Title of Invention

A SECURITY PAPER FOR PRODUCING DOCUMENTS OF VALUE, SUCH AS BANK NOTES, PASSPORTS, ID CARDS OR THE LIKE.

Abstract

The present invention discloses security paper (1) for producing documents of value, such as bank notes, passports, ID cards or the like, which is provided at least partly with a coating (5) ensuring longer fitness for circulation. The coating (5) is provided at least on one of the raw paper surfaces (4) of the security paper (1), and consists of a composition containing only a binder and no fillers.

Full Text

This invention relates to a security paper for producing documents of value, such as bank notes, passports, ID cards or the like, which is provided with a coating ensuring longer fitness for circulation, and to a method for producing such a security paper. Bank notes are usually made of so-called security papers consisting of cotton fibers and having special security features, such as a security thread at least partly worked into the paper, and a watermark. The period of circulation of a bank note depends on the stress it is subjected to. Certain denominations are preferably used in trade and thus have a shorter period of circulation due to the greater impact of envi- ronmental influences. The principal cause for the restricted period of circulation of bank notes is deemed to be premature soiling. Since bank note paper is very porous it has a large surface area or high surface roughness. Even if the resulting projections and cavities are in orders of magnitude which cannot be resolved by the human eye, they offer ideal conditions for dirt deposits in comparison with a smooth surface. AU-PS 488,652 has therefore proposed making bank notes completely from a plastic substrate. However, in this case one must do without customary and proven security elements such as portrait watermarks and window security threads, as well as special properties such as the sound and feel of bank note paper. Also, the steel intaglio printing customary in bank notes, which serves as an additional tactile authenticity mark due to the relief resulting from the inking, merely leads to a flat, hardly perceptible relief on plastic substrates. The problem of the invention is therefore to produce a security paper which is dirt-repellent and therefore has a long period of circulation and which remains un- changed in its other typical properties, such as printability, sound, color, etc. Accordingly, the present invention provides a security paper for producing documents of value, such as bank notes, passports, ID cards or the like, which is provided at least partly with a coating ensuring longer fitness for circulation, the coating being provided at least on one of the surfaces of the security paper, characterized in that the coating consists of a composition containing a polyamide lacquer or an acrylate system as the sole binder and no fillers and optionally one or more visually or machine testable additives for security features and/or codings. A binder within the meaning of the invention includes all substances which form insoluble films or structures in common solvents. The essential thing is that the binder, unlike customary coating materials, contains no fillers, i.e. pigments such as titanium dioxide, in high concentrations. This composition wets the fibers in the sur- face area of the paper, forming a complete surface film over the fiber. This mini- mizes the access of dirt to the fiber. The composition is applied in a layer thickness so as to form a sufficiently smooth surface and minimize the possibilities of dirt deposit, on the one hand. On the other hand, the layer thickness is so small as not to impair the other properties of the paper, such as its feel and printability. The weight per unit area of the coating is preferably about 1 to 6 g/m2, in particular 2 to 3 g/m2. The small coating thicknesses leave the transmission properties of the paper unchanged so that the recognizability of any portrait watermarks in the security pa- per is not impaired. The coating additionally has the advantage that one can do with- out the customary sizing of the paper. The kind of security paper is not subject to any conditions either, so that one can use customary security papers made of annual plant fibers, in particular cotton fibers, as well as security papers consisting at least partly of plastic fibers, preferably polyamide fibers. The binders used are preferably polyamide lacquers, acrylates or binder sys- tems containing a high percentage of acrylates. If the binder system has several polymer components, they can be present as a mixture or as copolymers. But one can fundamentally use other binder systems as well. Chemically or physically crosslinkable compositions have proved particularly useful. Particularly acrylate systems have a number of advantages over other binder systems, for example ones based on polyurethane. They thus have better printing properties and contain fundamentally less solvent so that their processing involves lower environmental impact. Acrylate coatings are in addition characterized by higher surface hardness so that the dirt-repellent effect is improved. Finally, acrylate systems offer the advantage of being considerably more cost-effective than other binder systems and being readily mixable with other polymers. The binder composition is knife-coated or printed on the paper after production of the latter. This can be done directly subsequent to papermaking in the paper ma- chine or in a separate operation, for example directly before printing the security paper. If required, the smoothness of the surface can subsequently be increased by corresponding calendering. The inventively coated paper offers an ideal printing sur- face for high print resolution and very good ink adhesion in case of attempted physi- cal and/or chemical attacks. Then the inventive security paper is printed and possibly processed further in accordance with the paper of value to be produced. A print or embossing, in par- ticular if produced by intaglio printing, leads to a rough surface again and therefore favors dirt deposits. In order to exclude this as well, it is proposed according to the invention that the print be covered with a further binder layer, e.g. lacquer layer. The lacquer layer is preferably adjusted in its composition to the inventive background layer to permit a good bond of the two layers. The bond might be improved by an additional crosslinking step. This can be done by the action of heat or irradiation (e.g. UV radiation). Since the print can be produced with any printing process, such as by steel intaglio or with a laser printer, it might be necessary to adapt the inven- tive binder composition to the printing process used in order to ensure not only low soiling but also improved adhesion of the inks to the substrate. A further advantage of the invention is that one can do without further pre- treatment of the inventive security paper when optically variable security elements are to be provided on the paper. Optically variable devices or inks showing a view- ing angle dependent interplay of colors due to diffraction or light interference re- quire a smooth background for good visibility of this effect. Security elements of this kind are for example holograms, kinegrams or other diffraction structures, as well as inks containing interference layer or liquid crystal pigments or other special-effect pigments such as glossy metallic-effect pigments. In special cases, however, it may still be useful to provide a further background layer in the area of said element. Liquid crystal pigments and interference layer pig- ments consisting only of thin mica plates coated with titanium dioxide are transpar- ent so that the color effect is not influenced by the smoothness alone but also by the color of the background. A black background absorbs light transmitted by the pig- ments, thereby increasing the brilliance of the colors reflected by the pigments. The same applies to security elements constructed of several thin layers and likewise showing an interplay of colors based on interference effects. For these and similar elements it may therefore be necessary to provide the security paper with a further background layer in the area of the security element to be applied. Alternatively, it may also be expedient to underlay the security element with a mechanically or visually detectable authenticity feature, as known for example from WO 97/35732. The inventive coating furthermore has an advantageous effect on other security elements. For example, it makes embossed structures more trenchant since the smoother background makes the embossings more prominent. Embossings are also more durable since not only the paper fibers are embossed. According to a preferred embodiment, the coating composition additionally contains a low concentration of at least one substance with a visually and/or me- chanically detectable physical property. The substance can have for example mag- netic, electroconductive, diffractive, light-polarizing or light-interfering properties and be uniformly distributed all over the total coating or applied in the form of pat- terns. One thereby preferably, in a first step, prints a certain pattern of a composition containing small amounts in the manner of a doping ( stance with at least one visually and/or mechanically detectable physical property. Only in a second step does one apply the same composition but not containing the detectable additive to the remaining part of the surface of the paper in register with the first pattern. Said additives can be for example luminescent substances excitable with UV light and emitting in the visible spectral region. In the case of a machine check, however, one can also use luminescent substances emitting in the invisible spectral region, preferably the IR spectral region. One can likewise use photochromic or thermochromic additives. Instead of physically detectable substances one can also use chemically react- ing additives. For example, one can admix a component of a color reaction system to the binder composition and apply it to the paper. When one applies the second com- ponent of the color reaction system at a later time, a colored area, pattern, writing or the like becomes visible on the security paper. This can serve as an authenticity fea- ture or as a cancellation mark for a check, airplane ticket or the like. By using a plurality of additives and/or varying the concentration of one or more additives one can very simply produce any kind of coding, for example a bar code, on the security paper. Said coding can for example constitute an independent additional security feature or serve as a reference feature for other data already pro- vided on the security paper. Thus, information visible to the naked eye on the bank note, such as denomination, the name of a person shown in the portrait or the like, can be encrypted and stored on the paper in the form of the inventive coding invisi- ble to the naked eye. In a machine check the coding is read, decrypted and tested for identity with the corresponding information visible to the naked eye. According to the inventive principle one can of course also produce a plurality of different codings. For example, one applies the binder compositions containing the particular additive to the paper in the form of the desired codings simultaneously or successively. One prints or coats the remaining part of the paper surface with ad- ditive-free binder composition, as explained above. Alternatively, the different cod- ings can also be disposed on different surfaces-of the security paper. Double-sided coating with the same additive is of course likewise possible. According to a further embodiment, the inventive coating can also have gaps. Said gaps can have any form, e.g. a striped form. Before or after application of the inventive coating they are provided with a print having certain special-effect inks. Said special-effect inks may be interference layer pigments, liquid crystal pigments or other gloss pigments. Said print can cover the gaps all-over or only partly. The inventive security paper can for example also be used advantageously for producing ID cards and passports. Since it has increased tear strength and dirt resis- tance, one might possibly do without the customary lamination with plastic foils. If lamination is nevertheless effected, the inventive coating ensures a firm, inseparable bond between paper and cover layer. In the following some examples of the inventive composition will be explained. Example 1 A bank note paper made of 100% cotton with a filler content of 3.0% is used for the coating test. The paper is adjusted to a wet strength of 50% based on the dry strength by using commercial melamine resin (e.g. Madurit MW167). The following formulation is used as the coating: Acronal 320D (BASF) 400 ml - aqueous dispersion of acrylic resin - Softened water 600 ml The mixture is prepared by stirring and applied to the surface of the paper. For this purpose one uses a rotating pair of rolls whose lower side dips into a dish with the diluted Acronal dispersion. Excess suspension is pressed off through the roll slit. • The paper is subsequently dried with a commercial photo drier. The treatment gives the paper the following properties: Example 2 A paper is coated in the same way as stated in Example 1 with the following formulation: Neocryl-AC 72 (Zeneca) 900 ml - aqueous dispersion of acrylate - Water 80 ml Crosslinker CX 100 (Zeneca) 20 ml Example 3 The paper can also be coated with the following binder composition: Primal 1-545 (Rohm & Haas) 900 ml - aqueous dispersion of acrylate - Water 80 ml Zirconium carbonate (Auer Remy) 20 ml Example 4 The inventive binder system can also consist of a mixture of several polymers. As an example the following formulation is stated: Glascol LS 26 (Ciba) 700 ml - aqueous dispersion of acrylate-styrene copolymer - Polyurethane U 400 N (Alberdink Boley) 200 ml Water ' 100 ml Further advantages and embodiments will be explained in more detail with ref- erence to the figures. It is pointed out that the figures show the layer structure of the inventive security paper only schematically. Fig. 1 shows an inventive security paper from the front, Fig. 2 shows a section along A - B through the inventive security paper ac- cording to Fig. 1, Fig. 3 shows a further embodiment of an inventive security paper from the front, Fig. 4 shows a cross section along A - B through the inventive security paper according to Fig. 3. Fig. 1 shows a detail of inventive security paper web 1 as is used for example for producing bank notes. Such security paper is usually made of cotton fibers or other annual plant fibers. For some applications, however, it may be useful to re- place part of said natural fibers by plastic fibers, in particular polyamide fibers. Pure plastic fiber papers are also possible. During production of paper web 1 individual security elements are already embedded in the paper, such as a portrait watermark or security thread 2 shown in Fig. 1. Security thread 2 is quasi woven into the paper so as to pass directly to the surface of the paper in areas 3 while being embedded com- pletely in paper pulp in the dash-lined areas. Thread 2 can be provided with any de- sired security features, such as an electroconductive, metallic layer, hologram or the like. Fig. 2 shows a section through inventive security paper 1 along dash-dotted line A - B in Fig. 1. Inventive security paper 1 consists of raw paper 4 as usually leaves the paper machine, and inventive binder coating 5 which was knife-coated or printed all over a surface of security paper 1 according to the shown embodiment. Alternatively, coating 5 can also be applied to security paper 1 on both sides. Figs. 3 and 4 show a further embodiment of inventive security paper 1. Fig. 4 shows a section through inventive security paper 1 along dash-dotted line A - B in Fig. 3. As shown in Fig. 4, security paper 1 likewise consists of customary paper web 4 provided with a pure binder composition without fillers according to the invention. However, the binder layer is composed of different areas 6, 9. In areas 6 the binder composition is doped with an additive which is testable visually and/or mechani- cally, while remaining areas 9 of the binder composition contain no additive. As evi- dent from Fig. 3, area 6 represented by the doped binder composition forms visually readable information. Areas 7 likewise represented with the doped binder composi- tion form coding 8 in the form of a bar code. The additive may be for example a luminescent substance transparent in nor- mal illumination but emitting in the visible spectral region and thus showing an in- tensive tone when irradiated with UV light. In this case information 6, 8, as shown in Fig. 3, is visible only in UV illumination. However, one can also provide a plurality of additives which are singly detect- able. The mixture ratio of the additives can be used to produce an additional coding. It is likewise conceivable to produce information 6, 8 with different additives. Thus, one can produce information 6 with the aid of a luminescent substance emitting in the visible spectral region, as explained above, while representing bar code 8 with the aid of a substance detectable solely by machine, e.g. a luminescent substance emitting in the IR spectral region. Marks 6 visible to the naked eye in UV illumina- tion can represent for example a picture, pattern or readable information. Machine- readable code 8, however, could represent certain information characteristic of the individual document of value, optionally in encrypted form. Said information could be properties inherent to the paper material, such as transmission properties, thick- ness distribution, etc., or other information essential to the particular document of value, such as denomination or the like. WE CLAIM: 1. A security paper for producing documents of value, such as bank notes, passports, ID cards or the like, which is provided at least partly with a coating ensuring longer fitness for circulation, the coating being provided at least on one of the surfaces of the security paper, characterized in that the coating consists of a composition containing A polyamide lacquer/ or an acrylate system as the sole binder and no fillers and optionally one or more visually or machine testable additives for security features and/or codings. 2. A security paper as claimed in claim 1, wherein the composition is present on the security paper in a coating weight of 1 to 6 g/m2, preferably 2 to 3 g/m2. 3. A security paper as claimed in claim 1 or 2, wherein the composition contains acrylates or a mixture of polymers or copolymers with a high acrylate content as a binder. 4. A security paper as claimed in at least one of claims 1 to 3, wherein the composition contains a low concentration of at least one substance with a visually and/or machine detectable property for security features and/or codings. 5. A security paper as claimed in claim 4, wherein the substance has luminescent, magnetic, electroconductive, diffractive, light-interfering or light-polarizing properties. 6. A security paper as claimed in claim 4 or 5, wherein the substance or substances are provided in the coating only partly, preferably in the form of a pattern. 7. A security paper as claimed in at least one of claims 1 to 6, wherein the security paper consists of fibers of annual plants, in particular cotton fibers. 8. A security paper as claimed in at least one of claims 1 to 7, wherein the security paper consists at least partly of plastic fibers, preferably polyamide fibers. 9. A security paper as claimed in at least one of claims 1 to 8, wherein the security paper is an unsized paper. 10. A security paper as claimed in at least one of claims 1 to 9, wherein the coating is applied to the security paper only in certain areas and the coating-free areas are printed with an ink containing special-effect pigments. 11. A document of value, such as a bank note, check, ID card or the like, wherein the document of value has a security paper as claimed in any one of claims 1 to 10. 12.A document of value as claimed in claim 11, wherein the document of value has over the coating a print which is in turn covered by a coating, such as a lacquer layer. 13.A method for producing a security paper as claimed in at least one of claims 1 to 10, wherein a paper layer is produced in a paper machine and subsequently a coating applied at least partly to at least one of the surfaces of the paper, the coating consisting of a composition containing a polyamide lacquer or an acrylate system as the sole binder and and no fillers and optionally one or more visually or machine testable additives for security features and/or codings. 14. A method as claimed in claim 13, wherein the paper is sized before application of the coating. 15. A method as claimed in claim 13 or 14, wherein the coating is printed on. 16. A method as claimed in any of claims 13 to 15, wherein the coating is applied in a plurality of steps. 17. A method as claimed in claim 16, wherein a composition containing small amounts of at least one substance with at least one visually and/or machine detectable physical property for security features and/or codings is applied in the form of a pattern in a first step, and the remaining part of the surface of the paper is provided with the same composition without the detectable substance in register with the pattern in a second step. The present invention discloses security paper (1) for producing documents of value, such as bank notes, passports, ID cards or the like, which is provided at least partly with a coating (5) ensuring longer fitness for circulation. The coating (5) is provided at least on one of the raw paper surfaces (4) of the security paper (1), and consists of a composition containing only a binder and no fillers.

Documents:

in-pct-2000-577-kol-granted-abstract.pdf

in-pct-2000-577-kol-granted-assignment.pdf

in-pct-2000-577-kol-granted-claims.pdf

in-pct-2000-577-kol-granted-correspondence.pdf

in-pct-2000-577-kol-granted-description (complete).pdf

in-pct-2000-577-kol-granted-drawings.pdf

in-pct-2000-577-kol-granted-examination report.pdf

in-pct-2000-577-kol-granted-form 1.pdf

in-pct-2000-577-kol-granted-form 18.pdf

in-pct-2000-577-kol-granted-form 3.pdf

in-pct-2000-577-kol-granted-form 5.pdf

in-pct-2000-577-kol-granted-gpa.pdf

in-pct-2000-577-kol-granted-reply to examination report.pdf

in-pct-2000-577-kol-granted-specification.pdf

in-pct-2000-577-kol-granted-translated copy of priority document.pdf