can be resorted to, while the latter is otherwise customized is to be produced. As such standard raw material, however, at the label manufacturers is only used as an intermediate product for your own production and not on the market unauthorized access is excluded. They are also small lot sizes and short delivery times possible.

In the expression according to the invention, z. B. fall back on the two-layer film material described in DE G 81 30 861.1 . Before coating and covering with release paper, however, the back is printed over the entire surface, using scatter printing or in particular with defined geometries. Printing inks with a high proportion of luminous pigments are preferably applied by screen printing in order to achieve layer thicknesses in the range from 0.5 to 50 μm, preferably from 2 to 25 μm. After the adhesive coating and covering, the label pre-material is punched for the desired formats and sizes or cut out with a laser beam. When stuck to these labels, there is no indication of a hidden level of counterfeiting, provided that phosphors are selected whose light emission is generated by excitation with light outside the visible range; Only after irradiation with suitable light sources does the luminous pigments on the edges of the label be excited. Here and only here, therefore, are markings visually recognizable, which result in a predetermined pattern of luminous dots. With different line widths and heights, the illuminated dots can be designed differently. This means that an easily detectable security level can be implemented simply, inexpensively and, if required, customer-specifically via geometry and color selection.

Such labels can be easily and quickly identified after application: except a suitable light source, usually a UV lamp, and, if necessary, a privacy screen in order to Hiding ambient light that disturbs the viewer is nothing special Equipment necessary. After checking, the label remains unchanged received previous function.

Example 1:

As described in detail in DE G 81 30 861.2, the patented two-layer laser label is made from a thin black top layer and a thicker white base layer - before the white side of the paint film is coated with self-adhesive, customer-specific security markings are applied to this side using screen printing. A UV screen printing ink is selected as the color, which is produced according to the following recipe: 10% by weight UV-Tronic HM luminescent paste 806.025 90% by weight Bargoscreen UV series 78-2 "transparent" (both ink components from SICPA Druckfarben GmbH).

Both components are mixed intensively and mixed with 2% UV-Tronic photo initiator 806.330. The printing is done with a Gallus screen printing unit and a Screeny DW screen (color layer thickness approx. 40 µm and a resolution of 300 µm). The printing takes place in a line grid and is cured with a commercially available UV lamp. Coating with a polyacrylate PSA of 50 g / m ² and covering with a commercially available silicone paper result in the label material for further customer-specific uses.

Punching or laser cutting turns sheet or roll goods into receive the desired label formats - when the label is irradiated with a UV lamp [Wavelength maximum at about 350 nm] are at the edges of the labels, where the printed lines meet the cut edges, bluish luminous dots visible. Depending on the selected line grid, there are characteristic point sequences. A screen protector to darken the lens is helpful for clear detection Label area in front of ambient light.

Example 2

Like example 1, but instead of the screen printing ink listed above, a recipe is made 10% by weight UV-Tronic HM luminescent paste 806.025 90% by weight Bargoscreen UV series 78-2 "white" with 2% UV-Tronic photo initiator 806.330 used (All ink components from SICPA Druckfarben GmbH).

Instead of printing with a line grid, full-area printing takes place, see above that after punching out the desired label formats around the label suitable UV radiation on the cut / punched surfaces is recognizable.

Claims (7)

1. Laser label comprising at least one polymer layer which is coated on one side with a self-adhesive composition, which is in turn optionally covered with a release paper or a release film, characterized in that a printing ink is applied by printing between polymer and self-adhesive composition, the printing ink comprising thermochromic pigments or luminescent substances, especially daylight fluorescent colours or, in particular, comprising long-afterglow colour pigments that can be excited by electron beams, X-rays, IR or UV radiation.
2. Laser label according to Claim 1, characterized in that the printing ink is applied by printing to the underside of the polymer before the latter has been coated with the self-adhesive composition.
3. Laser label according to Claim 1, characterized in that the printing ink is applied in the form of a mark which can be perceived in particular from the side of the laser label (at the label edge).
4. Laser label according to Claim 1, characterized in that the printing ink is applied in the form of patterns of lines and strokes, visible as points of luminescence at the edge of the laser label.
5. Laser label according to Claim 1, characterized in that the polymer comprises an additive which shows a reversal of colour change under laser irradiation.
6. Laser label according to Claim 1, characterized in that on that side of the polymer facing away from the self-adhesive composition there has been applied a further polymer layer which is partially removable by means of laser radiation, said further layer consisting in particular of an electron-beam-cured coating film whose thickness is 1 - 20 µm and whose colour contrasts with that of the underlying layer.
7. Use of a laser label according to one of Claims 1 - 6 for anti-counterfeit marking.