Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
  • B41M5/00—Duplicating or marking methods; Sheet materials for use therein
  • B41M5/26—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used
  • B41M5/28—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used using thermochromic compounds or layers containing liquid crystals, microcapsules, bleachable dyes or heat- decomposable compounds, e.g. gas- liberating
  • B41M5/282—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used using thermochromic compounds or layers containing liquid crystals, microcapsules, bleachable dyes or heat- decomposable compounds, e.g. gas- liberating using thermochromic compounds
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
  • B41M3/00—Printing processes to produce particular kinds of printed work, e.g. patterns
  • B41M3/14—Security printing
  • B41M3/142—Security printing using chemical colour-formers or chemical reactions, e.g. leuco-dye/acid, photochromes
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03C—PHOTOSENSITIVE MATERIALS FOR PHOTOGRAPHIC PURPOSES; PHOTOGRAPHIC PROCESSES, e.g. CINE, X-RAY, COLOUR, STEREO-PHOTOGRAPHIC PROCESSES; AUXILIARY PROCESSES IN PHOTOGRAPHY
  • G03C5/00—Photographic processes or agents therefor; Regeneration of such processing agents
  • G03C5/08—Photoprinting; Processes and means for preventing photoprinting
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
  • G03G21/00—Arrangements not provided for by groups G03G13/00 - G03G19/00, e.g. cleaning, elimination of residual charge
  • G03G21/04—Preventing copies being made of an original
  • G03G21/043—Preventing copies being made of an original by using an original which is not reproducible or only reproducible with a different appearence, e.g. originals with a photochromic layer or a colour background

Definitions

• the invention is directed to a photochromic system and an improved security document and, more particularly, to a photochromic system and a security document incorporating a photochromic system which undergoes a color change or change in optical density when exposed to electromagnetic radiation emitted by an image processing device such as a color photocopier, monochrome photocopier or computer scanner.
• Image processing devices have been used for years to make accurate copies of documents. In many cases, legitimate reasons exist for making such copies. Unfortunately, copies are also made and used for illegal purposes. Specifically, color copiers can be used to reproduce security documents, such as checks, reports, stock certificates, automobile title instruments, birth certificates, college transcripts, prescriptions and other documents of business and personal value, for illegal purposes. This concern has been heightened with the advent of desk top publishing software and hardware, including personal computers and computer scanners. Such desk top publishing systems allow sophisticated image processing and printing not generally available previously.
• a label, seal or stamped area of specularly reflecting material such as a metallic foil, a vacuum metallized polymer film or holograms
• specularly reflecting material such as a metallic foil, a vacuum metallized polymer film or holograms
• Image processing devices cannot reproduce the mirror-like specular reflectance of such materials.
• this approach does not include words indicating that a copy has been made, a person who does not have access to the original document will not be aware of the reflecting material and, consequently, will be unaware that t e document is a copy.
• Photochromism is a characteristic of certain organic and inorganic materials to undergo a color change when exposed to certain wavelengths of electromagnetic radiation. This radiation causes a change in the electron distribution or a change in the bond structure of the photochromic molecule causing a localized rearrangement in interatomic distances and vibrational frequencies. Accompanying this shift in vibrational frequency is a shift in resonant absorption of light energy in the visible spectrum, resulting in a perceived color change and/or change in optical density.
• the present invention is directed to a photochromic system and a security document incorporating the photochromic system which are useful in indicating that the security document has been copied on an image processing device and in interfering with the legibility of copies of the document made on an image processing device.
• One embodiment of the invention concerns a security document comprising a substrate having a top surface for carrying printed indicia; and a security portion carried on the top surface of the substrate, the security portion being formed from a photochromic system including a photochrome and a sensitizer which increases the wavelength at which the photochrome colorizes to a wavelength equal to a wavelength of electromagnetic radiation emitted by an image processing device, whereby, upon copying of the security document by an image processing device, the security portion undergoes a change in optical density.
• the security portion may also be placed on the security document so that the resulting copy of the security document is entirely obscured.
• the security portion may be a security term.
• Another embodiment of this invention concerns a photochromic system useful for making security documents comprising a photochrome; and a sensitizer which causes the photochrome to colorize at a wavelength of electromagnetic radiation emitted by an image processing device.
• the most useful photochromes for the photochromic system are spiropyrans, spirothiopyrans, spirooxazines and similar compounds, and, preferably, are benzoindolinospiropyrans, naphthoindolinospiropyrans , benzospiropyrans , naphthospiropyrans and bipyrans . It has been discovered that the photochromes can be sensitized so that their colorization is initiated by electromagnetic radiation emitted by an image processing device. Typically the wavelengths of electromagnetic radiation emitted by an image processing device are greater than 300 nm. Preferably, the photochromic systems of this invention will colorize and/or undergo a change in optical density when exposed to radiation between the wavelengths of about 300nm and about 500nm.
• Fig. 1 presents a top view of the security document of this invention with a photochromic security portion shown in broken lines.
• Fig. 2 presents a top view of the security document of Fig. 1 after the photochromic security portion has colorized.
• Fig. 3 presents a top view of a security document which bears a security term, shown in broken lines, as the security portion.
• Fig. 4 presents a top view of the security document of Fig. 3 after the security term has colorized.
• photochromes are photochromic because they have a C- C, C-O or similar bond which breaks when irradiated and reforms when the radiation ceases and a small amount of thermal energy is available.
• the critical wave length of radiation to break such a bond is found to be between 250 and 290nm. While the bond is broken, electron-density is fed back into a conjugated system, which is stabilized by resonance, to produce color. If a shift of electron density alone is responsible for coloration, then the process will occur very quickly.
• Modern image processing devices do not emit a sufficient quantity of radiation in the 250-290nm range to induce coloration of a photochrome because they are usually fitted with a glass cover which is specifically designed to limit the emission of ultraviolet radiation.
• the radiation emitted by a modern photocopier has wavelengths above 300nm.
• Certain photochromic materials can be sensitized to have the wavelength at which they change color altered by another molecular entity, so that they are useful to prevent the unauthorized copying of original security documents.
• a photochrome To be compatible for use in a security document, a photochrome must have certain characteristics. First, the photochrome must decolorize either thermally or when the source of radiation which causes the colorization is discontinued. Second, the photochrome must have a speed of coloration fast enough to produce a color change during the pass of the lamp of an image processing device. Third, the photochrome must have an extinction coefficient capable of producing a reflectance optical density (OD) such that the photochromic portion of the security document is discernible from the substrate when exposed to an exciting source of radiation. Fourth, the photochromic system must be non-selfscreening.
• OD reflectance optical density
• the photochrome must have triplet state excited levels.
• a photochromic reaction takes place according to the following equilibrium:
• K forward is a function of electromagnetic radiation and ⁇ backward is a function of temperature and/or electromagnetic radiation.
• ⁇ backward is a function of temperature and/or electromagnetic radiation.
• some photochromes will not colorize because the speed of the reverse reaction equals or exceeds the speed of the forward reaction.
• the forward reaction can be sensitized without affecting the reverse reaction.
• the photochrome must have triplet state excited levels. While not wishing to be bound by a particular theory, it is thought that chemical sensitization can be explained in terms of an energy transfer mechanism involving an energy donor and an energy acceptor. Essentially, the donor is excited at a longer wave length than the acceptor absorbs and a triplet state is formed in the excited donor.
• the lamp of a image processing device such as a photocopy machine or computer scanner, is focused into the form of a band of light which sweeps the page to be copied.
• the residence time of the lamp on the page is approximately 500ms. Therefore, to be useful, the photochrome should colorize in a time less than about 500ms so that the image processing device will be affected by the color change of the photochrome.
• the photochrome will colorize in from about 50ms to about 500ms and, more preferably, in from about 50ms to about
• image processing devices emit electromagnetic radiation at frequencies above about 300nm.
• the photochrome must be sensitized to undergo a change in color and/or optical density at frequency at or above about
• the photochromic systems of the present invention preferably undergo a color change and/or change in optical density from about 300nm to about 500nm.
• photochromes useful to produce security documents can be selected from the group consisting of spiropyrans, spirothiopyrans, spirooxazines and similar compounds.
• the photochromes are benzoindolinospiropyrans, naphthoindolinospiropyrans , benzospiropyrans , naphthospiropyrans and bipyrans .
• the photochrome is a benzoindolinospiropyran having the following formula (I) :
• R x -R 3 are hydro or alkyl groups and can be the same or different;
• R-R ⁇ 0 are hydro, halo, nitro, alkyl, alkoxy, phenyl or phenoxy groups and can be the same or different; and
• R is a hydro or alkyl group.
• the benzoindolinospiropyran is selected from the group consisting of unsubstituted spiro [2H-l-benzpyran-2 , 2-indoline] ; 6 ' , 8 ' -dinitro-1, 3,3- trimethyl-spiro [2H-l-benzpyran-2 , 2-indoline] ; 6 ' , 8 ' -dichloro- spiro [2H-l-benzpyran-2 , 2-indoline] ; 6 ' , 8 ' -dibromo-spiro [2H-1- benzpyran-2 , 2-indoline] ; 6-hydroxy-spiro [2H-l-benzpyran-2 , 2- indoline] ; 6 ' -bromo-8 ' -nitro-spiro [2H-l-benzpyran-2 , 2- indoline] ; 8 ' -bromo-6 ' -nitro-spiro [
• Sensitizers useful to induce the color change in a photochrome when exposed to the electromagnetic radiation emitted by the lamp of an image processing device will have the following characteristics.
• the sensitizer will absorb radiation within the window of the photochromic system spectrum, i.e., from about 300nm to about 500nm.
• the sensitizer will be subject to triplet state excitation.
• Third, it will have a high quantum yield to the triplet state.
• the excited state energy level of the sensitizer will be equal to or slightly greater than the triplet state of the photochrome.
• the color change process becomes less efficient as the energy levels of the photochrome and the sensitizer approach each other, in that the substrate and sensitizer become indistinguishable in the energy transfer process, i.e.
• the photochrome will be properly sensitized so that it will change color when exposed to the electromagnetic radiation emitted by an image processing device.
• the sensitizer should be present in the photochromic system in a concentration from about 1% to about 50% of the concentration of the photochrome .
• a sensitizer will be useful provided that orbital overlap occurs between the sensitizer and the photochrome; both the donor and acceptor have excited (triplet) states; and the energy levels of the excited states are compatible.
• Materials which meet these criteria are aromatic amine, nitro- and ketone compounds in which two centers of different electron affinity linked by a conjugated system exist.
• Sensitizers useful to increase the wavelength at which spiropyrans, spirothiopyrans, spirooxazines and other similar compounds undergo a change in color and/or optical density are selected from the group consisting of picramide; substituted benzophenones; 1,2- benzanthraquinone; 3-methyl-l-3-diazo-l, 9-benzanthrone; substituted ⁇ -naphthothiazolines; 2-methyl- ⁇ -nitro- ⁇ - naphthothiazolines ; substituted ⁇ -naphthothiazolines ; and thioxanthones .
• the sensitizer will be a substituted ⁇ -naphthothiazoline or a thioxanthone .
• Useful substituted ⁇ -naphthothiazolines have the following formula (II) :
• R x and R 2 are hydro, benzoyl, furoyl, substituted benzoyl, and substituted furoyl and can be the same or different .
• Useful thioxanthones have the following formula (III) :
• R is an alkyl, alkoxy, halo or a C ⁇ -C 3 haloalkyl group. It has been found that isopropylthioxanthone, chloropropylthioxanthone and chlorothioxanthone are particularly useful because they have absorptions at about 400 nm.
• An appropriate binder will not interfere with the colorization of the photochrome either by sterically hindering the photochrome or by quenching the excited state of the sensitizer.
• the binders typically present in the photochromic system bring the photochrome and the sensitizer into solution and ultimately fix the photochrome and sensitizer to the surface of a substrate. It is thought that, because the rate of colorization of the system is dictated by the efficiency of the sensitizer, the interaction of the sensitizer and binder must be monitored to insure that the above requirements are met.
• Useful binders are selected from the group consisting of polystyrene-acrylonitrile; polystyrene; poly (vinylchloride) ; polystyrene/butadiene; polyalkylmethacrylates; and poly (vinyl acetate) .
• the photochrome, sensitizer and binder can be dissolved in a solvent to provide for liquid delivery of the photochromic system.
• the solvent can be selected from the group consisting of methylethylketone, tetrahydrofuran, benzene, toluene, chloroform, ethylacetate, methanol, acetonitrile, dioxane, methyl ether of ethylene glycol, dimethylformamide, dimethylsulfoxide, ethylene glycol monomethyl ether, morpholine, ethylene glycol, petroleum hydrocarbon oils and vegetable oils, such as peanut oil and soybean oil.
• the final binder formulation can be a water borne formulation so that it can be applied to the substrate using conventional application methods.
• One useful system comprises an aqueous emulsion of poly (vinylacetate) stabilized with poly (vinylalcohol) .
• the photochrome and sensitizer can be dissolved in dibutylphthalate and added to the emulsion during high speed stirring in an emulsifier.
• the hydrophobic droplets of photochrome/sensitizer in the dibutylphthalate then migrate to the emulsified particles from the aqueous phase and are stabilized by the surfactant systems.
• the system may be further modified by mixing the emulsion with an aqueous solution of poly (vinylalcohol) .
• the primary feature of the photochromic system is contemplated to be useful as a copy indicator.
• the composition would also be useful for either manual or automatic authentication.
• the photochromic system containing the sensitized photochrome could be applied to the security document in a manner similar to the "void pantograph."
• the photochromic system can be applied to the security document so that, when the security document is exposed to the ultraviolet radiation emitted by an image processing device, a security portion appears on the copy.
• the original would also show the security portion for a period of time equal to the time required for the photochrome to return to its uncolored state. This would inhibit attempts to make multiple copies of the same document.
• the photochromic system can be applied to a security document to produce a security portion on the security document. Indicia can then be applied to the security portion.
• the security portion remains in an uncolored state, i.e., a state of low optical density, until it is activated by the electromagnetic radiation emitted by an image processing device. After being exposed to the radiation of an image processing device, the security portion undergoes a change in optical density so that a copy of the security portion is rendered illegible. As described below, the security portion can cover a portion of, portions of or the entire security document.
• the photochromic system is useful to produce security portions on security documents such as bank checks, personal checks, reports, stock certificates, automobile title instruments, birth certificates, college transcripts, prescriptions and other documents of business and personal value. After a period of time, the optical density of the security portion will decrease and the security portion (s) of the original security document will again become legible.
• Fig. 1 presents a top view of the security document of this invention with the nonvisible photochromic security portion shown in broken lines.
• the security document 10 comprises a substrate 12 onto which indicia is printed.
• the substrate 12 can be any substrate, such as paper or plastic, which is known in the art and onto which security terms can be printed.
• the top portion 14 of the substrate 12 bears a photochromic security portion 16.
• the photochromic security portion 16 is formed from the photochromic system which contains the photochrome and the sensitizer.
• the photochromic security portion 16 is placed onto the substrate 12 by any conventional means. Before being exposed to an image processing device, the security portion 16 remains in an uncolored state 18.
• Fig. 2 presents a top view of the same security document after the photochromic security portion has changed color and/or experienced a change in optical density.
• the security portion can cover a part of the substrate, parts of the substrate or the entire substrate. If the security portion covers the entire surface of the substrate, then, when the substrate is exposed to the electromagnetic radiation emitted by an image processing device, the entire background colorizes making the background indistinguishable from the printed indicia on the document . With the background being the same color as the document, the entire copy would then be illegible. After a certain period of exposure to visible light, the security portion, i.e., the photochromic system, on the original document decolorizes and the original document again becomes legible. The rate of decoloration is dependent upon the photochrome, binder and temperature used.
• the security portion may also be a security term.
• security term is intended to include not only words such as “VOID” as shown in the drawings but also words or phrases which make evident to the observer that the document being observed is not the original . Phrases such as “PHOTOCOPY,” “COPY,” or “DUPLICATE” may be used for this purpose. Also intended to be included in the definition of “security term” are words or symbols which signify to the individual making the copy that the original document is authentic. The phrase “security term” also encompasses cancellation terms such as “VOID” and "UNAUTHORIZED COPY” which make evident to the observer that the document being inspected is a copy of the original document and that the copy is not authentic.
• Fig. 3 presents a top view of a security document which bears a security term, shown in broken lines, as the security portion.
• a security document 30 comprises a substrate 32 onto which indicia is printed.
• the top portion 34 of the substrate 32 bears a photochromic security portion 36.
• the security portion 36 is a security term 38.
• the security term 38 remains in an uncolored state 40.
• Fig. 4 presents a top view of the security document of Fig. 3 after the security term has become visible.
• the security term 38 is activated from the uncolored state 40 to a colored state 42.
• the security term 38 becomes "visible" to the image processing device .
• the image processing device copies the security term 38 in its colored state 42 onto any copies after the security portion 16 has changed color.
• the security document of the present invention and the photochromic system of the present invention will be effective with any image processing device that produces reproductions or copies of a security document by means of a source of electromagnetic radiation.
• the security document and photochromic system are particularly effective with image processing devices such as duotone photocopiers, color photocopiers and computer scanners.
• image processing devices such as duotone photocopiers, color photocopiers and computer scanners.
• One skilled in the art will certainly appreciate the myriad of uses of the security document and the photochromic system of this invention. While certain representative embodiments and details have been presented for purposes of illustrating the invention, it will be apparent to those skilled in the art that various changes in the compositions and security documents disclosed herein may be made without departing from the scope of the invention, which is defined in the appended claims.

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• General Chemical & Material Sciences (AREA)
• Optics & Photonics (AREA)
• Non-Silver Salt Photosensitive Materials And Non-Silver Salt Photography (AREA)

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• 1997
  • 1997-12-02 ZA ZA9710835A patent/ZA9710835B/xx unknown
  • 1997-12-08 EP EP97954036A patent/EP0946371A1/de not_active Withdrawn
  • 1997-12-08 AU AU57915/98A patent/AU5791598A/en not_active Abandoned
  • 1997-12-08 CA CA002276043A patent/CA2276043A1/en not_active Abandoned
  • 1997-12-08 WO PCT/US1997/022048 patent/WO1998028154A1/en not_active Application Discontinuation
  • 1997-12-23 ID IDP973963A patent/ID19169A/id unknown
  • 1997-12-23 CO CO97074789A patent/CO4890890A1/es unknown

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