Note: Descriptions are shown in the official language in which they were submitted.
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Data Carrier Having a Halftone Image
The present invention relates to a data carrier having, produced by intaglio
printing, a halftone image that exhibits printed sub-areas having certain
tonal values, at least three printed sub-areas having different tonal values.
The present invention further relates to an intaglio printing plate and an
intaglio printing process for printing halftone images having three or more
different tonal values and a method for manufacturing such an intaglio
printing plate.
Data carriers within the meaning of the present invention are especially
security or value documents, such as banknotes, passports, identity
documents, check forms, stocks, certificates, stamps, vouchers, airline
tickets
and the like, as well as labels, seals, packaging and other elements for
product protection. In the following, the term "data carrier" encompasses all
such documents and product protection means.
Normally, security and value documents whose commercial or utility value
far exceeds their material value are, through suitable measures, made
recognizable as authentic and distinguishable from imitations and
counterfeits. For this, they are generally provided with special security
elements that ideally cannot be imitated, or only with great effort, and are
not counterfeitable.
In the past, particularly those security elements have proven successful that
can be identified by the viewer and recognized as authentic without aids, but
at the same time can be fabricated only with extensive technical or financial
outlay. This includes, for example, watermarks that can be introduced into
the data carrier only during paper manufacturing, or images produced in an
intaglio printing process that feature a characteristic tactility that is
easily
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recognizable, also for the layperson, and that cannot be reproduced by other
printing processes and especially by copiers or scanners.
Line or intaglio printing technology, especially steel intaglio printing
technology, is of great importance for the printing of data carriers,
especially
security papers, such as banknotes and the like. What distinguishes intaglio
printing is that linear depressions are introduced into the printing plates to
produce an image. The ink-transferring regions of the printing plate are thus
present as depressions in the printing plate surface. These depressions are
produced by a suitable engraving tool or by etching. In mechanically
produced printing plates for intaglio printing, a wider line is produced with
increasing engraving depth as a result of the usually conically tapered
engraving tools. Furthermore, the ink absorption capacity of the engraved
line, and thus the opacity of the printed line, increases with increasing
engraving depth.
In etching intaglio printing plates, the non-printing regions of the printing
plate are covered with a chemically inert coating. Subsequent etching
produces the engraving in the exposed plate surface, the depth of the scribe
lines depending especially on the etching time.
Before the actual printing process, ink of a pasty consistency is applied to
the
engraved printing plate and the excess printing ink is removed from the
surface of the printing plate with a doctor blade or a wiper cylinder so that
the ink remains only in the depressions. Thereafter, a substrate, normally
paper, is pressed against the printing plate, and thus also into the ink-
filled
depressions of the printing plate, and removed again, the ink being drawn
out of the depressions of the printing plate, sticking to the substrate
surface
and forming an image there. If transparent inks are used, the thickness of the
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inking determines the color tone. Thus, a light color tone is obtained when
printing a white data carrier with small ink film thicknesses, and darker
color
tones when printing with thick ink films. The ink film thickness, in turn, is
dependent to a certain extent on the engraving depth.
Line intaglio printing technology permits relatively thick inking on a data
carrier compared with other common printing technologies, such as offset
printing. The comparatively thick ink film produced in line intaglio printing
technology, together with the partial deformation of the paper surface
resulting from the paper being pressed into the engraving of the printing
plate, is easily feelable manually, even for the layperson, and thus also
readily recognizable as an authenticating feature based on its tactility. The
tactility cannot be imitated with a copier, so that line intaglio printing
technology offers valuable protection against counterfeits.
However, conventional line intaglio printing methods exhibit the
disadvantage that tactility in the image and simultaneous full-surface
printing cannot be realized in one printing operation. To remedy this, it was
suggested in publication WO 03/052702 A2 to provide a data carrier with a
halftone image produced by intaglio printing and including directly adjacent
printed partial surfaces in at least a partial area of the image, the partial
surfaces having certain tonal values, and at least a partial area of the image
being tactilely perceptible. Here, the term "halftone image" refers, as in the
present description, to an image having intermediate tones between the
lightest and the darkest places of the image. If a black-and-white image is
involved, "tonal value" is understood, as usual, to be a value on a gray scale
from white to black. However, the present invention relates not only to
black-and-white halftone images containing achromatic colors, namely
white, black and gray, but also one- or multicolor halftone images including
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so-called chromatic inks. In the case of chromatic halftone images, "tonal
value" is understood to be the brightness of the color in question.
To produce such an image, in WO 03/052702 A2, an original, such as a
portrait, is subdivided into partial surfaces based on halftone values, and
the
individual tonal values or groups of tonal values are assigned, in line with
the printing ink used, different engraving depths for the printing plate to be
produced. Here, the tonal values of the original are translated into
corresponding engraving depths on the printing plate, whereby the
engraving depth required to produce special tonal values can vary from
printing ink to printing ink.
Based on that, the object of the present invention is to create a data carrier
having greater counterfeit security and exhibiting, produced by intaglio
printing, a halftone image having a large number of available halftone
values.
This object is solved by the data carrier having the features of the main
claim.
An intaglio printing process and an intaglio printing plate for manufacturing
a data carrier according to the present invention, and a method for
manufacturing such an intaglio printing plate are specified in the
coordinated claims. Developments of the present invention are the subject of
the dependent claims.
According to the present invention, in a data carrier of the kind mentioned
above, one or more of the different tonal values are formed by printed sub-
areas appearing fully printed to the naked eye and having a certain portion
of unprinted white areas. Through the use of such white areas, the number of
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available halftone values can be significantly increased and, at the same
time,
selective halftone control achieved.
For example, if three different engraving depths are employed, through the
use of different amounts of white, eight different tonal values can easily be
realized that already allow an extraordinarily realistic rendering of halftone
images, such as portraits. Furthermore, it has been shown that the use of the
white areas according to the present invention leads to a stabilization of the
color tone of the printed sub-areas, which makes itself advantageously
noticeable particularly when poorly transparent printing inks are employed.
In a preferred embodiment, it is provided that the unprinted white areas of
at least one of the different tonal values are formed by a family of parallel
whitelines. Alternatively or additionally, according to a further, likewise
preferred embodiment, the unprinted white areas of at least one of the
different tonal values are formed by a regular crossline screen. Here, the
white areas result, for example, from the rhombic spaces remaining between
two intersecting families of parallel printing lines.
According to a further advantageous embodiment of the invention, the
unprinted white areas of at least one of the different tonal values form a
hidden piece of information, such as a pattern or a character string. The
counterfeit security of the data carrier can be further increased through such
an additional piece of information in the microstructure of the image,
imperceptible to the naked eye. Here, the information of the white areas can
be present as positive or negative information. It can also be provided in
only
a sub-area of the halftone image.
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Advantageously, at least one of the printed sub-areas of the halftone image is
tactilely perceptible or includes a tactilely perceptible structural element
and
in this way forms effective protection against imitation, e.g. through
copying.
The measure of the unprinted white areas is, in at least one dimension, less
than 100 gm, preferably less than 80 gm, particularly preferably less than 60
gm, even more preferably less than 40 gm and especially preferably less than
20 gm. To meet this condition, the white areas can, for example, be lines
having a width less than 100 gm (or less than 80 gm or 60 gm or 40 gm or
20 gm) or be formed by surface regions of any shape having a surface
measure less than 100 gm x 100 gm (or less than 80 gm x 80 gm or 60 gm x
60 gm or 40 gm x 40 gm or 20 gm x 20 gm).
In a preferred embodiment, at least six, for example, eight, printed sub-areas
have different tonal values and are each formed by printed sub-areas
appearing fully printed to the naked eye and having a certain portion of
unprinted white areas. With such a fine resolution of the tonal values, nearly
photorealistic representations can be achieved in intaglio printing.
The sub-areas of the halftone image can especially be derived from a screen
superimposed on an original halftone image, as described in international
application WO 03/052702. Also, the halftone image can, as described in
WO 03/052702, exhibit additional tactile structural elements, or at least be
superimposed in sub-areas with microstructures that influence its visual
appearance and that exhibit a different orientation in individual sub-areas.
WO 03/052702 also describes various possibilities for translating a halftone
original into an intaglio print image that can likewise be employed in the
present invention. With respect to the cited objects, the disclosure of
WO 03/052702 is incorporated herein by reference.
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The present invention further includes an intaglio printing plate for printing
a halftone image, having in the printing plate surface at least three
differently
engraved regions that serve to print different tonal values. Here, one or more
of the at least three engraved regions exhibit a certain portion of non-
printing
white areas that are formed by, lying at the level of the printing plate
surface,
patches whose measure in at least one dimension lies below the resolution
limit of the naked eye.
Advantageously, the non-printing white areas of at least one of the engraved
regions of such a printing plate can result from a family of parallel scribe
lines whose spacing is greater than the line width of the scribe lines. Here,
spacing is not understood as the non-printing space between the scribe lines,
but rather the distance e.g. from the left flank of one scribe line to the
left
flank of the next scribe line. Alternatively or additionally, the non-printing
white areas of at least one of the engraved regions can also result from two
families of scribe lines, each of which is parallel, intersecting at an angle.
Here, too, the spacing of the scribe lines within each family is greater than
the line width of the scribe lines, so that rhombic white areas result.
Advantageously, the two families intersect at an angle lying between 400 and
80 , preferably between 50 and 70 , for example, around 60 .
The scribe lines of the intaglio printing plate or the printed lines
preferably
exhibit a width below 60 gm, particularly preferably below 50 gm, especially
preferably below 30 gm.
According to a development of the invention, the non-printing white areas of
at least one of the engraved regions form a hidden piece of information, such
as a pattern or a character string, to further increase the counterfeit
security
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of the halftone images produced. Here, the hidden piece of information can
be present as positive or negative information and can also be provided in
only a sub-area of the halftone image.
The white area patches lying at the level of the printing plate surface
preferably continue into the depth of the printing plate at an included angle
a lying between 15 and 600, preferably between 30 and 50 , based in each
case on the surface normal of the printing plate. Advantageously, at least one
of the engraved regions exhibits a base area having a basic roughness pattern
like that, for example, which can be produced according to the method
described in publication WO 97/48555.
The present invention also includes a method for manufacturing an intaglio
printing plate for printing a halftone image having three or more different
tonal values, having the process steps:
- providing a printing plate having a printing plate surface,
- engraving at least three different regions in the printing plate, wherein
in one or more of the three regions is left a certain portion of non-
printing white areas that are formed by, lying at the level of the
printing plate surface, patches whose measure in at least one
dimension lies below the resolution limit of the naked eye.
The white area patches lying at the level of the printing plate surface are
advantageously formed such that they extend into the depth of the printing
plate at an included angle a lying between 15 and 60 , preferably between
and 50 , based on the surface normal of the printing plate. Here,
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expediently, an engraving tool having an appropriate included angle a is
employed for engraving.
Preferably, the intaglio printing plates according to the present invention
are
manufactured by engraving with a stylus, particularly preferably with a
quickly rotating, conically tapered stylus, as described in publication
WO 97/48555. In this way, especially colorful, in other words for example
monochrome blue or red halftone images with brilliant, intensive colors can
be produced that show no sign of gray or brown admixtures in the various
tone gradations. In principle, however, the engravings can also be produced
by laser engraving or etching or any other suitable abrasion method.
By employing intaglio printing technology, especially steel intaglio printing
technology, for the halftone images according to the present invention, a
characteristic print and embossing image is achieved that is easily
recognizable even for laypersons and that cannot be reproduced by other
common printing methods. Intaglio printing technology and the innovation
disclosed here are thus particularly suitable for printing valuable or
security-
relevant data carriers, such as security or value documents, which must
satisfy high requirements with respect to counterfeit security.
Further exemplary embodiments and advantages of the present invention are
explained below by reference to the drawings, in which a depiction to scale
and proportion was omitted in order to improve their clarity.
Shown are:
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Fig. 1 a schematic diagram of a banknote having, produced by
intaglio printing, a halftone image according to an exemplary
embodiment of the present invention,
Fig. 2 a view of a section of the banknote in fig. 1 in the area of the
halftone image, in cross-section,
Fig. 3 a corresponding section of the profile of the intaglio printing
plate used to manufacture the halftone image in fig. 2, likewise
according to an exemplary embodiment of the invention, and
Fig. 4 in (a) to (e), various top views of sub-areas of a data carrier
printed according to the present invention, viewed with a
magnifier or a microscope.
The present invention will now be explained using a banknote as an
example. Fig. 1 shows a banknote 10 that is provided with, produced by
intaglio printing, a halftone image 12 that is represented schematically in
the
drawing as a black-and-white portrait. Typically, the entire image of the
banknote is comprised of a superimposition of multiple images that are
produced with different printing methods. In addition to or instead of the
portrait 12, a further graphic theme 14 can also be executed as the intaglio
halftone image according to the present invention. In the last case, the
portrait 12 can also be produced with conventional intaglio printing.
Furthermore, the banknote 10 can include a pattern 16 produced by offset
printing, for example a Guilloche pattern of regularly interlaced lines or
another finely structured pattern, and a serial number 18 imprinted by
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letterpress printing. Regions produced by screen printing or other printing
methods can also be provided.
Fig. 2 shows, for illustration, a view of a section of the banknote 10 in the
area of the intaglio halftone image 12, in cross-section. The section pictured
shows the banknote paper 20, which is deformed by the contact pressure in
the printing process and which exhibits depressions 22 on the back of the
banknote and elevations 24 on the front of the banknote. In the printed sub-
areas 26 and 28, of which only a portion is pictured in the drawing, the
elevations 24 are each covered with ink films 36 or 38 that were absorbed, in
the printing process, from the engraved regions 46 and 48 (fig. 3) of the
printing plate 40.
The first printed sub-area 26 is covered with an ink film 36 of a certain ink
film thickness D and appears within the halftone image 12 in a first tonal
value that is determined by the consistency of the printing ink and the
banknote paper used.
The second printed sub-area 28 is covered with an ink film 38 exhibiting the
same thickness D as the ink film 36 of the first sub-area 26. In contrast to
the
first sub-area, however, the image of the second sub-area 28 is formed having
a certain portion of unprinted white areas W. The measure of the white areas
W in at least one dimension lies below the resolution limit of the naked eye,
so that it cannot be resolved without aids.
The second printed sub-area 28 thus appears to the naked eye as a uniform,
fully printed surface. However, due to the existing amount of white, it
appears within the halftone image 12, despite the identical ink film thickness
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D, in a second tonal value that is lighter than the first tonal value of the
sub-
area 26.
In this way, if ink film thickness is constant, the amount of white can be
used
to set each of multiple different tonal values, each ranging up to the
brightness of the continuous ink film 36 of the first sub-area 26. Thus,
through a combination of various ink film thicknesses D and different
amounts of white, a multitude of tonal values between "white" and "black"
(or the value for complete coverage of the printing ink used) can be obtained.
It is understood that, in a halftone image, there need not necessarily be a
tonal value that is represented by a full-surface ink film 36. Rather, it can
be
advantageous to represent all occurring tonal values through sub-areas
having a certain amount of white.
Fig. 3 shows the section of the profile of the associated intaglio printing
plate
40 that corresponds to the illustration in fig. 2. In the printing plate
surface 42
are engraved a first engraving area 46 and a second engraving area 48, each
having the same engraving depth T. While the first engraving area 46 is
formed continuously and thus leads to a continuous ink film 36 in the
printing process, the second engraving area 48 is equipped with, reaching to
the printing plate surface 42, partitions 50 whose faces 52 lying at the level
of
the printing plate surface 42 form non-printing white areas.
The partitions 50 continue from the faces 52 lying at the surface 42 of the
printing plate into the depth of the printing plate at an included angle a
that
is defined substantially by the engraving tool used. In the exemplary
embodiment, the engraving areas of the intaglio printing plate 40 are
engraved with a rotating stylus whose included angle corresponds to the
included angle to be produced in the partitions 50.
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To produce, at the same engraving depth, different white areas or different
amounts of white, the engraving tool can be guided along different tracks for
the various sub-areas. Fig. 4 shows, in (a) to (e), some exemplary
embodiments for this. Shown in each case is a top view of a uniformly
printed sub-area of a data carrier as seen when viewed with a magnifier or a
microscope.
Fig. 4(a) shows a first section 60 in which the associated intaglio printing
plate includes a family of parallel scribe lines whose spacing is greater than
the line width of the scribe lines. Produced in the exemplary embodiment at,
for example, an engraving depth of 15 gm were approximately 30-gm-wide
scribe lines having a spacing of 60 gm. In the image, this results in a
relatively light sub-area that appears fully printed to the naked eye and that
shows, under a magnifier or a microscope, the structure illustrated here in
fig. 4(a) comprising a family of parallel printing lines 62 and parallel
whitelines 64 lying there between.
Very good results are also produced by the use of cross-grating, such as that
resulting from two families of parallel scribe lines intersecting at a certain
angle 13. As shown in section 70 in fig. 4(b), the intersecting line families
72
produce small, rhombic white areas 74 in the image. On the corresponding
intaglio printing plate, the intersecting scribe lines leave small pyramid
stumps that extend to the printing plate surface and whose non-printing top
surface, in intaglio printing, results in just the rhombic white areas 74
shown.
The scribe lines of the printing plate need not necessarily run straight, as
illustrated in section 80, shown in fig. 4(c), which shows two intersecting,
curved line families 82 and white areas 84 enclosed thereby.
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The white areas can also form a hidden piece of information, such as a
pattern or a character string that is recognizable only with appropriate
magnification. Purely as an example, sections 90 and 94 of figures 4(d) and
(e) show simple variants of such designs, in which the white areas in the
form of the letter "D" form positive information (reference number 92, fig.
4(d)) or negative information (reference number 96, fig. 4(e)). Here, too,
different tonal values can be set by the line width of the scribe lines and/or
the spacing of the individual information elements (here the letter "D").
Substantially more complex information can, of course, also be introduced
into the image in this way.
