Note: Descriptions are shown in the official language in which they were submitted.
CA 02238743 2005-O1-07
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A data carrier with optically variable color
This invention relates to a data carrier, in particular a
paper of value, identity card or the like, which is provided
with an optically variable security element having optically
variable pigments without, or with only weak, body color of
their own.
There have been manifold efforts lately to mark data
carriers and protect them from falsification or forgery. In
particular the improved quality of photocopiers has caused
optically variable elements to be increasingly applied to
Security documents whose optically variable effect is not
reproducible by copying machines.
For example it is known from EP 0 317 514 A1 to apply to a
document a layer with iridescent substances which conveys a
different color effect at different viewing angles. It is in
particular proposed that the iridescent substance be applied
flat to a subjacent, black, all-over layer. In a further working
step the thus produced iridescent surface can be overlaid with
information by overprinting this surface.
EP 0 435 029 A3 furthermore discloses the use of liquid-
crystal polymers as optically variable elements whereby a color
tilting effect arises upon a change of viewing or lighting
angle. This effect is based substantially on the helical
structure of the liquid-crystal phase, which can be fixed by
crosslinking in polymers and furthermore adjusted via external
conditions, such as mechanical pretreatment. This also makes it
possible to selectively adjust the color tone of the color
change.
The problem of the invention is to propose a data carrier,
and a method for producing it, which has a novel optical effect
and thus increased protection from forgery.
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This problem is solved by the invention which provides in
one aspect, a data carrier for paper of value or identity card
comprising an optically variable security element having at
least one piece of information and one transparent optically
variable layer containing optically variable pigments. The
information is represented in a color contrasting with the data
carrier, and the optically variable layer is disposed at least
in partial areas over the information. The data carrier is
characterized in that the information has a fineness or line
width that is thinner than a fineness or line width that can be
created by using the optically variable pigments.
According to another aspect, the invention provides a method for
producing a data carrier for paper of value or identity card.
The method comprises providing an optically variable security
element which has at least one piece of information and one
transparent optically variable layer containing optically
variable pigments. The information is represented in a color
contrasting with the data carrier, and the optically variable
layer is disposed at least in partial areas over the informa-
tion. The data carrier is characterized in that the information
has a fineness or line width that is thinner than a fineness or
line width that can be created by using the optically variable
pigments. The data carrier is also characterized in that the
information is first applied to a separate carrier film, and the
information is then covered at least in part with the optically
variable layer.
According to yet another aspect, the invention provides an
optically variable security element having at least one piece of
information and one transparent optically variable layer con-
taining optically variable pigments. The information is
represented in a color contrasting with a data carrier and the
optically variable layer is disposed at least in partial areas
over the information. The security element is characterized in
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that the information has a fineness or line width that is
thinner than a fineness or line width that can be created by
using the optically variable pigments.
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The invention is based on the idea of first providing
the document with information contrasting with the data car-
rier, such as a finely structured print. One then provides
this information with an optically variable effect by apply-
ing a transparent layer having an optically variable effect
over at least a partial area of the information. One can use
in particular transparent optically variable layers having
optically variable pigments without, or with only slight,
body color of their own. One can furthermore use other trans-
parent optically variable layers, such as interference layer
structures or optically variable foils such as liquid-crystal
silicone polymer foils.
The layer having an optically variable effect can be ap-
plied according to the invention by coating, transfer print-
ing, another manner of application, applying a foil or im-
printing. The invention will be described by way of example
using imprinting, but the abovementioned other techniques can
also be used analogously for applying the optically variable
layer.
When conventional coloring pigments are used to apply
structured prints to a data carrier, the inventive method of-
fers the possibility of providing this information with an
optically variable effect. For this purpose the information
is provided flat at least in partial areas with a transpar-
ent, optically variable layer having e.g. an optically vari-
able pigment without, or with only slight, body color of its
own. The lack of body color in the optically variable pig-
ments makes these pigments especially effective at the places
where the first ink is located on the data carrier as a
structured background. In contrast, the optically variable
effect is not, or only hardly, visible at the places where no
background print is present. When the abovementioned,opti-
cally variable pigments are used in inks, the width or fine-
ness of the producible structures is limited and is consid-
erably greater than the line thicknesses achie~-able with con-
ventional pigments, since the optically variable pigments are
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much larger than conventional pigments so that one cannot
produce information as a high-resolution structure by di-
rectly printing the pigments. Furthermore the size of the op-
tically variable pigments makes them unprintable by screen
printing as of a certain mesh width of the screen, so that
this technique cannot be used to produce a high-resolution
structure anyway. It is therefore to be regarded as a par-
ticular advantage of the inventive method that this technique
can now be used to provide even high-resolution structures
with an optically variable effect when the high-resolution
structures are printed with the first ink and then covered
- with the ink containing the optically variable pigment.
The invention accordingly achieves the advantage of pro-
viding the document with a high-resolution fine structure
which furthermore has a previously unknown optically variable
effect for the viewer. The inventive procedure offers the
further advantage that the formation of the fine structure is
decoupled from the formation of the optically variable ef-
fect, so that the pigments optimized for the case of applica-
tion can be used for the particular desired effect.
Further advantages and developments can be found in the
subordinate claims and in the following figures, whose repre-
sentation is not true to scale for clarity's sake.
Fig. 1 shows an inventive data carrier,
Fig. 2 shows an inventive optically variable security
element,
Fig. 3 shows a further embodiment of the inventive opti-
cally variable security element,
Fig. 4 shows an embodiment of the inventive optically
variable security element,
Fig. 5 shows an embodiment of the inventive optically
variable security element,
Fig. 6 shows an embodiment of the inventive optically
variable security element,
Fiq. 7 shows an embodiment of the inventive optically
variable security element,
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- Fig. 8 shows an inventive optically variable security
element by transmitted light,
Fig. 9 shows an embodiment of the inventive optically
variable security element.
Fig. 1 shows inventive data carrier 1, in the present
case a bank note, with security element 2 applied thereto.
Security element 2 is positioned at a suitable place on the
data carrier so that its optical effect leads to easy test-
ability of the data carrier, on the one hand, and prevents
attempts at forgery, in particular with color copying ma-
chines, on the other hand.
Fig. 2 shows an enlarged detail of inventive data car-
rier 1 in the area of the optically variable element. Opti-
cally variable element 2 consists of a print of lines 3 in a
color contrasting with the data carrier. The print can be for
example a fine, high-resolution line pattern. Over lines 3
the substance with the optically variable pigments is applied
in area 4. Suitable inks are in particular ones which contain
optically variable pigments and are printed flat. Outside
printed lines 3 the optically variable pigments in area 4 are
not, or only extremely weakly, recognizable because of their
lack of body color. On lines 3, however, the optically vari-
able pigments are fully effective so that the high-resolution
printed pattern is overlaid with an optically variable effect
which can be clearly recognized solely in the areas of the
printed pattern. The selection of inks for printing lines 3
on the data carrier is subject only to the restriction that
these inks must be suitable for producing the structure,
which depends essentially on the desired line fineness. With
regard to the coloring, lines 3 of the structure can be
adapted to the particular requirements. However it has turned
out that particularly dark colors make superjacent flat print
of the optically variable pigments especially effective.
Furthermore high-resolution structure 3 can vary in color
and/or in the particular color tones. This leads to different
effects of the superjacent optically variable pigments in
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area 4. One can thus produce effects, such as a certain color
shade as exists e.g. in a halftone image, and transfer them
to the superjacent layer containing optically variable~pig-
ments.
In such cases it is favorable to overprint lines 3 in
their entirety with an ink containing optically variable pig-
ments, as shown in Fig. 3. This makes it possible to transfer
the total information content of the picture, logo, character
or the like produced by the structuring of the first print to
the optical efficacy of the superjacent optically variable
pigment. If the structure of the first ink is designed ac-
cordingly, e.g. as a halftone image, it is thus possible to
transform the halftone image information of the halftone im-
age into picture information with differently iridescent pic-
ture values through the flat overprint with coloring pigments
without, or with only slight, body color of their own. The
iridescent effect of the printed optically variable pigments
is determined by the particular subjacent color value and/or
intensity value of the high-resolution structure.
Additional protection from forgery results if first
print 3 is a high-resolution structure. As indicated by Fig.
4, inventive data carrier 1 can also be designed in such a
way that a high-resolution line structure already present on
the data carrier is used for producing the optically variable
element. One can overprint high-resolution printed lines 5,
which are executed for example as guilloches or high-
resolution lines of a picture motif, with the optically vari-
able coloring pigments at least in a partial area. Surface 4
constituted by the overprint can be executed as a geometric
shape or as characters, so that background lines 5 produce an
optically variable print with a tilting effect in the area of
overprint 4.
Fig. 5 shows data carrier 1 having optically variable
security element 2. Structure 3 again printed on and possibly
of high resolution is covered in area 4 by an ink with opti-
cally variable pigments applied flat. Within area 4 there is
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further information 6 which is represented in the present -
case by the letter "A". This information can be produced in
surface 4 for example by embossing or printing. For embossing
one can use conventional steel gravure printing methods with
or without ink. For printing the information it is possible
to produce the information clearly against an iridescent
background by selecting the ink so that it completely covers
the optically variable background. However the ink of print 6
can also be selected from the group of transparent or trans-
lucent colors, so that optically variable background 4 is re-
tained in the area of information 6 but modified in compari-
--, son with its immediate surroundings.
Fig. 6 shows a further example of inventive data carrier
1 to which optically variable element 2 is applied. Lines 3
of the first ink again present, which can be single- or mul-
ticolored, are covered by several single areas 7, 8, 9 and
10. Single areas 7 to 10 are produced by printing an ink con-
taining an optically variable pigment, the pigments again be-
ing recognizable in the areas where for example high-
resolution structure 3 extends thereunder. Individual areas 7
to 10 can contain different optically variable pigments in
this embodiment and thus each produce a different impression
on the viewer. This makes it possible for optically variable
areas 7 to 10 to carry an information content themselves,
which consists in the simplest case of a certain color se-
quence. This information content is then influenced, or actu-
ally made visible, by the particular structure of the first
print located under the optically variable colors.
The inventive optically variable element can also be
combined with the back of the document, as shown in Fig. 7,
so that complete information only appears by transmitted
light. For this purpose optically variable elemer_t 2 is ap-
plied to data carrier 1, a structured print again being first
applied to the data carrier in a first ink of any desired
kind. This is printed flat with the optically variable color
in area 4, which is executed as the letter "C" in the present
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case. Within area 4 elements 11, 12, 13 are incorporated by
embossing or printing in such a way as to be recognizable by
reflected light. The back of the document is printed or em-
bossed in exact register in the area of optically variable
element 2 in such a way that two elements 14 and 15 are fur-
thermore recognizable by transmitted light, which yield total
information together with elements 11, 12 and 13 when the
document is viewed by transmitted light.
The particular property of the viewing angle-dependent,
optically variable color overprints can also be used advanta-
geously in combination with further security elements. For
example the inventive security element can be linked with a
combination of an embossed structure with an embossed line
pattern as known basically from CA 1 019 012 to form a total
element which has fully novel properties.
Fig. 8 shows a preferred embodiment in this connection.
Optically variable element 2 applied to data carrier 1 con-
sists of several components. Lines 16 of a first high-
resolution structure are first printed. In the area of this
printed structure other lines 17 of a second high-resolution
structure are then printed which differ from the first in
their color, shape or the direction of the printed lines.
Second applied high-resolution structure 17 forms a first
part of information incorporated in the optically variable
element, in the following case the bottom part of the numeral
"10". A further surface area of the optically variable ele-
ment is formed by the combination of an embossing and a line
pattern as basically known from CA 1 019 012, lines being
printed which are recognizable differently in area 18 when
viewed at different viewing angles because of an additionally
applied embossing. Unembossed area 19 is covered all over
with a substance, in particular an ink, which again has an
optically variable pigment without, or with only weak, body
color of its own. Lines 16 and 17 of the optically variable
element thus have a viewing angle-dependent color effect.
Part 18 of the optically variable element contains the par-
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tial information supplementing print 17, which is applied in
exact register and is clearly visible only at certain viewing
angles because of the embossing and the line pattern. Thus
partial information 17 is visible at all viewing angles, but
a different color effect is produced depending on the viewing
angle. Part 18 of the optically variable security element
contains the supplementary partial information, which is
clearly visible only when the data carrier is tilted.
Fig. 9 shows a further example of an inventive data car-
rier. A high-resolution portrait consisting of fine lines 20
is first printed on data carrier 1 by steel gravure printing.
To produce the inventive effect one overlays this steel gra-
vure portrait completely or partly with the identical picture
in coarser resolution, for example in broader lines 21, using
optically variable colors for the second picture so that the
high-resolution steel engraving has an optically variable ef-
fect associated therewith. Along with overprinting the high-
resolution steel engraving flat with optically variable col-
ors, the latter technique provides the possibility of associ-
ating an optically variable impression with the steel en-
graved portrait despite the use of less optically variable
colors.
The preceding examples show that the embodiments based
on the idea of the invention lead to a great number of spe-
cific design possibilities. These can in turn also be com-
bined with one another or with other known optical security
elements for data carriers. To produce the first structured
print one can apply a suitable ink. It is furthermore possi-
ble to produce a structure by removing certain partial areas
from a flat print. One can do so using etching techniques, on
one hand, but also other methods, for example the laser abla-
tion method. Producing the structure with the help of a laser
can also be regarded as printing in this context. In all pre-
ceding embodiments the print can be of high resolution, sin-
gle- or multicolored and with different color tones in each
case. In especially advantageous embodiments the structure is
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produced as a line pattern, dot pattern, halftone image or
the like.
In the abovementioned embodiments it has furthermore
turned out that the brilliance of the optically variable ef-
fect can be increased further by smoothing the background be-
fore or after applying the optically variable colors.
The high-resolution fine structure can also be applied
as a so-called "negative structure", a fine line structure
being produced by gaps in an otherwise all-over print,
whereby one can produce not only straight lines but also
other ones, for example guilloches or microprints of alphanu-
meric characters, which are then overprinted flat with the
optically variable colors. For overprinting the fine line
structure one can use optically variable colors which contain-
one, several and/or different optically variable pigments,
for example liquid-crystal silicone polymers or iridescent
pigments. Obviously it is also possible to provide the color
containing the optically variable pigments, and/or the color
of'the fine structure background, with luminescent, magnetic,
conductive or other feature pigments.
To attain particular effects one can also coordinate the
color used to produce the structure with the color of the op-
tically variable pigments applied thereto, so that the color
of the optically variable element and the color of the back-
ground are the same at certain viewing angles. The optically
variable substance or color, which is applied so as to over-
lap in an area of the structure, contains optically variable
pigments having no, or only slight, body color of their own,
such as in particular interference layer pigments or pigments
produced on the basis of liquid-crystal polymers. They can be
printed on the particular structures produced by the first
ink in such a way as to cover them all over, even overlap
them or cover only a part of the structure in certain shapes,
characters or patterns.
Furthermore the inventive method is not restricted to
producing the optically variable element directly on the data
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- carrier. Instead it is also possible to produce the optically
variable element on a separate carrier and then transfer the
element to the data carrier using one of the known transfer
methods. The optically variable element can thereby also be
realized as a printed optically variable foil, in particular
one provided with a fine line print.
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