WO2004045864A1

WO2004045864A1 - A security paper, a method for manufacturing security paper, as well as a method and a device for detecting falsfication and/or forgery of documents printed on said security paper

Info

Publication number: WO2004045864A1
Application number: PCT/NL2003/000800
Authority: WO
Inventors: Steven Gerardus Tuinstra
Original assignee: Security Transfer B.V.
Priority date: 2002-11-20
Filing date: 2003-11-14
Publication date: 2004-06-03
Also published as: CA2513156A1; EP1562757A1; AU2003282622B8; NL1021956C2; AR042063A1; NZ540005A; AU2003282622B2; AU2003282622A1; ZA200504927B

Abstract

A security paper comprises a photoluminescent substance having an excitation wavelength ranging from about 220 to 300 nm, and an emission wavelength, which is higher than the excitation wavelength range. This emission wavelength is preferably 450 nm or higher. A coating is present on at least part of the security paper, on at least one side thereof, which coating is at least partially impervious to radiation in the excitation wavelength range to the photoluminescent substance. The security paper is manufactured by applying a coating, which is at least partially impervious to radiation in the excitation wavelength range to at least part of the security paper on at least on side thereof.

Description

A security paper, a method for manufacturing security paper, as well as a method and a device for detecting falsification and/or forgery of documents printed on said security paper

The invention relates to a security paper comprising a photoluminescent substance. The invention furthermore relates to a method for manufacturing such a security paper. Finally, the invention relates to a method and a device for detecting falsifications and/or forgeries of documents printed on said security paper.

Documents of value, such as cheques and bank transfer forms, are regular targets of fraud, which fraud usually consists of the falsification of data present on the docu- ments in question. Such falsifications are in particular carried out by removing alphanumerical information present thereon, such as a name, a bank account number or an amount, by mechanical or chemical means, e.g. by carefully scratching off letters or digits or removing them, e.g. by means of bleach, acetone or ethanol. Fraud is also possible by forging the entire document of value by photocopying or printing. Various kinds of security paper have been developed as the base material for documents of value, which security paper has been provided with special characteristics that al- lowing detection of any falsification or forgery by the human eye and/or by mechanical means .

WO 00/73582 discloses a security paper of the above kind wherein the security paper comprises an optical whit- ener. A coating that is impervious to visible light is used with this known security paper. Falsification of a document made of said security paper causes damage to said coating, which damage becomes visible under normal light or ultraviolet light. Falsifications can also be detected by mechanical means, through the use of suitable radiation sources and de- tection elements. Although detection of falsifications is possible when this known security paper is used, the known security paper has a few practical drawbacks. The use of optical whiteners having an excitation wavelength in the UV radiation range (300-400 nm) requires the use of a rela- tively thick coating comprising a large amount of costly material, such as zinc oxide or titanium dioxide. The thick coating, which is impervious to visible light, also blocks wavelengths that are needed for the detection of usual au- thenticity characteristics. Also watermarks or the like become difficult to detect.

The object of the invention is to provide a security paper wherein the drawbacks of the known security paper are overcome in an effective manner. In order to achieve that object, the security paper of the above-mentioned type is according to the invention characterized in that the photoluminescent substance has an excitation wavelength ranging from about 220 to 300 nm, and an emission wavelength which is higher than the excitation wavelength range, wherein a coating is present on at least part of the security paper, on at least one side thereof, which coating is entirely or partially impervious to radiation in the excitation wavelength range of the photoluminescent substance. The invention is based on the perception that radiation having an excitation wavelength ranging between 220 and 300 nm can be blocked relatively easily, so that a thin and thus relatively inexpensive coating will suffice. If the coating transmits radiation in the emission wavelength range, it will be possible to use usual authenticity characteristics in a preferred embodiment of the security paper according to the invention, which characteristics will retain their normal effect .

According to a preferred embodiment, the coating on at least a predetermined part of the paper is impervious to radiation in the excitation wavelength range of the photoluminescent substance to a limited extent, wherein the coating preferably exhibits a specific, limited degree of impervi- ousness . This achieves that any damage to the security paper resulting from falsification will be very hard to repair, because it will be necessary to restore exactly the correct degree of perviousness . In addition, this preferred embodiment makes it possible to detect falsifications wherein use is made of a correction fluid or tape for covering the original data.

The invention furthermore provides a method for manufacturing a security paper, wherein a photoluminescent substance is incorporated in and/or applied onto a paper, wherein according to the invention a photoluminescent substance having an excitation wavelength ranging from about 220 to 300 nm and an emission wavelength above the excitation wavelength range is used, wherein a coating which is at least partially impervious to radiation in the excitation wavelength range is applied to at least part of the security paper, on at least one side thereof.

According to the invention, said coating can be applied to the security paper as printing ink, wherein pref- erably at least an authenticity code is applied on the security paper. Alternatively, said coating may be applied to the security paper in a coating process.

The invention furthermore provides a method for detecting any falsification and/or forgery of a document, wherein the document is irradiated from one side with an excitation wavelength of about 220-300 nm and wherein an emission having a wavelength above 300 nm is detected, wherein the value of the detected emission is compared to a reference value for detecting any falsification or forgery. Finally, the invention relates to a device for detecting f lsifications and/or forgeries of documents, which device comprises a radiation source, a detection element, and a processing unit for processing a detection signal of the detection element, which device is characterized in that the radiation source delivers radiation having an excitation wavelength range of about 220-300 nm, and in that the detection element is arranged for detecting radiation having a wavelength above 300 nm, wherein the processing unit compares the detection signal to a reference value for the pur- pose of detecting any falsification.

The invention will be explained in more detail hereinafter with reference to the drawing, which schemati- cally shows an embodiment of the security paper according to the invention.

Fig. 1 schematically shows an embodiment of the security paper according to the invention. Fig. 2 is a diagram showing the excitation wavelength and the emission wavelength of the photoluminescent substance used in the security paper that is shown in Fig. 1, which diagram also shows the wavelength range within which usual lamps for checking secured documents operate. Figs. 3 and 4 are very schematic views of a few parts of a device for detecting falsifications and/or forgeries of documents.

Fig. 1 shows a security paper 1, which comprises a paper 2 provided with a photoluminescent substance . Said photoluminescent substance may be incorporated in the security paper 2 or in the usual film of glue of the paper. In the latter case, the composition of the film of glue is selected to ensure a proper bond of the photoluminescent substance to the paper fibres. In addition, the composition of the film of glue has been selected so that the glue of the paper will hardly dissolve, if at all, in solvents that forgers use for removing data from a document. This can e.g. be achieved by using so-called cross-linkers and/or compounds that make the glue impervious to solvent and/or sol- vent-repellent.

As an alternative for incorporating the photoluminescent substance in the paper or in the film of glue, the photoluminescent substance can be applied to the paper as a layer of ink by means of a printing process. It is also pos- sible to apply the photoluminescent substance to the paper in the form of a coating.

The photoluminescent substance of the security paper 1 has an excitation wavelength of 220-300 nm, whilst the emission wavelength is higher than the excitation wave- length; in the embodiment described herein it is even higher than 450 nm. Radiation having a wavelength ranging between 220 and 300 nm is usually referred to as UVC radiation or high-frequency UV radiation. The emission wavelength and the excitation wavelength are shown in Fig. 2. The advantage of using a photoluminescent substance having an excitation wavelength of about 220-300 nm is that radiation having such a wavelength can be blocked relatively easily, so that a thin coating 3 will suffice. The additional advantage of this is that the coating 3 can be applied to the safety paper 2 in the form of a printing ink. In addition, the coating 3 may be pervious to visible light. As a result, the normal effect of usual authenticity characteristics, such as fibres that light up in the security paper, can be retained. In the embodiment described herein, the wavelength range within which usual authenticity characteristics are effective lies between the excitation wavelength and the emission wavelength. Also watermarks and the like remain clearly per- ceptible, because the coating 3 transmits visible light normally. In addition, any reagents to solvents that may be present in the security paper are not covered, so that their use in combination with paper types that are usually used for cheques is possible. Europium-doped yttrium oxide (Y₂0₃:Eu) can be used as a photoluminescent substance. Alternatives are, CaS:Ce, SrGa₂S :Eu, (Mg) ₂P₂0₇ :Eu or Zn₂Si0 :Mn. The photoluminescent substance is preferably inorganic and insensitive to acids, bases and organic solvents. Furthermore, or alternatively, the photoluminescent substance of the security paper may be anchored to the paper in such a manner that said anchoring is insensitive to acids, bases and organic solvents.

The coating 3 preferably comprises an organic material as the substance that absorbs the excitation radiation, so that the coating will be sensitive to acids, bases and solvents. An example of a suitable material is uvinul 8088 of BASF. Alternatives are 2-hydroxy-4-methoxy-benzophenone and various benzotriazoles . It is noted that a large number of compounds usually present in printing inks already ex- hibit a sufficient absorbing effect as regards excitation radiation.

The coating 3 may be at least substantially fully impervious to radiation in the excitation wavelength range. The properties of the coating has been selected so that the coating 3 will be damaged when it is attempted to remove the data present on the coating 3, i.e. in case of a falsification attempt, as is schematically indicated at 4. When the security paper 1 is irradiated with radiation in the excitation wavelength range, the photoluminescent substance that is present in the security paper will not start to emit if the coating 3 is undamaged. If the coating 3 is locally (4) damaged, the photoluminescent substance will light up at that location, i.e. it will emit an emission wavelength, which is higher than 450 nm in the illustrated embodiment. The lighting up of the photoluminescent substance indicates damage to the coating caused by an attempt at manipulating data present on the security paper. As will be described hereinafter, said lighting up can be detected by means of a suitable detection element, wherein the detection signal is used to indicate falsifications.

According to a preferred embodiment, the coating is composed so that radiation in the excitation wavelength range is not fully blocked, i.e. it is impervious to a limited extent. Upon irradiation of the security paper at the excitation wavelength, a certain amount of emission radiation will be received at all times when this embodiment is used. This preferred embodiment makes it very difficult for falsifiers to repair any damage to the coating 3, because it will be necessary to restore exactly the correct degree of perviousness at every damaged location. In addition, this embodiment makes it possible to detect falsifications in which the original data that have been entered are covered by means of a correction fluid, correction tape or the like.

The fact is that such correction means are generally highly impervious to radiation in the excitation wavelength range. If a printing ink is used as the coating 3, an authenticity code 5 can also be placed on the security paper 1, which code is detected as a succession of light and dark positions by a detection device. This authenticity code is located outside the area where falsifications may occur. The authenticity code 5 provides a characteristic, by means of which forgery can be quickly detected. The authenticity code 5 may further contain information, e.g. information about the security paper, the identity of the printer or the like.

Embodiments of the security paper 1 comprising a coating 3 exhibiting a limited degree of imperviousness and/or an authenticity code 5 have the advantage that it is possible to detect not only falsifications but also forgeries . In the case of a document being forged by photocopying or printing, the forged document will not deliver the ex- pected amount of the emission radiation, or the expected authenticity code will not be detected.

It is possible to apply the coating 3 to the security paper 1 only at ^"those locations where data that are sensitive to fraud are placed. In the case of bank transfer forms, the coating is e.g. applied at those locations where the name, the account number and the amount are to be entered.

Figs. 3 and 4 are very schematic views of a device for detecting falsifications and/or forgeries of documents, which device comprises a radiation source 6 and a detection element 7. The radiation source 6 preferably comprises a low-pressure mercury lamp having an emission wavelength of 250-260 nm, with a UVC band-pass filter being placed in front of the mercury vapour lamp. As a result, the radiation source 6 will deliver excitation radiation having a wavelength of about 254.3 nm.

As appears from Figs. 3 and 4, the detection element may be disposed either on the same side of the security paper 1 as the radiation source 6 or on the opposite side. The detection element 7, which may comprise an assembly of elements sensitive to the emission wavelength, detects the light emitted by the photoluminescent substance and converts any emission radiation that may be received into a detection signal to be processed by a schematically represented proc- essing unit 8. The processing unit 8 may comprise a suitably programmed microprocessor, by means of which it can be determined, on the basis of measured deviations of the emission radiation from the emission radiation of other docu- ments and/or deviations from measured values within the same document, whether this is a case of falsification or forgery. It is noted that the device as shown can be built into an apparatus for the automatic processing of documents, such as bank giro forms, cheques and the like.

The invention is not restricted to the embodiments as described above, which can be varied in several ways within the scope of the invention as defined in the claims.

Claims

1. A security paper comprising a photoluminescent substance, characterized in that said photoluminescent substance has an excitation wavelength ranging from about 220 to 300 nm, and an emission wavelength which is higher than the excitation wavelength range, wherein a coating is present on at least part of the security paper, on at least one side thereof, which coating is entirely or partially impervious to radiation in the excitation wavelength range of the photoluminescent substance.

2. A security paper according to claim 1, wherein said emission wavelength is 450 nm or higher.

3. A security paper according to claim 1 or 2 , wherein the photoluminescent substance is an inorganic substance, which is insensitive to acids, bases and organic solvents and/or which is anchored to the security paper in such a manner that said anchoring is insensitive to acids, bases and organic solvents.

4. A security paper according to claim 1, 2 or 3, wherein said photoluminescent substance is Y₂0₃:Eu, CaS:Ce, SrGa₂S₄:Eu, (Mg)₂P₂0₇:Eu or Zn₂Si0₄:Mn.

5. A security paper according to any one of the preceding claims, wherein the coating on at least a predetermined part of the paper is impervious to radiation in the excitation wavelength range of the photoluminescent sub- stance to a limited extent, with the coating preferably exhibiting a specific, limited degree of imperviousness .

6. A security paper according to any one of the preceding claims, wherein said coating is pervious to radiation in the emission wavelength range, preferably it is per- vious to radiation having a wavelength of at least 340 nm.

7. A security paper according to any one of the preceding claims, wherein an authenticity code is provided in printing ink, which printing ink is at least partially impervious to radiation in the excitation wavelength range.

8. A security paper according to any one of the preceding claims, wherein the entire coating is embodied as printing ink.

9. A security paper according to any one of the preceding claims provided with authenticity characteristics, such as a watermark, fibres that light up or the like.

10. A method for manufacturing a security paper according to any one of the preceding claims, wherein a photoluminescent substance is incorporated in and/or applied onto a paper, characterized in that a photoluminescent substance having an excitation wavelength ranging from about 220 to 300 nm and an emission wavelength above the excitation wavelength range is used, wherein a coating which is at least partially impervious to radiation in the excitation wave- ^' length range is applied to at least part of the security paper, on at least one side thereof.

11. A method according to claim 10, wherein said photoluminescent substance is applied to the paper in a layer of ink by means of a printing process.

12. A method according to claim 10, wherein said photoluminescent substance is applied to the paper in a coating.

13. A method according to any one of the claims 10-

12, wherein said photoluminescent substance is applied to the security paper as printing ink, wherein preferably at least an authenticity code is applied on the security paper.

14. A method according to any one of the claims 10-

13, wherein said coating is applied onto the security paper in a coating process.

15. A method for detecting any falsification and/or forgery of a document, wherein the document is irradiated from one side with an excitation wavelength of about 220-300 nm and wherein an emission having a wavelength above 300 nm is detected, wherein the value of the detected emission is compared to a reference value for detecting any falsification or forgery.

16. A method according to claim 15, wherein said reference value has been obtained from a reference document corresponding to the document being examined, wherein preferably the value of the detected emission is also compared to values of detected emission of the document being examined or to a second reference value obtained from said val- ues .

17. A device for detecting falsifications and/or forgeries of documents, which device comprises a radiation source, a detection element, and a processing unit for processing a detection signal of the detection element, which device is characterized in that the radiation source delivers radiation having an excitation wavelength range of about 220-300 nm, and in that the detection element is arranged for detecting radiation having a wavelength above 300 nm, wherein the processing unit compares the detection signal to a reference value for the purpose of detecting any falsification.

18. A device according to claim 17, wherein said radiation source comprises a low-pressure mercury lamp.