[0001] The invention relates to a chip protecting against counterfeiting security printing,
especially for banknotes and other security printing (e.g. pre-numbered forms), enabling
the verification of the authenticity of a document.
[0002] Security printing is a type of printing, the execution of which by unauthorised persons
is hampered by deliberate application of safeguards by which the safety of legitimate
users is ensured. Used securities in varying degrees can protect against certain forms
of counterfeiting. Securities, banknotes or important documents sometimes have a number
of different security features difficult enough to falsify that they are called highly
protected prints.
[0003] There are three levels of security:
- a) the first degree - security based on organoleptic properties - for users without
tools,
- b) the second degree - securities verified using basic tools, e.g. magnifying glass,
UV lamp,
- c) the third degree - security verified by experts (specialists) in appropriately
equipped la boratories.
[0004] Banknotes have securities to protect against counterfeiting and thus belong to the
group of security printing. The most widely used securities are:
- special, secret recipe paper conferring specific mechanical and optical properties;
- replacing paper with polymer substrate difficult to print on;
- use of microprinting;
- recto-verso; it is a picture visible in the lumen, created with the finely fitting
elements located on both sides of a banknote.
- a description on the recto;
- hot-stamping foil with metallic holographic pattern;
- embossment resulting from intaglio printing;
- complex graphics, yet distinct, with strong saturation and gloss paint;
- watermark, especially visible against the light;
- a security thread in the form of a metal strip recessed inwardly in paper with spacing
forming an inscription;
- printing with an optically variable ink - seen in front and at a sharp angle it changes
colour;
- ribbing;
- drawings visible under UV light.
[0005] Part of banknote security is kept secret and is a strict secret data of central banks
issuing banknotes.
[0006] Due to the continuous development of counterfeiting techniques constant search for
new methods of document protection against illegal copying is needed. The aim of the
present invention is therefore to provide a new kind of security.
[0007] This objective was achieved through the use of graphene quantum dots (
Graphene Quantum Dot, GQD).
[0008] Quantum dots (QD) are semiconductor nanocrystals with sizes ranging from 2-10 nm.
They are very specific type of substance with properties intermediate between semiconductors
and quantum particles. A limited number of atoms and a diametre of a few nanometres
gives the quantum dots unique properties of absorption and emission of radiation,
which result from the presence of the effect of the quantum limit (quantum confinement
effect). This means that the excitation energy emitted by the photons will depend
on the composition of the crystal and its size. Just as semiconductors, quantum dots
absorb photons of light with such energy that gives you the ability to transfer electrons
from the non-activated to one of the higher available energy levels. Otherwise, there
is an emission process, because the wavelength emitted by light depends on the size
of the dots. Hence, having a semiconductive material we can get markers having different
colours, which are characteristic of quantum dots.
[0009] N anoparticles with a small diameter core (2 nm) have fluorescence at a wavelength
corresponding to blue light and even ultraviolet radiation (UV). When the diameter
of the quantum dot core increases, the wavelength of the radiation emitted by the
visible light increases, up to infrared radiation (IR). By modifying the composition
and choosing the size of the nanocrystals, fluorescence in the full spectrum from
ultraviolet (UV) to the infrared (IR) is obtained.
[0010] The radiation may be absorbed by quantum dots in a broad spectrum (Fig. 1), and their
molar absorption coefficient increases towards the UV. Thus the excitation can be
made of many kinds of dots using one light source, since there is no requirement to
apply excitation at a pre-set wavelength. In turn, the profile of the fluorescence
emission of quantum dots is narrow and has a small half-width value (FWHM 125 nm).
This allows for simultaneous use of multiple markers having different colours without
fear of overlapping of the signals. The nanocrystals can be repeatedly excited, with
no noticeable decrease in fluorescence because they have a high quantum yield of fluorescence
and long radiation (10-100 ns).
[0011] Graphene quantum dots (GQD) can also be prepared from graphite carbon fibres. This
was successfully done with acids and chemical exfoliation (Fig. 2). By varying the
process parameters a whole family of graphene quantum dots the size of the order of
1-4 nm can be made. It should be noted that the optical properties of the dots (quantum
confinement effect) depend directly on their size, i.e. the colour of photoluminescence.
The resulting structures are two-di mensional, so in fact they produce graphene quantum
discs.
[0012] Grapheme quantum dots are stable because the level of luminescence (resistant to
photobleaching).
[0013] The invention relates to a security element against counterfeiting, in particular
banknotes, comprising at least one graphene quantum dot (GQD) that is graphene nanoparticle
with a diametre of from 0.5 nm to 60 nm, preferably from 1 nm to 11 nm, containing
from 1 to 90, preferably from 1 to 20 layers of graphene disposed in the flexible
layer of graphene nanocomposite material, wherein the elastic layer of graphene nanocomposite
material comprises at least one graphene layer disposed on the adhesive layer, preferably
a polymer.
[0014] Preferably, the security element comprises graphene quantum dots (GQDs) of different
sizes.
[0015] Preferably at least one quantum dot (GQD), preferably all quantum dots (GQDs) are
an integral part of the flexible layer of graphene nanocomposite material.
[0016] Grapheme in the security element is in a pure or doped form.
[0017] Preferably, the security feature comprises a layer of graphene, and two adhesive
layers, w herein the graphene layer is located directly between the two layers of
adhesive.
[0018] The invention also includes the use of the security feature according to the invention
for securing banknotes, holograms, documents, passports, credit cards, excise bands,
excise forms, personal identifiers, certificates or product labels.
[0019] The invention is further a system for checking the authenticity of security printing,
in particular banknotes, comprising:
- the security element according to the invention,
- A device adapted to emit radiation in the range suitable for excitation of at least
one graphene quantum dot (GQD), preferably all of graphene quantum dots (GQDs) contained
in the security element, and
- A detector adapted to detect luminescence radiation of at least one graphene quantum
dot (GQD), preferably all of graphene quantum dots (GQDs) contained in the security
element.
[0020] The invention also applies to a method for checking the authenticity of security
printing, in particular banknotes, characterized in that the system is used according
to the invention.
[0021] The security feature is made of nanocomposite, one of whose components is a binder,
preferably a polymer, which ensures its integrity, hardness, flexibility and resistance
to compression, and the other is the second layer of plotted quantum dots (GQDs).
Flexible nanocomposite material is a material of heterogeneous structure composed
of two or more components with different properties. The properties of the composites
are not the sum or average of the properties of its components, and the material used
in its construction exhibits amisotropy of physical properties.
[0022] The security feature is made of a composite material resistant to:
- moisture and condensation
- splashing
- water-damage
- corrosion
- dust
- multiple deformation
- changes in temperature in the range -40°C to + 70°C
[0023] The mere presence of the structure of the graphene in a protected document is an
additional security factor, as commercial production of graphene in the form of a
single structure is not yet available to potential counterfeiters.
[0024] The invention will now be further described in preferred embodiments with reference
to the accompanying drawings, in which successive figures show:
Fig. 3 - pattern made of graphene quantum dots (GODs) on a flexible substrate - a
polymer,
Fig. 5 - examples of setting of GQDs nanolayers in an elastic nanocomposite layer,
Fig. 6 - operating principle of inherent security feature.
[0025] Security feature is one of the layers of security printing (3). The security feature
(1) in the above example is not an integral part of other securities and may, but
does not need to be placed in the same layer as other securities such as a hologram.
[0026] The presented security is a separate solution, not interfering directly with any
other group of the above mentioned securities.
[0027] The security feature (1) based on the modification technology is not limited by current
layout, shape and size. It does not require a constant power source. But dedicated
devices by which detection is carried out (5) require it.
[0028] The structure of the nanocomposite material (2) of the security feature (1) takes
into account:
- the use of a variable number of layers of polymer (P) in the material - the number
of coats applied is dependent on the conditions in which the security element will
operate.
- The use of a variable number and size of the graphene quantum dots (GQD), if the use
such structure gives is necessary to increase the efficiency of the security feature
(1).
The operation of GQD security feature
[0029] Security feature (1) designed with quantum dots (GQDs) will be unique for each security
printing (3). After treatment with a source of radiation (4), it starts to emit light
in an adequate band characteristics. The luminescent effect will then be identified
by the assigned detection device (5), verified and compared with the standard base
(6), followed by a confirmation or denial of compliance.
Examples of application of the security chip
[0030] Other examples of the use of the security chip (1) are authentication of pre-numbered
documents, such as:
- a passport -the chip is an integral part of the cover;
- payment cards - the top layer of the card;
- other documents in the form of a payment card, such as a driving license, ID card;
- excise bands and prints;
- personal identifiers;
- license forms, certificates, etc.;
- label for products with high value and at risk of counterfeiting;
1. A security feature (1) against counterfeiting security printing (3), in particular
banknotes, characterised in that it comprises at least one graphene quantum dot (GQD) that is graphene nanoparticle
with a diametre of from 0.5 nm to 60 nm, preferably from 1 nm to 11 nm, containing
from 1 to 90, preferably from 1 to 20 layers of graphene disposed in the flexible
layer of graphene nanocomposite material (2), wherein the elastic layer of graphene
nanocomposite material (2) comprises at least one graphene layer disposed on the adhesive
layer (P), preferably a polymer.
2. The security feature according to claim 1, characterised in that it comprises graphene quantum dots (GQDs) of different sizes.
3. The security feature according to claim 1 or 2, characterised in that at least one quantum dot (GQD), preferably all quantum dots (GQDs) are an integral
part of the flexible layer of graphene nanocomposite material (2).
4. The security feature according to claim 1, 2 or 3, characterised in that the graphene is present in pure or doped form.
5. The security feature according to any one of claims 1 to 4, characterised in that it comprises a layer of graphene (G) and two layers of adhesive (P), said graphene
layer (G) is located directly between the two layers of adhesive (P).
6. Use of the security feature (1) according to any one of claims from 1 to 5 for securing
banknotes, holograms, documents, passports, credit cards, excise bands, excise forms,
personal identifiers, certificates or product labels.
7. A system for checking the authenticity of security printing (3), in particular banknotes,
characterised in that it comprises:
- A security feature (1) according to any one of claims 1 to 5,
- A device (4) adapted to emit radiation in the range suitable for excitation of at
least one graphene quantum dot (GQD), preferably all of graphene quantum dots (GQDs)
contained in the security element, and
- A detector (5) adapted to detect luminescence radiation of at least one graphene
quantum dot (GQD), preferably all of graphene quantum dots (GQDs) contained in the
security element.
8. The method of verifying the authenticity of security printing (3), in particular banknotes,
characterised in that the system of claim 7 is used.