KR20010071507A - Security paper - Google Patents

Abstract

The security structure of paper (1), to prevent forgery, has a coating (5) on at least one side in a composition which contains simply a bonding agent without any filling materials. The composition gives a coating weight of 1-6 g/m2 and preferably 2-3 g/m2 on the paper. The bonding agent in the coating composition is an acrylate or a mixture of polymers or copolymers with a high acrylic content. The composition has at least one material, in a small concentration, with a visual and/or machine readable characteristic. The material can also be luminescent, magnetic, electrically conductive, light refractive or interfering or polarizing. The added material is present only partially in the coating, preferably as a pattern. The paper is of fibers from annual plants, and preferably cotton, and it can be at least partially of synthetic fibers and preferably of polyamide. The paper is not glued. The coating is applied only partially over the paper surface, and the uncoated zones are printed with effect ink pigments. The printing on the paper can also be covered by the applied coating. An Independent claim is included for a production process where the paper is produced on a papermaking machine, followed by surface coating with a number of layers in register. The paper can be glued before coating.

Description

Safety paper {Security paper}

Banknotes are usually made of cotton fibers and are made of so-called safety paper with special safety features such as security threads and watermarks that are at least partially processed within the paper. The circulation period of the bill depends on the stress the bank is subjected to. Some denominations are preferably used for trade and therefore have a shorter shelf life because they are more environmentally affected. The main reason for the limited shelf life of paper money is to get dirty quickly. Since banknote paper is very porous, it has a large surface area or a roughness of the surface. Although the raised protrusions and cavities are of a size that is invisible to the human eye, they provide ideal conditions for contaminant accumulation when compared to smooth surfaces.

Therefore, AU-PS 488,652 proposed making banknotes made entirely of plastic substrates. However, in this case it must be handled without the usual properties such as the sound and feel of paper money, as well as the usual proven safety elements such as portraits and window seals. In addition, the steel engraved printing commonly used in banknotes, which serves as a certainty mark that can be perceived as an additional tactile sensation due to the relief generated by inking, is simply flattened, plastic It is hard to recognize embossed on the substrate.

The present invention relates to a safety paper for producing valuable documents, such as banknotes, passports, ID cards, etc., provided with a coating to ensure a good condition for a long time for distribution and a method of manufacturing such safety paper.

1 is a front view of the safety paper of the present invention,

Figure 2 is a cross-sectional view of the safety paper of the present invention according to Figure 1 (A-B cutting),

3 is a front view of another embodiment of the safety paper of the present invention,

Figure 4 is a cross-sectional view (A-B cutting) of the safety paper of the present invention according to FIG.

Accordingly, it is an object of the present invention to produce safety paper that is dirt-repellent and therefore has a long shelf life, and other typical properties such as printability, sound, color, etc., remain unchanged. .

This object is solved from the independent claim of the present invention. Other variations are solved from the dependent claims.

According to the present invention, there is provided a safety paper coated with at least one side of a paper with a coating composed of a composition comprising only a binder and no filler. In the context of the present invention, binders include all materials that make up insoluble films or structures in conventional solvents. Unlike conventional coating materials, the binder is characterized in that it does not contain a high concentration of fillers, i.e. pigments such as titanium dioxide. The composition wets the fibers in the surface of the paper and forms a complete surface film on the fibers. This minimizes contamination access to the fibers.

The composition is applied at a layer thickness that achieves a sufficiently smooth surface while minimizing the possibility of contaminant accumulation. On the other hand, since the layer thickness is so small, it does not impair other properties of the paper, such as the feel and printability of the paper. The weight per unit area of the coating is preferably about 1 to 6 g / m 2, especially 2 to 3 g / m 2.

Since the small coating thickness does not change the conductivity of the paper, the perceptibility of any portrait non-patterned pattern on the safety paper is not impaired. The coating has the additional advantage of being able to process the paper without the usual size. Since the type of safety paper is not limited to any conditions, it is possible to use at least partly safety paper made of plastic fibers, preferably polyamide fibers, as well as conventional safety paper made of annual plant fibers, especially cotton fibers.

The binders used above are preferably binder systems comprising polyamide lacquer, acrylate or a high percentage of acrylates. If the binder system has several polymer components, they may be present as a mixture or copolymer. However, other binder systems may also be used. Compositions capable of chemical or physical crosslinking have proved particularly useful.

In particular, acrylate systems have many advantages over other binder systems, such as polyurethane based systems. Thus, they have better printability and inherently contain less solvent so that their processes are subject to lower environmental impact. The acrylate coating is also characterized by higher surface hardness, thus improving the stain resistance effect. As a result, the acrylate system is considerably more cost effective than other binder systems and offers the advantage of being easily mixed with other polymers.

The binder composition is printed or knife-coated on the paper after producing the paper. This can be done continuously after making the paper in the paper machine or as a separate job, for example just before printing the safety paper. If necessary, the smoothness of the surface can be continuously increased by corresponding calendering. The coated paper of the present invention provides an ideal printing surface for high print clarity and very good ink adhesion in the case of attempted physical and / or chemical attack.

Thereafter, the safety paper of the present invention can be further printed and processed according to the paper worth producing. Particularly if produced by intaglio printing, the printing or embossing again results in a rough surface, and contaminants tend to accumulate. In order to exclude this, it is proposed in the present invention that the print is further covered with a binder layer, for example, a lacquer layer. The lacquer layer is preferably adjusted to its composition relative to the background layer of the present invention in order to allow good bonding of the two layers. The binding can be improved by an additional crosslinking step. This is possible by heating or irradiation (eg UV radiation). Since the print can be produced according to any printing process, such as a steel engraving or laser printer, it is necessary to apply the binder composition of the present invention to the printing process used to ensure not only low contamination but also improved adhesion of the ink to the substrate. have.

Another advantage of the present invention is that when the optically variable safety elements are provided on the paper, the safety paper of the present invention can be processed without further pretreatment. Optically variable devices or inks that exhibit the appearance of angle-dependent interactions of colors due to diffraction or optical interference require a smooth background for good visibility of the effect. Safety elements of this kind are for example holograms, kinegrams or other diffractive structures, as well as inks containing other special effect pigments such as interference layers or liquid crystalline pigments or pigments with a shiny metallic effect.

In special cases, however, it may also be useful to provide a background layer within the area of the element described above. Since liquid crystal pigments and interference layer pigments composed only of thin mica plates coated with titanium dioxide are transparent, the color effect is not only affected by the smoothness, but also by the color of the background. The black background absorbs light conducted by the pigment, thus increasing the gloss of the color reflected by the pigment. The same applies to safety elements consisting of several thin layers or the like that exhibit color interaction based on interference effects. Thus, for elements similar to these elements, it is necessary to provide a safety sheet with an additional background layer in the area of the safety element to be applied.

It may also be desirable to underlay a safety element with certain features that can be detected mechanically or visually, for example, as is known from WO 97/35732.

Moreover, the coating of the present invention has an advantageous effect on other safety factors. For example, a smoother background makes embossing more pronounced, thus creating a more pronounced embossing structure. Since embossing does not apply only to paper fibers, it may be more durable.

According to a preferred embodiment, the coating composition additionally comprises at least one low concentration of material having physical properties that can be visually and / or mechanically sensed (machined). The materials may, for example, have magnetic, conductive, diffractive, polarizing or optical coherence, may be uniformly distributed over the entire coating, or may be applied in the form of a pattern. Thus, preferably, any pattern comprising a composition comprising, in a first step, a small amount of at least one material having at least one visually and / or mechanically detectable physical property by the method of doping (<1% by weight). Print with In the second step, the same composition can be applied to the remaining areas on the surface of the paper recorded in the first pattern, which does not contain the detectable additive.

The additive may be, for example, a luminescent material that is susceptible to UV light, and may be a luminescent material that emits within the visible spectral range. However, in the case of mechanical inspection, it is also possible to use luminescent substances which emit in the visible spectrum, preferably in the IR spectral range. Photochromic or thermochromic additives can likewise be used.

Instead of physically detectable materials, chemically reactive additives can be used. For example, the binder composition may mix the components of a color reaction system and apply it to paper. Over time, when the second component of the color reaction system is applied, the area of colouration, pattern and text printing on the safety paper can be seen. This can serve as a definite feature or check mark for checks, flight tickets, and the like.

By changing the use of multiple additives and / or the concentration of one or more additives, it is possible to make some kind of coding very simple, for example a bar code, on a sheet of paper. The coding may, for example, constitute independent and additional safety features or serve as a reference feature for other data already provided on the safety paper. Therefore, information visible to the naked eye on a banknote, such as a person's name shown in money, portraits, etc., can be coded, and stored on paper in the coding form of the present invention not visible to the naked eye. In mechanical inspection, the coding is read, decrypted and tested to confirm that the corresponding information is visible to the naked eye.

Of course, according to the principles of the present invention, many different codings can be made. For example, it is possible to apply a binder composition comprising special additives to the paper simultaneously or continuously in the form of the desired coding. The rest of the paper surface can be printed or coated with the binder composition without the above-mentioned additives. Different coding may also be applied to other surface areas of the paper. Of course, double sided coatings with the same additives are likewise possible.

According to another embodiment, the coating of the present invention may also have a gap. The gap may be in the form of, for example, a striped form. Before or after applying the coating of the present invention, a print comprising an ink having any particular effect is provided. The ink having the special effect may be an interference layer pigment, a liquid crystal pigment, or another shiny pigment. The print may cover the whole or only part of the gap.

The safety paper of the present invention can be advantageously used, for example, to make ID cards and passports. Since it has increased tear strength or contamination resistance, it can be easily applied without the usual lamination with plastic foil. Nevertheless, upon lamination, the coating of the present invention ensures a tight and inseparable bond between the paper and the cover layer.

The composition of the present invention is illustrated by the following examples.

Example 1

Banknote paper made from 100% cotton with a 3.0% filler content was used for the coating test. The paper was adjusted to 50% wet strength based on dry strength using a commercial melamine resin (eg Madurit MW167).

The following formulations were used as coatings:

Acronal 320D (BASF) 400ml

-Aqueous Acid Solution of Acrylic Resin-

600 ml of softened water

The mixture was prepared by stirring and applied to the surface of the paper. To this end, a pair of rotary rolls were used in which the lower side of the roll was immersed in a dish containing a diluted acronal dispersion. The extra suspension was pushed through a roll slit. The paper was rolled up as a commercial light dryer.

The treatment gave the following properties to the paper.

Property Before treatment After treatment Air permeability 25ml / min 5ml / min 60 seconds water absorption 50g / ㎡ 20g / ㎡ Oil Absorption GFL 30 seconds 150 sec

Example 2

The paper was coated with the following formulation according to the same method described in Example 1.

Neoocryl-AC 72 (Zeneca) 900ml

-Aqueous Acid Solution of Acrylate-

80 ml of water

Crosslinker CX 100 (Zeneca) 20ml

Example 3

The paper could also be coated with the following binder composition:

Primal 1-545 (Rohm & Haas) 900ml

-Aqueous Acid Solution of Acrylate-

80 ml of water

Zirconium carbonate (Aer Remy) 20ml

Example 4

The binder system of the present invention may consist of a mixture of several polymers. By way of example, the following formulations are mentioned:

Glasscol LS 26 (Ciba) 700ml

-Aqueous acid solution of acrylate-styrene copolymer-

Polyurethane U400N (Alberdink Boley) 200ml

100 ml of water

Other advantages and embodiments will be described in more detail with reference to the drawings. The drawings only show the layer structure of the safety paper of the present invention.

Figure 1 shows in detail the safety paper web 1 of the present invention, for example, used to make banknotes. Such safety paper is usually made of cotton or other annual plant fibers. In other applications, however, it may be useful to replace the natural fibers with plastic fibers, in particular polyamide fibers. Pure plastic fiber papers are also possible. During the manufacture of the paper web 1, the respective safety elements, i.e. the parabolic pattern or the safety chamber 2, as shown in FIG. 1, are already integrated into the paper. The safety chamber 2 is woven into the paper so that it passes directly to the paper surface of the area 3 and is fully integrated into the paper pulp within the area drawn in a dash-line. The seal 2 may be provided with any desired safety features such as a conductive layer, a metal layer, holograms, and the like.

FIG. 2 shows a cross section of the safety paper 1 of the present invention along the dashed-dotted line A-B of FIG. 1. The safety paper 1 of the present invention is a binder coating of the present invention which is knife-coated or printed over the entire surface of the raw paper 1 from the paper machine and the safety paper 1 according to the described embodiment. It is made as (5). The coating 5 may also be applied to both sides of the safety paper 1.

3 and 4 further show an embodiment of the safety paper 1 of the invention. Figure 4 shows a cross section of the safety paper 1 of the present invention along the dashed-dotted line A-B in Figure 3.

As shown in FIG. 4, the safety paper 1 also consists of a conventional paper web 4 to which a pure binder composition without filler according to the invention is applied. However, the binder layer is composed of different areas 6 and 9. In area 6, the binder composition is doped with additives that are measured visually and / or mechanically, while the binder composition in the remaining area 9 does not contain additives. As is apparent from FIG. 3, the area 6 indicated by the doped binder composition makes visually readable information. Area 7 also indicated as the doped binder composition makes a coating 8 in the form of a barcode.

The additive may be, for example, a transparent luminescent material in normal illumination, but is emitted in the visible spectral range and shows a strong hue when irradiated with UV light. In this case, as shown in Fig. 3, the information 6, 8 can be visually seen only under UV illumination.

However, a number of additives that can be sensed alone can also be applied. The mixing ratio of the additives can be used to make additional coding. It can also be seen that information 6 and 8 can be made from different fillers. Thus, as described above, information 6 can be produced with the aid of luminescent materials emitting within the visible spectral range, whereas, for example, luminescent materials emitting within the IR spectral range can only be detected by the machine. A barcode 8 is made which is displayed with the help of a substance which can be made. The mark 6 visible to the naked eye under UV illumination may represent, for example, a picture, pattern or readable information. However, the machine readable code 8 may represent some information feature of each valuable document, optionally in encrypted form. The information may be inherent properties of the paper material such as, for example, conductivity, thickness distribution, or the like, or may be other information essential to a particular document of value, such as, for example, currency.

Claims (17)

A coating is provided on at least one side of the safety paper, the coating consisting of a composition comprising only a binder without fillers, wherein banknotes, passports, ID cards and Safety paper for manufacturing the same valuable documents. The safety paper according to claim 1, wherein the composition is present on the surface of the safety paper at a coating weight of 1 to 6 g / m 2, preferably 2 to 3 g / m 2. The safety paper according to claim 1 or 2, wherein the composition comprises a acrylate or a mixture of polymers or copolymers having a high acrylate content as a binder. The safety paper according to any one of claims 1 to 3, wherein the composition comprises a low concentration of at least one substance having a visually and / or mechanically detectable property. 5. The safety paper of claim 4, wherein the material has magnetic, conductive, diffractive, optical coherence, or polarization. 6. The safety paper as claimed in claim 4, wherein the substance or substances are applied by partial coating only, preferably in the form of a pattern. 7. 7. The safety paper according to any one of claims 1 to 6, wherein the safety paper is composed of fibers of annual plants, in particular cotton fibers. 8. The safety paper according to claim 1, wherein the safety paper is at least partially composed of plastic fibers, preferably polyamide fibers. 9. 10. The safety paper according to any one of claims 1 to 8, wherein the safety paper is an unsized paper. 10. The safety paper according to any one of the preceding claims, wherein the coating is applied only to a portion of the safety paper, and the portion without the coating is printed with an ink containing a pigment of special effect. Valuable document, such as a bill, passport, or ID card, characterized in that it has a safety sheet according to any one of claims 1 to 10. 12. A valuable document according to claim 11, wherein the valuable document in turn comprises a print on the coating which is covered by a coating such as, for example, a lacquer layer. A paper layer is produced in a paper machine, and then a coating is at least partially applied to at least one surface of the paper, wherein the coating consists of a composition comprising only a binder without fillers. Method for producing a safety paper according to any one of the preceding. The method of claim 13, wherein the paper is sized before coating. 15. The method of claim 13 or 14, wherein the coating is printed. 16. The method of claim 13, wherein the coating is applied in a plurality of steps. 17. The method of claim 16, wherein in a first step a composition comprising a small amount of at least one material having at least one visually and / or mechanically detectable physical property is applied in the form of a pattern, and the second step is recorded in the pattern. Method for producing a safety paper, characterized in that for applying the same composition does not contain the detectable material on the remaining portion of the surface of the paper.