CA2173413C

CA2173413C - Methods of cancellation and compositions therefor

Info

Publication number: CA2173413C
Application number: CA002173413A
Authority: CA
Inventors: Eric Arnold Lyen; Ianthe Elizabeth Murray Graham
Original assignee: Canada Post Corp
Current assignee: Canada Post Corp
Priority date: 1996-04-03
Filing date: 1996-04-03
Publication date: 2005-10-25
Anticipated expiration: 2016-04-03
Also published as: CA2173413A1

Abstract

The invention relates to the cancellation of printed values by use of colour former/colour developer systems. Thus the invention provides ink compositions for conferring a value on an article, the compositions comprising a taggant having a characteristic UV absorption or emission spectrum to indicate said value and a first component of a two component colour former/colour developer system wherein the composition contains sufficient of said first component so that when the second component of said colour former/colour developer system is applied to the first component, the colour developed masks and effectively cancels the value indicated by the taggant. The invention also provides articles coated with the ink compositions and methods of cancelling printed values by use of the compositions.

Description

METHODS OF CANCELLATION AND COMPOSITIONS THEREFOR
The invention relates to cancellation such as the cancellation of printed values.
Various articles, such as travellers' cheques, passports, visas, stock certificates, gift certificates, events tickets, identification documents, bonds, public transit tickets, passes and postage stamps, have values conferred on them by applying a printed image. The value may be visually detectable from the image, or machine detectable, or both. When the value has expired, for example by the performance of some service, the value must be cancelled.
A substance which indicates the value is sometimes referred to as a taggant. The value may be applied by means of a taggant as a component of an ink. In the case of postage stamps the taggant may be a compound having a characteristic UV absorption or emission spectrum, such as a compound having UV fluorescence. The image obtained is thus readable by an apparatus which detects the characteristic UV
spectrum of the taggant. In this way, the authentic value of the stamp can be verified at high speed. The design of the fluorescent image can be used to convey information such as different individual values for different stamps.
For postage stamps, in the past, the value has been cancelled by the application to the stamp of a black postmark which also serves as a cancellation ink. This form of cancellation is visible and has machine readability. The mark has a design to convey information about the date and ~1'~~~-1~

2 time of sorting. It does not cover the whole of the stamp.
Rt the high speeds of postage sorting, although a stamp may have been cancelled in this way, it is possible for it to be re-used and escape detection.
It has now been discovered that an effective means of cancelling a printed value is provided when the ink containing the taggant further contains a first compound which when activated, or combined with a second compound, will mask the taggant. Such an ink may be referred to as a connotative ink. The first and second compounds thus function as first and second components of a two-component masking or cancelling system.
Suitable two-component masking systems are colour developer/colour former systems. These are two component systems which develop a colour when combined. Thus for an ink composition which contains one of the components of a colour developer/colour former system together with a taggant which is a UV fluorescent compound, when the complementary component of the system is applied, the characteristic UV
fluorescence will be masked by the development of the colour.
Since the fluorescent compound is responsible for indicating the value, the value can be effectively cancelled.
According to one aspect of the present invention there is provided an ink composition for conferring a value on an article, the composition comprising a taggant having a characteristic UV absorption or emission spectrum to indicate said value and a first component of a two component colour 727'50-401

3 former/colour developer system wherein the composition contains sufficient of said first component so that when the second component of said colour former/colour developer system is applied to the first component, the colour developed masks and effectively cancels the value indicated by the taggant.
According to other aspects, the present invention provides an article coated with the above composition, a method of coating an article by applying the above composition and a method of cancelling the printed value of an article coated with the above composition.
In accordance with another aspect of the present invention, there is provided a method of cancelling a value of an article, the value indicated by a taggant ink composition applied to the article, said taggant ink composition comprising a taggant having a characteristic W
absorption or emission spectrum to indicate said value and further comprising a first component of a two component colour former/colour developer system, wherein said taggant ink composition contains sufficient of said first component that when the second component of said colour former/colour developer system is applied to the first component, the colour developed masks and effectively cancels the value indicated by the taggant, which method comprises applying the second component to the taggant ink composition.
In accordance with yet another aspect of the present invention, there is provided a method of printing an article with a cancellable value which method comprises applying to the article a taggant ink composition comprising a taggant having a characteristic UV absorption or emission spectrum to indicate said value and a first component of a two component colour former/colour developer system wherein 3a the composition contains sufficient of said first component so that when the second component of said colour former/colour developer system is applied to the first component, the colour developed masks and effectively cancels the value indicated by the taggant.
In accordance with yet another aspect of the present invention, there is provided an article coated with a taggant ink composition comprising a taggant having a characteristic W absorption or emission spectrum to indicate said value and a first component of a two component colour former/colour developer system wherein the composition contains sufficient of said first component so that when the second component of said colour former/colour developer system is applied to the first component, the colour developed masks and effectively cancels the value indicated by the taggant.
In accordance with yet another aspect of the present invention, there is provided an ink composition for conferring a value on an article, the composition comprising a taggant having a characteristic UV absorption or emission spectrum to indicate said value and a first component of a two component colour former/colour developer system wherein the composition contains sufficent of said first component so that when the second component of said colour former/colour developer system is applied to the first component, the colour developed masks and effectively cancels the value indicated by the taggant.
In accordance with yet another aspect of the present invention, there is provided an ink composition for conferring a value on an article, the composition comprising a taggant having a characteristic W absorption or emission spectrum to indicate said value and a colour former, wherein ' 72750-401 3b the composition contains sufficient colour former so that when a complementary colour developer is applied to the colour former, the colour developed masks and effectively cancels the value indicated by the taggant.
If the colour developer is in the ink with the taggant, the first component of the two component colour former/colour developer system is the colour developer and the second component would be the colour former and would be in the cancelling ink composition. Conversely, if the colour former is in the taggant ink composition then the first component is the colour former and the colour developer will be in the cancelling ink composition .and will be the second component. In a preferred embodiment, the colour developer is in the taggant ink composition and the colour former is in the cancelling ink composition.
Any colour developer and colour former that combine to produce a colour which masks the taggant can be used. The precise combinations should be selected so that they do not interfere with the other ink components before the cancellation step. For postage stamps, it is preferred that

4 the component with the taggant, the first component, should be daylight invisible. The colour formed should not be readily solvent removable, because otherwise cancellation could be reversed. Of course, if the colour is only removable by a solvent which also removes the taggant, then cancellation could not be reversed without loss of the postage value.
Colour developers that can be used in the invention are well known in the art and are generally solid acidic substances including phenolic resins, beta naphthol, kaolin, attapulgite, montmorillonite, bentonite and acid bleaching earth. Suitable colour developers also include those disclosed in U.S. Patent 4,263,047 (Miyamoto et al.), Colour developers are available in various forms such as powders or resins. These can be incorporated into aqueous, solvent or oil based vehicles to produce inks for any printing process.
The colour formers for use in the invention include 2a those compounds referred to in the art as leuco dyestuffs and can be any colour formers which generate sufficient colour to mask the taggant upon reaction with the colour developers.
Suitable colour formers include those disclosed in the above U.S. Patent 4,263,047 (Miyamoto et al.). Commercially available colour formers include: the React Dyes of BASF AG
of Ludwigshafen, Germany, for example React Yellow R (a pyridine derivative) and React Blue G (benzoyl-leucomethylene

5 blue); the PERGASCRIPT colour formers of Ciba-Geigy Corporation (triarylmethane dyes); and the COPIKEM colour formers of Hilton-Davis of Cincinnati, Ohio. Suitable Pergascript colour formers which are daylight invisible are=
Pergascript Blue I-2R; Pergascript Blue I-2G; Pergascript Black I-2G; Pergascript Red I-6B. Pergascript Hlue I-2R is preferred.
Colour formers may be available as powders or encapsulated and dispersed in an aqueous medium. The powders can be incorporated into aqueous, solvent or oil based vehicles for any printing process. The colour formers may be pale coloured, but are preferably colourless.
The colour former should form a sufficiently intense colour upon reaction with the colour developer to reduce the UV fluorescent signal below the machine detectable limit, and maintain a stable colour. In the case of postage stamps, the colour former should not develop colour on envelope paper before reaction with the colour developer.
The masking effect is dependant on the colour and the density of the colour developed. The darker the developed colour, the greater the masking effect.
Practically any colour former and colour developers can combine to develop colour and reduce the UV fluorescent signal of a taggant. Particular formulations can be selected according to factors such ass the permanence of the developed colour= the suitability of the colour developers, or colour formers, for use in the particular ink, for example a ;~-1 '7 3413

6 lithographic ink; the inertness of the colour former or colour developer to any other components of the inks in which they are formulated and to any filler or other additives in the paper which is to be printed; and the odour or toxicity of the formulation.
Solvents that may be used for dissolving colour formers are preferably those which dissolve at least 0.2~ by weight of the colour former. Suitable solvents for cancelling ink formulations which contain the colour former are chlorinated solvents, xylene or dipentene such as is commercially available as "Xylene substitute", alcohols such as methanol, isopropyl alcohol and ethanol and alkylated benzenes such as SURESOL 150ND and ethyl acetate. Ethanol and ethyl acetate give satisfactory colour intensity and are preferred for health and environmental reasons.
Taggants suitable for the present invention may be any compounds which have a characteristic UV absorption or emission spectrum which can be masked by a two component colour developer/colour former system. The cancelling system depends on colour development, thus it is preferred to use colourless (white body) fluorescent taggants in colourless (invisible) or lightly coloured inks. In the case of postage values, such as stamps, effective taggants are fluorescent compounds such as Cartax DXDP from Sandoz, Scanning compounds #4, #5 and #6 available from Angstrom Industries and some pigments in the CD series from Hoechst such as CD 704, CD312 and CD 340. A particular fluorescent compound which is ~ ~'~~41 ~

7 suitable is the Hoechst fluorescent pigment CD 704.
The components of a typical taggant ink composition would depend on whether it contained the colour former, or the colour developer. For example, a typical taggant ink containing colour former might suitably be: from about 1.0%
to about 15.0% of taggant; from about 1.0% to about 5.0% of colour former; and from about 80.0% to about 95.0% of a vehicle or solvent. A typical taggant ink containing colour developer might suitably be: from about 1.0% to about 15.0%
of taggant; from about 5.0% to about 85.0% of colour developer; and from about 10.0% to about 90.0% of a vehicle or solvent. The vehicle or solvent may be, for example, a drying oil such as linseed oil, tung oil or a varnish such as a resin dissolved in a solvent. Other additives may be, for example, up to 5% by weight of a wax and up to 10% by weight of an extender. However, waxes and extenders have little or no effect on colour development and it is preferred that they are not added to the ink formulations. Of course, the quantities of colour former and colour developer should be such as to ensure that the developed colour is sufficient to reduce the UV signal of the taggant below the level of detection desired and thus effect cancellation.
The components of the cancelling ink formulation would also depend on whether the formulation contains the colour developer or the colour former. Preferably the cancelling ink formulation will be a solution of the colour former or colour developer in a suitable vehicle or solvent ,2-~'~ ~~13

8 in a concentration suitable to mask or cancel the taggant value.
Colour developer/colour former systems are suitable for any printing process including letterpress, lithographic, flexographic, gravure, silk-screen and intaglio printing.
The taggant and cancelling inks can be formulated in the conventional way by mixing the required ingredients.
A lithographic off-set ink formulation is preferably non-yellowing and retains its fluorescence and ability to develop colour after heat aging.
A taggant ink composition containing a colour developer does not require any special means of application.
In the case of application of the ink to postage stamps, lithographic or letterpress printing is suitable.
The taggant inks may be cancelled by spray application of the cancelling ink, such as a colour former cancelling ink, using a propane propelled air brush or by ink jet printing (controlled sprayingy. Such non contact methods are suitable in the case of postage stamps since they provide ease of application onto the stamp face area and reduce dye transfer contamination of the applicator. An anilox roller with wiper blade may also be suitable. The cancelling inks may also be applied by hand with an aerosol spray or a felt tipped marking pen.
In a mechanized postage value system, the means for cancellation can follow the fluorescent marker detection, either before or after the conventional cancellation machine ,~1~7 ~A-l~

9 which applies a postmark.
Examples of conventional cancellation machines are the culler-facer-canceller (CFC) machines such as TOSHIBA
models 42 and 81 or AEG model 885. Culling removes non-standard size mail pieces, facing includes scanning the mail for the fluorescent taggant to verify the postal value, and cancelling applies the postmark.
Depending on the speed of the CFC machines a longer drying section or drying unit may be appropriate after applying a colour forming solution to avoid set-off onto an adjacent mail piece.
Since the first component (masking precursor) is already present with the taggant, wherever the taggant appears, cancellation may be effected by applying the second component to the whole of the printed image. Thus the taggant and masking precursor will simultaneously receive the cancelling component and any taggant in the image will be masked by the ensuing colour development. If the taggant is only applied to a specific area of the whole printed image, then application of the cancelling component can be directed to that specific area alone to effect masking and thus cancellation.

10 FORMULATIONS
TAGGANT INK COMPOSITIONS
Formulation No.l 15% w/w CD 704 fluorescent Pigment - Hoechst 85% w/w Schenectady HRJ 4476 Resin Colour Developer Formulation No.2 15% w/w CD 704 fluorescent Pigment - Hoechst 85% w/w OPAS Print-On CF Coating (FA-378) - Mead CANCELLING INK COMPOSITIONS
Formulation No.3 0.33% w/w Ciba Geigy Pergascript Hlue I-2R
99.67% w/w Ethyl Alcohol 2H
Formulation No.4 2.0% w/w Ciba Geigy Pergascript Hlue I-2R
98% w/w Ethyl acetate Formulation No.S
1.0% w/w Ciba Geigy Pergascript Blue I-2R
99% w/w Ethyl acetate Formulation No.6 0.5% w/w Ciba Geigy Pergascript Hlue I-2R
90% ethyl alcohol 9.5% dipentene Example 1 Three hundred stamps were printed using a colour developer taggant ink comprising 15% CD 704 pigment dispersed ~:1'~~~-~ ~
m in a commercially available colour developer ink (taggant ink formulation No. 2 above). One hundred and fifty of these stamps were cancelled by spraying the whole stamp with a solution according to cancelling ink formulation No. 6 above.
The cancellation ink developed a blue colour only in the areas on which the taggant ink composition had been applied.
The other one hundred and fifty stamps were left uncancelled.
The stamps were then applied to envelopes and passed through a conventional postage value detection and cancellation system (CFC). The envelopes bearing the 150 stamps which had been cancelled by application of the cancelling ink spray were rejected within the rejection limits of the system (from 95.3% to 100%). The envelopes bearing the 150 uncancelled stamps were all accepted as authentic postage values.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A method of cancelling a value of an article, the value indicated by a taggant ink composition applied to the article, said taggant ink composition comprising a taggant having a characteristic UV absorption or emission spectrum to indicate said value and further comprising a first component of a two component colour former/colour developer system, wherein said taggant ink composition contains sufficient of said first component that when the second component of said colour former/colour developer system is applied to the first component, the colour developed masks and effectively cancels the value indicated by the taggant, which method comprises applying the second component to the taggant ink composition.

2. A method according to claim 1 wherein the first component is a colour former and the second component is a colour developer.

3. A method according to claim 1 wherein the first component is a colour developer and the second component is a colour former.

4. A method according to claim 2 wherein the taggant ink composition comprises from about 1% to about 15% by weight of the taggant and from about 1% to about 5% of the colour former.

5. A method according to claim 3 wherein the taggant ink composition comprises from about 1% to about 15% by weight of the taggant and from about 5% to about 85% of the colour developer.

6. A method according to claim 3 wherein the taggant is a fluorescent compound.

7. A method according to claim 1 wherein the article is a postage stamp.

8. A method according to claim 3 wherein the article is a postage stamp.

9. A method according to claim 6 wherein the article is a postage stamp.

10. A method of printing an article with a cancellable value which method comprises applying to the article a taggant ink composition comprising a taggant having a characteristic UV absorption or emission spectrum to indicate said value and a first component of a two component colour former/colour developer system wherein the composition contains sufficient of said first component so that when the second component of said colour former/colour developer system is applied to the first component, the colour developed masks and effectively cancels the value indicated by the taggant.

11. A method according to claim 10 wherein the first component is a colour former and the second component is a colour developer.

12. A method according to claim 10 wherein the first component is a colour developer and the second component is a colour former.

13. A method according to claim 12 wherein the taggant is a fluorescent compound.

14. A method according to claim 10 wherein the article is a postage stamp.

15. A method according to claim 12 wherein the article is a postage stamp.

16. A method according to claim 13 wherein the article is a postage stamp.

17. An article coated with a taggant ink composition comprising a taggant having a characteristic UV absorption or emission spectrum to indicate said value and a first component of a two component colour former/colour developer system wherein the composition contains sufficient of said first component so that when the second component of said colour former/colour developer system is applied to the first component, the colour developed masks and effectively cancels the value indicated by the taggant.

18. An article according to claim 17 wherein the first component is a colour former and the second component is a colour developer.

19. An article according to claim 17 wherein the first component is a colour developer and the second component is a colour former.

20. An article according to claim 19 wherein the taggant is a fluorescent compound.

21. An article according to claim 17 which is a postage stamp.

22. An article according to claim 19 which is a postage stamp.

23. An article according to claim 20 which is a postage stamp.

24. An ink composition for conferring a value on an article, the composition comprising a taggant having a characteristic UV absorption or emission spectrum to indicate said value and a first component of a two component colour former/colour developer system wherein the composition contains sufficient of said first component so that when the second component of said colour former/colour developer system is applied to the first component, the colour developed masks and effectively cancels the value indicated by the taggant.

25. An ink composition for conferring a value on an article, the composition comprising a taggant having a characteristic UV absorption or emission spectrum to indicate said value and a colour former, wherein the composition contains sufficient colour former so that when a complementary colour developer is applied to the colour former, the colour developed masks and effectively cancels the value indicated by the taggant.

26. An ink composition for conferring a value on an article, the composition comprising a taggant having a characteristic UV absorption or emission spectrum to indicate said value and a colour developer, wherein the composition contains sufficient colour developer so that when a complementary colour former is applied to the colour developer, the colour developed masks and effectively cancels the value indicated by the taggant.

27. A composition according to claim 25 comprising from about 1% to about 15% by weight of the taggant and from about 1% to about 5% of the colour former.

28. A composition according to claim 26 comprising from about 1% to about 15% by weight of the taggant and from about 5% to about 85% of the colour developer.

29. A composition according to claim 26 wherein the taggant is a fluorescent compound.