DE20016660U1 - Luminescent coating material - Google Patents

Description

Gesthuysen, by Rohr & Eggert

00.974.6.de Essen, 25 September 2000

Utility model application

the company

Jackstädt GmbH Bembergstrasse 1-4

42103 Wuppertal

with the label

"Luminescent coating agents"

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Luminescent coating agents

The present invention relates to a luminescent coating composition. In particular, the present invention relates to a coating composition comprising a binder and luminescent fibers and to the use of this coating composition, in particular for marking objects.

The term "luminescence" generally refers to the emission of light produced by gases, liquids or solids after a suitable energy supply, whereby the emitted light can be in the visible range, the UV range, the infrared range and/or the spectral range. Two forms of luminescence are distinguished, namely fluorescence and phosphorescence. For further details, please refer to Römpp Lexikon Chemie, 10th edition, keywords "luminescence", "fluorescence" and "phosphorescence" as well as to the literature cited there.

Coatings in which luminescent dyes or pigments are homogeneously incorporated are already commercially available. For example, adhesives with fluorescent color pigments are used for the optical detection of labels. However, these coatings are not used for security markings because they are relatively unspecific. In the case of paper and textile coatings, they would also be outshone by the whitening agents (OBA) that they usually contain. In addition, the quantities of fluorescent dyes that need to be used in these cases are relatively large.

From the German laid-open specifications 195 10 468 and 195 49 374, which go back to the applicant itself, a translucent film which permanently fluoresces in daylight is known, wherein the fluorescence effect is produced by incorporating color pigments in large quantities into the fluorescent film, evenly distributed over the entire film.

A similar, permanently fluorescent adhesive film made of a translucent film material that is coated with larger amounts of a fluorescent dye.

·

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material, coloured over the entire film, in particular for use in the sign and advertising industry, is described in the German utility model 91 17 086 and in the European patent 0 594 765.

However, the previously mentioned state-of-the-art films are not suitable for security marking, but rather are designed to create an optical effect that is preferably used for advertising purposes, because these films display a permanent luminescence that is visible to the naked eye. Furthermore, a relatively large amount of dye pigments is required to create the luminescence effect evenly distributed across the entire film.

The object of the present invention is to provide a system which enables objects to be marked. The ability of certain substances to luminesce is to be exploited. In particular, the system should enable the attachment of a security or identification function.

The present invention therefore relates to a coating composition which contains at least one organic binder and luminescent fibers, wherein the luminescent fibers consist of a fiber-forming material with at least one luminescent dye or pigment distributed therein.

The coating composition according to the invention can be used to mark objects of all kinds by applying the coating composition according to the invention to the surface of these objects.

The organic binder can be any type of binder. However, the organic binder must be selected in such a way that the luminescent pigments or dyes are not attacked or dissolved from the fiber. This also applies to other substances contained in the coating compound, in particular to any solvents contained in the coating compound.

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Examples of organic binders suitable according to the invention are varnishes of all kinds, in particular clear varnishes. The organic binder can also be paper or film coating slips. Furthermore, the organic binder can be adhesives of all kinds; examples of adhesives that can be considered according to the invention are pressure-sensitive adhesives, e.g. solvent-based pressure-sensitive adhesives, dispersion-based pressure-sensitive adhesives or hot-melt pressure-sensitive adhesives.

The organic binder used in the coating composition according to the invention is in particular a clear, i.e. transparent or essentially transparent organic binder. However, it is equally possible to use cloudy to opaque binders, in particular if the coating composition is applied thinly and the fibers "come out" of the coating.

The luminescent fibers used according to the invention are known per se from the prior art (see, for example, German laid-open specifications 195 39 315 and 198 02 588 and US patent specification 5,674,437) and are commercially available. Manufacturers of such fibers include, for example:

the company Honeywell, Speciality Chemicals, formerly Riedel-de-Haen, which sells a variety of luminescent fibers under the brand name Lumilux®, whereby the luminescent dye pigments distributed in the fibers emit light of different wavelengths or colors depending on the molecule (e.g. fibers of the type Lumilux® Blue MF-P 831/22/3-LT, Lumilux® Red MF-P-870/LT, Lumilux® Yellow MF-P 833/22/3-LT etc.).

Up to now, fibers of the type described above have only been incorporated into the production of fibrous materials such as paper or textiles; in paper production, these fibers are added to the pulp and in textile production, to the raw material from which the fibers are spun. This results in relatively large production batches. The luminescent fibers serve as a security feature in these products that is difficult to counterfeit, e.g. in banknotes. The basis of these fibers are, for example, silk, cellulose, cellulose acetate, polyamides, polyesters, etc.; these are colored with organic or inorganic luminescent dyes (see the

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German laid-open specifications 195 39 315 and 198 02 588 and US patent specification 5,674,437).

However, in the state of the art, fibres of the type in question have not yet been used to produce functional coatings.

The production of the luminescent fibers used according to the invention is known from the prior art. For example, reference can be made to the publications already mentioned, the German laid-open specifications 195 39 315 and 198 02 588 and the US patent specification 5,674,437, the content of which is hereby incorporated by reference.

The general procedure for producing luminescent fibers is to add the luminescent dye to the fiber-forming material or a solution thereof and spin fibers from it. It is also possible to bring the fibers or the fiber-forming material into contact with a solution or dispersion of the luminescent dye (e.g. by spraying, dipping, soaking, etc.) and to dry the fibers thus obtained.

The amount of luminescent fibers used in the coating composition according to the invention and the nature of the fibers, in particular the length and thickness of the fibers and the type of fiber material and dye, are coordinated so that the coating process is not disturbed. On the other hand, however, it must be possible to achieve an identification function.

In general, the coating composition according to the invention contains, based on 100 parts by weight of the coating composition, 0.0001 to 10 parts by weight, in particular 0.001 to 7.5 parts by weight, preferably 0.001 to 5 parts by weight, of the luminescent fibers.

The length of the luminescent fibers used according to the invention can vary within wide limits and is generally in the range from 0.05 to 10 mm, in particular in the range from 0.1 to 5 mm.

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The thickness of the luminescent fibers used according to the invention can also vary within wide limits and is typically in the range from 1 to 1,000 μιλ, in particular in the range from 10 to 100 μιλ.

The fiber-forming material can be any known fiber-forming material, provided that it is compatible with the coating composition according to the invention. Examples of fiber-forming materials suitable according to the invention are silk, cellulose, cellulose acetate, polyamides, polyesters, polyacrylates, polyolefins, polyurethanes, cotton, etc., as well as mixtures of the aforementioned materials.

The fibers used according to the invention typically contain the luminescent dye or the luminescent pigment in an amount of more than 5 up to 50 wt.%, in particular from 7 to 40 wt.%, preferably 10 to 20 wt.%, based on the total weight of the fiber.

The luminescent dye or pigment may be inorganic or organic in nature.

In particular, the luminescent dye or pigment should - at least partially - exhibit a luminescence effect when excited by ultraviolet irradiation. The luminescence effect can be based on fluorescence or phosphorescence.

According to one embodiment of the present invention, the luminescent dye or the luminescent pigment is selected such that it emits in the visible and/or infrared light range when excited with ultraviolet radiation. In particular, the luminescent dye or the luminescent pigment is selected such that it emits at least in the visible light range when excited with ultraviolet radiation.

For example, the luminescent pigment can be an inorganic phosphor. Examples of this are phosphates, tungstates, oxides, silicates and aluminates of the alkaline earth metals, transition group elements or rare earths, as well as the halides of the alkali or alkaline earth metals, which are

one or more activators (e.g. Mn ²⁺ , Mn ⁴⁺ , Sb ³⁺ , Sn ²⁺ , Pb ²⁺ , Cu ⁺ , Ag ⁺ , rare earths). Further examples are zinc sulfides, zinc cadmium sulfides, alkaline earth aluminates, alkaline earth sulfides and alkaline earth silicates and mixtures thereof, each doped with at least one transition metal and/or lanthanide element. For further examples, reference can be made to the publications already cited, German Offenlegungsschriften 195 39 315 and 198 02 588 and US Patent 5,674,437, the content of which is hereby incorporated by reference.

The luminescent dye or pigment can also be an organic phosphor. Examples of these are luminescent, in particular fluorescent, homo- or heterocyclic aromatic systems, such as in particular luminescent, preferably fluorescent, benzene, acridine, xanthene, thioxanthene, pyrene, stilbene, coumarin and pyrazoline derivatives and mixtures of the aforementioned compounds.

The luminescent dye or luminescent pigment is generally a fluorochrome (fluorescent dye). However, the invention also envisages the possibility that the luminescent dye or luminescent pigment is a fluorogen which is only converted into a fluorescent chemical compound by a chemical reaction (e.g. enzymatically catalyzed or not). In other words, the term "luminescent dye or luminescent pigment" as used in the context of the present invention refers to both the luminescent dye (pigment) itself and a suitable precursor which is converted into the luminescent dye (pigment) by a chemical reaction.

According to a particular embodiment of the present invention, it is possible to combine different fibers in the coating composition according to the invention, to which different luminescent dyes or pigments are applied, which emit light of different wavelengths or spectral colors after excitation with suitable energy.

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In addition to the organic binder and the luminescent fibers, the coating composition according to the invention can also contain conventional additives, processing aids or additives of all kinds. However, the additives, processing aids or additives must be selected in such a way that the luminescent pigments or dyes are not attacked or dissolved from the fiber. Examples of additives, processing aids or additives suitable according to the invention are fillers, antioxidants, anti-aging agents, additives for protection against UV radiation, additives that affect flowability, solvents and dispersants, emulsifiers or color pigments.

According to a particular embodiment of the present invention, the coating composition according to the invention can contain a selective UV anti-aging additive which absorbs the short-wave portion of sunlight. This preserves the durability or luminescence ability of the fibers over longer periods of time.

The present invention also relates to a process for producing a luminescent coating on surfaces made of plastic, paper, cardboard, textiles or metals by applying the coating composition according to the invention. The coating is generally applied to the surface with a layer thickness of 0.1 to 1,000 μηι, in particular 1 to 500 μια. The coating process is designed in such a way that it is not disturbed by the presence of the fibers, due to the composition of the coating composition according to the invention, in particular the amount, length and thickness of the luminescent fibers used according to the invention. For the layer thicknesses in question here of 0.1 to 1,000 μηι, in particular 1 to 500 μια, methods such as doctor blade application, roller application, spray application or pouring application can preferably be used.

This opens up, for example but not exclusively, the following new application possibilities:
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The coating composition according to the invention is used in particular to produce a luminescent coating on the surface of objects. Almost any type of surface can be coated with the coating composition according to the invention, for example surfaces made of plastics, paper, cardboard, textiles or metals.

The application of the luminescent surface coating can be used to mark objects, i.e. to provide an identification or security function. If the fibers are incorporated into a pressure-sensitive adhesive, for example, this can be used in combination with transparent films as a laminating film for valuable documents; the laminating film enables the efficient production of small and very small batch sizes. Small stickers, possibly in combination with easily tearable security film, can be used as security labels, for example.

In conjunction with the coatings described above, different color combinations, i.e. combinations of fibers with different phosphor pigments, enable identification under UV light. In this way, differently marked objects can be easily and uniquely identified.

Furthermore, the luminescent coating composition according to the invention can also be used to create an optical effect. For example, if the luminescent fibers are incorporated into a paint, interesting lighting effects for advertising or product design can be achieved in conjunction with suitable light sources.

The coating composition according to the invention can be used in particular to coat web-shaped materials of all kinds, such as metal foils or plastic films, in particular label films or self-adhesive label films, adhesive tapes, paper, cardboard and cartons of all kinds, textiles of all kinds, or fiber materials. The plastic films can be transparent or non-transparent, e.g. colored films.

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According to a particular embodiment, the coating composition according to the invention can be used in the production of label film.

Label film generally consists of an actual film layer, on one side of which a pressure-sensitive adhesive layer is applied, whereby the latter can be covered with a removable protective paper (e.g. siliconized or wax-coated paper); if necessary, the film layer on the side facing away from the pressure-sensitive adhesive layer can also be coated with a printing varnish to improve printability.

According to the present invention, a coating composition according to the invention comprising pressure-sensitive adhesive, luminescent fibers and optionally conventional additives can be used as the pressure-sensitive adhesive layer; this film can then be used, for example by punching or cutting, to produce labels or stickers whose pressure-sensitive adhesive layer has a security function.

It is also possible to coat the label film with a coating composition according to the invention made of varnish (e.g. printing varnish), luminescent fibers and optionally conventional additives on the side of the film facing away from the pressure-sensitive adhesive layer; this film can then be used, e.g. by punching or cutting, to produce labels or stickers whose varnish layer has a security function. The varnish can be, for example, a so-called printing varnish, which enables or improves the printability of the label film.

Of course, in the case of the label film described above, both the pressure-sensitive adhesive layer and the optionally present lacquer layer can be produced starting from a coating composition according to the invention.

The present invention also relates to the objects to whose surface the coating composition according to the invention is applied. For examples of such objects, reference can be made to the possible uses described above.

-&Igr;&Ogr;-

An advantage of the present invention is that luminescent fibers with luminescent dyes applied to them - compared to homogeneous coloring with the luminescent dye particles themselves - enable a local concentration of the emission intensity and thus better detectability. This allows the use of much lower pigment or dye concentrations overall. In other words, by applying the dye pigments to the fiber material, high local concentrations of dye can be achieved with a low absolute concentration in relation to the coating mass and thus good detectability.

&iacgr;&ogr; i.e. achieve a favorable signal-to-noise ratio.

By mixing fibers of different luminescence colors and by using different mixing ratios of the fibers, there is almost unlimited scope for different codings.

One advantage of introducing the fibers into a coating compound and then coating paper, textiles, foils or other objects, for example, is that it can be used much more universally. Above all, small batch sizes can be produced economically. Using a coating compound according to the invention in the form of an adhesive or a varnish as a coating results in additional safety functions.

The amount of fibers in the coating mass and the fiber dimensions are generally such that when viewed with the naked eye in daylight, the fibers are not or hardly recognizable; in the case of clear, transparent coating masses, for example, they are perceived at most as a slight clouding in the coating. When stimulated by a suitable light source, for example under a UV lamp, the luminescence of the fibers is easily visible to the naked eye due to the high local dye concentration, provided that dyes are used which emit at least partially in the visible wavelength range after stimulation.

The safety function can be controlled almost arbitrarily by selecting the phosphor. If you choose phosphor pigments that only emit in the IR spectral range after excitation with light of suitable energy, you get

an additional safety feature, since the emission is not visible to the naked eye and can only be detected using suitable methods, e.g. IR spectroscopy.

Further embodiments, variations and advantages of the present invention will be readily apparent and achievable by those skilled in the art upon reading the description without departing from the scope of the present invention.

&iacgr;&ogr; The present invention is illustrated by the following embodiments, which, however, do not limit the invention in any way.

Examples of implementation
example 1

0.01 part of commercially available fibers of the type Lumilux® Red MF-P 8 70/LT (Honeywell, Speciality Chemicals, formerly Riedel-de-Haen) which luminesce when exposed to UV radiation are stirred homogeneously into 100 parts of a solution of a polyacrylate pressure-sensitive adhesive in ethyl acetate (solids content: 30%).

The adhesive is then applied to a PVC film as a thin layer of 200 μm using a doctor blade and then dried using warm air. The dried adhesive layer (60 μm) is then covered with siliconized paper.

After further processing of the adhesive film by cutting or punching, you finally get self-adhesive labels or adhesive tapes whose adhesive layer shows a red fluorescence in the area of the incorporated fibers when irradiated with UV light. When viewed with the naked eye in daylight, the fibers are therefore not recognizable. Under the UV lamp, however, the luminescence phenomenon is clearly visible to the naked eye.

Example 2

A mixture of various commercially available fibers that luminesce when exposed to UV radiation, namely 0.005 parts of luminescent fibers of the type Lumilux® Red MF-P 870/LT, 0.004 parts of luminescent fibers of the type Lumilux® Blue MF-P 871/LT and 0.002 parts of luminescent fibers of the type Lumilux® Green MF-P 877/LT, is stirred homogeneously into 100 parts of the solution of a polyacrylate pressure-sensitive adhesive in ethyl acetate (solids content: 30%).

The adhesive is then applied to a transparent polyester film as a thin layer of 60 μm using a doctor blade and dried using warm air. The dried adhesive layer (20 μm) is covered with siliconized paper.

After further processing of the adhesive film (e.g. by cutting or punching), a self-adhesive laminating film is obtained which, when irradiated with UV light, displays a locally colored fluorescence - red, blue or green, depending on the fiber - in the area of the incorporated fibers. When viewed with the naked eye in daylight, the fibers are therefore not recognizable. Under the UV lamp, however, the luminescence phenomenon is clearly visible to the naked eye.

Example 3

A mixture of various commercially available fibers that luminesce when exposed to UV radiation, namely 0.005 parts of luminescent fibers of the type Lumilux® Red MF-P 870/LT, 0.004 parts of luminescent fibers of the type Lumilux® Blue MF-P 871/LT and 0.002 parts of luminescent fibers of the type Lumilux® Green MF-P 877/LT, is stirred homogeneously into 100 parts of the aqueous dispersion of a polyacrylate pressure-sensitive adhesive (solids content: 50%).

The adhesive is applied to a silicon paper as a thin layer of 40 μια using an engraved roller and dried using warm air. The dried adhesive (20 μια) is laminated with paper so that the adhesive layer is transferred to the paper. After further processing of the adhesive paper (e.g. cutting or punching), self-adhesive labels are obtained.

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which, when irradiated with UV light, shows a locally colored fluorescence (red, blue or green) in the area of the fibers. When viewed with the naked eye in daylight, the fibers are therefore not recognizable. Under the UV lamp, however, the luminescence phenomenon is clearly visible to the naked eye.

Example 4

A mixture of various commercially available fibers that luminesce when exposed to UV radiation, namely 0.007 parts of luminescent fibers of the type Lumilux® Red MF-P 870/LT and 0.003 parts of luminescent fibers of the type Lumilux® Green MF-P 877/LT, is stirred homogeneously into 100 parts of a polyester varnish.

After the varnish has been applied as a thin layer (20 μηι) to various surfaces, it dries and, when exposed to UV light, displays red or green fluorescence locally in the area of the incorporated fibers. When viewed with the naked eye in daylight, the fibers are therefore not recognizable. Under the UV lamp, however, the luminescence phenomenon is clearly visible to the naked eye.

Claims (28)

1. Coating composition containing at least one organic binder and fibers which comprise a fiber-forming material with at least one luminescent dye or pigment distributed therein. 2. Coating composition according to claim 1, wherein the coating composition contains, based on 100 parts by weight of the coating composition, 0.0001 to 10 parts by weight, in particular 0.001 to 7.5 parts by weight, preferably 0.001 to 5 parts by weight, of the fibers. 3. Coating composition according to claim 1 or 2, wherein the organic binder is selected from the group of lacquers, in particular clear lacquers, paper or film coating slips, adhesives such as pressure-sensitive adhesives, in particular solvent-based pressure-sensitive adhesives, dispersion-based pressure-sensitive adhesives or hot-melt pressure-sensitive adhesives, and mixtures of the aforementioned binders. 4. Coating composition according to one of claims 1 to 3, wherein the fiber-forming material is selected from the group of silk, cellulose, cellulose acetate, polyamides, polyesters, polyacrylates, polyolefins, polyurethanes and cotton and mixtures thereof. 5. Coating composition according to one of claims 1 to 4, wherein the organic binder is transparent (clear) or substantially transparent. 6. Coating composition according to one of claims 1 to 4, wherein the organic binder is opaque or substantially opaque. 7. Coating composition according to one of claims 1 to 6, wherein the length of the fibers is in the range from 0.05 to 10 mm, in particular in the range from 0.1 to 5 mm. 8. Coating composition according to one of claims 1 to 7, wherein the thickness of the fibers varies in the range from 1 to 1,000 µm, in particular in the range from 10 to 100 µm. 9. Coating composition according to one of claims 1 to 8, wherein the fiber contains the luminescent dye or the luminescent pigment in an amount of more than 5 up to 50 wt.%, in particular from 7 to 40 wt.%, preferably from 10 to 20 wt.%, based on the total weight of the fiber. 10. Coating composition according to one of claims 1 to 9, wherein the luminescent dye or the luminescent pigment is of inorganic or organic nature. 11. Coating composition according to one of claims 1 to 10, wherein the luminescent dye or the luminescent pigment, at least partially, gives a luminescent effect when excited with ultraviolet radiation. 12. Coating composition according to one of claims 1 to 11, wherein the luminescent dye or the luminescent pigment emits when excited with ultraviolet radiation in the range of visible and/or infrared light. 13. Coating composition according to one of claims 1 to 12, wherein the luminescent dye or the luminescent pigment is an inorganic phosphor. 14. Coating composition according to claim 13, wherein the inorganic phosphor is selected from the group of zinc sulfides, zinc cadmium sulfides, alkaline earth aluminates, alkaline earth sulfides and alkaline earth silicates and mixtures thereof, each doped with at least one transition metal and/or lanthanide element. 15. Coating composition according to one of claims 1 to 12, wherein the luminescent dye or luminescent pigment is an organic phosphor. 16. Coating composition according to claim 15, wherein the organic phosphor is selected from the group of luminescent, in particular fluorescent, homo- or heterocyclic aromatic systems, in particular benzene, acridine, xanthene, thioxanthene, pyrene, stilbene, coumarin, pyrazoline derivatives and mixtures of the aforementioned compounds. 17. Coating composition according to one of claims 1 to 16, wherein the luminescent dye or the luminescent pigment is a fluorochrome (fluorescent dye). 18. Coating composition according to one of claims 1 to 16, wherein the luminescent dye or the luminescent pigment is a fluorogen which is only converted into a fluorescent chemical compound by chemical reaction. 19. Coating composition according to claim 18, wherein the chemical reaction can be catalyzed enzymatically. 20. Coating composition according to one of claims 1 to 19, wherein the coating composition can also contain conventional additives, processing aids or additional substances such as fillers, antioxidants, anti-aging agents, additives for protection against UV radiation, flowability-influencing additives, solvents and dispersants, emulsifiers or color pigments. 21. Coating composition according to claim 20, wherein the additive for protection against UV radiation is a selective UV anti-aging additive which absorbs the short-wave portion of sunlight. 22. An article having applied to its surface a coating composition according to any one of claims 1 to 21. 23. Article according to claim 22, wherein the coating composition is applied with a layer thickness of 0.1 to 1000 µm, in particular 1 to 500 µm. 24. An article according to claim 22 or 23, wherein the surface consists of plastic, paper, cardboard, paperboard, textiles or metals. 25. Article according to one of claims 22 to 24, wherein the coating serves to mark the article, in particular to provide a security or identification function. 26. Article according to one of claims 22 to 24, wherein the coating serves to produce an optical effect, in particular for advertising purposes. 27. Article according to one of claims 22 or 26, wherein the article comprises films of all kinds, such as metal foils or plastic films, in particular label films, preferably self-adhesive label films, adhesive tapes; paper, cardboard and cartons of all kinds, textiles of all kinds, or fibrous materials. 28. Article according to one of claims 22 to 27, wherein the article is a pressure-sensitive adhesive label in which the pressure-sensitive adhesive layer and/or the optionally present lacquer layer is formed as a luminescent layer.