Note: Descriptions are shown in the official language in which they were submitted.
CA 02263616 1999-03-O1
DURABLE TACTILE INDICIA FOR BANKNOTES/
DOCUMENTS AND ME THOD OF MAKING SAME
Field of the Invention
The invention is in the field of document printing and
production and, in particular, relates to the production of
documents, such as banknotes, having embossments therein which
provide durable tactile indicia for use, for example, by persons
who are blind.
Backcrround
The denominational value or identity of banknotes and many
other types of documents can be readily discerned by persons
whose eyesight is not impaired but for persons who are blind it
is necessary to use other means, such as a portable reader
designed for the particular document in question, to determine
such information. A printed Braille section placed on such a
document could provide a means for such identification and,
advantageously, would be integral to the document and avoid the
need for an auxiliary reading device. However, the broad
circulation and public handling of documents such as banknotes
subjects them to substantial wear and any Braille printing
applied to such documents in the normal manner of embossed
printing would not be sufficiently durable because the
embossments would soon be compressed and become non-tactile.
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Consequently, there is a need in the industry for a means
of providing to security documents, banknotes, etc. durable
(i.e. relatively permanent) tactile identifying indicia which
are able to withstand the substantial wear caused by public
circulation and handling and can be readily used by persons with
impaired eyesight to determine the denomination or
identification of such document.
Summary of the Invention
In accordance with the invention there is provided a sheet
material (e. g. a sheet or laminate comprising paper) having
tactile indicia the tactility of which is resistant to
deterioration. The sheet material has therein at least one
embossment forming the indicia. A first surface and a second
surface are provided by the sheet material and one of the
surfaces defines a cavity in the area of the embossment. A
layer of reinforcing material is provided to at least the area
of that one surface which comprises the cavity. The reinforcing
material may be selected from the group consisting of varnishes,
inks, adhesives and caulking compounds. Preferably, the
thickness of the sheet material is between 75 micrometers and
150 micrometers, the outer width of the embossment is between
500 micrometers and 1200 micrometers and, for varnish, the
thickness of the reinforcing material is between 20 micrometers
and 40 micrometers.
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The indicia may comprise a plurality of embossments
arranged in a predetermined pattern such that the indicia
enables a sight impaired person to identify one or more
predetermined characteristics of the sheet material (e.g. the
denomination) by means of feel. Preferably the indicia comprise
one or more spaced symbols and each symbol comprises a plurality
of rows and columns of embossments (four rows and two columns
being preferred) wherein the outer width of each embossment is
about 1000 micrometers, the embossments are spaced apart about
2000 micrometers in the symbols and the symbols are spaced apart
about 14,500 micrometers.
Also provided in accordance with the invention is a method
of making a sheet material having tactile indicia the tactility
of which is resistant to deterioration. The steps of the method
include embossing a sheet material comprising first and second
surfaces with at least one embossment to form the indicia
whereby one of the surfaces defines a cavity in the area of the
embossment. A layer of a reinforcing material is applied to
that one surface of the sheet material in at least the area
comprising the cavity and the reinforcing material is dried
and/or cured.
Brief Description of the Drawincrs
The invention is described in detail below with reference
to the following drawings which illustrate a preferred
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embodiment of the invention.
Figure 1 is a cross-sectional view of a banknote substrate
showing a single embossment therein which is reinforced in
accordance with the present invention;
Figure 2 is a front view of a banknote having incorporated
therein, in a pattern in the upper right-hand corner of the
banknote, tactile embossed indicia comprised according to that
shown in Figure 1;
Figure 3 is an enlarged, schematic cross-sectional view as
seen at section III-III of Figure 2;
Figure 4 shows examples of three different patterns ((a),
(b) and (c)) of tactile embossed indicia comprised according to
that shown in Figure 1; and,
Figure 5 shows a ten dollar banknote with a preferred
configuration of embossments therein.
Detailed Description of a Preferred Embodiment
Figure 1 of the drawings shows a cross-sectional view of a
sheet material 30 in accordance with the claimed invention. In
this example the sheet material 30 is a banknote 10 (see Figures
2 and 3) which has been embossed in a conventional manner by
pressing the sheet between male and female dies or between a
male die and compressible blanket. The sheet material may, for
example, be comprised of paper or a lamination of a
thermoplastic layer sandwiched by two paper layers and,
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alternatively, could be any of a variety of other substrates,
such as plastic, which will be readily recognized by one skilled
in the art. The sheet material 30 has first and second
surfaces, one of which is the top surface 35 and the other of
which is the bottom surface 37. In the illustrated embodiment
the embossments are situated to provide raised areas on the top
surface of the bank note but, if desired, an embodiment
providing the embossments on the bottom surface of the bank note
could instead be selected.
In the embodiment shown by the drawings, each embossment 20
creates a raised area in the top surface 35 of the sheet
material and a cavity 25 in the bottom surface 37 of the sheet
material. As shown by Figure 2, the banknote 10 is embossed
with a plurality of embossments 20 forming tactile indicia which
are arranged in a predetermined pattern and can be used by a
sight impaired person to identify the characteristic
denomination of that banknote by feeling and decoding the
indicia.
For each embossment 20 the bottom surface of the sheet
material in (at least) the area comprising the cavity 25 is
provided with a layer of a fluid reinforcing material 40 which,
when dried and/or cured, reinforces the cavity 25. This layer
is applied to the surface of the sheet material by coating the
surface and some of the reinforcing material is absorbed into
the sheet material. The thickness of the reinforcing layer (C)
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specified herein means the thickness of the layer when it is
applied (i.e. before some of it is absorbed into the sheet
material).
This reinforcement of the embossment renders its tactility
resistant to deterioration when the sheet material 30 is
subjected to wear (i.e. since the walls of the embossment are
strengthened the embossment is less likely to be flattened if
pressure is applied to it). The reinforcing material 40 may be
any suitable material whose nature and durability is such that'
it reinforces the embossment so as to render it more permanent
and is able to bond satisfactorily to the selected sheet
material and retain flexibility when dried and/or cured (i.e.
without becoming brittle) such as by radiation curing,
oxidation, polymerization, solvent evaporation, solvent
penetration or electron beam. Preferably the reinforcing
material to be selected should be compatible with the printing
means used to print the banknote or other document utilizing the
sheet material such that, for example, it may be applied by
roller coating, blade coating, screen printing, gravure
printing, flexographic printing or spray coating.
Any number of the varnishes, inks, adhesives and caulking
compounds which are readily available in the marketplace may be
suitable for selection as the reinforcing material 40. For
banknotes comprised of sheet materials made of paper, or having
a paper layer on the bottom, a satisfactory reinforcing material
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is varnish such as the W overprint varnish produced by Sun
Chemical of Brampton, Ontario having the product number 82708-
136 which demonstrates good adhesion to paper, provides good
flexibility and does not significantly change colour on aging.
Surprisingly, it has been found that the application of a
relatively thin layer of such reinforcing material, as shown in
Figure 1, as compared to a complete filling of the cavity 25, is
more effective and preferable because in the case of the latter
there is tendency for the whole of the material of a filled
cavity to become detached from the walls of the cavity and pop
out of the cavity when being handled (the degree of flexibility
provided by the reinforcing material determining the extent of
this) .
Figure 1 illustrates, in cross-section, the structure of
the tactile indicia (embossment 20) of a preferred embodiment of
the invention. For this embodiment the thickness B of the sheet
material 30 is in the range of 75 and 150 micrometers, the
embossment 20 has a relief D of between 70 and 150 micrometers
and an outer width A of between 500 and 1200 micrometers, and
the thickness C of the reinforcing layer (varnish) 40 when it is
applied is between 20 and 40 micrometers. However, since some
of the varnish is absorbed into the sheet material before it
dries/cures, the final thickness is less than this. The size of
the relief to be selected for the embossments is dependent on
the particular application and the type of sheet material to be
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used since some materials will allow larger reliefs to be formed
(without tearing) than will others but too high and/or too thin
an embossment is undesirable as these may be subj ect to breaking
or tearing off of the sheet material. It has been found that
some materials will permit a larger relief than their thickness.
In the example shown by the banknote of Figure 2 the
embossments 20 are circular which is a preferred shape for use
by sight impaired persons due to its simplicity and uniformity.
However, any shape may be utilized for the embossments in
accordance with the invention and for different applications the
use of different shapes may be preferred.
The banknote 10, provided as an example, includes two
spaced symbols 50 which, together, may be designated to identify
the denomination of the bank note. A lesser or greater number
of these symbols can be designated to identify a different
denomination for the banknote. Equally, the number of
embossments making up a symbol may be varied as shown by Figure
4 in which Figure 4(a) shows two symbols 50 each comprising one
column of four embossments 20, Figure 4(b) shows two symbols 50
each comprising two adjacent columns of four embossments 20
(being four adjacent rows of two embossments) and Figure 4(c)
shows two symbols 50 each comprising three adjacent columns of
four embossments (being four adjacent rows of three
embossments). It is preferred to use more than one column of
embossments per symbol because there is a chance that the
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banknote could be damaged in such a way as to create a tactile
impression therein in the area of the tactile indicia and,
particularly if the symbol were to comprise only one column,
such an impression could more readily be misread as a symbol by
a sight impaired person.
The preferred arrangement of embossments on banknotes to
enable sight impaired persons to identify their denomination is
shown by Figure 5 in which each symbol 50 is comprised of two
columns of four embossments 20, with each embossment having a
relief D of 140 micrometers and an outer width A of 1000
micrometers, and the thicknesses B and C of the sheet material
30 and reinforcing layer 40 when applied are 125 and 20
micrometers, respectively. Further, in this preferred
arrangement the edge to edge distance E between each embossment
20 within each symbol 50 is 2000 micrometers and the distance of
the spacing F between each symbol 50 is 14.5 millimeters (14,500
micrometers). The embossments 20 are preferably spaced about 3
millimeters (3000 micrometers) from the top and side edges of
the bank note. This arrangement has been shown to provide the
optimal combination of tactile indicia to result in successful
detection of the denomination of a banknote when subject to the
wear of circulation.
If desired, the selected reinforcing material 40 may
include additives such as optically variable pigments, coloured
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pigments, phosphors, fluorescors, or any taggants which can be
activated by a specific energy wavelength so as to emit in
response detectable energy in a specific but different
wavelength, in order to provide to the banknote a covert
security feature within the tactile indicia.
A further aspect of the invention (not illustrated)
utilizes a sheet material comprising thermoplastic, specifically
a laminate of outer paper sheets and an inner thermoplastic
sheet as described above, to mold tactile indicia into the sheet
material. According to this aspect of the invention a sheet
material comprising a thermoplastic layer is embossed with a
plurality of embossments so as to form tactile indicia therein
in such a manner that heat is applied to the sheet material, in
at least the area in which the embossments are to be formed, at
the same time that the embossments are formed or immediately
prior thereto. Thereafter, the sheet material is cooled.
Accordingly, the thermoplastic layer of sheet material in the
area of the embossments is caused to soften and harden into the
form of the embossments and a reinforcing layer of varnish or
other suitable material is applied to the embossed laminate, as
described above, to provide durable tactile indicia.
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