The present invention relates to a method of manufacturing
a security thread equipped with a microchip, a security thread, and a document comprising
It is already known to provide a document such as a bank
note with a security thread in order to provide a possibility to verify whether
the banknote is genuine or not. A method of manufacturing of such a security thread
is disclosed in the Italian Patent Application MI2001A001914. For the public use,
such security thread allows a simple visual examination.
However, it remains a need to provide the banknote with
DE 198 33 746 A1 discloses a generic security thread comprising
a substrate, a support material provided on the substrate, a microchip fixedly attached
to or at least partly embedded in the support material.
EP-1 254 765 A1 discloses a further security thread without
It is the object of the present invention, to provide a
method of manufacturing a security thread and a generic security thread which enable
variable positioning of the microchip at a variable distance.
This object is solved by the method of manufacturing a
security thread having the features of claim 1 and by the security thread having
the features of claim 9.
The invention is further developed as it is defined in
the dependent claims.
With the continuous progress of the technology, particularly
of the miniaturisation technique of microprocessors, a microchip has been developed
which has a suitable dimension for the use in plastic or paper documents.
Advantageously, the invention provides a method for precisely
depositing such a microchip into a security thread, and also a security thread which
is capable to accommodate the microchip. Thereby, the microchip is fixedly attached
to or embedded in the thread. The security thus manufactured is suitable for banknotes,
passports or passenger tickets, for instance.
Advantageously, the deposition of the microchip can be
carried out in a paper mill during the production of the paper. The security thread
having the microchip incorporated therein can be introduced into the paper by means
of a conventional system as it is used in a paper mill.
In the following, the invention is described on the basis
of preferred embodiments thereof with reference to the figures.
- Fig. 1 shows a method of manufacturing a security thread equipped with a microchip
according to an embodiment of the invention;
- Fig. 2 shows a structural view of a thread according to an embodiment of the
- Fig. 3 shows a structural view of a thread according to another embodiment of
The embodiment shown in Fig. 1 is applied to the paper
manufacture in a paper mill, wherein a security thread 1 is introduced in banknotes,
for example. However, the invention is not restricted to this embodiment.
The security thread 1 is constituted by a substrate which
can be a tape or film, preferably of polyester.
In a first step, the substrate, which usually is a transparent
or printed polyester film, is metalized under vacuum with aluminium and/or copper
etc. with a thickness from 6 to 50 µm.
Thereafter, on at least one side of the substrate, a suitable
support material is applied, which can be quickly (preferably within a few milliseconds)
brought from its solid state to a soft or "gum-like" state.
As the support material, a thermoplastic material containing
a resin having a low melting point (approximately 70 °C) is applied by painting,
transferring, spraying, for example. In more detail, as the thermoplastic material,
wax, vinyl-polymer, polyurethane or any polymer or compound distributed in solvents
on water basis or on solvent basis is suitable, provided that it has the capability
to modify its state from solid to a soft or "gum-like" state. The amount of this
material depends on the type and the capability of modifying its state. For example,
wax, vinyl-polymers, polymers or parafina can be put in a solvent based varnish
and applied on the film. Optionally, the thermoplastic material can be subjected
to a roll embossing or stencil printing process wherein the thickness of deposition
in a dried state is approximately 10 µm.
In order to enhance the adhesion of the thermoplastic material,
a special treatment for enhancing the adhesion can be carried out before applying
the thermoplastic material.
Once the varnish has been applied and dried, it provides
a sealing to the atmosphere, and the film is cut in stripes having a width of approximately
0.5 to 6 mm, particularly if the thread 1 shall be introduced within the paper by
means of a total embedding or windows technique.
Alternatively, the film is kept in larger sizes, if the
film is transformed into tapes and is, therefore, applied on the surface of another
If the thread 1 shall be introduced in the paper together
with the microchip 2, the thread 1 preferably has a width of 2.5 mm which is necessary
to accommodate a microchip 2, because a conventional microchip 2 has side lengths
of 0.5 mm to 1.5 mm.
After cutting the film into threads 1, the threads 1 are
winded up around bobbins (not shown) as they are usually used for the security threads
The thus winded thread 1 is positioned on appropriate reels
3 which comprise a motor spindle that winds off the thread 1 in a controlled manner
so as to maintain a constant output.
By winding off the thread 1, the thread 1 is heated by
means of a contact with a heat cylinder 4. The method of heating and of modifying
the state of the varnish can also be a mechanic operation by means of a contact
of the polyester with a heat source 4, for example. Alternatively, the thread 1
is radiated by a beam that emits heat such as a laser beam, an infrared beam or
an ultraviolet beam (not shown).
Considering the heat-sensitive characteristic of waxes,
several 10 µm of the previously deposited compound are softened (it is obvious
that the softening can be performed by any heating system).
After the softening, the microchip 2 falls from an appropriate
distributor 5 onto the thread 1, wherein the microchip 2 falling on the thread 1
is embedded therein.
When the microchip is appropriately deposited, a curing
process of the support material is performed, preferably by cooling the support
material. Directly after the cooling process by an air cooling means 6, the compound
returns to its solid state and holds and supports the microchip 2. Also in this
case, the cooling process can be performed in various ways.
At this point, the thread 1 is supplied together with the
microchip 2 in the interior of a paper compound 7 when the paper is produced.
In this embodiment of the paper manufacture, the start
of the impulses for the fall of the microchip 2 from the distributor 5 and the cooling
process are controlled by the detection of a corresponding notch 8 in a watermark
cylinder 9, for example. Thereby, the microchip 2 is introduced in register with
the watermark of the banknote. As for the control means, any conventional means
known in the field of the paper manufacture can be used.
Depending from the speed with which the paper is manufactured,
and from the relative thickness of the varnish, when the varnish is still in the
gum-like state and has already the microchip 2 deposited thereon, it may be used
a pressing means (not shown) that provides two rubber layers or two rubber cylinders
spaced to each other by a fixed gap there between and which compress the microchip
2 into the varnish until the microchip 2 is embedded therein.
As a numeric example, the polyester substrate may have
a thickness of 10 µm, on which aluminium is deposited under vacuum with a thickness
of 0.2 µm. On the aluminium, a vinyl protecting varnish is applied which has
a thickness of approximately 2 µm. On the protecting layer, a heat-sensitive
varnish is applied so as to obtain a layer of 10 µm of the heat-sensitive varnish
in the dried state. As a result, the total thickness of the thread 1 is approximately
22 to 23 µm.
when the heat-sensitive varnish is activated and when the
microchip 2 falls on it which has a thickness of 60 µm, for example, the microchip
2 can be embedded a few µm.
Then, thread 1 is optionally passed between two cylinders
(not shown) of the pressing means which are spaced to each other with a gap of 75
µm so that that the microchip 2 is embedded for at least 8 to 9 µm into
the heat-sensitive varnish.
It is obvious that the preferred numeral values can be
varied according to the materials which are used, in particular the target material
that thereafter will receive the thread 1 with the embedded microchip 2.
The advantage of the invention is the possibility to position
the microchip 2 at a variable distance. Thereby, it is not necessary to use a pre-constructed
thread magazine, for instance, which would involve excessive costs. Moreover, the
thread 1 suitable for accommodating the microchip 2 and the microchip 2 itself are
the same for all banknotes independently from the kind of the banknotes. On the
other hand, during the manufacturing process in the paper mill, data or signals
are programmable and machine-readable from the security thread 1.
In the following, embodiments of the structure of the thread
will be described with reference to Figs. 2 and 3. As an alternative to the thread
1 used in the embodiment of Fig. 1, the thread can be embodied in the following
Fig. 2 shows a thread 11 comprising a substrate 12 of polyester
On the substrate 12, a medium layer 13 is applied which
carries specific characters, signs, data or any other information which are helpful
for an individualisation of a document in which the thread 11 is to be inserted.
The medium layer 13 preferably has a thickness of 6 to 50 µm.
This medium layer 13 may comprise a varnish or coloured
inks (red, green, blue, yellow, for instance). The varnishes or inks may be applied
sequentially and/or completely or partially overlapping. Alternatively, the varnish
or ink may be mixed with the substrate of polymer. The medium layer 13 may absorb.light
having long or short wavelengths (about 360 nm or 254 nm). The medium layer 13 may
comprises a fluorescent dye.
Alternatively, the medium layer 13 may comprise a varnish
or an ink which exhibits a chromatic variation according to the diffraction angle.
Also in this case, the varnish or the ink can be applied sequentially and/or completely
or partially overlapping.
Alternatively, the medium layer 13 may comprise a magnetic
ink having different coercitivities by applying the magnetic ink continuously, discontinuously
or in a manner like SISMA which is a Mantegazza Patent.
Alternatively, the medium layer 13 may comprise images
or holograms of any type, i.e. exelgrams, pixelgrams, dot matrix, depicted in a
two dimensional or three dimensional manner.
Alternatively, the medium layer 13 may comprise a metallic
material which may be applied under vacuum such as aluminium, copper, nickel having
a characteristic of reflecting light or a larger gloss. It is obvious that the metallic
materials may be applied in different quantities, thickness' and types.
The medium layer 13 constituted by any one of the above-mentioned
with interruptions or even a partly lack of material. The materials may be applied
in a negative or positive manner.
Alternatively, the medium layer 13 may comprise substances
for checking the magnetoresistance or an inductivity such as "Micro Tag".
Alternatively, the medium layer 13 may comprise a varnish
or an ink being conductive, transparent (for example polyaniline) or visual (for
example a silver-based varnish or ink).
On the medium layer 13, as it is described above, a heat-sensitive
support material 14 is applied. Preferably, the heat-sensitive material 14 is a
thermoplastic having a thickness of about 10 µm.
Fig. 3 shows a structural view of a thread 21 according
to another embodiment of the invention.
The thread 21 according to this embodiment includes the
substrate 22 and the medium layer 23 in a same way as the thread 11 shown in Fig.
Instead of the heat-sensitive support material, an adhesive
support material or a glue support material 24 is applied on the medium layer 23.
The adhesive support material 24 may have a thickness of about 8 µm. The microchip
2 is adhered to the adhesive support material 24.
Preferably, an additional siliconated layer 25 is applied
on the adhesive support material 24. The siliconated layer 25 may comprise paper
with a density of 45 to 90 g/m2 or polyester having a thickness of 10
to 20 µm. Although it is not shown in the figures, the siliconated layer 25
can alternatively be applied on that side of the thread 21 which is opposite of
the adhesive support material 24. This is advantageously in particular when the
thread 21 is winded up around a bobbin (in general, the siliconated layer 25 may
also be provided on the heat-sensitive material 24 of the thread according to the
embodiment shown in Fig. 2).
Alternatively, a thread may comprise both the heat-sensitive
support material 14 and the adhesive support material 24.
The invention has been described with reference to the
preferred embodiment. However, it is obvious for the skilled person that the invention
can be modified in various ways. Such modifications are also within the scope of
protection which is defined by the claims.
For example, the microchip 2 may comprise an antenna (not
shown) for a wireless data transmission.