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
• • 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
  • B41M5/281—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 liquid crystals only
• • 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
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B42—BOOKBINDING; ALBUMS; FILES; SPECIAL PRINTED MATTER
  • B42D—BOOKS; BOOK COVERS; LOOSE LEAVES; PRINTED MATTER CHARACTERISED BY IDENTIFICATION OR SECURITY FEATURES; PRINTED MATTER OF SPECIAL FORMAT OR STYLE NOT OTHERWISE PROVIDED FOR; DEVICES FOR USE THEREWITH AND NOT OTHERWISE PROVIDED FOR; MOVABLE-STRIP WRITING OR READING APPARATUS
  • B42D15/00—Printed matter of special format or style not otherwise provided for
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B42—BOOKBINDING; ALBUMS; FILES; SPECIAL PRINTED MATTER
  • B42D—BOOKS; BOOK COVERS; LOOSE LEAVES; PRINTED MATTER CHARACTERISED BY IDENTIFICATION OR SECURITY FEATURES; PRINTED MATTER OF SPECIAL FORMAT OR STYLE NOT OTHERWISE PROVIDED FOR; DEVICES FOR USE THEREWITH AND NOT OTHERWISE PROVIDED FOR; MOVABLE-STRIP WRITING OR READING APPARATUS
  • B42D25/00—Information-bearing cards or sheet-like structures characterised by identification or security features; Manufacture thereof
  • B42D25/20—Information-bearing cards or sheet-like structures characterised by identification or security features; Manufacture thereof characterised by a particular use or purpose
  • B42D25/24—Passports
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B42—BOOKBINDING; ALBUMS; FILES; SPECIAL PRINTED MATTER
  • B42D—BOOKS; BOOK COVERS; LOOSE LEAVES; PRINTED MATTER CHARACTERISED BY IDENTIFICATION OR SECURITY FEATURES; PRINTED MATTER OF SPECIAL FORMAT OR STYLE NOT OTHERWISE PROVIDED FOR; DEVICES FOR USE THEREWITH AND NOT OTHERWISE PROVIDED FOR; MOVABLE-STRIP WRITING OR READING APPARATUS
  • B42D25/00—Information-bearing cards or sheet-like structures characterised by identification or security features; Manufacture thereof
  • B42D25/20—Information-bearing cards or sheet-like structures characterised by identification or security features; Manufacture thereof characterised by a particular use or purpose
  • B42D25/29—Securities; Bank notes
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B42—BOOKBINDING; ALBUMS; FILES; SPECIAL PRINTED MATTER
  • B42D—BOOKS; BOOK COVERS; LOOSE LEAVES; PRINTED MATTER CHARACTERISED BY IDENTIFICATION OR SECURITY FEATURES; PRINTED MATTER OF SPECIAL FORMAT OR STYLE NOT OTHERWISE PROVIDED FOR; DEVICES FOR USE THEREWITH AND NOT OTHERWISE PROVIDED FOR; MOVABLE-STRIP WRITING OR READING APPARATUS
  • B42D25/00—Information-bearing cards or sheet-like structures characterised by identification or security features; Manufacture thereof
  • B42D25/30—Identification or security features, e.g. for preventing forgery
  • B42D25/36—Identification or security features, e.g. for preventing forgery comprising special materials
  • B42D25/364—Liquid crystals
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
  • C09D11/00—Inks
  • C09D11/30—Inkjet printing inks
• • B42D2033/26—
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/24—Structurally defined web or sheet [e.g., overall dimension, etc.]
  • Y10T428/24802—Discontinuous or differential coating, impregnation or bond [e.g., artwork, printing, retouched photograph, etc.]
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/24—Structurally defined web or sheet [e.g., overall dimension, etc.]
  • Y10T428/24802—Discontinuous or differential coating, impregnation or bond [e.g., artwork, printing, retouched photograph, etc.]
  • Y10T428/24835—Discontinuous or differential coating, impregnation or bond [e.g., artwork, printing, retouched photograph, etc.] including developable image or soluble portion in coating or impregnation [e.g., safety paper, etc.]

Definitions

• the present invention relates to a marking based on chiral nematic (also called cholesteric) liquid crystal polymers.
• the invention also relates to a method for the modification of chiral nematic liquid-crystal films, in which a chiral nematic liquid- crystal layer is locally or selectively (one or more region(s)) modified with the aid of a modifying agent.
• cholesteric liquid crystal which exhibits viewing-angle dependent color.
• the cholesteric liquid crystal structure When illuminated with white light the cholesteric liquid crystal structure reflects light of a predetermined color (predetermined wavelength range) which is a function of the employed materials and generally varies with the angle of observation and the device temperature.
• the precursor material itself is colorless and the observed color (predetermined wavelength range) is only due to a physical reflection effect at the cholesteric helical structure adopted at a given temperature by the liquid crystal material (cf. J. L. Fergason, Molecular Crystals, Vol. 1 , pp. 293-307 (1966), the entire disclosure whereof is incorporated by reference herein).
• liquid crystal materials cholesteric liquid crystal polymers (CLCPs)
• the cholesteric helical structure is "frozen" in a predetermined state through polymerization and thus rendered temperature-independent.
• the chiral nematic liquid crystal phase is typically composed of nematic mesogenic molecules which comprise a chiral dopant that produces intermolecular forces that favor alignment between molecules at a slight angle to one another. The result thereof is the formation of a structure which can be visualized as a stack of very thin 2-D nematic-like layers with the director in each layer twisted with respect to those above and below.
• An important characteristic of the chiral nematic liquid crystal phase is the pitch p (see Figure 1).
• the pitch p is defined as the (vertical) distance it takes for the director to rotate one full turn in the helix.
• a characteristic property of the helical structure of the chiral nematic phase is its ability to selectively reflect light whose wavelength falls within a specific range. When this range overlaps with a portion of the visible spectrum a colored reflection will be perceived by an observer.
• the center of the range is approximately equal to the pitch multiplied by the average refractive index of the materi l.
• One parameter which has an influence on the pitch is the temperature because of the dependence thereon of the gradual change in director orientation between successive layers which modifies the pitch length, resulting in an alteration of the wavelength of reflected light as a function of the temperature.
• the angle at which the director changes can be made larger, thereby tightening the pitch, by increasing the temperature of the molecules, hence giving them more thermal energy.
• a second possibility to overcome this problem is to insert directly the code inside the liquid crystal polymer film.
• U.S. Patent No. 6,207,240 the entire disclosure whereof is incorporated by reference herein, describes an effect coating of a cholesteric liquid ciystal polymer (CLCP) with viewing angle dependent reflection color, which further comprises absoiption type pigments exhibiting a specific absorption color.
• a marking such as a symbol or a text, is generated in the CLCP coating by laser iiTadiation. The laser radiation carbonizes the CLCP material in the irradiated area.
• the method requires high-power lasers to carbonize the material such that the markings are visible,
• the present invention provides a liquid crystal polymer marking.
• the marking is obtainable by a process which comprises, in the following order:
• one or both (preferably both) of the first and second chiral liquid crystal precursor compositions may comprise (i) one or more (e.g. two, thi'ee, four, five or more and in particular, at least two) different nematic compounds A and (ii) one or more (e.g., two, thi'ee, four, five or more) different chiral dopant compounds B which are capable of giving rise to a cholesteric state of the chiral liquid crystal precursor composition upon heating.
• both the one or more nematic compounds A and the one or more chiral dopant compounds B may comprise at least one compound which comprises at least one polymerizable group.
• all of the one or more nematic compounds A and all of the one or more chiral dopant compounds B may comprise at least one polymerizable group.
• at least one (and preferably both) of the first and second chiral liquid crystal precursor compositions (and in particular, the first composition) may comprise at least one chiral dopant compound B of formula (I):
• Ri , R. 2 , R.3, R4, R5, R 0 , R7 and Rg each independently denote Ci-C 6 alkyi and C]-C 6 alkoxy;
• Ai and A 2 each independently denote a group of formula (i) to (iii):
• D 2 denotes a group of formula
• n, o, p, q, r. s, and t each independently denote 0, 1, or 2;
• y denotes 0, 1 , 2, 3, 4, 5, or 6;
• z 0 if y equals 0 and z equals 1 if y equals 1 to 6.
• the first chiral liquid crystal precursor composition and the second chiral liquid crystal precursor composition may be identical.
• the first and second chiral liquid crystal precursor compositions may be different from each other.
• the second chiral liquid crystal precursor composition may differ from the first chiral liquid crystal precursor composition at least in that the second composition comprises at least one of the one or more chiral dopant compounds B in a concentration which is different from a concentration of the same chiral dopant compound in the first composition and/or at least in that the second composition comprises at least one chiral dopant compound B which is different from any of the one of the one or more chiral dopant compounds B that are present in the first composition.
• the second chiral liquid crystal precursor composition may further comprise at least one pigment and/or dye that absorbs in the visible or invisible region of the electromagnetic spectmm and/or may further comprise at least one luminescent pigment and/or dye.
• stage (ii) of the process may comprise a heating of the applied composition to a temperature of from about 55°C to about 150°C, e.g., from about 55°C to about 100°C, or from about 60°C to about 100°C and/or stage (iv) of the process may comprise a heating of the at least one of the one or more areas to a temperature of from about 55°C to about 150°C, e.g., from about 55°C to about 100°C, or from about 60°C to about 100°C.
• stage (i) and/or stage (iii) of the process may comprise an application (e.g., deposition) of the first or second chiral liquid crystal precursor composition by continuous ink-jet printing and/or drop-on-demand ink-jet printing and/or spray coating and/or valve-jet printing.
• an application e.g., deposition of the first or second chiral liquid crystal precursor composition by continuous ink-jet printing and/or drop-on-demand ink-jet printing and/or spray coating and/or valve-jet printing.
• a stream of air may be passed over the surface of the one or more areas, preferably (substantially) parallel thereto.
• the marking of the present invention may be in the form of at least one of an image, a picture, a logo, indicia, or a pattern representing a code selected from one or more of 1 -dimensional barcodes, stacked 1 -dimensional barcodes, 2- dimensional barcodes, 3-dimensional barcodes, and a data matrix.
• the present invention also provides a substrate which comprises (e.g., carries on a surface thereof) the marking of the present invention as set forth above, including the various aspects thereof.
• the marking may serve as at least one of a security element, an authenticity element, an identification element, and a tracking and tracing element.
• the substrate may be, or comprise, at least one of an identity document, a label, packaging, a banknote, a security document, a passport, a stamp, an ink-transfer film, and a reflective film.
• a security ink that comprises (i) one or more nematic compounds A and (ii) one or more chiral dopant compounds B which are capable of giving rise to a cholesteric state of the security ink upon application of heat thereto.
• the security ink may comprise at least one chiral dopant compound B of formula (I) as set forth above.
• the present invention also provides a method of providing a substrate with a liquid crystal polymer marking.
• the method comprises, in the following order:
• the present invention also provides a substrate which comprises a marking (e.g., on at least one (outer) surface thereof).
• the marking comprises a layer or film of a first chiral liquid crystal polymer that has a first optical property.
• the layer or film comprises in at least one area (region) thereof a second liquid crystal polymer that has at least one second optical property which is different from the first optical property.
• Fig. 1 is a schematic drawing which illustrates nematic, smectic and cholesteric liquid crystals
• Fig. 2 is a graph which illustrates the spectral reflectance of a first chiral liquid crystal polymer, a second chiral liquid crystal polymer and of both polymers together.
• Fig. 3 shows photographs of a marking in accordance with the present invention viewed from two different angles.
• the substrate for use in the present invention is not particularly limited and can be of various types.
• the substrate may, for example, consist (essentially) of or comprise one or more of a metal (for example, in the form of a container such as a can for holding various items such as, e.g., beverages or foodstuffs), optical fibers, a woven, a coating, and equivalents thereof, a plastic material, glass (for example, in the form of a container such as a bottle for holding various items such as, e.g., beverages or foodstuffs), cardboard, packaging, paper, and a polymeric material. It is pointed out that these substrate materials are given exclusively for exemplifying memeposes, without restricting the scope of the invention.
• the substrate will preferably have a limited porosity (and may, for example, be substantially non-porous).
• the substrate further will advantageously have a dark or black surface or background onto which the precursor composition is to be applied. Without wishing to be bound by any theory, it is speculated that in the case of a dark or black background the light transmitted by the cholesteric liquid crystal material is largely absorbed by the background, whereby any residual backscattering from the background does not disturb the perception of the cholesteric liquid crystal material's own reflection with the unaided eye.
• a cholesteric liquid crystal material can always be identified with the help of a circular polarization filter because it selectively reflects only one of the two possible circular polarized light components, in accordance with its chiral helical structure.
• Non-limiting examples of suitable substrates include: cardboard darkened with black gravure ink (no oveiprinted varnish); cardboard darkened with black offset ink (no overprinted varnish); cardboard darkened with any black ink and overprinted with water based varnish; cardboard darkened with any black ink and overprinted with solvent varnish; metal treated with black coating.
• any (preferably non-porous and preferably black) substrate (which may not necessarily be flat and may be uneven) whose coating is not soluble, or only slightly soluble, in the solvent(s) used in the chiral liquid precursor composition and in the modifying agent is a suitable substrate for the purposes of the present invention.
• the first chiral liquid crystal precursor composition that is used for making the marking according to the present invention and is applied (e.g., deposited) onto at least a part of at least one surface of the substrate comprises a mixture of (i) one or more nematic compounds A and (ii) one or more cholesteric (i.e., chiral dopant) compounds B (including cholesterol) which are capable of giving rise to a cholesteric state of the composition.
• the pitch of the obtainable cholesteric state depends on the relative ratio of the nematic and the cholesteric compounds.
• the (total) concentration of the one or more nematic compounds A in the chiral liquid ciystal precursor composition for use in the present invention will be about five to about twenty times the (total) concentration of the one or more cholesteric compounds B.
• a precursor composition with a high concentration of cholesteric compounds is not desirable (although possible in many cases) because the one or more cholesteric compounds tend to crystallize, thereby making it impossible to obtain the desired liquid crystal state having specific optical properties.
• Nematic compounds A which are suitable for use in the first and second chiral liquid crystal precursor compositions employed according to the present invention are known in the art; when used alone (i.e., without cholesteric compounds) they arrange themselves in a state characterized by its birefringence.
• Non-limiting examples of nematic compounds A which are suitable for use in the present invention are described in, e.g., WO 93/22397, WO 95/22586, EP-B-0 847 432, U.S. Patent No. 6,589,445, US 2007/0224341 Al and JP 2009-300662 A. The entire disclosures of these documents are incorporated by reference herein.
• a preferred class of nematic compounds for use in the present invention comprises one or more (e.g., 1 , 2 or 3) polymerizable groups, identical or different from each other, per molecule.
• polymerizable groups include groups which are capable of taking part in a free radical polymerization and in particular, groups comprising a carbon-carbon double or triple bond such as, e.g., an acrylate moiety, a vinyl moiety or an acetylenic moiety.
• Particularly preferred as polymerizable groups are acrylate moieties.
• the nematic compounds for use in the present invention further may comprise one or more (e.g., 1 , 2, 3, 4, 5 or 6) optionally substituted aromatic groups, preferably phenyl groups.
• optional substituents of the aromatic groups include those which are set forth herein as examples of substituent groups on the phenyl rings of the chiral dopant compounds of formula (I) such as, e.g., alkyl and alkoxy groups.
• Examples of groups which may optionally be present to link the polymerizable groups and the aryl (e.g., phenyl) groups in the nematic compounds A include those which are exemplified herein for the chiral dopant compounds B of formula (I) (including those of formula (IA) and formula (IB) set forth below).
• the nematic compounds A may comprise one or more groups of formula (i) to (iii) which are indicated above as meanings for A] and A 2 in formula (I) (and fonnulae (IA) and (IB)), typically bonded to optionally substituted phenyl groups.
• Specific non-limiting examples of nematic compounds which are suitable for use in the present invention are given below in the Example.
• the one or more nematic compounds A (and also the one or more chiral dopant compounds B) for use in the present invention to be substantially free of compounds which do not comprise any polymerizable group (i.e., to preferably comprise compounds without any polymerizable group merely as impurities, if at all). It also is preferred for the nematic compounds to be different from cellulose derivatives.
• the one or more cholesteric (i.e., chiral dopant) compounds B for use in the present invention preferably comprise at least one polymerizable group.
• suitable examples of the one or more chiral dopant compounds B include those of formula (I):
• R each independently denote C ⁇ -Ce alkyl and Cj-C 3 ⁇ 4 alkoxy;
• a [ and A 2 each independently denote a group of formula (i) to (iii):
• D 2 denotes a group of formula
• n, o, p, q, r, s, and t each independently denote 0, 1 , or 2;
• y denotes 0, 1 , 2, 3, 4, 5, or 6;
• z 0 if y equals 0 and z equals 1 if y equals 1 to 6.
• the one or more chiral dopant compounds B may comprise more isomannide derivatives of formula (IA):
• Ri, R 2s R 3 , 4, R5, f t, R and Rg each independently denote C]-C 6 alkyl and Ci-C 6 alkoxy;
• Ai and A 2 each independently denote a group of formula (i) to (iii):
• Dj denotes a group of formula
• D 2 denotes a group of formula
• n, 0, p, q, r, s, and t each independently denote 0, 1 , or 2;
• y denotes 0, 1 , 2, 3, 4, 5, or 6;
• z 0 if y equals 0 and z equals 1 if y equals 1 to 6.
• Rj, R2, Rj, R4> s, 0, R7 and R ⁇ each independently denote Ci-C 6 alkyl.
• Ri, R 2 , R3, 4, Rs, restoration 7 and Rs in formula (IA) (and in formula (I)) each independently denote C 1 -C alkoxy.
• a s and A2 each independently denote a group of formula R], R 2 , R3 and R4 each independently denote Cj-C 6 alkyl; and m, n, o, and p each independently denote 0, 1, or 2.
• the one or more chiral dopant compounds B may comprise one or more isosorbide derivatives represented by formula (IB):
• R-i, R >, R-3, R , 5, R3 ⁇ 4, R7 and R 8 each independently denote C ( -Q alkyl and Ci-C ⁇ ; alkoxy;
• a I and A 2 each independently denote a group of formula (i) to (iii):
• D 2 denotes a group of formula
• n 0, p, q, r, s, and t each independently denote 0, 1 , or 2;
• y denotes 0, 1, 2, 3, 4, 5, or 6; z equals 0 if y equals 0 and z equals 1 if y equals 1 to 6.
• Rj , R , R3, R4, R5, Rfi, 7 and Rg each independently denote C i-C 3 ⁇ 4 alkyl.
• R t , R 2 , R3, R4, R 5 , Re, R ? and Rg in fonnula (IB) each independently denote C r C 6 alkoxy.
• R ⁇ , R 2 , R3 and R 4 each independently denote Ci-C 6 alkyl; and
• m, n, o, and p each independently denote 0, 1 , or 2.
• Rj , R 2 , R 3 and R 4 each independently denote Ci- , alkoxy; and
• m, n, o, and p each independently denote 0, 1 , or 2.
• the alkyl and alkoxy groups of R], R 2 , R 3 , R 4 , R 5s Re, R 7 and Rg in formulae (I), (IA) and (IB) may comprise 3, 4, 6 or 7 carbon atoms and in particular, 4 or 6 carbon atoms.
• alkyl groups comprising 3 or 4 carbon atoms include isopropyl and butyl.
• alkyl groups comprising 6 or 7 carbon atoms include hexyl, 2- methylpentyl, 3-methylpentyl, 2,2-dimethylpentyl, and 2,3-dimethylpentyl.
• alkoxy groups comprising 3 or 4 carbon atoms include isopropoxy, but- l -oxy, but-2-oxy, and /erf-butoxy.
• alkoxy groups comprising 6 or 7 carbon atoms include hex-l-oxy, hex-2-oxy, hex-3-oxy, 2-niethylpent-l -oxy, 2- methylpent-2 ⁇ oxy, 2-methylpent-3-oxy, 2 ⁇ methylpeni-4-oxy, 4-methylpent-l-oxy, 3- methylpent- 1 -oxy, 3-methylpent ⁇ 2-oxy, 3-methyIpent-3-oxy, 2,2-dimethylpent-l-oxy, 2,2-dimethylpent-3-oxy, 2,2-dimethylpent-4-oxy, 4,4-dimethylpent-l -oxy, 2,3- dimethylpent-l-oxy, 2,3-dimethylpent-2-oxy, 2,3-dimethylpent-3-oxy, 2,3-dimethylmethylmethylpent-3
• Non-limiting specific examples of chiral dopant compounds B of formula (I) for use in the present invention are provided in the Example below.
• the one or more chiral dopant compounds B will usually be present in a total concentration of from about 0.1% to about 30% by weight, e.g., from about 0.1 % to about 25%, or from about 0.1 % to about 20% by weight, based on the total weight of the composition. The best results will often be obtained with concentrations of from 3% to 10% by weight, e.g., from 5% to 8% by weight, based on the total weight of the precursor composition.
• the one or more nemaiic compounds A will often be present in a concentration of from about 30% to about 50% by weight, based on the total weight of the precursor composition.
• the application e.g., deposition
• the application is preferably carried out with a printing technique, and in particular, a printing technique selected from at least one of continuous ink-jet printing, drop -on-demand ink-jet printing, and spray coating.
• a printing technique selected from at least one of continuous ink-jet printing, drop -on-demand ink-jet printing, and spray coating.
• ink-jet printing is employed.
• the industrial ink-jet printers, commonly used for numbering, coding and marking applications on conditioning lines and printing presses, are particularly suitable.
• Preferred ink-jet printers include single nozzle continuous ink-jet printers (also called raster or multi level deflected printers) and drop-on-demand ink-jet printers, in particular valve-jet printers.
• the thickness of the applied precursor composition (and in particular, the first precursor composition) will usually be from about 3 to about 20 ⁇ , e.g., from about 5 to about 15 ⁇ .
• the precursor composition is to be applied by the printing techniques set forth above, for example, by ink-jet printing
• the composition will usually comprise a solvent to adjust its viscosity to a value which is suitable for the employed application (printing) technique.
• Typical viscosity values for ink-jet printing inks are in the range of from about 4 to about 30 mPa.s at 25°C. Suitable solvents are known to those of skill in the art.
• Non-limiting examples thereof include low-viscosity, slightly polar and aprotic organic solvents, such as, e.g., methyl ethyl ketone (MEK), acetone, ethyl acetate, ethyl 3-ethoxypropionate, toluene and mixtures of two or more thereof.
• MEK methyl ethyl ketone
• the precursor composition for use in the present invention will usually also comprise at least one conductivity agent (for example, a salt).
• the conductivity agent will have a non-negligible solubility in the composition.
• Non-limiting examples of suitable conductivity agents include salts such as, e.g., tetraalkyl ammonium salts (e.g., tetrabutyl ammonium nitrate, tetrabutyl ammonium perchlorate and tetrabutyl ammonium hexafluorophosphate), alkali metal thiocyanates such as potassium thiocyanate and alkali metal perchlorates such as lithium perchlorate.
• the conductivity agent will be present in a concentration which is sufficient to provide the conductivity which is required or desirable. Of course, mixtures of two or more different conductivity agents (salts) can be used.
• the composition for use in the present invention is to be cured/polymerized by UV radiation the composition will also comprise at least one photo initiator that shows a non-negligible solubility in the composition.
• the many suitable photoinitiators include a-hydroxyketones such as 1 - hydroxy-cyclohexyl -phenyl- ketone and a mixture (e.g., about 1 : 1 ) of 1 -hydroxy- cyclohexyl-phenyl-ketone and one or more of benzophenone, 2 -hydroxy-2 -methyl- 1 - phenyl-l -propanone, and 2-hydroxy- l -[4-(2-hydroxyethoxy)phenyl]-2-methyI- I - propanone; phenyl glyoxyl ate s such as methylbenzoylforrnate and a mixture of oxy- phenyl -acetic acid 2-
• the precursor composition is to be cured by a method which is different from irradiation with UV light such as, e.g., by means of high-energy particles (e.g., electron beams), X-rays, gamma-rays, etc.
• a photoinitiator can, of course, be dispensed with.
• the chiral liquid crystal precursor compositions for use in the present invention may also comprise a variety of other optional components which are suitable and/or desirable for achieving a particular desired property of the composition and in general, may comprise any components/substances which do not adversely affect a required property of the precursor composition to any significant extent.
• optional components are resins, silane compounds, sensitizers for the photoinitators (if present), etc.
• the composition may comprise one or more silane compounds which show a non-negligible solubility in the composition.
• Non-limiting examples of suitable silane compounds include optionally polyme izable silanes such as those of formula R ⁇ Rs-Si-R ⁇ wherein R?, and R independently represent alkoxy and alkoxyalkoxy having a total of from 1 to about 6 carbon atoms and R represents vinyl, allyl, (C)_io)alkyl, (meth)acryloxy(C 1 -6)alkyl 5 and glycidyIoxy(Ci_6)alkyl such as, e.g., vinyltriethoxysilane, vinyl trimethoxysilane, vinyltris(2-methoxyefhoxy)silane, 3- methacryloxypropyl-trimethoxysilane, octyltri-ethoxysilane.
• the concentration of the one or more silane compounds, if present, in a precursor composition will usually be from about 0.5% to about 5% by weight, based on the total weight of the composition.
• the precursor composition is brought to a chiral liquid crystal state having specific optical properties.
• the first chiral liquid crystal precursor composition is heated, the solvent contained in the composition, if present, is evaporated and the promotion of the desired first chiral liquid crystal state takes place.
• the temperature used to evaporate the solvent and to promote the formation of the first liquid crystal state depends on the components of the first chiral liquid crystal precursor composition and will in many cases range from about 55°C to about 150°C, e.g., from about 55°C to about 100°C, preferably from about 60°C to about 100°C.
• suitable heating sources include conventional heating means and in particular, radiation sources such as, e.g., an IR lamp. In many cases a heating time of from about 1 second to about 30 seconds such as, e.g., not more than about 20 seconds, not more than about 10 seconds, or not more than about 5 seconds will be sufficient.
• the term ''specific optical properties is to be understood as a liquid crystal state with a specific pitch that reflects a specific wavelength range.
• An advantage of a precursor composition which contains a chiral dopant according to formula (I) and related formulae is the ability to generate a stable liquid crystal state quickly after the heating (and evaporation of the solvent).
• the liquid crystal states which are obtained after heating and evaporation of the solvent with precursor compositions of the prior art see, e.g., EP 1 299 375, EP 1 669 431 , and EP 1 339 812, the entire disclosures of which are incorporated by reference herein) very often can easily be disrupted by minor temperature changes.
• a (at least one) second chiral liquid crystal precursor composition is applied onto one or more regions of the applied first composition in the first chiral liquid crystal state.
• the second chiral liquid crystal precursor composition may be applied while the first chiral liquid crystal precursor composition is still in a heated state (e.g., immediately following the completion of the heating operation) or may be applied after the first chiral liquid crystal precursor composition has cooled down to at least some extent (e.g., is at substantially room temperature).
• the cooling of the first precursor composition can be accelerated by means known to those of skill in the art such as, e.g., by blowing ambient air onto the previously heated composition.
• Applying the second chiral liquid crystal precursor composition to the first precursor composition in a cooled-down state may improve the resolution of the marking.
• applying the second chiral liquid crystal precursor composition immediately after completion of the heating operation may be desirable if the entire process of making the marking is to be conducted in an as simple and speedy as possible manner.
• the second chiral liquid crystal precursor composition which is applied in one or more areas on the first chiral liquid precursor composition in the first chiral liquid crystal state may be the same as or different from the first chiral liquid ciystal precursor composition. Further, everything that is set forth above with respect to the first chiral liquid precursor composition (e.g., components, application methods, etc.) applies equally and without exception also to the second chiral liquid precursor composition.
• the one or more chiral dopant compounds B will usually be present in the second chiral liquid crystal precursor composition in a total concentration of from about 0.1 % to about 30% by weight, e.g., from about 0.1 % to about 25%, or from about 0.1 % to about 20% by weight, based on the total weight of the second composition.
• the one or more nematic compounds A will often be present in the second chiral liquid ciystal precursor composition in a concentration of from about 30% to about 50% by weight, based on the total weight of the second precursor composition.
• the one or more differences may relate to, e.g., one or more of the compounds A and B that are present in these compositions and/or to the concentrations of one or more of these compounds.
• a or the only difference between these compositions may be that one or more (or all) of the chiral dopant compounds B are present in the second composition in a concentration/concentrations that is/are different from the corresponding concentration/concentrations in the first composition.
• first and second compositions may be that the one or more chiral dopant compounds B in the first composition are of formula (I) above and/or related formulae and at least one of the one or more chiral dopant compounds B in the second composition is different from formula (1) and/or related formulae.
• at least one of the one or more chiral dopant compounds B in the second composition may be an isosorbide or isomannide derivative as described in, e.g., EP-B-0 847 432, GB-A-2 330 139, and U.S. Patent No. 6,589,445, the entire disclosures of which are incorporated by reference herein.
• the second precursor composition After the application (e.g. deposition) of the second chiral liquid crystal precursor composition to one or more areas of the first chiral liquid crystal precursor composition in the first chiral liquid crystal state having first specific optical properties, the second precursor composition is brought to a second chiral liquid crystal state having second specific optical properties.
• the solvent contained in the composition if present, is evaporated and the promotion of the desired second chiral liquid crystal state takes place.
• the temperature used to evaporate the solvent and to promote the formation of the second liquid crystal state depends on the components of the second chirai liquid crystal precursor composition and will in many cases range from about 55°C to about 150°C, e.g., from about 55°C to about 100°C, preferably from about 60°C to about 100°C.
• suitable heating sources include conventional heating means and in particular, radiation sources such as, e.g., an IR lamp.
• the marking according to the present invention is not identical or comparable to a simple superposition of two chirai nematic liquid crystal layers. This constitutes a significant difference and a great advantage over the existing prior art.
• this state is characterized by a pitch pi .
• the second chirai liquid ciystal precursor composition is deposited on one or more areas of the applied first composition and brought to the second chirai liquid crystal state the second state is characterized by a pitch p2 (which may be the same or different from pi ).
• the product that is obtained after stage (iv) and further cured/polymerized in stage (v) of the process of the present invention is not a superposition of a first chirai liquid crystal state having a pitch pi and a second chirai liquid crystal state having a pitch p2. Rather, an area carrying the second chirai liquid crystal precursor composition, once brought to the second chirai liquid crystal state, has a pitch p2' which is different from pi and p2 but it is somewhat dependent on the nature of p i . Without wishing to be bound by any theory it is speculated that the first chirai liquid crystal state has an impact on the formation of the second chirai liquid crystal state.
• the induction of the first chirai liquid crystal state on the second chirai liquid ciystal precursor composition will accelerate and promote a second chirai liquid crystal state which is different from the chirai liquid ciystal state that would be expected based solely on the second chirai liquid crystal precursor composition alone.
• the marking according to the present invention is controlled by the first chirai liquid ciystal precursor composition which is only known by the producer of the marking. From different first chiral liquid crystal precursor compositions a large number of specific markings and codings can be generated and stored in a specific database which contains all of the markings or codings produced. Without wishing to be bound by any theory it is speculated that the second precursor composition will initiate a very local and controlled reorganization of the first chiral liquid crystal state. It further is to be noted that the method of the present invention is fast and easy to implement industrially, and does not require complex means.
• the area of the applied first precursor composition onto which the second precursor composition is applied will usually be from about 0.1 % to about 99.9% of the total area of the applied first precursor composition.
• the area will often be at least about 1 %, e.g., at least about 5% or at least about 10% and not higher than about 99%, e.g., not higher than about 95% or not higher than about 90% of the total area of the applied first precursor composition.
• the marking according to the present invention may be in the form of an image, a picture, a logo, indicia, and/or a pattern representing a (I D, 2D, 3D) code such as, e.g., a 1 -dimensional barcode, a stacked 1 -dimensional barcode, a 2-dimensional barcode, a 3- dimensional barcode and/or a data matrix.
• a corresponding marking is represented by Figure 2.
• the second chiral liquid crystal precursor composition may further comprise one or more pigments and/or dyes which absorb in the visible or invisible region of the electromagnetic spectrum and/or may further comprise one or more pigments and/or dyes which are luminescent.
• suitable pigments and/or dyes which absorb in the visible or invisible region of the electromagnetic spectrum include phthalocyanine derivatives.
• suitable luminescent pigments and/or dyes include lanthanide derivatives. The presence of pigment(s) and/or dye(s) will enhance and reinforce the security of the marking against counterfeiting.
• the second chiral liquid ciystal precursor composition for use in the present invention may comprise any other components/substances which do not adversely affect the required properties of the second chiral liquid crystal precursor composition to any significant extent.
• the deposition of the second precursor composition is performed onto one or more regions of the first chiral liquid crystal precursor composition in the first liquid crystal state preferably with a printing technique and in particular, a technique selected from continuous ink-jet printing, drop- on-demand ink-jet printing, valve-jet printing and spray coating.
• a printing technique and in particular, a technique selected from continuous ink-jet printing, drop- on-demand ink-jet printing, valve-jet printing and spray coating.
• ink-jet techniques are used for applying the second precursor composition.
• the industrial ink-jet printers commonly used for numbering and coding and marking applications on conditioning lines and printing presses, are particularly suitable.
• Preferred ink-jet printers are single nozzle continuous ink-jet printers (also called raster or multi level deflected printers) and drop-on-demand ink-jet printers, in particular valve-jet printers.
• a stream of air is passed over the surface of the first precursor composition, preferably (substantially) parallel thereto.
• the stream of air can be generated by any means, e.g., with an (industrial) air dryer.
• the stream of air will preferably not be intense and/or of high speed.
• the temperature of the air will usually be ambient (e.g., about 20 C) but may also be somewhat lower or higher, e.g., up to about 60°C, up to about 40°C, or up to about 30°C.
• the phrase "immediately after the application of the second precursor composition" is intended to mean without delay, e.g., within a period of not more than about 10 seconds, for example, not more than about 5 seconds, not more than about 3 seconds, not more than about 2 seconds, or not more than about 1 second following the completion of the application of the second precursor composition.
• the marking according to the present invention is finally obtained by curing and/or polymerizing the composition in the first chiral liquid crystal state that has been locally modified (in one or more region(s)) by the application of the second precursor composition in the second chiral liquid crystal state.
• the fixing or hardening is preferably performed by irradiation with UV-light, which induces polymerization of the polymerizable groups present in the precursor composition.
• the marking according to the invention is easy to implement industrially, and reliable.
• Figure 2 clearly demonstrates that the spectral reflectance of the cured product in the region(s) where the second chiral liquid crystal precursor composition has been applied is not the sum of the two spectral reflectances of the two chiral liquid crystal precursor compositions taken independently, even when the first and second precursor compositions are identical.
• Another advantage of the marking according to the present invention is that the natural random variations inherently present in the printing process according to the present invention can be used as a unique identifier ("fingerprint") which is virtually impossible to reproduce.
• fingerprint unique identifier
• the second precursor composition serves to generate a "marking within/on a marking”.
• the marking according to the present invention can be incoiporated, for example, in a security feature, an authenticity feature, an identification feature or a tracking and tracing feature.
• a security feature is an overt feature with a 3D effect.
• a marking according to the present invention is prepared as follows:
• a chiral liquid ciystal precursor composition (1 ) was prepared as follows:
• a chiral liquid crystal precursor composition (2) was prepared as follows:
• the chiral liquid crystal precursor composition (1 ) or (2) was then used to print a plain pattern by continuous ink-jet printing on a paper substrate with a dark background.
• the chiral liquid crystal state was developed from the plain pattern by exposure to an IR lamp for about 1 to 5 seconds (depending on the substrate).
• the second chiral liquid crystal state in the regions with the code or design printed thereon was developed by exposure of the resulting product including the marking to an IR lamp for about 1 to 5 seconds (depending on the substrate). This resulted locally in a novel anisotropic state different from the first one.
• the resultant product with the marking printed thereon was then cured by a UV dryer with a mercury low-pressure lamp having a UV irradiance of 10 mW/cm 2 .
• nematic compound A2 in the above-described procedure the following compounds may, for example, be employed:
• 2-methoxybenzene-l 4-diyl bis ⁇ 4-[4-(acryloyloxy)butoxy]-3,5-dimethoxybenzoate ⁇ ;

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