Note: Descriptions are shown in the official language in which they were submitted.
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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.
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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
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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.
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