Note: Descriptions are shown in the official language in which they were submitted.
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SECURITY DOCUMENT
The invention relates to security documents, such as banknotes, and
methods for processing those documents.
A variety of devices have been proposed in the past to help visually impaired
users in the recognition of security documents, particularly banknotes. For
example,
blind people must rely upon their sense of touch to determine the nature and
validity
of a document, such as through the sensing of a Braille feature.
Tactile features to assist visually-impaired users in the recognition of
security
documents have been described in the prior art
EP1159139 describes security documents, particularly banknotes bearing
durable embossings that may be perceived by the sense of touch. The invention
disclosed therein seeks to overcome a particular problem that arises in
providing
tactile indicia, notably the very high rate at which such features are damaged
through handling both by the general public and by cash sorting machines
employed
by banks and other such institutions.
US2004008871 describes security documents bearing tactually-perceptible
alphanumeric characters. The applicant describes a number of ways in which
tactile
perceptibility might be introduced, including embossing; tactile ink
features;. the
application of textured coatings containing, for example, particulate matter;
overlays;
and the application of characters having contrasting thermal conductivity or
coefficient of friction to that of the substrate.
Similarly, US2006119096 discloses security documents provided with a variety
of tactile features including raised or recessed characters; perforations;
areas of
contrasting roughness, hardness, elasticity, coefficient of friction, thermal
conductivity or stickiness.
FR-A-2925924 describes a security document such as a banknote including a
bright watermark and a security structure having a semi-reflecting zone
superimposed on the watermark.
WO 2009/062229 published on 22 May 2009 (after the priority date of the
present application) describes a security document having transparent edge
windows whose shape varies with different denominations of banknotes.
In accordance with a first aspect of the present invention, we provide a
banknote which is one of a series of banknotes of different denominations, the
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banknote comprising a polymer substrate having a substantially opaque region
defining or carrying indicia relating to the banknote, and a substantially
transparent peripheral region wherein the substantially opaque central region
has a shape unique to the denomination of the banknote.
We have appreciated that with partially sighted users, it is possible to take
advantage of the fact that they have some viewing capability by providing a
substantially opaque secure banknote with a substantially transparent
peripheral
region. Such a banknote would offer excellent contrast between the transparent
and
opaque regions provided thereupon enabling partially-sighted users to perceive
the
distinctive shape of the opaque region silhouetted against the light
background
visible through the transparent periphery. Such partially sighted users will
be able to
perceive the edge of the banknote and thus identify the transparent region.
Furthermore, the use of a substantially transparent region prevents the
generation of
a "simple" counterfeit arising from the increasing popularity of colour
photocopiers
and other imaging systems and the improving technical quality of colour
photocopies. In addition the clear transparent region provides a feature that
is easily
verifiable by the general public. The present invention thus provides a
feature that is
at once difficult to reproduce whilst also providing tactility and a high
visual contrast
for recognition by visually impaired users.
High visual contrast in security documents has been provided in the past by
the incorporation of transparent features into an otherwise opaque substrate.
However, it has not been recognized in the past that transparent features
could be
used not only for security purposes but also to assist the partially sighted.
W08300659 describes a polymer banknote formed from a transparent
substrate comprising an opacifying coating on both sides of the substrate. The
opacifying coating is omitted in localised regions on both sides of the
substrate to
form a transparent region.
W00039391 describes a method of making a transparent aperture in a
paper substrate. This is achieved by blinding one or more selected areas of a
porous support surface, depositing a first layer of paper fibres onto the
porous
support surface around the blinded areas, bringing an impermeable elongate
security thread to lie in contact with the blinded areas of the support
surface such
that at least the edges of the elongate security thread overlie the deposited
layer,
and depositing a further layer of paper fibres over the first layer and the
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impermeable strip to securely embed the edges of the elongate security thread
within the paper. The blinded areas are impermeable, which substantially
prevents
the deposition of fibres thereon before the elongate security thread is laid
thereover.
Thus, substantially no paper fibres are deposited on one side of the elongate
security thread in a central region between edges of the elongate security
thread to
thereby expose a continuous area of the elongate security thread at a first
surface of
the paper. Additionally a plurality of discrete translucent or transparent
windows is
formed in a second surface of the paper in which the elongate security thread
is
exposed.
An alternative method for forming a transparent region in a paper document
is to apply a transparent film in the form of a patch or a strip over a hole
formed in
the document either during- or post manufacture of the substrate. Such
approaches
have been described within the prior art for example EP723501, EP724519 and
W003054297.
Another example of banknote incorporating transparent windows is the
commemorative 5 polymer banknote issued on 21 December 1999 by Northern
Bank of Northern Ireland.
In preferred constructions, the substantially transparent peripheral region
extends fully around the periphery of the banknote. However, in some cases,
the
substantially transparent peripheral region may only extend substantially
fully
around the periphery of the banknote, in other words having some small breaks
defined by opaque portions.
For the purpose of the current invention a transparent region is defined as
one whose optical density when measured on a transmission densitometer, with
an
aperture area equivalent to that of a circle with a 1 mm diameter, is
preferably less
than 0.3, more preferably less than 0.2 and even more preferably less than
0.1. A
suitable transmission densitometer is the MacBeth TD932.
The contrasting opaque region typically has an optical density when
measured on a transmission densitometer, with an aperture area equivalent to
that
of a circle with a 1 mm diameter, preferably greater than 0.4, more preferably
greater than 0.5 and even more preferably greater than 0.6. A suitable
transmission
densitometer is the MacBeth TD932.
Preferably, the ratio of the optical density of the substantially transparent
peripheral region to the optical density of the substantially opaque central
region is
no more than 0.6.
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Additional indicia such as micro-text, fine lined filigree patterns,
metallised or
demetallised indicia, embossings and other similar indicia may be applied to
the
transparent area of the banknote, provided that there is no significant
reduction in
the optical contrast between the transparent and opaque regions. In the same
manner semi-transparent or transparent optically variable devices may be
applied to
the transparent area of the banknote for example liquid crystal films or
coatings,
photonic crystal films or coatings and iridescent coatings.
Furthermore, additional opaque features including those produced by
printing, the application of foils or transfers including those bearing
optically variable
interference or diffractive structures; and other known security indicia
bearing
substrates may be applied to either the opaque or transparent regions. In the
latter
case, the additional opaque feature will be perceived by a partially-sighted
user as
an additional island of high contrast between the transparent and opaque
regions of
the banknote.
Additional security features known in the art such as optically-variable
interference or diffractive structures may be incorporated into the banknote
such that
they may be viewed through the said window area.
We have also realized that it is possible to utilize transparent regions in
banknotes to assist banknote sorters to distinguish between banknotes of
different denominations. Thus, in accordance with a second aspect of the
present invention, a method of operating a banknote sorter to distinguish
between banknotes of different denominations, wherein each banknote is one of
a series of banknotes of different denominations each including at least one
substantially transparent region, the shape and/or location of the transparent
region being unique to the denomination of the banknote, the method comprising
operating the banknote sorter to detect a transparent region in a banknote
being
processed, to determine the shape and/or location of the detected transparent
region, and to use the detected shape and/or location to identify the
denomination of the banknote.
Conventional banknote sorters typically use information such as the size of
the banknote to determine its denomination but this, of course, is not helpful
in
countries where banknotes all have the same size, such as the US. In those
countries, typically pattern recognition is used to detect denomination
related indicia
on the banknotes. However, in this aspect of the invention, it is possible not
only to
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use transparent windows or other peripheral regions to provide security
features
and/or benefits to the partially sighted, but also to enable banknote sorters
to sort
the banknotes according to denomination. The detection of the opaque and
transparent regions can be achieved very easily by monitoring variations in
intensity
5 of light transmitted through the banknotes as they pass a suitable detector.
It will be recognized that the inventive concept can be applied more
widely than banknotes. Thus in accordance with a third aspect of the present
invention, we provide a security document comprising a polymer substrate
having a substantially opaque region defining or carrying indicia relating to
the
document, and a substantially transparent peripheral region. Examples of
security documents include vouchers, tickets, gift tokens and the like. The
shape of the opaque region can define the value of the security document.
Some examples of banknotes according to the invention will now be
described with reference to the accompanying drawings, in which:-
Figures 1 a-1 d illustrate schematically a first series of banknotes of
different
denominations;
Figures 2a-2d are views similar to Figures 1 a-1 d but of a second example;
Figure 3 illustrates a third example of a banknote according to the invention;
Figure 4 illustrates a fourth example of a banknote according to the
invention; and,
Figures 5a and 5b illustrate cross-sections through two further examples of
banknotes according to the invention.
Figure 1 shows examples of a series of secure documents, for example,
banknotes of increasing monetary value, according to examples of the current
invention in plan-view in transmitted light as they would be viewed by a user
or
banknote sorting machine. In this example, each secure document or banknote
comprises a transparent polymeric substrate 1 onto which is applied an opaque
coating in a region 2A-2D. The opaque regions 2A-2D need not be disposed
centrally upon the security document 1, nor do they need to be regular,
symmetrical
nor bounded by straight lines, i.e. polygonal. However, rotationally symmetric
designs are to be preferred for their compatibility with cash handling
systems. In the
present example, the five denomination is represented by an oval printed
region 2A;
the ten denomination by a rectangle 2B; the twenty denomination by a hexagon
3C;
and the fifty denomination by a parallelogram 2D. Each opaque region is fully
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surrounded by a transparent region 3A-3D. Each opaque region typically has an
optical density when measured on a transmission densitometer, with an aperture
area equivalent to that of a circle with a 1 mm diameter, preferably greater
than 0.4,
more preferably greater than 0.5 and even more preferably greater than 0.6.
Each
transparent region 3A-3D typically has an optical density when measured on a
transmission densitometer, with an aperture area equivalent to that of a
circle with a
I mm diameter, preferably less than 0.3, more preferably less than 0.2 and
even
more preferably less than 0.1. The high contrast obtained between the printed
opaque and transparent regions of documents prepared according to the present
teaching is readily apparent and is typically no more than 0.6.
In order to identify the denomination of one of these banknotes, it can be
held up to a light so that light is transmitted through the transparent region
of the
banknote and the distinctive shape of the opaque region will be readily
recognized
even by a partially sighted person.
Figure 2 shows a further embodiment of the current invention where the
documents have the same main opaque regions 2A-2D as in Figure 1 but
additionally the 5 denomination document has two opaque islands 4A within the
transparent periphery 2A (Figure 2a), and the 10, 20 and 50 denomination
documents have a transparent window area 5B-5D wholly enclosed within the
opaque region of the document as with conventional polymeric banknotes.
Figures 3 and 4 show similar documents but where the transparent periphery
comprises micro-text 6 (Figure 3 not shown to scale) and fine line detail 7
(Figure 4
not shown to scale) respectively.
The opaque regions 2A-2D can be in the form of a coating applied by any
conventional printing process, but typically this is a gravure printing
process. The
opaque coating may comprise a single layer applied to one side of the
transparent
substrate 1 or one or more layers (10A,10B Figure 5a; 11A-11D Figure 5b)
applied
to both sides of the transparent substrate. The opaque coating is omitted in
one or
more regions of the document to provide a transparent periphery and,
optionally,
additional transparent areas of the secure document.
Figure 5 illustrates examples of the documents in cross-section. Figure 5a
illustrates an example where the transparent periphery 3 (corresponding to 3A-
3D in
Figure 1) is formed by omitting the opaque pigmented coatings in that region
and
thus fully exposing the transparent polymeric substrate. In a further example,
illustrated in Figure 5b, the transparent periphery 3 only has one layer 11B
of
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pigmented coating while the remainder of the document has four layers. The
coating in the transparent periphery must be sufficiently light transmitting
that the
optical density of the region does not exceed 0.3.
The opaque coating of the secure document, such as a banknote, then
undergoes further standard security printing processes including one or more
of the
following; wet or dry lithographic printing, intaglio printing, letterpress
printing,
flexographic printing, screen-printing, and/or gravure printing.
A transparent periphery or other transparent window also enables the
transparent region to be easily detected by transmitted light detectors on
cash
handling equipment. I n some detector systems however it may be difficult to
differentiate between the edge of the document and the transparent periphery
and
the detector may inaccurately interpret the transparent periphery as the edge
of a
document having an incorrect length. This problem may simply be overcome by
programming the detector to recognise the length of the opaque region rather
than
the length of the full document. Alternatively, unlike a void, the polymeric
substrate
forming the periphery will reflect a fraction of the incident light and this
reflected light
could be detected by a second detector to confirm that this is part of the
document
and not an edge. A similar method for determining the presence of enclosed
transparent regions in polymer banknotes is described in US20030043365.
In a further embodiment, to avoid confusion with the edge of the note, the
transparent periphery can be provided with an optical structure which provides
a
scattering or diffusing screen. This will reduce the level of transmitted
light below
that observed for a fully transparent substrate or a void, but the level of
transmitted
light will still be such that a significant portion of light can pass through
the screen
and activate the detectors.
