Note: Descriptions are shown in the official language in which they were submitted.
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Paper of Value and Method for ProducingIt
This invention relates to a document with a security element and a method for
producing the document. Documents of value and security documents must meet
high
requirements for forgery-proofness and checkability of authenticity and are
equipped
for this purpose with security elements to protect them from forgery and
imitation.
Conventional security elements are, for instance, watermarks and security
threads in
the paper, and printed images produced with special, for example fluorescent,
inks or
by special printing processes, for example intaglio printing. Use has also
been made
for purposes of protection from forgery of so-called metallic effect inks,
which in
particular have a specific luster and thus imitate the visual impression of a
metal.
Prints with such metallic effect inks, for example with a gold or silver
color, have the
advantage that their typical luster cannot be imitated with customary printers
or
photocopiers. However, since metallic effect inks are offered on the market
without
limitation and are thus readily available, security elements having metallic
effect inks
can actually be imitated easily.
Forgery of documents is impeded for example by integrating into the printed
image complicated, fine line patterns that can only be reproduced with
sufficient
clarity and line sharpness by high-resolution printing processes. However,
when such
fine line patterns, for example guilloches, are printed with metallic effect
inks, their
resolution is limited due to the metallic effect ink pigments that are
frequently very
coarse and relatively large compared to usual inks, on the one hand, and the
visual
metallic impression is not striking and conspicuous enough in fine lines due
to the
small print area, on the other hand.
The present invention is therefore based on the problem of increasing the
forgery-proofness of documents in which metallic effect inks are used as a
security
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element. This problem is solved according to the invention by the features of
the
independent claims.
The inventive data carrier is provided with a first print that is printed with
color
ink and interrupted by negative contours. It is further provided with an
overlying
second print whose print area is substantially continuous and uninterrupted.
The
second print is printed with metallic effect ink. This contiguous area with
its
characteristic color and luster impression is readily perceptible and striking
to the eye.
The visual impression of this security element is further strengthened if the
intensity
and color tone of the security element is strengthened or influenced by
printing a color
ink under the metallic effect ink. The metallic effect ink must be applied
only in a
quantity or layer thickness such that the second print is not opaque but
translucent. The
preferably finely structured negative contours in the color ink print are then
visible to
the eye through the contiguous metallic effect ink layer.
The structuring of the color ink area with negative contours not only
increases
the possibilities for designing the document but also impedes its imitation.
The
specific appearance of the negative contours shimmering through the metallic
effect
ink layer cannot be imitated either by a single print or by color
photocopiers. If the
negative contours are executed as a fine line pattern, many attempts at
reproduction
will fail because of the necessary resolution. The proven guilloched line
patterns of
security printing are especially preferred since such structures are difficult
to calculate
and print and require especially high resolution and line sharpness. With a
dimension
of the negative contours, for example the line width, in the range of
approximately 50
to 300 microns, they are just recognizable to the eye at a normal viewing
distance,
while the resolution and contour acuity of the realization by printing
technology must
meet very high requirements presupposing printing methods and corresponding
technical knowledge that are not accessible to everyone.
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The first and second prints are preferably executed in equal size and
positioned in
exact register with each other so that the total area printed with metallic
effect ink,
with the exception of the negative contours deliberately left blank, is
underlaid by a
color ink layer and thus has a uniform, homogeneous appearance. The exactly
registered arrangement of the first and second prints avoids non-overlapping
edge
areas and furthermore increases the requirements for the precision of the
execution by
printing technology. To avoid problems of register it is fundamentally also
possible to
execute the two prints in different sizes. For example, the first lower print
can be
executed somewhat smaller than the second upper print.
The inventive, at least two-layer security element can be produced cost-effec-
tively if the first and second prints are both produced by the same printing
process.
Production is especially economical if the first and second prints are
produced during
one print run. Application of both prints in one run furthermore substantially
facilitates
the exactly registered positioning of the two ink layers. The prints can
fundamentally
be applied by any printing process suitable for transferring inks to the
document to be
printed in the necessary layer thickness and resolution. Flexography is
mentioned as an
example. The offset method is especially preferred since it is very economical
and
permits very high resolution. Indirect letterpress is especially preferred in
particular for
high numbers of copies since it involves an especially high service life of
the printing
plates, and the method furthermore yields especially good printing quality and
high
color brilliance.
Preferred metallic effect inks are ones having a gold, silver, bronze or
copper
tone since their appearance is most familiar to the average owner or user of
the
documents. In addition, particularly gold and silver colors, due to their
association
with the expensive precious metals, convey an impression of value that is
especially
desired in particular for documents of value, for example bank notes. The
characteristic look of said inks, referred to here as a "metallic effect," can
be produced
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for example by small and thin metal plates. In addition, the finely crushed,
platelike
fragments of vacuum metalized polyester film can be used, which are known for
example under the brand name of "Metalure ".
The attractiveness and strikingness of the security element are enhanced by
increasing the luster of the metallic effect ink. An especially simple way of
increasing
luster is to smooth the surface of the document at least in the area of the
metallic effect
ink print. Since in particular security documents and documents of value are
first
provided with a background print, applied by offset for example, and then
printed by
intaglio whereby the substrate surface is smoothed due to the high contact
pressure of
the printing plate, it is especially economical to perform the smoothing of
the metallic
effect ink during intaglio printing.
A further way of obtaining especially lustrous security elements is to apply
the
security element to a plastic film. Because of the especially smooth surface,
a metallic
effect ink print shows very pronounced luster on such substrate materials.
The attractiveness, strikingness and forgery-proofness of the security element
are
increased even further by additionally providing the area printed with
metallic effect
ink with a blind embossing. Blind embossings are particularly attractive,
appealing and
difficult to imitate when they have a continuously modulated, three-
dimensional relief,
as found on medals for example. Corresponding security elements can again be
produced especially economically if the blind embossing is produced during
intaglio
printing, the negative corresponding to the relief being integrated into the
non-ink-
carrying part of an intaglio printing plate.
The color ink used for the first print may be an ink of any color, including
white,
black, gray and any mixed colors. However, certain combinations of metallic
effect
inks and color inks are preferred since said combinations yield especially
attractive,
intensely colored and luminous security elements. Gold and bronze tones are
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preferably combined with yellow, brown and red tones, while metallic effect
ink with
a copper tone is preferably combined with orange, red and brown tones. It is
suitable
to combine metallic effect inks with a silvery tone, however, in particular
with colors
having a gray, blue or green tone.
Documents within the meaning of the invention are all security prints, in
particular bank notes, shares, bonds and certificates as well as admission
tickets,
vouchers, ID cards and passports.
The inventive security element can be applied directly to the document or
prefabricated on a film element that is incorporated into the document as a
continuous
thread, strip or individual element (patch) or applied to its surface. It is
also possible to
prefabricate the security element on a film serving as a transfer film. The
security
element is transferred from said film to the object to be protected and the
film removed
after transfer. With this procedure the two prints can be disposed on the
transfer film in
reverse order. In the viewing direction of the security element, however, the
metallic
effect ink layer is always above the color ink layer. Further release,
adhesive and/or
protective layers may be added as required. The color ink and metallic effect
ink prints
can be printed for example on a narrow, transparent film strip made of
plastic. The
negative contours left blank in the color ink print can also render finely
structured
symbols or characters, for example, instead of lines. If such a film strip is
embedded
into a document as a so-called "window security thread," the film strip is on
top in the
area of the windows and freely accessible to the eye. In these areas one can
readily
perceive the metallic luster of the metallic effect ink that is especially
pronounced on
the smooth surface of the film. Additionally, the translucent negative
contours can be
perceived or checked upon closer viewing.
In the following an example of the invention will be explained with reference
to
the drawing, in which:
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Fig. 1 shows an inventive document in a top view,
Fig. 2 shows a schematic representation of the first and second prints,
Fig. 3 shows a detail of the cross section along line A - B in Fig. I.
Fig. I shows a bank note as an example of inventive document 1. Field 2
usually
contains document- or bank note-typical information, for example denomination,
currency, portrait, etc., which is not specifically rendered in the Figure. In
bank-note
printing, one part of said information is usually applied by offset or
indirect letterpress
and another part by intaglio. Security element 3 is of circular form here but
may also
have a different geometry. The two prints 4, 6 disposed one above the other to
form
security element 3 are shown schematically in Fig. 2. First print 4 is
produced by
indirect letterpress for example, whereby a strong yellow standard ink of the
type
Pantone Yellow U can be used. The color preferably used for said first print
is one that
also occurs in the remaining printed image of document 1. In this case no
additional
print run or additional printing mechanism is necessary for first print 4.
First print 4
serving as a background print can also be realized with a plurality of
different colors
via a color separation.
Print 4 is traversed by unprinted negative contours 5 forming a guilloche-like
interlaced pattern of fine lines. To facilitate representation of the total
security
element, linear negative contours 5 left blank in print 4 are rendered in Fig.
1 as
continuous, dark lines against a light background. Second print 6 can likewise
be
printed by indirect letterpress, for example with a gold ink of the type
Pantone 871 U.
Second print 6 forms a homogeneously printed, uninterrupted area and has the
same
size and contour as first print 4. Prints 4 and 6 in exact register one over
the other form
security element 3.
To improve forgery-proofness and the high protection against reproduction by
photocopiers, security element 3 can additionally be provided with blind
embossing 7,
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which is preferably formed as a continuously modulated relief. Blind embossing
7 is
merely indicated by its contour line in Fig. 1. The blind embossing renders
for
example a logo, national emblem, alphanumeric characters, a person or
building. It is
preferably produced by an accordingly engraved intaglio printing plate and
during
printing of document 1 by intaglio.
The high pressure with which an intaglio printing plate is pressed against the
substrate to be printed during the printing operation can smooth the metallic
effect ink
located on top on the document surface through the smooth, non-ink-carrying
areas of
the intaglio printing plate. This strengthens the characteristic luster of the
metallic
effect ink.
Fig. 3 shows schematically a detail of the cross section through document 1
along line A - B in Fig. 1. Document 1 is preferably made of paper, but other
materials
such as plastic films can also be used as long as they are printable in the
necessary
fashion. Thin second print 6 with metallic effect ink located on top is
slightly
translucent so that the visual appearance of security element 3 is influenced
by first
print 4 executed in color ink. The color of first lower print 4 shimmering
through the
metallic effect ink influences the tone and brightness of security element 3
in desirable
fashion. Negative contours 5 left blank, which have a line width of 200
microns for
example, are also visually recognizable as a filigree pattern and form an
authenticity
feature that is hard to imitate.
If an attempt is made e.g. to reproduce the pattern formed by the negative
contours in the background by a homogeneous, uninterrupted background print
and
corresponding gaps in the print of the metallic effect ink, such an attempt
would be
doomed to failure. To produce a sufficiently intense metallic color or luster
impression
e.g. by offset or indirect letterpress, said printing processes require
relatively high
settings for ink quantity transfer, which mean that fine negative contours
cannot be
reproduced precisely and cleanly in a metallic effect ink layer due to
blurring, running
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and smearing. Printing processes having a fundamentally much higher ink
transfer, for
example screen printing, would additionally have the problem of insufficient
resolution and could furthermore not be integrated as economically into the
process of
producing documents of value and security documents since they would require
additional printing operations. A metallic effect ink layer interrupted by
negative
contours would furthermore have a busy, uneven appearance. In the inventively
produced documents, in contrast, the negative contours are integrated into the
print of
normal color ink which need only be printed in a very small quantity or layer
thickness
to produce a sufficiently intense color effect. The printing processes used
for this
purpose can preferably be very economical ones, such as offset or indirect
letterpress,
which also permit high resolution. The metallic effect ink print, on the other
hand, is
effected in a substantially unified, uninterrupted layer, resulting in a
uniform and
pleasing appearance, which is reminiscent of a coin or medal particularly in
connection with a blind embossing.
