WO1998036376A1 - Fil de securite active par un champ et comprenant un polymere disperse dans des cristaux liquides - Google Patents

Fil de securite active par un champ et comprenant un polymere disperse dans des cristaux liquides Download PDF

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Publication number
WO1998036376A1
WO1998036376A1 PCT/US1998/002316 US9802316W WO9836376A1 WO 1998036376 A1 WO1998036376 A1 WO 1998036376A1 US 9802316 W US9802316 W US 9802316W WO 9836376 A1 WO9836376 A1 WO 9836376A1
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WO
WIPO (PCT)
Prior art keywords
security thread
liquid crystal
dispersed liquid
polymer dispersed
crystal material
Prior art date
Application number
PCT/US1998/002316
Other languages
English (en)
Inventor
Nabil M. Lawandy
Original Assignee
Spectra Science Corporation
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Spectra Science Corporation filed Critical Spectra Science Corporation
Priority to AU62717/98A priority Critical patent/AU6271798A/en
Publication of WO1998036376A1 publication Critical patent/WO1998036376A1/fr

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Classifications

    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06K—GRAPHICAL DATA READING; PRESENTATION OF DATA; RECORD CARRIERS; HANDLING RECORD CARRIERS
    • G06K19/00—Record carriers for use with machines and with at least a part designed to carry digital markings
    • G06K19/06—Record carriers for use with machines and with at least a part designed to carry digital markings characterised by the kind of the digital marking, e.g. shape, nature, code

Definitions

  • This invention relates generally to document and currency authentication and, in particular, to security threads used in documents and currency.
  • a light scattering state in an a.c. electric field off state depends on optical heterogeneities such as a spatial distortion of nematic directions and/or mismatching in refractive indices of the compounds.
  • the light scattering and light switching properties of the composite films are decisively influenced by the phase separation structure of the composite films.
  • the size of a liquid crystal domain (channel) can be controlled on the basis of the solvent evaporation rate or the curing rate during the separation of the composite film.
  • the authors used hydrophilic monomers of 2- hydroxythyl methacrylate (HEMA) and acrylic acid (Aa) , hydrophobic monomers of methyl methacrylate (MMA) and styrene (St) that were purified by distillation in vacuo under nitrogen.
  • 2-Methoxy-2phenylacetophenome (benzoin methyl ether, BME) was used without purification.
  • the hydrophilic monomers were found to be suitable for the PDLC system. UV radiation was employed to photopolymerize the mixture, and it was found that sufficient UV irradiation was needed to complete the phase separation of the liquid crystals in the polymer matrix.
  • a multi-phase gain medium including an emission phase (such as dye molecules) and a scattering phase (such as Ti ⁇ 2 ) .
  • a third, matrix phase may also be provided in some embodiments. Suitable materials for the matrix phase include solvents and polymers. The material is shown to provide a laser-like spectral linewidth collapse above a certain pump pulse energy. Figs.
  • FIG. 9a and 9b illustrate a display system embodiment having, in one embodiment, a liquid crystal display (LCD) array that is positioned adjacent to a surface of a pixel plane comprised of pixels or sub-pixels of the inventive gain medium.
  • the LCD array is arranged so as to be selectively energized for passing the emission from the pixels through to an observer.
  • the pixels operate so as to be substantially non-saturable and to output electromagnetic radiation within a narrow band of wave1engths.
  • a polymer dispersed liquid crystal material layer that includes at least one orientable dye, such as a dichroic or an isotropic dye
  • this invention provides a security thread comprising an electrically actuated optical switch comprised of a layer of polymer dispersed liquid crystal material.
  • this invention provides a document or currency that comprises a paper matrix that includes at least one security thread, the at least one security thread being comprised of at least one layer of electrically actuated polymer dispersed liquid crystal material.
  • this invention provides a device for verifying an authenticity of a document or security of a type that includes at least one security thread.
  • the device includes first and second electrodes and an excitation source coupled to the electrodes.
  • the first and second electrodes are spaced apart for accommodating therebetween the document or currency, and at least one of the electrodes is transparent.
  • the at least one security thread includes at least one layer of polymer dispersed liquid crystal material having a visual characteristic that is switched between two states as a function of a presence or absence of an electric field between the first and second electrodes.
  • the polymer dispersed liquid crystal material layer may include at least one orientable dye, such as a dichroic or an isotropic dye, for enhancing the contrast between the on and off states of the PDLC material.
  • at least one orientable dye such as a dichroic or an isotropic dye
  • a security thread has a polymer dispersed liquid crystal material layer that includes at least one orientable dye, such as a dichroic or an isotropic dye, wherein the security thread is capable of laser-like action when excited by a source, and wherein the laser-like action can be switched on and off by switching an electric field on or off.
  • at least one orientable dye such as a dichroic or an isotropic dye
  • a security thread that includes a polymer dispersed liquid crystal film that contains a material for generating a stimulated emission, in response to an optical pump, and scattering sites for scattering the stimulated emission.
  • the liquid crystal domains function as the scattering sites, either alone or in combination with additional scattering sites.
  • Figs. 1A and IB are each a cross-sectional view, not to scale, showing a security thread and the operation of PDLC domains without and with, respectively, an applied electric field;
  • Figs. 2A and 2B are each a top view of the security thread of Figs. 1A and IB, and illustrate a visual appearance of the security thread for a field off and a field on case, respectively ;
  • Fig. 2C is a top view of a security thread having patterned PDLC material
  • Fig. 2D is a top view of a security thread having bar code patterned PDLC material.
  • Figs. 3A and 3B are each a cross-sectional view of a paper matrix, and illustrate the use of the security thread in a buried and in a windowed configuration, respectively, within the paper matrix.
  • the security thread 1 is a multilayered structure that includes outer polymer dispersed liquid crystal (PDLC) layers 10 and 12, and inner layers comprised of a polyester or any suitable flexible thread-like material layer 14 and a thin metal layer 16, such as a layer of aluminum foil.
  • the layers 10 and 12 are comprised of a polymer matrix having an exemplary thickness of 5 micrometers that includes liquid crystal (LC) domains 10a distributed throughout.
  • the layers 10 and 12 can be fabricated in accordance with, by example, the procedure disclosed in the above-mentioned journal article by J.-H. Liu et al.
  • the LC material is added to a liquid polymer.
  • the mixture is then used to coat on the layers 14 and 16, and is then dried or cured, depending on the liquid polymer.
  • the LC domains 10a form within the surrounding polymer matrix, which is the desired result.
  • the polymer matrix may also function as a protective coating for the layers 14 and 16.
  • the polymer matrix can be a transparent varnish or some other suitable coating material selected to adhere to the layers 14 and 16.
  • a striped pattern can be formed by applying UV light through a suitable mask.
  • the PDLC is formed only in the irradiated regions, resulting in a visually distinctive appearance when compared to a security thread wherein the entire layer 10 and 12 contains PDLC material.
  • the resulting security thread 1 is then placed into a matrix material, such as a paper matrix 11, and can then be printed on to provide the desired document or currency.
  • a matrix material such as a paper matrix 11
  • the paper matrix 11 containing the security thread 1 is placed between opposed electrodes 18 and 20 that define a viewing area that encompasses all or a portion of the paper or document or currency within which the security thread 1 is disposed.
  • the paper or document or currency may include a plurality of such security threads arranged in random or predetermined ways.
  • At least one of the electrodes 18 and 20 is comprised of a transparent material such as indium- tin-oxide (ITO) or a thin, transparent film of a metal such as gold.
  • ITO indium- tin-oxide
  • the electrodes 18 and 20 may be provided on surfaces of transparent electrode substrates (such as glass) , which are then arranged so as to place the electrodes 18 and 20 adjacent to the opposing major surfaces of the paper matrix 11 containing the security thread 1.
  • a suitable electrical excitation source 22 shown as battery
  • SW switch
  • a suitable potential for the source is in the range of IV to 2V per micrometer.
  • the switch is shown as being open, while in Fig. IB the switch is shown as being closed.
  • the switch being closed establishes an electric field through the intervening portion of the polymer matrix that contains the LC domains 10a. This causes the LC molecules within the LC domains 10a to align with the electrical field (as shown in the enlarged view of Fig. IB) in a known manner.
  • the LC molecules in the LC domains 10a within a portion of the polymer matrix that is not subjected to an electric field remain in a random orientation, as shown in Fig. 1A.
  • each such LC domain functions to absorb incident light and to prevent the light from reaching and/or reflecting from the underlying layer 14 or 16.
  • the properties of aligned and non-aligned LC molecules are employed to provide a security thread capable of assuming two distinct visual characteristics.
  • the LC molecules in a first visual characteristic the LC molecules are not aligned, and the visual characteristic of the thread 1 may be that of an essentially opaque, featureless substrate.
  • the LC molecules in a second visual characteristic the LC molecules are aligned by the electric field applied by transparent electrodes 18 and 20 in cooperation with excitation source 22, and the visual characteristic of the thread 1 is determined by the underlying layer or layers 14 and 16. That is, when the LC molecules of the domains 10a are aligned by the electric field caused by closing the switch (SW) of Fig. IB, the domains 10a become substantially transparent.
  • SW closing the switch
  • the security thread 1 takes on the visual characteristic of the one or more of the underlying layers 14 and 16.
  • Fig. 2C illustrates an embodiment of the above-mentioned selectively cured security thread 1.
  • the security thread 1 contains regions la without PDLC, and regions lb with PDLC. Only in the PDLC-containing regions lb does the presence of the electric field result in the underlying layer becoming visible.
  • the underlying layer may be colored and/or may include an indicia that becomes visible only in the regions lb.
  • Fig. 2D illustrates a further embodiment of the invention, wherein all or a portion of the layers 10 and/or 12 are patterned in accordance with a bar code.
  • the bar code can encode the denomination, serial number, and/or any other desired information.
  • an underlying portion of the layer 14 or 16 is made visible, which may be colored black or some other color selected to provide a high contrast ratio.
  • the PDLC layers 10 and 12 function as an electrically actuated optical switch. When off, the PDLC layers prevent an observer from seeing the underlying layers 14 and 16, while when on these layers become visible.
  • one or more dyes or phosphors can be added to the polymer material that comprises the layers 10 and 12.
  • one or more isotropic or dichroic dyes can be added to the polymer matrix and liquid crystal material.
  • the LC material can be added to the polymeric material of the layer 14 , and not to the layers 10 and 12.
  • the layers 10 and 12 may be eliminated, or can be retained for providing a protective coating for the layers 14 and 16.
  • Figs. 3A and 3B illustrate the use of the security thread 1 in a buried configuration (as in Figs. 1A and IB) , and in a windowed configuration, respectively, within the paper matrix 11.
  • the use of the security thread 1 provides both a public security feature and a machine readable security feature that can be readily verified using a low cost and simple reading apparatus.
  • a lamp 21a and an optical detector 21b which are arranged for sensing a difference in light transmission and/or reflection due to the activation of the PDLC material.
  • the metal layer 16, if used, may have openings or apertures that permit light from the lamp 21a to pass through to the photodetector 21b.
  • the use of the security thread 1 can be coupled with additional security features.
  • the foil layer 16 could be printed with a holographic pattern that is only visible when an electric field of a suitable magnitude is applied across the paper matrix 11.
  • a document or currency containing the security thread 1 would be verified as being authentic only when an applied electric field renders an expected holographic pattern visible to an observer.
  • the layers 10 and/or 12 include dye molecules and may optionally contain scattering particles or sites.
  • the dye molecules are selected to provide a desired color or emission wavelength.
  • An exemplary dye molecule concentration is in the range of about 5 milli oles to about 10 millimoles.
  • the scattering particles which may be Ti0 2 or alumina, are optionally employed to provide some degree of scattering, but not an amount sufficient to provide a laser-like emission from the layers 10 and/or 12.
  • each such LC domain functions as a scattering site which, in combination with the dye molecules, provides a laser-like emission from the layers 10 and or 12 when excited by an external pump source, such as a frequency double Nd:YAG laser (shown as 24 in Figs. 1A and IB) .
  • an external pump source such as a frequency double Nd:YAG laser (shown as 24 in Figs. 1A and IB) .
  • the presence of the laser like emission having a specified narrow bandwidth can be detected by a suitable optical detector 26 that is fitted with a narrow passband filter (F) 28.
  • the additional scattering sites may be provided so as to "bias" the material of the layers 10 and 12 below the point required to support the laser-like emission.
  • the additional scattering provided by the LC domains 10a having LC molecules in the random orientation as in Fig. 1A is sufficient to exceed the threshold required to support the laser-like emission, whereas the reduction in scattering caused by the aligned LC domains of Fig. IB is not sufficient to support the laser-like emission.
  • these properties of aligned and non-aligned LC molecules are employed to provide a high brightness and high contrast security thread. It can thus be appreciated that the teaching of this invention provides an electrically actuated lasing security thread having a large contrast between the on and off states.
  • the dye molecules may be replaced by semiconductor nanocrystals selected for their emission wavelength(s) (e.g., GaN for blue, ZnSe for green, CdSe for red) .
  • the semiconductor nanocrystals may also function as scattering sites for the stimulated emission in combination with the LC domains 10a.
  • the polymer matrix of the layers 10 and 12 may itself may provide the stimulated emission, such as a polymer matrix comprised of, by example, PPV, MEHPPV, BuEH-PPV, BEH-PPV, HEH-PF, or CN- PPP.
  • the PDLC layers 10 and 12 may have a thickness of, by example, 5-10 micrometers.
  • An electric potential in the range of approximately 15-50 volts is sufficient to align the LC molecules within the LC domains 10a.

Abstract

Selon un premier aspect de cette invention, un fil de sécurité (1) comporte un commutateur optique électrique pourvu d'une couche d'un polymère dispersé dans un matériau à cristaux liquides (10, 12). Ce matériau à cristaux liquides a une caractéristique visuelle qui est commutée entre deux états en fonction de la présence ou de l'absence d'un champ électrique. Selon un deuxième aspect de l'invention, un document ou papier-monnaie comporte une matrice en papier (11) renfermant ce fil de sécurité. Selon un troisième aspect de l'invention, un dispositif permet de vérifier l'authenticité d'un document ou papier-monnaie renfermant ce fil de sécurité. Ce dispositif comprend une première et une seconde électrode (18 et 20) dont au moins une est transparente. Ces électrodes créent le champ électrique qui active le matériau à cristaux liquides.
PCT/US1998/002316 1997-02-18 1998-02-06 Fil de securite active par un champ et comprenant un polymere disperse dans des cristaux liquides WO1998036376A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU62717/98A AU6271798A (en) 1997-02-18 1998-02-06 Field activated security thread including polymer dispersed liquid crystal

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US80059097A 1997-02-18 1997-02-18
US08/800,590 1997-02-18

Publications (1)

Publication Number Publication Date
WO1998036376A1 true WO1998036376A1 (fr) 1998-08-20

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Cited By (21)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2000017103A2 (fr) * 1998-09-18 2000-03-30 Massachusetts Institute Of Technology Gestion d'inventaire
US6207229B1 (en) 1997-11-13 2001-03-27 Massachusetts Institute Of Technology Highly luminescent color-selective materials and method of making thereof
US6251303B1 (en) 1998-09-18 2001-06-26 Massachusetts Institute Of Technology Water-soluble fluorescent nanocrystals
US6306610B1 (en) 1998-09-18 2001-10-23 Massachusetts Institute Of Technology Biological applications of quantum dots
FR2813134A1 (fr) * 2000-08-21 2002-02-22 Banque De France Procede d'authentification de documents sensibles
US6602671B1 (en) 1998-09-18 2003-08-05 Massachusetts Institute Of Technology Semiconductor nanocrystals for inventory control
US6819692B2 (en) 2000-03-14 2004-11-16 Massachusetts Institute Of Technology Optical amplifiers and lasers
US6861155B2 (en) 1997-11-13 2005-03-01 Massachusetts Institute Of Technology Highly luminescent color selective nanocrystalline materials
FR2889335A1 (fr) * 2005-07-29 2007-02-02 Fideix Sarl Support d'information
US7190870B2 (en) 2001-09-17 2007-03-13 Massachusetts Institute Of Technology Semiconductor nanocrystal composite
US7229497B2 (en) 2003-08-26 2007-06-12 Massachusetts Institute Of Technology Method of preparing nanocrystals
US7316967B2 (en) 2004-09-24 2008-01-08 Massachusetts Institute Of Technology Flow method and reactor for manufacturing noncrystals
US7319709B2 (en) 2002-07-23 2008-01-15 Massachusetts Institute Of Technology Creating photon atoms
US7326365B2 (en) 2001-02-09 2008-02-05 Massachusetts Institute Of Technology Composite material including nanocrystals and methods of making
US7390568B2 (en) 2002-08-13 2008-06-24 Massachusetts Institute Of Technology Semiconductor nanocrystal heterostructures having specific charge carrier confinement
US7394094B2 (en) 2005-12-29 2008-07-01 Massachusetts Institute Of Technology Semiconductor nanocrystal heterostructures
US7449237B2 (en) 2004-07-26 2008-11-11 Massachusetts Institute Of Technology Microspheres including nanoparticles in the peripheral region
US7912653B1 (en) 2003-04-17 2011-03-22 Nanosys, Inc. Nanocrystal taggants
US8134175B2 (en) 2005-01-11 2012-03-13 Massachusetts Institute Of Technology Nanocrystals including III-V semiconductors
DE102014117877A1 (de) * 2014-12-04 2016-06-23 Leonhard Kurz Stiftung & Co. Kg Sicherheitselement
US9530928B2 (en) 1997-11-25 2016-12-27 The Regents Of The University Of California Semiconductor nanocrystal probes for biological applications and process for making and using such probes

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4652015A (en) * 1985-12-05 1987-03-24 Crane Company Security paper for currency and banknotes
US4702558A (en) * 1983-09-14 1987-10-27 The Victoria University Of Manchester Liquid crystal information storage device

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4702558A (en) * 1983-09-14 1987-10-27 The Victoria University Of Manchester Liquid crystal information storage device
US4652015A (en) * 1985-12-05 1987-03-24 Crane Company Security paper for currency and banknotes
US4761205A (en) * 1985-12-05 1988-08-02 Crane & Co. Security paper for currency and banknotes

Cited By (43)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6861155B2 (en) 1997-11-13 2005-03-01 Massachusetts Institute Of Technology Highly luminescent color selective nanocrystalline materials
US6207229B1 (en) 1997-11-13 2001-03-27 Massachusetts Institute Of Technology Highly luminescent color-selective materials and method of making thereof
US7374824B2 (en) 1997-11-13 2008-05-20 Massachusetts Institute Of Technology Core-shell nanocrystallite comprising tellurium-containing nanocrystalline core and semiconductor shell
US9790424B2 (en) 1997-11-13 2017-10-17 Massachusetts Institute Of Technology Highly luminescent color-selective nanocrystalline materials
US9441156B2 (en) 1997-11-13 2016-09-13 Massachusetts Institute Of Technology Highly luminescent color-selective nanocrystalline materials
US6322901B1 (en) 1997-11-13 2001-11-27 Massachusetts Institute Of Technology Highly luminescent color-selective nano-crystalline materials
US7125605B2 (en) 1997-11-13 2006-10-24 Massachusetts Institute Of Technology Highly luminescent color-selective nanocrystalline materials
US7060243B2 (en) 1997-11-13 2006-06-13 Massachusetts Institute Of Technology Tellurium-containing nanocrystalline materials
US9530928B2 (en) 1997-11-25 2016-12-27 The Regents Of The University Of California Semiconductor nanocrystal probes for biological applications and process for making and using such probes
US6319426B1 (en) 1998-09-18 2001-11-20 Massachusetts Institute Of Technology Water-soluble fluorescent semiconductor nanocrystals
US6602671B1 (en) 1998-09-18 2003-08-05 Massachusetts Institute Of Technology Semiconductor nanocrystals for inventory control
US6617583B1 (en) 1998-09-18 2003-09-09 Massachusetts Institute Of Technology Inventory control
US6774361B2 (en) 1998-09-18 2004-08-10 Massachusetts Institute Of Technology Inventory control
US6444143B2 (en) 1998-09-18 2002-09-03 Massachusetts Institute Of Technology Water-soluble fluorescent nanocrystals
US7943552B2 (en) 1998-09-18 2011-05-17 Massachusetts Institute Of Technology Inventory control
WO2000017103A2 (fr) * 1998-09-18 2000-03-30 Massachusetts Institute Of Technology Gestion d'inventaire
US6306610B1 (en) 1998-09-18 2001-10-23 Massachusetts Institute Of Technology Biological applications of quantum dots
US6251303B1 (en) 1998-09-18 2001-06-26 Massachusetts Institute Of Technology Water-soluble fluorescent nanocrystals
WO2000017103A3 (fr) * 1998-09-18 2000-08-31 Massachusetts Inst Technology Gestion d'inventaire
US6819692B2 (en) 2000-03-14 2004-11-16 Massachusetts Institute Of Technology Optical amplifiers and lasers
FR2813134A1 (fr) * 2000-08-21 2002-02-22 Banque De France Procede d'authentification de documents sensibles
EP1182048A1 (fr) * 2000-08-21 2002-02-27 Banque De France Procédé d'authentification de documents sensibles
US7326365B2 (en) 2001-02-09 2008-02-05 Massachusetts Institute Of Technology Composite material including nanocrystals and methods of making
US7690842B2 (en) 2001-02-09 2010-04-06 Massachusetts Institute Of Technology Composite material including nanocrystals and methods of making
US7190870B2 (en) 2001-09-17 2007-03-13 Massachusetts Institute Of Technology Semiconductor nanocrystal composite
US7319709B2 (en) 2002-07-23 2008-01-15 Massachusetts Institute Of Technology Creating photon atoms
US7390568B2 (en) 2002-08-13 2008-06-24 Massachusetts Institute Of Technology Semiconductor nanocrystal heterostructures having specific charge carrier confinement
US9410959B2 (en) 2002-08-13 2016-08-09 Massachusetts Institute Of Technology Devices comprising coated semiconductor nanocrystal heterostructures
US8277942B2 (en) 2002-08-13 2012-10-02 Massachusetts Institute Of Technology Semiconductor nanocrystal heterostructures
US7825405B2 (en) 2002-08-13 2010-11-02 Massachusetts Institute Of Technology Devices comprising coated semiconductor nanocrystals heterostructures
US7912653B1 (en) 2003-04-17 2011-03-22 Nanosys, Inc. Nanocrystal taggants
US7917298B1 (en) 2003-04-17 2011-03-29 Nanosys, Inc. Nanocrystal taggants
US7229497B2 (en) 2003-08-26 2007-06-12 Massachusetts Institute Of Technology Method of preparing nanocrystals
US7862892B2 (en) 2004-07-26 2011-01-04 Massachusetts Institute Of Technology Microspheres including nanoparticles
US7449237B2 (en) 2004-07-26 2008-11-11 Massachusetts Institute Of Technology Microspheres including nanoparticles in the peripheral region
US9708184B2 (en) 2004-07-26 2017-07-18 Massachusetts Institute Of Technology Microspheres including nanoparticles
US7316967B2 (en) 2004-09-24 2008-01-08 Massachusetts Institute Of Technology Flow method and reactor for manufacturing noncrystals
US8134175B2 (en) 2005-01-11 2012-03-13 Massachusetts Institute Of Technology Nanocrystals including III-V semiconductors
US8748933B2 (en) 2005-01-11 2014-06-10 Massachusetts Institute Of Technology Nanocrystals including III-V semiconductors
FR2889335A1 (fr) * 2005-07-29 2007-02-02 Fideix Sarl Support d'information
US7394094B2 (en) 2005-12-29 2008-07-01 Massachusetts Institute Of Technology Semiconductor nanocrystal heterostructures
DE102014117877A1 (de) * 2014-12-04 2016-06-23 Leonhard Kurz Stiftung & Co. Kg Sicherheitselement
US10759212B2 (en) 2014-12-04 2020-09-01 Leonhard Kurz Stiftung & Co. Kg Security element

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