Note: Descriptions are shown in the official language in which they were submitted.
CA 02714639 2010-08-10
Security element
[0001] The invention relates to a security element for the protection of
objects
of value and to a data carrier provided with the security element. The
invention
further relates to a method for the manufacturing of such a security element
and to
a method for the authenticity check of a security element and of a data
carrier.
[0002] Data carriers such as documents of value or identification documents
but
also other objects of value, such as for example branded products, often are
provided with security elements for their protection, which allow the data
carrier
to be authenticity-checked and which at the same time serve as a protection
against unauthorized reproduction. The security elements can have the form,
for
example, of a security thread embedded in a bank note, a cover foil for a bank
note with hole, an applied security strip, a self-supporting transfer element
or also
the form of a feature area that is printed directly onto a document of value.
[0003] For example, for the authenticity protection there are used security
elements which, when brought into a magnetic or electrical field, produce
optically recognizable or machine-measurable effects. These effects can only
be
imitated with very great difficulties and protect from unauthorized copying.
From
EP 1 747 906 A2 there are known security documents with micro capsules which
upon the application of an external electrical or magnetic field change their
alignment and thus optically change the security element.
[0004] The disadvantage of the variants described in the prior art is that the
authenticity check is only possible when an external electrical or magnetic
field is
available. Thus, a quick and simple check is not possible.
[0005] On these premises the invention is based on the object to further
improve a security element of the above-mentioned kind and in particular to
create a security element with high forgery-proofness whose authenticity,
however, can be easily checked.
CA 02714639 2010-08-10
2
[0006] This object is achieved by the security element having the features of
the
main claim. A method for manufacturing such a security element, an accordingly
equipped data carrier and a method for the authenticity check of a security
element and of a data carrier are stated in the independent claims. Further
developments of the invention are subject matter of the dependent claims.
[0007] According to the invention a generic security element comprises a
substrate with a multitude of particles. The particles are suitable for
representing
at least two distinguishable information states, whereby the change between
the
information states is reversible and effected under the action of gravity and
optionally an external mechanical force.
[0008] The entirety of the particles, upon the action of only the gravity,
represents a first information state. Upon the additional action of an
external
mechanical force, the entirety of the particles represents a second
information
state. When the action of the external mechanical force is changed or removed,
so
that only gravity still acts, the entirety of the particles, for example,
again
represents the first information state or turns into a third information state
distinguishable from the first and second information state.
10009] An information state according to the invention means the following.
Each particle is in a certain first state which represents a first partial
information.
The entirety of the first pieces of partial information of all particles forms
a first
information state. Upon the action of an external force, the respective state
of the
particles changes and each particle conveys a second partial information
distinguishable from the first partial information. The entirety of the second
pieces
of partial information then yields the second information state.
[0010] The external mechanical force is preferably tilting or shaking.
CA 02714639 2010-08-10
[0011] "Tilting" according to the invention means the rotation of the security
element around any desired axis, preferably around an axis laid by the
security
element.
100121 Upon shaking, the security element is moved on a path forward and
backward, so that a shaking motion is the result.
[0013] The particles, which upon tilting show an information change, are
mounted to be rotatable, their respective surface is composed of at least two
distinguishable surface areas and their respective center of mass does not
correspond to the respective geometric center of volume, so that the particles
are
aligned spatially in the field of gravity.
100141 In preferred embodiments the information change is observable at a
rotation angle or tilt angle of a maximum of 90 , especially preferably at a
rotation angle or tilt angle between 30 and 60 . For example, this means for a
viewer, for whom the first information state is recognizable, that after
tilting the
security element by a maximum of 90 around a suitable axis, he recognizes the
second information state. In an especially preferably embodiment according to
the
invention, upon tilting back there may be restored the first information
state.
100151 Preferably, the particles are bodies with concave or spherical boundary
surfaces, preferably spheres, cylinders, barrel-shaped bodies or ellipsoids,
especially preferably spheres.
100161 It goes without saying that the designations of the geometric bodies do
not only mean the ideal case of the perfect geometric design of the bodies,
they
rather also include the bodies deviating from the ideal case. For example, the
term
"sphere" does not only mean the sphere as a geometrically perfect body, but
also
spherical formations.
CA 02714639 2010-08-10
4
[0017] The particles are preferably micro particles. This means, that all size
dimensions, such as e.g. length or diameter, lie in the micrometer range.
[00181 The particle diameter of a sphere according to the invention preferably
amounts to 200 pm or less, preferably 50 pm or less, especially preferably 10
to
30 m.
100191 The respective surfaces of the particles are composed of at least two
distinguishable surface areas.
[0020] The distinguishable surface areas each occupy preferably at least a
third
of, preferably half the particle surface. Especially preferably, the surface
areas do
not overlap. When the surface areas do not overlap, this has the advantage
that the
properties of the particle surfaces can be observed especially well.
[0021] Of course, it is also possible to provide more than two distinguishable
surface areas on the particle surface. Thus, even three or four
distinguishable
surface areas can readily be present.
100221 The surface areas are preferably distinguishable with very simple aids,
especially preferably with the naked eye.
[0023] E.g. magnifying glass, UV lamp, polarizing filter and the like arc
suitable as simple aids.
[0024] In a further embodiment, the surface areas can additionally be
distinguished by machine. The differentiation can be effected here via the
machine measurement of that property which is also perceived with the simple
aids or the naked eye. But the surface areas preferably differ in a further,
only
machine-measurable property.
CA 02714639 2010-08-10
[00251 For example, one of the surface areas or at least two of the surface
areas
have magnetic, electrical, light-polarizing, in the non-visible wavelength
range
absorbing and/ or emitting and similar properties.
[0026] All particles or only a part of the particles in the security element
can be
provided with the additional machine-measurable properties.
[0027] With the help of the magnetic and electrical properties the particles
can
be additionally controlled.
[0028] Especially preferably, the at least two surface areas differ in a
property
distinguishable only with the naked eye and in a property only machine-
measurable.
100291 Properties distinguishable with the naked eye according to the
invention
are properties that a viewer can perceive in the visible spectral range (VIS).
100301 Especially preferably, the surface areas differ in spectral properties,
such
as absorption, emission and/or reflection.
[0031] For example, a particle has two colors differing in the visible
spectral
range. The color can be produced by applying a color pigment.
100321 Alternatively, the at least two surface areas show different
interferences
due to thin-layer elements or LC coatings, different diffraction structures or
luminescent properties etc.
[0033] The distinguishable properties can also be combined in any desired
fashion. One surface area can be provided e.g. with a color pigment, the other
surface area with a luminescent substance.
(0034] The properties of a surface area can occupy the entire surface area all
over or only a partial area. For example, the properties are distributed in
the form
of a grid or in the form of other patterns, characters or numbers.
CA 02714639 2010-08-10
6
[0035] The surface properties of all particles can be identical. But it is of
course
also possible to provide a part of the particles with other properties. For
example,
a part of the particles may have the color combination white/black, while
other
particles have the color combination blue/red.
[00361 Preferably, the distinguishable surface areas are produced by the body
surfaces being fractionally vapor-deposited. Alternatively, the coating can
also be
produced by "cold coating".
100371 Moreover, the center of mass of a particle according to the invention
does not correspond to its geometric center of volume. This means that the
particle spatially aligns itself in the field of gravity.
[0038] The center of mass and the center of volume do normally not coincide
when the density distribution of the body is inhomogeneous.
[0039] inhomogeneous densities are achieved for example by means of a
fractional coating with suitable specific weight on the body surface.
[0040] Due to the resulting density differences the particle aligns itself in
space.
Consequently, the distinguishable surface areas, too, align themselves in
space.
[0041] The fractional coating which leads to an inhomogeneous density
distribution of the bodies can already have the properties which make the
surface
areas distinguishable. In this case, the areas with different density and the
distinguishable surface areas are identical.
[0042] If the surface areas differ but have the same density, an additional
coating with suitable specific weight is to be applied onto the body surface.
100431 If an additional coating is applied, this can also be located beside or
below the distinguishable surface areas. Preferably, it is located below the
fractional coating which makes the surface areas distinguishable.
CA 02714639 2010-08-10
7
[0044] The additional coating, besides the property influencing the density,
may
have additional security-relevant properties, which are e.g. only machine-
measurable, such as luminescence, light polarization, absorption, emission,
reflection, in each case in the UV and/or IR etc.
[0045] The areas in which the densities differ may be distributed
independently
of the distinguishable surface areas.
[0046] In preferred embodiments, the areas with different density are disposed
such that the distinguishable surface areas differ in the density.
[0047] Preferably, the density in the area of the first surface area is
greater or
smaller than the density of the second surface area.
[0048] The density distribution of all particles may be identical. It is, of
course,
also possible to provide a part of the particles with different density
distributions.
So, for example, in a part of the particles the areas with different density
may be
congruent with the distinguishable surface areas, while in other particles the
areas
with different density do not correspond with the distinguishable surface
areas. In
this variant, the alignment of the surface areas in the respective groups of
particles
is different, so that further attractive optical effects result therefrom.
[0049] The center of mass and the center of volume of a sphere do not coincide
when, for example, the densities of the two hemispheres differ from each
other.
For example, there is located a correspondingly heavy coating on a part of a
hemisphere surface or it covers the entire hemisphere. Preferably, one of the
at
least two surface areas is congruent with the less dense hemisphere, the other
surface area is congruent with the more dense hemisphere.
[0050] Upon suitable density distribution in relation to the surface areas,
the
particles align themselves such that the viewer recognizes the surface areas
which
form the first information state. In the case of spheres which for example
have a
CA 02714639 2010-08-10
8
black and a white hemisphere and all have the same density distribution, the
viewer sees, for example, only the black hemispheres. If the security element
is
tilted, the black hemispheres will be covered and the white hemispheres will
appear.
[0051] A special effect can be achieved by using particles which have two
transparent hemispheres that are separated by a non-transparent layer. By a
suitable alignment of the security element in the field of gravity, such
particles
can be brought either in a non-transparent position, in which the non-
transparent
separation layer in the individual particles stands perpendicular to the
viewing
direction. By a different alignment of the security element it can be ensured
that
the viewing direction onto the particles is shifted by 90 and thus the non-
transparent separation layers in the particles each lie in parallel to the
direction of
vision of the viewer. Thus, a material layer built up by means of the
particles
becomes transparent, since the viewer can see through between the separation
layers of the particles, like through vertical blinds whose lamella are
aligned in
parallel to the viewing direction of the viewer.
10052] For example, in the case of a perpendicular view onto the substrate,
the
opaque separation layers can be aligned in parallel to the substrate and the
substrate appears non-transparent. If the substrate is tilted by 90 and the
viewer
again looks perpendicularly onto the substrate, the separation layers are
aligned
perpendicularly to the substrate and the viewer can look through. If the
security
element is disposed above a window, the viewer can look through, if the
security
element is applied above a print onto an opaque substrate, the print may be
exposed in this way.
[0053] So as to guarantee that the alignment of the particles is reversible,
these
are mounted to be rotatable.
CA 02714639 2010-08-10
9
[0054] The rotatable mounting can be achieved by embedding the particles in
micro cavities. Each particle is located in its own micro cavity.
[00551 The micro cavities are located directly in the substrate or in an
additional
layer.
100561 For manufacturing a substrate which has particles mounted to be
rotatable in micro cavities, for example, particles are incorporated in a
binder.
From the binder there can be manufactured foils which contain the particles.
Then, a liquid swelling the polymer of the foil, e.g. oil or a high-boiling
solvent, is
added. The such triggered swelling leads to the fact that the particles now
lie in a
cavity which is filled with the swelling agent.
100571 In a preferred embodiment the particles are encapsulated and are
mounted to be rotatable in the encapsulation. The particles are encapsulated
with
usual encapsulation techniques.
[00581 The capsule is firmly incorporated in the substrate or the additional
layer
and itself not mounted to be rotatable. The rotatable mounting of the particle
is
effected for example by a liquid or a gas, which is also enclosed in the
capsule
and acts as a kind of "lubricant" for the particles in the capsule.
Information about
the micro encapsulation and the further processing of the micro capsules can
be
obtained e.g. from EP 0 721 176 A2.
[00591 The particles, which upon shaking show an information change, are
formed as translucent micro capsules. The micro capsules are filled with at
least
two liquids of different density or surface tension.
100601 Within the framework of the present description "translucent" here
means diaphanous within the meaning of a certain or complete light
transmittance
and thus also includes transparency. A translucent layer allows a viewer to
see the
objects located behind or below said layer, even when by the translucent layer
the
CA 02714639 2010-08-10
brightness of the objects may be reduced and/ or the color of the objects may
be
changed. If, however, the light transmittance of a layer is so poor, that the
objects
located behind or below it are not recognizable, it is not translucent but is
referred
to as opaque or covering.
100611 Due to the different density or surface tension, under the action of
gravity the two liquids are present in the segregated state. If the particles
are
shaken, the two liquids mix. If the mixed liquids are left alone, phase
separation
occurs. Preferably, the segregated liquids appear to a viewer as a translucent
liquid, while the mixed liquids appear dull. Reversible color changes between
the
segregated and mixed state are also thinkable.
[00621 The information change results from the different states of"'
segregated"
and "mixed". The information change is preferably recognizable with the naked
eye.
100631 For example, the two liquids are water and oil.
10064] Preferably, the micro capsules are bodies with concave or spherical
boundary surfaces, preferably spheres, cylinders, barrel-shaped bodies or
ellipsoids, especially preferably spheres.
100651 It goes without saying that the designations of the geometric bodies do
not only mean the ideal case of the perfect geometric design of the bodies,
they
rather also include the bodies deviating from the ideal case. For example, the
term
"sphere" does not only mean the sphere as a geometrically perfect body, but
also
spherical formations.
[00661 In case of the micro capsules all size dimensions, such as e.g. length
or
diameter, lie in the micrometer range.
CA 02714639 2010-08-10
11
[0067] The capsule diameter of a sphere according to the invention amounts to
preferably 200 jum or less, preferably 50 m or less, especially preferably 10
to 30
m.
[00681 In a preferred embodiment the micro capsule has a diameter of approx.
50 m, the inside particle a diameter of 40 m.
[0069] The manufacturing of the particles and capsules is effected according
to
known methods such as coacervation, polymerization/polycondensation, "in situ"
polymerization, "emulsion diffusion" technique, "miniemulsion" polymerization.
[0070] According to the invention a multitude of particles is used.
[0071] The particles can be embedded in the substrate or applied onto the
substrate in an additional layer.
[0072] The particles or capsules can be distributed over the volume of the
substrate or of the additional layer. Preferably, the particles or capsules
lie in one
plane.
[0073] Preferably, the share of the particles or capsules in the volume of the
substrate or of the additional layer amounts to 5 weight percent to 50 weight
percent.
[0074] The additional layer is preferably a printed layer. The particles are
incorporated in printing inks here.
[0075] The additional layer is especially preferably formed by a screen
printing
layer or flexographic printing layer, in some embodiments also by an intaglio
printing layer.
[0076] For example, an intaglio printing ink comprises of 30 to 40 weight
percent binder and 10 to 20 weight percent particles. The additives usual for
CA 02714639 2010-08-10
12
intaglio printing inks are additionally contained. All components complement
each other accordingly to form 100 weight percent.
[0077] For example, a flexographic printing ink comprises of 70 to 90 weight
percent binder and 10 to 30 weight percent particles. The additives usual for
flexographic printing inks can be additionally contained. All components
complement each other accordingly to form 100 weight percent.
[0078] For example, a screen printing ink comprises of 70 to 90 weight percent
binder and 10 to 30 weight percent particles. The additives usual for screen
printing inks, such as antifoaming agents and cross-linking agents, are
additionally contained. All components accordingly complement each other to
form 100 weight percent.
10079] The different particles according to the invention can be combined in
any desired fashion in a security element. Thus, particles which upon tilting
show
an information change can be present in one security element together with
particles which upon shaking show an information change.
[00801 In further embodiments, a part of the particles in the security element
is
no longer suitable for the representation of at least two information states.
Preferably, this part of the particles is selectively destroyed or changed in
its
movability.
[0081] When particles are selectively destroyed, these are preferably capsule
systems. If the capsule is destroyed by means of heat, pressure, UV light or
laser,
e.g. by bursting the capsule, in the case of tilting systems, the embedded
body is
no longer mounted to be rotatable. Increasing the viscosity of the liquid in
the
capsule, e.g. by cross linking, also disturbs the rotatability. In the case of
shaking
systems, the container of the liquids is destroyed.
CA 02714639 2010-08-10
l3
[0082] Especially preferably, a laser is used for destroying the capsules,
because in this way particles can be targeted and changed in an especially
selective and simple way.
[0083] In other embodiments, only by decreasing the viscosity of the liquid in
the capsule the rotatability can be triggered.
[0084] Thus, in these variants a simple individualization of the security
element
is possible.
[0085] The security element according to the invention offers an attractive
visual effect, namely an information change interactively produced by the
user,
which can be prompted and recognized without additional aids. In this case,
one
talks of a so-called human inspection feature.
[0086] Most different materials can be employed as a substrate. Preferably,
every kind of paper is suitable, in particular cotton vellum paper. Of course,
there
can also be employed paper which contains a portion x of polymeric material,
whereby x can amount to between 0 and 100 weight percent.
[0087] The substrate can also be a plastic foil, such as a polyester foil. The
foil
can be stretched in a monoaxial or biaxial fashion. A stretching of the foil
results
in, among other things, the foil getting light polarizing properties which can
be
used as a further security feature.
[0088] The substrate can also be a multi-layer compound which contains at
least one layer made of paper or a paper-like material. Such a compound, which
can also be used as a substrate for bank notes, is characterized by an
extraordinarily great stability, which is of great advantage for the
durability of the
note or of the data carrier.
CA 02714639 2010-08-10
14
[00891 As a substrate there can further be used a multilayer, paper-free
composite material, which can be advantageously used in particular in some
climate zones of the earth.
[00901 All substrates may contain additives which may serve as authenticity
features. Here in particular those luminescent substances are suitable which
in the
visible wavelength range are preferably transparent and in the not visible
wavelength range can be excited by suitable aids, such as e.g. a UV or IR
radiation emitting source, so as to produce a luminescence radiation directly
visible or at least detectable with aids.
[00911 A transparent or translucent foil is also suitable as a substrate. In
this
case the security element can be advantageously used in or above a window area
or a through opening of a document of value as a lookthrough security element.
The foil may be formed as a patch covering a partial surface of the substrate
or as
a strip extending over the entire length or width of the data carrier. As
materials
for the foil there are suitable first of all the plastic materials PET
(polyethylene
terephthalate), PBT (polybutylene terephthalate), PEN (polyethylene
naphthalate),
PP (polypropylene), PA (polyamide), PE (polyethylene). Furthermore, the foil
can
be stretched in a monoaxial or biaxial fashion, as already explained
hereinabove.
100921 An opening in a bank note can be produced already upon the
manufacturing of the security paper used for the bank note and then has a
fibrous,
irregular edge. Such an edge is characteristic for openings produced already
upon
the sheet formation and cannot be subsequently produced. Details about the
manufacturing of such irregular edges can be inferred from the print WO
03/054297 A2, whose disclosure is included in the present application in this
respect. In other embodiments the opening is not produced until after the
papermaking by punching or cutting, for example by laser beam cutting.
CA 02714639 2010-08-10
[00931 The invention also comprises a method for manufacturing a security
element for the protection of objects of value, wherein a substrate is
provided with
a multitude of particles which are suitable for the representation of at least
two
distinguishable information states, the change between the information states
being reversible and effected under the interaction of an external mechanical
force
and of gravity on the substrate. The particles are preferably printed onto the
substrate or incorporated in the substrate.
100941 The invention further comprises a data carrier, in particular a
document
of value, such as a bank note, a passport, a deed, an ID card or the like,
which is
provided with a security element of the described type. The security element
can
also be disposed, in particular when it is present on a transparent or
translucent
substrate, in or above a window area or a through opening of the data carrier.
[00951 Further embodiments and advantages of the invention are explained in
the following with reference to the Figures, for clarity's sake the Figures do
without a true-to-scale and true-to-proportion representation.
[00961 Fig. 1 shows a schematic representation of a bank note with a
security element according to the invention,
[00971 Fig.2 shows a cross section through a security element according
to an embodiment of the invention,
[00981 Fig. 3a, b, c show a security element according to an embodiment of
the invention in a top view representation as in Fig. 2,
100991 Fig. 4 shows a cross section through a security element according
to an embodiment of the invention,
[01001 Fig. 5a, b show a security element according to another embodiment
of the invention in a top view representation as in Fig. 4.
CA 02714639 2010-08-10
16
[01011 In the following the invention is explained by the example of a bank
note. Fig. 1 shows a schematic representation of a bank note 10 with a
security
element in the form of a foil strip 11, which was transferred onto the bank
note
paper 13, and with a security element 12 directly printed onto the bank note
paper
13. It is obvious, that the invention is not restricted to these security
elements and
bank notes, but can be used with all types of security elements, for example
with
labels on goods and packages or for the protection of documents, identity
documents, passports, credit cards, health cards and the like. For bank notes
and
similar documents it is also suitable to use, for example, transfer elements,
security threads or security strips, besides printed elements, and also
lookthrough
elements, besides top view elements.
[0102] Fig. 2 shows a cross section along the line A-A through the BN paper 13
provided with the foil strip 11. The strip comprises a translucent plastic
foil 21, in
the micro cavities 22 of which the particles 23, 25 according to the invention
are
embedded. The particles 23, 25 are encapsulated and mounted to be freely
rotatable in their capsule 24. The capsule 24 itself is not mounted to be
rotatable,
but firmly anchored in the foil.
(01031 The encapsulated particles preferably are spherical micro particles. In
the example, one hemisphere is configured white, the other hemisphere black.
Additionally, the black and the white hemisphere have different densities.
101041 Due to gravity and the not corresponding centers of volume and centers
of mass the particles align themselves in space with a preferred direction.
The
density distribution of a first group of particles 23 is configured such that
the
white hemisphere has a higher density, compared with the black hemisphere, and
the spheres align themselves in the field of gravity such that the white
hemispheres point in the direction of gravity. The density distribution of a
second
group of particles 25 is configured such that the black hemisphere has a
higher
density, compared with the white hemisphere, and the spheres align themselves
in
CA 02714639 2010-08-10
17
the field of gravity such that the black hemispheres point in the direction of
gravity. By a skilful arrangement of the particles 23 and 25, there can thus
be
incorporated an additional information in the security element via the white
and
black areas.
[0105] How the reversible change of the visual appearance of the security
element 11 is achieved, is now explained in more detail with reference to the
top
view representations of the Fig. 3a, b and c.
[0106] Fig. 3a shows a detail of the bank note with the security element 11 of
Fig. 2 applied onto the bank note paper 13 in top view. The plane in which the
bank note lies is aligned perpendicular to gravity here. The direction, in
which
gravity acts, is indicated by arrow 35. When a viewer looks perpendicularly
onto
the bank note, namely in the direction in which gravity acts, he sees the
particles
23, 25 aligned by gravity. The viewing direction is indicated by arrow 30. The
particles 23 of the first group are oriented with their black hemisphere
towards the
viewer, the particles 25 of the second group with their white hemisphere. By a
suitable arrangement of the particles 23 and 25 there can be conveyed a
complex
information to the viewer. In the present case, the letter "L" appears as a
white
letter in a black environment. The entirety of all pieces of partial
information,
which represent the surface areas of the individual particles, reproduces a
first
information state.
10107] Fig. 3b shows the bank note 10 tilted by 90 around the longitudinal
axis
C-C (see Fig. 1). The plane where the bank note lies is now aligned in
parallel to
gravity. The direction in which gravity acts is again indicated by arrow 35.
The
particles 23 and 25 maintain their spatial alignment through the action of
gravity.
The black hemispheres of the particles 23 and the white hemispheres of the
particles 25 further point against the direction of gravity. The viewer again
looks
perpendicularly onto the bank note and in this case also perpendicularly to
the
direction of gravity. The viewing direction is indicated by arrow 30. By the
tilting
CA 02714639 2010-08-10
18
now other partial areas of the particle surfaces are exposed to the viewer.
Thus, in
this position of the bank note the viewer looks onto spheres that are colored
half
white and half black. In the case of very small spheres, to the viewer appears
a
mixed effect of the two colors, so that the spheres seem to be colored gray.
The
area which is provided with the particles thus appears completely gray to the
viewer. The letter "L" disappears. The entirety of all pieces of partial
information,
which represent the surface areas of the individual particles, reproduces a
second
information state.
[0108] Fig. 3c shows the bank note 10 tilted by further 90 around the
longitudinal axis C-C (see Fig. 1). The bank note was tilted by a total of 180
compared with the position shown in Fig. 3a. The plane where the bank note
lies
is again aligned perpendicularly to gravity here. The direction in which
gravity
acts is indicated by arrow 35. The viewer again looks perpendicularly onto the
bank note, but now against the direction of gravity. The particles 23 and 25
further
maintain their spatial alignment through the action of gravity. The viewing
direction is indicated by arrow 30. The particles 23 of the first group are
now
oriented with their white hemisphere towards the viewer, the particles 25 of
the
second group with their black hemisphere. The letter "L" now appears black in
a
white environment. The entirety of all pieces of partial information, which
represent the surface areas of the individual particles, reproduces a third
information state.
[0109] By tilting back the bank note by 90 in each case, the first and second
information state can be restored. A reversible change between the states thus
is
easily possible.
101101 By tilting the bank note, the user can interactively and reversibly
make
visible different information. Such an interactive design has a high recall
value for
the viewer and thus has in general a very high forgery proofness.
CA 02714639 2010-08-10
19
[0111] Fig. 4 shows a cross section along the line B-B through the bank note
paper 13 provided with the security element 12. The security element is
applied in
the form of a square as a printed layer onto the bank note paper. The printed
layer
comprises at least a binder 40 in which the particles according to the
invention are
incorporated. The particles are capsules 41 filled with two liquids 42, 43.
Below
the printed layer according to the invention there is located a further print
44.
[0112] Fig. 5a shows the security element 12 of Fig. 4 in a top view, the two
liquids 42, 43 being present in the resting state in a segregated manner and
thus
appear translucent, preferably clear, to a viewer. In a segregated state the
security
element 12 is at least translucent for a viewer and he can recognize the
additional
print 44, here in the form of the letters "XY".
[0113] When the viewer shakes the bank note, the liquids mix and the result is
a
dispersion appearing dull. Looking through which was possible before is
disturbed. Due to the cloudiness the print is no longer recognizable. This
state is
shown in Fig. 5b.
[0114] If the bank note is no longer moved, the liquids again segregate and a
looking through, as described in Fig. 5a, is again possible.
