Note: Descriptions are shown in the official language in which they were submitted.
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Data Carrier Having an Intaglio Motif
The present invention relates to a data carrier having an intaglio motif and
an intaglio plate, and an intaglio printing method for printing a motif, and a
method for manufacturing such an intaglio plate.
Data carriers within the meaning of the present invention especially include
security or value documents, such as banknotes, passports, identification
documents, check forms, stocks, certificates, stamps, vouchers, plane 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, through suitable measures, security and value documents whose
commercial or utility value far exceeds their material value are made
distinguishable as authentic and discriminable from imitations and
counterfeits. For this, they are most often provided with special security
elements that ideally can be imitated only with great effort or not at all,
and
are not counterfeitable.
In the past, particularly such security elements have proven successful that
can be identified by the viewer and recognized as authentic without
auxiliary means, but at the same time can be manufactured only with
extensive technical or financial outlay. This includes, for example,
watermarks that can be introduced into the data carrier only during paper
manufacture, or images produced in an intaglio printing process that feature
a characteristic tactility that is easily distinguishable, also for the
layperson,
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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 especially for printing on security papers,
such as banknotes and the like. What distinguishes intaglio printing is that
linear depressions are introduced into the printing plates to produce a print
image. The ink-transferring regions of the printing plate are thus present as
depressions in the printing plate surface. These depressions are produced by
means of a suitable engraving tool, by laser ablation or by means of 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.
Compared with other common printing technologies, such as offset printing,
line intaglio printing technology permits relatively thick inking on a data
carrier. The comparatively thick ink layer produced in the line intaglio
printing process, together with the partial deformation of the paper surface
resulting from the paper being pressed into the engraving of the printing
plate, is, with an appropriate depth of the engraving, easily tangible
manually, also for the layperson, and thus easily perceptible as an
authenticating feature based on its tactility. The tactility cannot be
imitated
with a copier, such that line intaglio printing technology offers valuable
protection against counterfeits.
To be able to combine contiguous printing with tactile elements in one
printing operation, it was suggested in publication WO 03/052702 A2 to
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provide a data carrier with a halftone image produced in intaglio printing
and including directly adjacent printed sub-areas in at least one sub-region
of the image, the sub-areas exhibiting certain tonal values, and at least one
sub-region of the image being tactilely perceptible. Here, the term "halftone
image" refers to an image that exhibits intermediate tones between the
lightest and darkest place of the image.
To manufacture such a print image, in WO 03/052702 A2, an original is
subdivided into sub-areas 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, the engraving depth required to produce
special tonal values being able to vary from printing ink to printing ink. In
practical application, particularly technical depictions can be rendered well
with such methods, while other halftone depictions, especially portraits,
often seem unnatural.
Based on that, it is the object of the present invention to create a data
carrier
having high counterfeit security that exhibits a motif produced in intaglio
printing and appearing as a halftone image when viewed. In particular, the
intaglio motif is intended to be able to be advantageously combined with
tactile elements.
The term "halftone image" is not used consistently in the literature on
printing technology and especially also in patent literature. In some cases,
it
refers to only "true" halftone images, in other words images whose tonal
values display true gradations between black and white, as can be produced
for example, with photographic methods. In the field of printing technology,
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however, the term is also often used for line images that actually consist of
only discrete, printing (e.g. black) and non-printing (e.g. white) image
elements in which, however, the printing and non-printing image elements
are developed to be so fine that, due to the integrative effect of the eye, an
image is created that appears for the viewer to exhibit true halftone
gradations. The printing or non-printing image elements are typically
halftone dots that are arranged in a regular grid having a small screen
ruling.
For example, at normal reading distance, the human eye can no longer
distinguish the individual dots above a 60 screen, that is, a grid having a
line
screen frequency of 60 lines/cm, the image appears for the viewer visually
smoothed and seems like a true halftone image (see, for example, H.
Kipphan, Ed., Handbuch der Printmedien (Handbook of Print Media),
Springer, 2000, pages 92-93).
That said, in the context of this description, the term "halftone image" is
used
in the sense of a true halftone image. The fact that also a line image, in
other
words an image having discrete, printing and non-printing image elements,
can, in an appropriately fine execution of the image elements, have the visual
effect of a true halftone image for a human viewer, is expressed in the
context of this description by the formulation that such an image appears as
a halftone image when viewed with the naked eye.
According to the present invention, the above-mentioned 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.
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According to the present invention, a data carrier of the kind cited above
includes an intaglio motif that appears as a halftone image having a
continuous tonal gradation when viewed with the naked eye. Here, the
intaglio motif comprises a plurality of fine, raised print lines that are not
resolvable with the naked eye and that are continuously modulated in their
width and/or height to produce the different tonal values of the halftone
image.
Also the phrase "continuous tonal gradation" is based on the perception of
the motif with a human eye. A continuous tonal gradation thus need not
exhibit infinitely many different tonal values, but rather merely such a large
number that the impression of a continuous gradation is created for a human
viewer.
In an advantageous embodiment, the intaglio motif of the data carrier
comprises a family of parallel print lines. According to current knowledge,
particularly good results can be achieved if the intaglio motif comprises a
regular cross-line screen that is preferably formed by two families of
parallel
print lines that intersect at an angle a. For the angle a, values between 40
and 80 , especially between 50 and 70 , have proven to be particularly
favorable.
The parallel print lines of the intaglio motif advantageously exhibit a center-
to-center distance of 400 m or less, preferably of 50 m to 200 gm,
particularly preferably of 60 ~tm to 150 m and very particularly preferably
of 70 gm to 120 um.
The spacing of the print lines can be constant across the entire intaglio
motif,
or it can also vary. For example, the intaglio motif can be subdivided into
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sub-regions and each sub-region exhibits a certain spacing of the lines that
differs from the other sub-regions. But the spacing of the lines can also vary
across the entire motif.
Furthermore, it is alternatively possible that the line spacing of two
adjacent
lines is continuously modulated, in other words no parallel lines are present.
With a larger spacing, lighter tones are obtained, and with smaller spacing,
darker tones. In this way, the tonal gradation can be increased even further.
In an advantageous embodiment of the data carrier according to the present
invention, the print lines are arranged with a precision of +/- 5gm or less,
preferably of +/- 2.5 gm or less, particularly preferably of about +/- 1 m or
less, especially are arranged in one or more parallel families.
The width of the print lines is preferably below 250 m and, in non-tactile
regions, advantageously between 3gm and 150 m. In tactile regions, the
width of the print lines can also be larger. In dark motif regions and
especially in tactile print regions, the print lines can also partially
overlap.
In a further advantageous embodiment, the motif is surrounded, as an outer
contour, with a print line that is modulated in its width and/or height. Here,
the line ends of the motif are covered by the print tine that serves as the
outer contour. In particular, the print line that serves as the outer contour
is
modulated such that lines that taper off widely, corresponding to dark motif
regions, are superimposed with a wider outer contour, and line ends that
taper off narrowly, corresponding to light motif regions, with aiiarrow outer
contour. The line width of the print line that serves as the outer contour is
preferably in the range of 5 m to 250 m, preferably in the range of 10 m to
120 m. Coordinated with the brightness levels in the motif, for light motif
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regions, the width of the outer contour line is preferably in the range of 5
m
to 30 m, for dark motif regions, preferably in the range of 60 m to 150 m.
According to an advantageous embodiment of the present invention, the
intaglio motif includes print lines having a width of 15 m or less,
especially
even having a width of 10 m or less. On the one hand, a particularly large
width range with a correspondingly large dynamic range can be made
usable through the use of also such narrow print lines, and on the other
hand, very high resolutions and very fine tonal gradations can be realized
through the use of very narrow print lines.
The width and height of the print lines are preferably modulated together
such that wider print lines exhibit a greater height and narrower print lines
a
smaller height.
The intaglio motif exhibits especially a non-tactile print region in which the
print lines are not tactilely discernible. Further, the intaglio motif
advantageously exhibits a tactile print region in which the print lines are
tactilely discernible. Here, the tactile print region is expediently arranged
in
particularly dark image portions of the halftone image.
Compared with conventional methods, the present invention shows
particularly great advantages in intaglio motifs that depict a representation
of a person, or a portrait.
In contrast to conventional intaglio depictions in hand engraving style, in
which the individual lines and dots are clearly distinguishable with the
naked eye and in which the engraving inks often appear having a gray cast,
the individual print lines of a print depiction produced according to the
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present invention are not distinguishable with the naked eye, and the
engraving inks of the halftone images appear vibrant, crisp and luminous
due to the high resolution.
The present invention further includes an intaglio plate for printing a motif
that appears as a halftone image having a continuous tonal gradation when
viewed with the naked eye. The intaglio plate includes an engraving motif
that comprises a plurality of fine engraving lines that are not resolvable
with
the naked eye and that are continuously modulated in their width and/or
depth to produce the different tonal values of the halftone image.
The engraving motif advantageously comprises a family of parallel
engraving lines. Particularly good results are achieved when the engraving
motif comprises a regular cross-line screen, composed of engraving lines,
that is preferably formed by two families of parallel engraving lines that
intersect at an angle a. For the angle a, values between 40 and 80 ,
especially between 50 and 70 , have proven to be particularly favorable.
The parallel engraving lines preferably exhibit a center-to-center distance of
400 gm or less, preferably of 50 gm to 200 m, particularly preferably of 60
m to 150 m and very particularly preferably of 70 m to 120 m. In
particularly advantageous embodiments, the engraving lines are arranged
with a high precision of +/- 5 m or less, preferably of +/- 2.5 m or less,
particularly preferably of about +/-1 gm or less, especially are arranged in
one or more parallel families.
In dark motif regions, the engraving lines can also partially overlap one
another. To produce correspondingly narrow print lines, the engraving motif
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advantageously includes engraving lines having a width of 15 m or less,
especially even having a width of 10 m or less.
The spacing of the engraving lines can be constant across the entire intaglio
motif, or it can also vary. For example, the intaglio motif can be subdivided
into sub-regions and each sub-region exhibits a certain spacing of the lines
that differs from the other sub-regions. But the spacing of the lines can also
vary across the entire motif.
Furthermore, it is alternatively possible that the line spacing of two
adjacent
lines is continuously modulated, in other words no parallel lines are present.
With a larger spacing, lighter tones are obtained, and with smaller spacing,
darker tones. In this way, the tonal gradation can be increased even further.
The width and height of the engraving lines are preferably modulated
together such that wider engraving lines exhibit a greater depth and
narrower engraving lines a smaller depth. Such a joint modulation can be
achieved, for example, using a conically tapering engraving stylus.
The engraving motif advantageously exhibits a shallow engraving region for
printing a non-tactile print region in which the engraving lines exhibit a
depth of up to 80 m, preferably of 2gm to 70 m. The width of the
engraving lines in the shallow engraving region is preferably below 250 gm,
especially between 3 m and 150 m.
Further, the engraving motif advantageously exhibits a deep engraving
region for printing a tactile print region in which the engraving lines
exhibit
a depth of 70 gm to 300 m, preferably of 70 m to 200 m, particularly
preferably of 80 m to 120 m. The width of the engraving lines in the deep
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engraving region is preferably below 400 m, especially between 120 gm and
250 m.
The present invention also includes a method for manufacturing an intaglio
plate for printing a motif that appears as a halftone image having a
continuous tonal gradation when viewed with the naked eye, having the
method steps:
- providing a printing plate having a printing plate surface,
- engraving in the printing plate surface a plurality of fine engraving
lines, not resolvable with the naked eye, with a continuous
modulation in their width and/or depth such that an engraving motif
is created for producing the different tonal values of the halftone
image.
Here, the local engraving line width and/or depth to be engraved is
advantageously determined at this local position from the tonal value of the
halftone image to be depicted. Here, lighter tonal values correspond to
narrower and/or less deep engraving lines, darker tonal values to wider
and/or deeper engraving lines. The engraving lines determined in this way
can then be produced with an electronically controlled stylus or another
method in the respective locally required width and depth.
In the method according to the present invention, preferably,
a) in the motif, a tactile and a non-tactile print region are established,
and associated deep and shallow engraving regions are established
for printing the tactile and the non-tactile print region, and
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b) for both print regions, the local engraving line width and/or depth to
be engraved are determined at this position from the tonal value of
the halftone image to be depicted.
Further, in an advantageous method variant,
cl) the engraving lines in both engraving regions are produced in the
printing plate in accordance with the determined local width and/or
depth, and
di) in the deep engraving region, further engraving lines having a depth
of 70 m to 300 m, preferably of 70 m to 200 m, particularly
preferably of 80 m to 120 gm are produced.
According to another likewise advantageous method variant,
cz) the engraving lines in the shallow engraving region are produced in
the printing plate in accordance with the determined local width
and/or depth, and
d2) the engraving lines in the deep engraving region are produced having
a depth of 70 m to 300 m, preferably of 70 gm to 200 m,
particularly preferably of 80 pim to 120 m.
According to a further, likewise advantageous method variant,
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c3) the engraving lines in the shallow engraving region can also be
produced in the printing plate in accordance with the determined
local width and/or depth, and
d3) the engraving lines in the deep engraving region can also be produced
having an excessive width and/or depth compared with the
determined local width and/or depth such that, at least in part,
engraving lines are produced having a depth of 70 m to 300 ttm,
preferably of 70 gm to 200 m, particularly preferably of 80 m to 120
m.
The engraving of the printing plate can, in principle, be carried out by means
of laser beam or through etching, but engraving by means of an
electronically controlled, rotating stylus is currently preferred.
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:
Fig. 1 a schematic diagram of a banknote having an intaglio motif
according to the present invention,
Fig. 2 a detailed section of the banknote in fig. 1 in the region of the
intaglio motif, in top view,
Fig. 3 schematically, in cross section, an intaglio plate according to the
present invention for printing a motif appearing as a halftone
image, and
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Fig. 4 in (a) and (b), two simplified representations of detailed top
views of printing plates according to the present invention,
having engraving lines in the form of cross-line gratings.
The invention will now be explained using a banknote as an example. Fig. 1
shows a banknote 10 that is provided with an intaglio motif 12 that appears
as a halftone image having a continuous tonal gradation when viewed with
the naked eye. In dark image regions, the intaglio motif 12 optionally
additionally includes tactile sub-regions 18 in which the relief pattern of
the
intaglio printing is tactilely discernible for the user and thus forms a
tangible
marking.
In addition to the intaglio motif 12, the banknote 10 typically exhibits
further
print images that are produced with different printing processes. For
example, the banknote 10 can include a pattern 14 produced in offset
printing, such as a guilloche pattern composed of regularly interlaced lines,
as well as a serial number 16 imprinted in letterpress printing. Regions
produced by screen printing or other printing methods can also be provided.
To allow the impression of a continuous tonal gradation to be created in the
intaglio motif 12, this motif comprises a plurality of fine, raised print
lines 20
that are not resolvable with the naked eye, as shown in top view in the
detailed section in fig. 2. In the exemplary embodiment, the print lines 20
form a family of parallel print lines having a spacing d measured from center
to center.
To produce the different tonal values of the halftone image, the print lines
20
are continuously modulated in their width and height, as can be seen in fig. 2
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for the print line width. Here, in lighter image regions (such as at the right
and left edge of the section in fig. 2), the print lines 20 exhibit a small
width
and height, in darker image regions (such as in the center of the section in
fig. 2) a greater width and height. In the non-tactilely-discernible regions,
the
width b of the print Iines 20 varies between a minimum width bm;I, and a
maximum width bna, The maximum width can also be larger in some
regions than the spacing d of the lines such that the print lines 20 overlap
and form particularly dark motif regions.
In the exemplary embodiment, due to the production of the engraving lines
in the intaglio plate with a conical stylus, the width and height of the print
lines are positively correlated, in other words, wide print lines exhibit a
greater height, narrower print lines a smaller height. Thus, in accordance
with the width varying between b,,,iõ and bn,z,,,, also the height of the
print
lines 20 in the non-tactilely-discernible regions varies between a minimum
height hn,lõ and a maximum height hn,,,. Here, the maximum height hn,a, is
chosen taking into account the composition of the printing ink used and of
the banknote paper such that the print lines 20 are not tangible for the user
in
the non-tactile region.
In contrast, the width bt and the height ht of the print lines 20 in the
tactilely
discernible regions 18 are above the maximum values of the non-tactilely-
discernible regions, thus, they constitute very dark image regions. In
particular, taking into account the composition of the printing ink and
banknote paper, the height ht is chosen to be so large that a tangible marking
18 in the intaglio motif 12 is created for the user. Within a tactilely
discernible region 18, the width and height of the print lines 20 can be
constant or exhibit a modulation to still render drawing portions within the
dark image regions 18.
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The spacing d of the print lines is below 400 m, preferably in the range of
70 gm to 120 m, and is 100 m in the exemplary embodiment in fig. 2. The
width b of the print lines 20 in the exemplary embodiment varies between
bmiõ = 4 m and bmaX = 140 gm in the non-tactilely-discernible regions. The
height h of the print lines 20 is always below 70 gm such that they are not
tactilely discernible.
In the tactilely discernible regions 18, in contrast, the height of the print
lines
is preferably between 80 m and 120 m, for example 100 m, such that a
tactilely well discernible marking is created there. In this region, the
center-
to-center spacing d of the print lines is, for example, only 80 m.
With these parameters, the print lines 20 are not resolvable even for the
naked eye, the intaglio motif 12 thus appears for a viewer as a halftone
image having a continuous tonal gradation that is determined by the local
width and height of the print lines 20. The tactilely discernible regions 18
lend the intaglio motif an additional authenticating mark that can be easily
distinguished and checked upon rubbing the banknote 10 between the
fingers. Since the tactile regions 18 are arranged in particularly dark image
portions of the depicted halftone image, they merge visually inconspicuously
with the remaining regions of the halftone image.
Fig. 3 shows schematically, in cross section, an intaglio plate 30 for
printing a
motif appearing as a halftone image, such as the above-described intaglio
motif 12. In the intaglio plate 30, an engraving motif that comprises a
plurality of fine engraving lines that are not resolvable with the naked eye
and that are continuously modulated in their width and/or depth to
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produce the different tonal values of the halftone image corresponds to the
printed motif 12.
In the illustration in fig. 3 are shown, for example, three sections of the
engraving lines 32, 34, 36 that serve to produce a light tonal value in the
motif (engraving line 32), a dark tonal value in the motif (engraving line 34)
and to produce the tactilely discernible region 18 (engraving line 36).
All engraving lines are produced with an electronically controlled, conically
tapering engraving stylus, through which an increasing width of the
engraving lines results with increasing engraving depth. For example, in the
exemplary embodiment, when an engraving stylus having a conical opening
angle of about 80 is used, an engraving depth t- b/(2*tan(80 /2)) results, in
other words, the engraving depth is nearly 60% of the engraving width.
According to the present invention, for the engraving of the intaglio print
motif, it is also possible to use different engraving styli having different
conical opening angles. The conical opening angle preferably ranges from
60 to 100 . For example, the intaglio motif can be subdivided into sub-
regions that are worked with engraving styli having different conical
opening angles. Preferably, sub-regions having a lighter tone are engraved
with an engraving stylus that exhibits a conical opening angle of 40 , while
sub-regions having a darker tone are engraved with an engraving stylus that
exhibits a conical opening angle of 100 . Instead of subdividing the motif
into sub-regions, also individual lines can be engraved with different
engraving styli.
Of the engraving lines shown for illustration in fig. 3, the section of the
engraving line 32 exhibits an engraving depth of ti = 25 m and,
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accordingly, a width b1 of around 40 m, the section of the engraving line 34
an engraving depth of t2 = 50 m and, accordingly, a width b2 of around 80
m, and the section of the engraving line 36 an engraving depth of t3 = 100
m and, accordingly, a width b3 of around 165 m.
Even if, in fig. 3, only one engraving line 32, 34, 36 is depicted in each
case,
the intaglio plate 30 includes, of course, a plurality of such engraving
lines,
which can be arranged in parallel or especially in the form of a cross-line
grating composed of parallel engraving lines. Here, the spacing of the
parallel engraving lines 32, 34 in the non-tactile print region is 100 m in
the
exemplary embodiment, the spacing of the parallel engraving lines 36 in the
tactile print region 80 m.
With a width of 40 ttm and a distance of 100 m, the engraving lines 32
produce a light tonal value within the motif 12 upon printing. The engraving
lines 34 having a width of 80 gm and a spacing of 100 m already produce a
very dark tonal value upon printing. The engraving Iines 36 that, at a spacing
of 80 m, exhibit a width of 165 ttm, additionally produce upon printing,
besides a very dark tonal value, a tangible marking 18 due to the thick inking
and the deformation of the banknote paper.
Following the above, it is understood that the width and depth of the
engraving lines are modulated along their dimension in accordance with the
tonal value to be depicted locally, such that the cross section in fig. 3
shows,
in each case, only a local width and depth of a section of the engraving lines
32, 34, 36. The sections 32, 34, 36 can even represent sections of the same
engraving line at different spots along its dimension. It is further
understood
that the width and depth of the engraving lines are varied continuously in a
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specified width and depth range, and do not exhibit only the discrete values
shown for illustration in fig. 3.
The parallel engraving lines are produced in the intaglio plate 30 with a high
precision of +/- 5 m, preferably even with the extraordinarily high
precision of +/-1 gm. Due to this high precision, extraordinarily fine tonal
value differences can be achieved.
Furthermore, through series of tests, the inventors found that, with an
arrangement of the engraving lines in a suitable cross-line screen,
particularly stable printing is possible at different engraving depths. With
reference to fig. 4(a), which shows a section 40 of a top view of a printing
plate according to the present invention, such a cross-line screen consists of
two families 42, 44 of parallel engraving lines that intersect at an angle a.
To
improve diagram clarity, the width/depth modulation of the engraving lines
that is, of course, present in practice, is not depicted in fig. 4(a).
Particularly
good results are obtained with cross-line screens in which the angle a is
between 40 and 80 , especially about 60 . For the spacing, widths and
depths of the engraving lines 42, 44, each of which are parallel, the above
explanations given for parallel engraving lines in general apply.
The engraving lines of the printing plate 30 need not necessarily run
straight,
as illustrated in the section 50 depicted in fig. 4(b), which shows two
intersecting, curving line families 52, 54. Here, too, to improve diagram
clarity, the existing width/ depth modulation of the engraving lines is not
depicted.
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To obtain from a specified halftone original an intaglio plate 30 having an
appropriate engraving motif, according to the present invention, the
following approach, for example, can be used:
As the base modulation for the halftone image, a cross-line screen having
engraving lines of an orientation of +/- 40 (in other words an intermediate
angle a = 80 ) is used, as depicted schematically in fig. 4(a). Such a cross-
line
screen can be printed particularly stably with the values for width, depth
and spacing of the engraving lines considered here.
The calculation of the form and position of the engraving lines is preferably
done with the aid of a computer, it being possible to use commercially
available programs that permit the calculation of the engraving depth based
on the tonal values to be depicted in the halftone image.
In a next step, a press proof is effected of a grayscale ramp with the desired
steel printing ink with a continuous range of 0 - 100% area coverage and the
chosen engraving rendition, for example in the form of the chosen cross-line
screen.
The ha]ftone region to be used, called impact region in the following, is
established based on the press proof. The established scope can comprise, for
example, a region of 3% - 40% area coverage.
Then the halftone original is rendered within the impact region, with lighter
tonal values corresponding to a shallower engraving, darker tonal values to
a deeper engraving. Here, the halftone image must generally be adapted to
the desired specific printing conditions through image retouching. The
particular print characteristics of the steel printing ink are also taken into
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account here, especially the very high pigment content, which leads to a very
large spread from light to dark, as well as different additives, such as
absorbers, lithopone, transparent white, maschine readable features and the
like, which in some cases change the scumble behavior of the chromatic ink
considerably.
In a further method step, the desired tactile regions of the motif are
established. For this, particularly dark regions of the halftone original are
detected and supplemented with the desired extra sections. To achieve the
tactile properties, the patterns created in this way are overdrawn
(superelevated), possibly likewise subjected to retouching, and first saved
separately.
Then, with the aid of a computer and a suitable program, the halftone
original (projection), with the engraving definition and the desired tactile
region, is calculated and, based on the calculated engraving lines, a printing
plate produced with an electronically controlled stylus.
Here, the base modulation can be combined with the tactile portion in
different ways. In the simplest rendition, the tactile portion is simply
transferred to the existing basic cut model. Alternatively, the tactile
portion
can be omitted from the basic model and then be newly applied to the uncut
area. In a further variant of the present invention, the tactile portion is
omitted from the basic model and, thereafter, the tactile region again
calculated anew from the halftone image such that a depth modulation can
be created here that renders individual drawing portions.
As a result, a cut printing plate is present that, through the different
depths
and widths of the engraving lines, renders the desired tonal gradation of the
CA 02699234 2010-03-10
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halftone image and exhibits the tactile elements integrated in the halftone
rendition. After press proof, review and, if applicable, correction, the
design
for the motif 12 can be incorporated into the cut file of the banknote or
another desired value document.
The approach according to the present invention offers especially the
following advantages:
- The steel printing ink facilitates a broad spectrum of light to dark that
can be taken advantage of with the method according to the present
invention.
- Desired tactile elements can be integrated in the motif design.
- The method permits an attractive rendering of halftone originals,
especially also for the banknote reverse.
- Line printing is an attractive alternative to stochastic screening.
- When manufacturing the printing plate, the cutter can stay in the
material continuously without permanent striking and, in this way,
facilitate an execution favored by the method.
