Classifications

• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
  • C09K19/00—Liquid crystal materials
  • C09K19/02—Liquid crystal materials characterised by optical, electrical or physical properties of the components, in general
• • 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
  • 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
  • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
  • C09K19/00—Liquid crystal materials
  • C09K19/04—Liquid crystal materials characterised by the chemical structure of the liquid crystal components, e.g. by a specific unit
  • C09K19/38—Polymers
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
  • C09K19/00—Liquid crystal materials
  • C09K19/04—Liquid crystal materials characterised by the chemical structure of the liquid crystal components, e.g. by a specific unit
  • C09K19/38—Polymers
  • C09K19/3833—Polymers with mesogenic groups in the side chain
  • C09K19/3842—Polyvinyl derivatives
  • C09K19/3852—Poly(meth)acrylate derivatives
• • 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
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
  • C09K19/00—Liquid crystal materials
  • C09K19/04—Liquid crystal materials characterised by the chemical structure of the liquid crystal components, e.g. by a specific unit
  • C09K2019/0444—Liquid crystal materials characterised by the chemical structure of the liquid crystal components, e.g. by a specific unit characterized by a linking chain between rings or ring systems, a bridging chain between extensive mesogenic moieties or an end chain group
  • C09K2019/0448—Liquid crystal materials characterised by the chemical structure of the liquid crystal components, e.g. by a specific unit characterized by a linking chain between rings or ring systems, a bridging chain between extensive mesogenic moieties or an end chain group the end chain group being a polymerizable end group, e.g. -Sp-P or acrylate
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
  • C09K19/00—Liquid crystal materials
  • C09K19/04—Liquid crystal materials characterised by the chemical structure of the liquid crystal components, e.g. by a specific unit
  • C09K19/06—Non-steroidal liquid crystal compounds
  • C09K19/34—Non-steroidal liquid crystal compounds containing at least one heterocyclic ring
  • C09K19/3402—Non-steroidal liquid crystal compounds containing at least one heterocyclic ring having oxygen as hetero atom
  • C09K19/3405—Non-steroidal liquid crystal compounds containing at least one heterocyclic ring having oxygen as hetero atom the heterocyclic ring being a five-membered ring
  • C09K2019/3408—Five-membered ring with oxygen(s) in fused, bridged or spiro ring systems
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
  • C09K2219/00—Aspects relating to the form of the liquid crystal [LC] material, or by the technical area in which LC material are used
  • C09K2219/03—Aspects relating to the form of the liquid crystal [LC] material, or by the technical area in which LC material are used in the form of films, e.g. films after polymerisation of LC precursor

Definitions

• the present invention relates to a composite marking based on chiral nematic (also called cholesteric) liquid crystal precursors and in particular, a marking wherein a modifying resin changes the position of the selective reflection band exhibited by a cured chiral liquid crystal precursor composition in the chiral liquid crystal state.
• the invention also relates to a method of providing a substrate with the composite marking and to a method of changing the selective reflection band exhibited by a cured chiral liquid crystal precursor composition on a substrate.
• Counterfeit is no longer a national or a regional problem but a worldwide problem which has an impact not only on manufacturers but also on the consumer. Counterfeiting is a significant problem with goods like clothes and watches but becomes even more serious when it affects medicines and drugs. Each year thousands of people around the world die because of counterfeit drugs. Counterfeiting has also an impact on government revenues in that it affects the collection of taxes for, e.g., cigarettes and alcohol because of the existence of a black market where it is impossible to track and trace counterfeit (smuggled, diverted, etc.) products with no valid tax stamps.
• optically variable inks Its principle is based on the difference in observable color of a marking made with optically variable inks when a packaging, security document, etc. carrying the marking is viewed from different angles ("viewing-angle dependent color").
• Optically variable inks provide first-line recognizability not only by a person, but also facilitate machine -readability.
• Many patents describe this security product, its composition and its application.
• One example of the many types of optically variable inks is the class of compounds called cholesteric liquid crystals.
• the cholesteric liquid crystal structure When illuminated with white light, the cholesteric liquid crystal structure reflects light of a certain color which depends on the material in question and generally varies with the viewing angle and the temperature.
• the cholesteric material itself is colorless and the observed color is the result of a physical reflection effect at the cholesteric helical structure that is adopted by the liquid crystal precursor composition at a given temperature. See, e.g., J.L. Fergason, Molecular Crystals, Vol. 1 , pp. 293-307 (1966).
• EP-A-1 381 520 and EP-A-1 681 586 disclose a birefringent marking and a method of applying the same in the form of a liquid crystal layer having a non-uniform pattern of regions of different thickness.
• the applied liquid crystal coating or layer may provide for a hidden image on a reflected substrate, which image is invisible when viewed under nonpolarized light but is rendered visible under polarized light or with the help of a polarization filter.
• U.S. Patent No. 5,678,863 discloses means for the identification of documents of value which include a paper or polymer region, said region having a transparent and translucent characteristic.
• a liquid crystal material is applied to the region to produce an optical effect, which differs when viewed in transmitted and reflected light.
• the liquid crystal material is in liquid form at room temperature and must be enclosed in a containing means such as microcapsules in order to be suitable for use in a printing process such as gravure, roller, spray or ink-jet printing.
• the ordered liquid crystalline state depends upon the presence of a chiral dopant.
• Nematic liquid crystals without chiral dopant show a molecular arrangement that is characterized by its birefringence.
• Nematic polymers are known from, e.g., EP-A-0 216 712, EP-A-0 847 432, and U.S. Patent No. 6,589,445.
• the liquid crystal based security feature provides first-line recognizability by the consumer and also by retailers and producers of goods and articles. Like for many other security features which are used in the market, there is always the temptation for counterfeiters to reproduce these security features and therefore misleads consumers and retailers. In view of the foregoing facts, there continues to be a need to improve the security of liquid crystal polymer materials based on liquid crystal precursors.
• U.S. Patent No. 6,207,240 describes an effect coating of a cholesteric liquid crystal polymer (CLCP) with viewing angle dependent reflection color that further comprises absorption type pigments exhibiting a specific absorption color.
• a marking such as a symbol or a text, is generated in the CLCP coating by laser irradiation.
• the laser radiation carbonizes the CLCP material in the irradiated area.
• the color of the substrate on which the CLCP is coated, or the color of absorption pigments incorporated into the CLCP becomes visible in the irradiated area.
• the method requires high-power lasers to carbonize the material and to make the markings visible.
• US 2006/0257633 Al which is applied not only to liquid crystal polymers but to polymers in general.
• the method consists of applying a permeating substance to a predetermined region on the surface of the polymer substrate and bringing a supercritical fluid into contact with the surface of the polymer substrate to which the permeating substance has been applied to cause the permeating substance to permeate into the polymer substrate.
• the method makes it possible to selectively (partially) modify a portion of the surface of the polymer.
• the method is complex and expensive to implement.
• US 2012/0141697 Al discloses a substrate having thereon a marking or layer that comprises a cured chiral liquid crystal precursor composition.
• the chiral liquid crystal precursor composition comprises at least one salt that changes the position of a selective reflection band exhibited by the cured composition compared to a position of the selective reflection band exhibited by the cured composition that does not contain the at least one salt.
• a modifying resin made from one or more polymerizable monomers is disposed between the substrate and the marking or layer and in contact with the marking or layer in one or more areas thereof.
• This modifying resin changes the position of the selective reflection band exhibited by the cured chiral liquid crystal precursor composition comprising the at least one salt on the substrate in the one or more areas in which it is disposed between the substrate and the marking or layer.
• the problem underlying the present invention is to improve the substrate disclosed in US 2012/0141697 Al , and in particular, to enhance the selective reflection band exhibited by the cured chiral liquid crystal precursor composition whose position has been changed by the modifying resin to thereby obtain an enhanced color and a better contrast of the marking..
• the present invention provides a substrate having thereon a marking or layer that comprises a chiral liquid crystal precursor composition in the chiral liquid crystal state in cured (hardened) form.
• the composition does not contain any salt that would cause a change of the position of the selective reflection band exhibited by the cured chiral liquid crystal precursor composition.
• a modifying resin made from one or more polymerizable monomers comprising an average of at least one ether functionality (-C-0-C-) per polymerizable group;
• n is 0 or an integer of from 1 to 4
• m is an integer of from 2 to 20
• R 1 and R 2 may be independently be hydrogen or C 1-4 alkyl (such as methyl, ethyl, propyl and butyl); is disposed between the substrate and the marking or layer and in contact with the marking or layer in one or more areas thereof.
• the modifying resin changes the position of the selective reflection band exhibited by the cured chiral liquid crystal precursor composition (when in a chiral liquid crystal state) on the substrate in the one or more areas.
• the chiral liquid precursor composition may be in a salt-free form, that is it does not contain any salt.
• the chiral liquid precursor composition contains a salt but not a salt that would change the position of the selective reflection band.
• the present invention also provides a marking or layer that is locally modified by a modifying resin as such (i.e., without the presence of a substrate).
• modifying resin as used in the present specification and in the appended claims includes cured resins as set forth below, and also includes aqueous resins such as, e.g., polyacrylates.
• the chiral liquid crystal precursor composition may comprise one or more (e.g. two, three, four, five or more and in particular, at least two) different nematic compounds A and one or more (e.g., two, three, 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.
• the chiral liquid crystal precursor composition may comprise at least one chiral dopant compound B of formula (I):
• Ri, R 2 , R 3 , R4, R5, R 6 , R7 and Rs each independently denote Ci-C 6 alkyl and Ci-C 6 alkoxy;
• 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 polymerizable monomers for the modifying resin (a) may comprise an average of at least four ether functionalities per polymerizable group.
• the ether functionalities of the one or more polymerizable monomers comprising an average of at least one ether functionality per polymerizable group may be provided by one or more alkyleneoxy units having 2, 3 or 4 carbon atoms such as, for example, ethyleneoxy groups (-CH2-CH2-O-) and/or propyleneoxy groups (-CH2-CH2- CH2-O- and/or -CH 2 -CH(CH 3 )-0-).
• At least 80 mole-% of the one or more polymerizable monomers for making the modifying resin (a) above may comprise at least one ether functionality and/or at least 90 mole-% of the one or more polymerizable monomers for making the modifying resin (a) may comprise at least four ether functionalities.
• one or more polymerizable groups e.g., one, two, three, four, five, six, or more groups
• Non- limiting examples of corresponding monomers include polyether acrylates, modified polyether acrylates (such as, e.g., amine -modified polyether acrylates), polyester acrylates, modified polyester acrylates (such as, e.g., amine-modified polyester acrylates), hexafunctional polyester acrylates, tetrafunctional polyester acrylates, aromatic difunctional urethane acrylates, aliphatic difunctional urethane acrylates, aliphatic trifunctional urethane acrylates, aliphatic hexafunctional urethane acrylates, urethane monoacrylates, aliphatic diacrylates, bisphenol A epoxy acrylates, modified bisphenol A epoxy acrylates, epoxy acrylates, modified epoxy acrylates (such as, e.g., fatty acid modified epoxy acrylates), acrylic oligomers, hydrocarbon acrylate oligomers, ethoxylated phenol acrylates, polyethylene glycol diacrylates, propoxylated
• R 1 and R 2 in formula (II) may, for example, both be hydrogen and/or n may be 1, 2 or 3.
• R 1 and R 2 in formula (II) may both be hydrogen and n may be 1.
• the modifying resin for changing the position of the selective reflection band exhibited by the cured chiral liquid crystal precursor composition may comprise a radiation-cured resin, for example, a UV- cured resin.
• the modifying resin may shift the position of the selective reflection band exhibited by the cured chiral liquid crystal precursor composition by at least 5 nm and/or may shift the position to shorter wavelengths or may shift the position to higher wavelengths and/or the shifted position of the selective reflection band may be in the visible range.
• shifting the position of the selective reflection band means shifting max as measured using an analytical spectral device that measures the reflectance of a sample in the infrared-near-infrared-visible -UV range of the spectrum, such as the LabSpec Pro device made by Analytical Spectral Devices Inc. of Boulder, Colorado.
• At least one of the one or more areas of the substrate which carry the modifying resin may be in the form of at least one of an image, a picture, a logo, indicia, and a pattern representing a code selected from one or more of a 1 -dimensional barcode, a stacked 1 -dimensional barcode, a 2-dimensional barcode, a 3-dimensional barcode, and a data matrix
• at least a part of the cured chiral liquid crystal precursor composition may be in the form of at least one of an image, a picture, a logo, indicia, and a pattern representing a code selected from one or more of a 1 -dimensional barcode, a stacked 1 -dimensional barcode, a 2-dimensional barcode, a 3-dimensional barcode, and a data matrix.
• the substrate of the present invention may be or comprise at least one of a label, packaging, a cartridge, a container or a capsule that contains pharmaceuticals, nutraceuticals, foodstuffs or a beverage (such as, e.g., coffee, tea, milk, chocolate, etc.), a banknote, a credit card, a stamp, a tax label, a security document, a passport, an identity card, a driver's license, an access card, a transportation ticket, an event ticket, a voucher, an ink-transfer film, a reflective film, an aluminum foil, and a commercial good.
• a label such as, e.g., coffee, tea, milk, chocolate, etc.
• a banknote such as, e.g., a credit card, a stamp, a tax label, a security document, a passport, an identity card, a driver's license, an access card, a transportation ticket, an event ticket, a voucher, an ink-transfer film, a reflective film, an aluminum
• the marking according to the present invention can also be created on a substrate such as, e.g., a film or sheet of polyethylene terephthalate (PET) or polyolefin such as polyethylene for later transfer to a permanent substrate (e.g., one of the substrates set forth in the preceding sentence).
• a substrate such as, e.g., a film or sheet of polyethylene terephthalate (PET) or polyolefin such as polyethylene for later transfer to a permanent substrate (e.g., one of the substrates set forth in the preceding sentence).
• PET polyethylene terephthalate
• polyolefin such as polyethylene
• the present invention further provides a method of providing a marking on a substrate.
• the method comprises the application of a curable chiral liquid crystal precursor composition which does not contain any salt that would cause a change of the position of the selective reflection band exhibited by the cured chiral liquid crystal precursor composition onto a surface of a substrate which carries in one or more areas of the surface of the substrate a modifying resin made from one or more polymerizable monomers which comprise an average of at least one ether functionality (-C-0-C-) per polymerizable group (and/or a modifying resin (b) as set forth above).
• the modifying resin is capable of changing the position of the selective reflection band exhibited by the cured chiral liquid crystal precursor composition on the substrate in the one or more areas in which it is present.
• the curable chiral liquid crystal precursor composition is applied in such a way that the composition covers at least a part of the one or more areas that carry the modifying resin and also covers at least one area of the surface of the substrate that does not carry the modifying resin.
• the method further comprises the heating of the applied chiral liquid crystal precursor composition to bring same to a chiral liquid crystal state; and the curing of the composition in the chiral liquid crystal state (e.g., by radiation, such as UV-radiation).
• the chiral liquid precursor composition is salt-free, that is it contains no salt. In another example, the chiral liquid precursor composition only contains a salt that does not cause a change in the position of the selective reflection band exhibited by the cured chiral liquid crystal precursor composition.
• the chiral liquid crystal precursor composition may be heated to a temperature of from about 55°C to about 150°C, preferably from about 60°C to about 120°C and more preferably from about 60°C to about 90°C, to bring the chiral liquid crystal precursor composition to a chiral liquid crystal state.
• the liquid crystal precursor composition may be applied onto the substrate by at least one of spray coating, knife coating, roller coating, screen coating, curtain coating, gravure printing, flexography, screen-printing, pad printing, and ink-jet printing (for example, drop-on-demand ink-jet printing, valve -jet printing), and/or may be applied in the form of at least one of an image, a picture, a logo, indicia, and a pattern representing a code selected from one or more of a 1 -dimensional barcode, a stacked 1 -dimensional barcode, a 2-dimensional barcode, a 3-dimensional barcode, and a data matrix.
• spray coating for example, drop-on-demand ink-jet printing, valve -jet printing
• ink-jet printing for example, drop-on-demand ink-jet printing, valve -jet printing
• the modifying resin may be present in at least one of the one or more areas in the form of at least one of an image, a picture, a logo, indicia, and a pattern representing a code selected from one or more of a 1 -dimensional barcode, a stacked 1- dimensional barcode, a 2-dimensional barcode, a 3-dimensional barcode, and a data matrix and/or may have been provided on the substrate by at least one of continuous ink- jet printing, drop-on-demand ink-jet printing, valve -jet printing, spray printing, flexography, gravure printing, offset, dry offset printing, letterpress printing, pad printing and screen printing.
• the substrate may be or may comprise at least one of a label, packaging, a cartridge, a container or a capsule that contains pharmaceuticals, nutraceuticals, foodstuffs or a beverage (such as, e.g., coffee, tea, milk, chocolate, etc.), a banknote, a credit card, a stamp, a tax label, a security document, a passport, an identity card, a driver's license, an access card, a transportation ticket, an event ticket, a voucher, an ink-transfer film, a reflective film, an aluminum foil, and a commercial good.
• a label such as, e.g., coffee, tea, milk, chocolate, etc.
• a banknote such as, e.g., coffee, tea, milk, chocolate, etc.
• a credit card such as, e.g., coffee, tea, milk, chocolate, etc.
• a stamp such as, e.g., a stamp, a tax label, a security document, a passport, an identity
• the modifying resin may be capable of shifting the position of the selective reflection band exhibited by the cured chiral liquid crystal precursor composition on the substrate by at least 5 nm.
• the chiral liquid crystal precursor composition may comprise one or more (e.g. two, three, four, five or more and in particular, at least two) different nematic compounds A and one or more (e.g., two, three, 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.
• the chiral liquid crystal precursor composition may comprise at least one chiral dopant compound B of formula (I):
• Ri, R 2 , R3, R4, Rs, R 6 , R7 and Rs each independently denote Ci-C 6 alkyl and Ci-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, 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.
• At least one of the one or more polymerizable monomers having an average of at least one ether functionality per polymerizable group for providing the above modifying resin (a) that changes the position of the selective reflection band exhibited by the cured chiral liquid crystal precursor composition may comprise at least two unsaturated carbon-carbon bonds.
• Non-limiting examples of corresponding monomers include polyether acrylates, modified polyether acrylates (such as, e.g., amine-modified polyether acrylates), polyester acrylates, modified polyester acrylates (such as, e.g., amine-modified polyester acrylates), hexafunctional polyester acrylates, tetrafunctional polyester acrylates, aromatic difunctional urethane acrylates, aliphatic difunctional urethane acrylates, aliphatic trifunctional urethane acrylates, aliphatic hexafunctional urethane acrylates, urethane monoacrylates, aliphatic diacrylates, bisphenol A epoxy acrylates, modified bisphenol A epoxy acrylates, epoxy acrylates, modified epoxy acrylates (such as, e.g., fatty acid modified epoxy acrylates), acrylic oligomers, hydrocarbon acrylate oligomers, ethoxylated phenol acrylates, polyethylene glycol diacrylates, propoxylated ne
• the modifying resin (a) or (b) may comprise a radiation-cured resin, for example, a UV-cured resin.
• the modifying resin may comprise an aqueous resin which may be dried by conventional means such as heat.
• the present invention further provides a substrate that is provided with a marking, wherein the substrate is obtainable by the method of the present invention as set forth above (including the various aspects thereof).
• the present invention also provides a method of shifting the position of the selective reflection band exhibited by a chiral liquid crystal precursor made from a composition that comprises one or more nematic compounds and one or more chiral dopant compounds which are capable of giving rise to a cholesteric state of the chiral liquid crystal precursor composition and does not comprise any salt that would cause a change of the position of the selective reflection band exhibited by the cured chiral liquid crystal precursor composition.
• the method comprises contacting the chiral liquid crystal precursor composition with a modifying resin (a) which is made from one or more polymerizable monomers which comprise an average of at least one ether functionality (-C-0-C-) per polymerizable group and is capable of changing the position of the selective reflection band exhibited by the cured chiral liquid crystal precursor composition (and/or a modifying resin (b) as set forth above).
• a modifying resin (a) which is made from one or more polymerizable monomers which comprise an average of at least one ether functionality (-C-0-C-) per polymerizable group and is capable of changing the position of the selective reflection band exhibited by the cured chiral liquid crystal precursor composition (and/or a modifying resin (b) as set forth above).
• the chiral liquid crystal precursor composition is then heated to a temperature of from about 55°C to about 150°C, preferably from about 60°C to about 120°C, more preferably from about 60°C to about 90°C, to bring it to a
• the chiral liquid precursor composition is salt-free, that is it contains no salt. In another example, the chiral liquid precursor composition only contains a salt that does not cause a change in the position of the selective reflection band exhibited by the cured chiral liquid crystal precursor composition.
• the position of the selective reflection band may be shifted by at least 5 nm.
• Other aspects of the method such as, e.g., aspects relating to compounds A and compounds B include those set forth above with respect to the substrate/marking of the present invention.
• Fig. 1 is a diagram showing the position of the selective reflection band ( max ) of a cured chiral liquid crystal precursor composition according to a first example suitable for use in the present invention as a function of the concentration of the chiral dopant contained therein, based on dry matter;
• Fig. 2 is a diagram showing the position of the selective reflection band ( max ) of a cured chiral liquid crystal precursor composition according to a second example suitable for use in the present invention as a function of the concentration of the chiral dopant contained therein, based on dry matter; and
• Fig. 3 shows an object of the present invention which uses a modifying resin to create perfect register, compared to other existing technologies.
• 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 a capsule or a closed cartridge for holding various items such as, e.g., nutraceuticals, pharmaceuticals, beverages or foodstuffs), a fabric, a coating, and equivalents thereof, glass (for example, in the form of a container such as a bottle for holding various items such as, e.g., nutraceuticals, pharmaceuticals, beverages or foodstuffs), cardboard (e.g., in the form of packaging), paper, and a polymeric material such as, e.g., PET or polyethylene (e.g., in the form of a container or as a part of a security document).
• a metal for example, in the form of a container such as a can a capsule or a closed cartridge for holding various items such as, e.g., nutraceutic
• any substrate which may not necessarily be fiat and may be uneven
• any substrate whose surface is not soluble, or only slightly soluble, in solvent(s) used in the chiral liquid polymer precursor composition is a suitable substrate for the purposes of the present invention.
• the substrate may advantageously have a dark or black surface or background onto which the precursor composition is to be applied.
• 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.
• the reflection color of the cholesteric liquid crystal material is less visible when compared with a black or dark background, due to the strong backscattering from the background.
• the substrate according to the present invention may further comprise additional security elements, such as organic and/or inorganic pigments, dyes, flakes, optically variable elements, magnetic pigments, etc.
• the 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 (and over at least a part of the modifying resin on the at least one surface of the substrate) preferably 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 crystal precursor composition for use in the present invention will be about four to about fifty times the (total) concentration of the one or more cholesteric compounds B.
• a chiral liquid crystal 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.
• the chiral liquid crystal precursor composition for use in the present invention although it could be salt-free, does not have to be entirely salt- free. All that is required is that the composition does not contain any salt that would cause a noticeable change of the position of the selective reflection band exhibited by the cured chiral liquid crystal precursor composition. Accordingly, the precursor composition may contain one or more salts which do not noticeably shift the position of the selective reflection band exhibited by the cured chiral liquid crystal precursor composition.
• the composition may even contain one or more salts which are capable of causing a noticeable change of the position of the selective reflection band exhibited by the cured chiral liquid crystal precursor composition but are present in such a small concentration that they do not cause a noticeable shift of the position of the selective reflection band, e.g., do not cause a shift of the position of the selective reflection band by more than 1 nm, and preferably do not cause a shift of the position by more than 0.5 nm.
• the composition could be salt-free.
• salt-free means that the chiral liquid crystal precursor composition does not contain more than trace amounts of salt(s), e.g., not more than 0.1 % by weight and preferably not more than 0.01 % by weight, and preferably not more than 0.001 % by weight, based on the solids content of the precursor composition. Most preferably, the composition is entirely free of salt or at least contains not more than 5 ppm of salt.
• Nematic compounds A which are suitable for use in the chiral liquid crystal precursor composition 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.
• 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 formulae (IA), ( ⁇ '), (IB) and (IB') set forth below).
• the nematic compounds A may comprise one or more groups of formulae (i) to (iii) which are indicated above as meanings for Ai and A 2 in formula (I), 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 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):
• Ri, R 2 , R 3 , R4, Rs, R 6 , R7 and Rs each independently denote Ci-C 6 alkyl and Ci-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.
• Chiral dopant compounds B of formula (I) include compounds of the following formulae (IA), (IA'), (IB) and (IB'):
• Ri, R 2 , R3, R4, Rs, R 6 , R7 and Rs each independently denote Ci-C 6 alkyl and Ci-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, 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.
• Ri, R 2 , R3, R4, Rs, R 6 , R7 and Rs each independently denote Ci-C 6 alkyl.
• Ri, R 2 , R3, R4, Rs, Re, R? and Rs in formulae (IA), ( ⁇ '), (IB) and (IB') (and in formula (I)) each independently denote Ci-C 6 alkoxy.
• Ri, R 2 , R3 and R4 each independently denote Ci-C 6 alkyl; and
• m, n, 0, and p each independently denote 0, 1 , or 2.
• Ai and A 2 in formula (I) and in formulae (IA), ( ⁇ '), (IB) and (IB')each independently denote a group of formula -[(CH 2 ) y -0] z -C(0)-CH CH 2 ; Ri, R 2 , R 3 and R 4 each independently denote Ci-Ce alkoxy; and m, n, 0, and p each independently denote 0, 1 , or 2.
• the alkyl and alkoxy groups of Ri, R 2 , R 3 , R 4 , Rs, R 6 , R7 and Rs in formulae (I), (IA), ( ⁇ '), (IB) and (IB') may comprise 1 , 2, 3, 4, 5 or 6 carbon atoms (such as, e.g., methyl, methoxy, ethyl, ethoxy, propyl, propoxy, isopropyl, isopropoxy, butyl, butoxy, pentyl, pentoxy, hexyl, hexoxy) and in particular, 4 or 6 carbon atoms.
• alkyl groups comprising 3 or 4 carbon atoms include isopropyl and butyl.
• alkyl groups comprising 6 carbon atoms include hexyl, 2-methylpentyl, 3- methylpentyl, 2,2-dimethylbutyl, and 2,3-dimethylbutyl.
• alkoxy groups comprising 3 or 4 carbon atoms include isopropoxy, but-1- oxy, but-2-oxy, and tert-butoxy.
• alkoxy groups comprising 6 carbon atoms include hex-l-oxy, hex-2-oxy, hex-3-oxy, 2-methylpent-l-oxy, 2-methylpent-2-oxy, 2- methylpent-3-oxy, 2-methylpent-4-oxy, 4-methylpent-l-oxy, 3-methylpent-l-oxy, 3- methylpent-2-oxy, 3-methylpent-3-oxy, 2,2-dimethylbut-l-oxy, 2,2-dimethylbut-3-oxy, 2,2-dimethylbut-4-oxy, 4,4-dimethylbut-l-oxy, 2,3-dimethylbut-l-oxy, 2,3-dimethylbut- 2-oxy, 2,3-dimethylbut-3-oxy, and 3,4-dimethylbut-l -oxy.
• Ri, R 2 , R3, and R4 each independently denote Ci-C 6 alkyl and Ci-C 6 alkoxy;
• 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.
• Ri, R 2 , R3 and R4 each independently denote C1-C3 alkyl (i.e., methyl, ethyl, propyl or isopropyl).
• Ri, R 2 , R3, R4, in formulae (I), (IA), ( ⁇ '), (IB) and (IB') each independently denote C1-C3 alkoxy (i.e., methoxy, ethoxy, propoxy or isopropoxy).
• alkyl and alkoxy groups methyl and methoxy groups are preferred.
• Ri, R 2 , R3 and R4 each independently denote methyl or ethyl (preferably methyl); and the sum (m+n) is 0 or 1 and the sum (o+p) is 0 or 1.
• Ri, R 2 , R3 and R4 each independently denote methoxy or ethoxy (preferably methoxy); and the sum (m+n) is 0 or 1 and the sum (o+p) is 0 or 1.
• Non-limiting specific examples of chiral dopant compounds B of formula (I) for use in the present invention are provided below.
• the one or more chiral dopant compounds B will usually be present in a total concentration of from 0.1% to 30% by weight, e.g., from 0.1% to 25%, or from 0.1 % to 20% by weight, based on the total weight of the composition.
• concentrations of from 3% to 10% by weight, e.g., from 5% to 8% by weight, based on the total weight of the polymer composition will often be present in a concentration of from 30% to 50% by weight, based on the total weight of the polymer composition.
• the modifying resin (a) for use in the present invention is not particularly limited as long as it is made from one or more polymerizable monomers which comprise an average of at least one ether functionality (-C-0-C-) (e.g., at least two, at least three, at least four, at least five, at least six or at least seven ether functionalities) per polymerizable group and is capable of changing the position of the selective reflection band exhibited by the cured chiral liquid crystal precursor composition on the substrate to a noticeable extent.
• ether functionality e.g., at least two, at least three, at least four, at least five, at least six or at least seven ether functionalities
• the resin is preferred for the resin to be capable of shifting the position of the selective reflection band by at least 5 nm, e.g., by at least 10 nm, by at least 20 nm, by at least 30 nm, by at least 40 nm, or by at least 50 nm.
• This capability depends on various factors such as, inter alia, the components of the chiral liquid crystal precursor composition, for example, the chiral dopant(s) comprised therein, and the presence or absence of functional groups in the modifying resin (and thus on the surface thereof).
• polymerizable monomer includes polymerizable oligomers such as, e.g., oligomers which have been formed by polymerizing two or more (e.g. up to 20, up to 30, up to 40, up to 50 or even more) polymerizable monomers and still contain at least one polymerizable group (e.g. at least two or at least three polymerizable groups).
• ether functionalities e.g., at least two, at least three, at least four, at least five, at least six or at least seven
• the polymerizable monomers are not limited to those which are polymerizable by free radical polymerization. Rather, these monomers also include, for example, monomers which are polymerizable by cationic and/or anionic polymerization and/or by polycondensation.
• resins which are suitable for the purposes of the present invention include organic resins such as poly aery lates, polymethacrylates, polyvinylethers, polyvinylesters, polyesters, polyethers, polyamides, polyurethanes, polycarbonates, polysulfones, phenolic resins, epoxy resins, and mixed forms of these resins.
• Mixed inorganic/organic resins such as silicones (e.g., polyorganosiloxanes) are suitable as well.
• One particular type of resin that can be used in the present invention are aqueous resins.
• Non-limiting examples of modifying resins (a) and (b) for use in the present invention further include those which are made from one or more monomers selected from polyether acrylates, modified polyether acrylates (such as, e.g., amine -modified polyether acrylates), polyester acrylates, modified polyester acrylates (such as, e.g., amine-modified polyester acrylates), hexafunctional polyester acrylates, tetrafunctional polyester acrylates, aromatic difunctional urethane acrylates, aliphatic difunctional urethane acrylates, aliphatic trifunctional urethane acrylates, aliphatic hexafunctional urethane acrylates, urethane monoacrylates, aliphatic diacrylates, bisphenol A epoxy acrylates, modified bisphenol A epoxy acrylates, epoxy acrylates, modified epoxy acrylates (such as, e.g., fatty acid modified epoxy acrylates), acrylic oligomers, hydrocarbon acrylate oligomers,
• Non-limiting specific examples of monomers which can be used for making the modifying resins for use in the present invention are polyethylene glycol diacrylates and polyethylene glycol dimethacrylates which comprise 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 , 12, 13, 14, 15, 20, 25 or 30 ethyleneoxy groups, triacrylates and trimethacrylates of ethoxylated trimethylopropane which comprise 2, 3, 4, 5, 6, 7, 8, 9, 10, 1 1 , 12, 13, 14, 15, 20, 25 or 30 ethyleneoxy groups, tetraacrylates and tetramethacrylates of ethoxylated pentaerythritol which comprise 2, 3, 4, 5, 6, 7, 8, 9, 10, 1 1 , 12, 13, 14, 15, 20, 25 or 30 ethyleneoxy groups, and diacrylates and dimethacrylates of ethoxylated bisphenol A which comprise 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 , 12, 13, 14, 15, 20, 25 or 30 ethyleneoxy groups, as well as the corresponding propoxylated and mixed ethoxylated/propoxylated monomers.
• a part of the polymerizable monomers which are used to prepare the modifying resin (a) for use in the present invention may not contain any ether functionalities at all or may contain less than one ether functionality per polymerizable group. However, in this case the remaining monomer(s) must contain sufficient ether functionalities per polymerizable group to bring the average to the required minimum of one ether functionality per polymerizable group present in the two or more polymerizable monomers.
• At least 80 mole-%, e.g., at least 90 mole-%, at least 95 mole-% or 100 mole-% of the one or more polymerizable monomers for making the modifying resins for use in the present invention comprise at least one ether functionality (e.g., at least two ether functionalities or at least three ether functionalities). Further, preferably at least 90 mole-%, e.g., at least 95 mole-% or 100 mole-% of the one or more polymerizable monomers for making the modifying resin comprise at least four ether functionalities.
• a modifying resin for use in the present invention does not have to be completely cured (polymerized) or dry before it is contacted with a chiral liquid crystal precursor composition as long as it is able to withstand the components and in particular, the solvent that may be (and usually will be) present in the (uncured) chiral liquid crystal precursor composition (e.g., that the modifying resin does not get dissolved thereby to any significant extent).
• the curing of an only partially cured modifying resin may be completed, for example, together with the curing of the chiral liquid crystal precursor (e.g., by UV- radiation).
• perfect register it is meant the possibility to have in very few steps and/or process(es) steps a single layer of liquid crystal polymer wherein two or more zones with simultaneously different color shifting properties and/or different positions of the selective reflection band are present, and these zones can be perfectly adjacent without either a gap or an overlap between them, as shown in Fig. 3.
• This advantage stems from the fact that the liquid crystal precursor composition is applied in one step, and its properties are locally modified by the modifying resin.
• the instant method allows straightforward creation of logo, marking, coding, barcode, pattern, data matrix which contains different information and/or color at the same time.
• the possibilities afforded by the instant method include using mixtures of modifying resins (e.g., mixtures of two, three, four or more modifying resins), both in the form of cured physical mixtures of two or more modifying resins and in the form of two or more different modifying resins which are (separately) present on different locations of the surface of the substrate.
• two or more different chiral liquid crystal precursor compositions which differ, for example, in the concentration of chiral dopant(s) B and/or with respect to the type of chiral dopant(s) B therein may also be used.
• the present invention also contemplates and encompasses the use of chiral liquid crystal precursor compositions and modifying resins which comprise such additional specific security elements.
• first (modifying) resin material with modifying properties
• second modifying resin or even two or more different modifying resins in different areas
• first and second (and third, etc.) resins differ in their ability to shift the position of the selective reflection band exhibited by the cured chiral liquid crystal precursor composition (or of two or more different cured chiral liquid crystal precursor compositions).
• a modifying resin may shift all or a part of the selective reflection band exhibited by a cured chiral liquid crystal precursor composition from the IR range to the visible range or vice versa, or from the visible range to the UV range or vice versa, or from the IR range to the UV range or vice versa.
• the chiral liquid crystal precursor composition can be applied onto the surface of the substrate by any suitable method such as, for example, spray coating, knife coating, roller coating, screen coating, curtain coating, gravure printing, flexography, offset printing, dry offset printing, letterpress printing, screen-printing, pad printing, and ink-jet printing (for example, drop-on-demand ink-jet printing, valve -jet printing).
• suitable method such as, for example, spray coating, knife coating, roller coating, screen coating, curtain coating, gravure printing, flexography, offset printing, dry offset printing, letterpress printing, screen-printing, pad printing, and ink-jet printing (for example, drop-on-demand ink-jet printing, valve -jet printing).
• the application (e.g., deposition) of a composition for making the marking or layer and/or a composition for making the modifying resin is carried out with a printing technique such as, e.g., ink-jet printing (continuous, drop-on-demand, etc.), flexography, pad printing, rotogravure printing, screen-printing, etc.
• a printing technique such as, e.g., ink-jet printing (continuous, drop-on-demand, etc.), flexography, pad printing, rotogravure printing, screen-printing, etc.
• ink-jet printing continuous, drop-on-demand, etc.
• 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 liquid crystal polymer composition, after curing, according to the above described application techniques will usually be at least 1 ⁇ , e.g., at least 3 ⁇ , or at least 4 ⁇ , and will usually be not more than 20 ⁇ , e.g., not more than 15 ⁇ , not more than 10 ⁇ , or not more than 6 ⁇ .
• the thickness of the applied modifying resin, after curing, according to the above described application techniques will usually be at least about 1 ⁇ , e.g., at least 3 ⁇ , or at least 5 ⁇ , but will usually be not more than 10 ⁇ .
• a polymer composition for use in the present invention i.e., a composition for making a chiral liquid crystal precursor or a composition for making a modifying resin
• 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 fiexographic printing inks are in the range of from about 40 seconds to about 120 seconds using e.g. a cup DIN number 4. 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, cyclohexanone, ethyl acetate, ethyl 3- ethoxypropionate, and mixtures of two or more thereof.
• MEK methyl ethyl ketone
• a polymer composition for use in the present invention i.e., a composition for making a chiral liquid crystal precursor or a composition for making a modifying resin
• the polymer composition will usually also comprise at least one conductivity agent known by those of skill in the art.
• a chiral liquid crystal precursor composition and/or a composition for making a modifying resin for use in the present invention is to be cured/polymerized by UV radiation the composition will also comprise at least one photoinitiator.
• Non-limiting examples of the many suitable photo initiators 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- 1 -propanone, and 2-hydroxy- 1 -[4-(2-hydroxyethoxy)phenyl]-2-methyl-l - propanone; phenylglyoxylates such as methylbenzoylformate and a mixture of oxy- phenyl-acetic acid 2-[2-oxo-2-phenyl-acetoxy-ethoxy]-ethyl ester and oxy-phenyl-acetic 2-[2-hydroxy-ethoxy]-ethyl ester; benzyldimethyl ketals such as alpha, alpha-dimethoxy- alpha-phenylaceto
• a polymer composition for use in the present invention i.e., a composition for making a chiral liquid crystal precursor or a composition for making a modifying resin
• 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.
• high-energy particles e.g., electron beams
• X-rays e.g., X-rays
• gamma-rays e.g., X-rays
• the use of a photoinitiator can, of course, be dispensed with.
• the composition will usually contain at least one thermal polymerization initiator such as, e.g., a peroxide or an azo compound.
• thermal polymerization initiators are well known to those of skill in the art.
• a chiral liquid crystal precursor composition and a composition for providing a modifying resin 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 composition to any significant extent.
• Such optional components are resins, silane compounds, adhesion promoters, sensitizers for the photoinitators (if present), etc.
• especially a chiral liquid crystal precursor composition for use in the present invention may comprise one or more silane compounds..
• Non-limiting examples of suitable silane compounds include optionally polymerizable silanes such as those of formula R1R2R3-S1- R4 wherein Ri, R 2 , and R3 independently represent alkoxy and alkoxyalkoxy having a total of from 1 to about 6 carbon atoms and R4 represents vinyl, allyl, (Ci-io)alkyl, (meth)acryloxy(Ci-6)alkyl, and glycidyloxy(Ci-6)alkyl such as, e.g., vinyltriethoxysilane, vinyltrimethoxysilane, vinyltris(2-methoxyethoxy)silane, 3-methacryloxypropyl- trimethoxysilane, octyltriethoxysilane, and 3-glycidyloxypropyl triethoxysilane from the Dynasylan ® family supplied by Evonik.
• Ri, R 2 , and R3 independently represent alkoxy and alkoxyalk
• a composition for making a modifying resin and/or a composition for making a chiral liquid crystal precursor for use in the present invention may further comprise one or more pigments and/or dyes which absorb in the visible or invisible region of the electromagnetic spectrum and/or one or more pigments and/or dyes which are luminescent and/or one or more magnetic pigments.
• suitable pigments and/or dyes which absorb in the visible or invisible region of the electromagnetic spectrum include phthalocyanine derivatives.
• Non-limiting examples of suitable luminescent pigments and/or dyes include lanthanide derivatives.
• suitable magnetic pigments include particles of transitional metal oxides such as iron and chromium oxides. The presence of pigment(s) and/or dye(s) will enhance and reinforce the security of the marking against counterfeiting.
• the polymer composition is brought to a chiral liquid crystal state having specific optical properties.
• specific optical properties is to be understood as a liquid crystal state with a specific pitch that reflects a specific wavelength range (selective reflection band).
• the solvent contained in the composition if present, is evaporated and the promotion of the desired chiral liquid crystal state takes place.
• the temperature used to evaporate the solvent and to promote the formation of the liquid crystal state depends on the components of the chiral liquid crystal precursor composition and will in many cases range from about 55°C to about 150°C, preferably from about 60°C to about 120°C, more preferably from about 60°C to about 90°C.
• suitable heating sources include conventional heating means such as a hot plate, an oven, a stream of hot air and in particular, radiation sources such as, e.g., an IR lamp.
• the required heating time depends on several factors such as, e.g., the components of the polymer composition, the type of heating device and the intensity of the heating (energy output of the heating device). In many cases a heating time of from about 0.1 s, about 0.5 s, or 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 marking according to the present invention is finally obtained by curing and/or polymerizing the (entire) composition in the chiral liquid crystal state.
• the fixing or hardening will often be performed by irradiation with UV-light, which induces polymerization of the polymerizable groups present in the polymer composition. Accordingly, an entire process for making a marking of the present invention may comprise the following steps:
• the marking according to the present invention can be incorporated, for example, in a security feature, an authenticity feature, an identification feature or a tracking and tracing feature.
• a chiral liquid crystal precursor composition was prepared as follows, the indicated percentages being by weight based on the total weight of the composition:
• a chiral dopant compound B of formula (I) shown above (3 %), a nematic compound A (47 %), cyclopentanone (47 %) and a salt KPF 6 (0.5%) were placed into a flask which was thereafter heated until a solution was obtained.
• To the solution were added 2-methyl- l [4-(methylthio)phenyl]-2-morpholinopropan-l-one (Irgacure 907® from Ciba, photoinitiator, 1.5 %) and a surface additive (1 %).
• the final mixture was stirred until complete dissolution was achieved to result in the chiral liquid crystal precursor composition.
• Example 1 Preparation of a layer of a cured chiral liquid crystal precursor composition
• the above precursor composition of Example 1 was coated on black paper substrate functionalized in some areas with a modifying resin (UV curable varnish) of the following formula (in % by weight):
• Genomer 5275 (acrylated oligoamine resin, available from RHAN, for improving the solvent resistance, etc. of the modifying resin)
• Esacure Kip 160 photoinitiator, oligo[2-hdroxy-2-methyl-l-[4-(l- methylvinyl)phenyl]propanone, available from ESACURE
• the resultant layer was heated to about 80°C for about 30 seconds to evaporate the solvent and to develop a cholesteric liquid crystal phase, i.e., a state that shows a specific reflection band whose position depends on the concentration of the chiral dopant compound B in the composition.
• the composition was cured by irradiation with a UV lamp (mercury low-pressure lamp having a UV irradiance of 10 mW/cm 2 ) for about 1 second to freeze the cholesteric liquid crystal phase through co-polymerization of the polymerizable groups of compounds A and B.
• the composition was substantially free of solvent (only trace amounts of cyclopentanone were present) and comprised the above components (in polymerized form) in the following weight percentages, based on the total weight of the composition:
• a chiral liquid crystal precursor composition was prepared as follows, the indicated percentages being by weight based on the total weight of the composition:
• Example 2 Preparation of a layer of a cured chiral liquid crystal precursor composition
• the above precursor composition of Example 2 was coated on a black paper substrate that was functionalized in some areas with a modifying resin (UV curable varnish) made from a composition of the following formula (in % by weight):
• Genomer 5275 (acrylated oligoamine resin, available from RHAN, for improving the solvent resistance, etc. of the modifying resin)
• Esacure Kip 160 photoinitiator, oligo [2 -hdroxy-2 -methyl- 1 - [4-( 1 - methylvinyl)phenyl]propanone, available from ESACURE)
• the resultant layer precursor composition was heated to about 80°C for about 30 seconds to evaporate the solvent and to develop a cholesteric liquid crystal phase, i.e., a state that shows a specific reflection band whose position depends on the concentration of the chiral dopant compound B in the composition. Thereafter the composition was cured by irradiation with a UV lamp (mercury low-pressure lamp having a UV irradiance of 10 mW/cm2) for about 1 second to freeze the cholesteric liquid crystal phase through co- polymerization of the polymerizable groups of compounds A and B. After the curing the composition was substantially free of solvent (only trace amounts of cyclopentanone were present) and comprised the above components (in polymerized form) in the following weight percentages, based on the total weight of the composition:
• the concentration of chiral dopant compounds B in the cholesteric liquid crystal precursor of Examples 1 or 2 can be varied to control the position of the selective reflection band and as a result thereof, the color of the cured chiral liquid crystal precursor layer.
• Fig. 1 which is a plot of the wavelength of the maximum normal reflection as a function of the concentration of the chiral dopant compound B of Example 1 in the dry composition
• Fig. 2 which is a plot of the wavelength of the maximum normal reflection as a function of the concentration of the chiral dopant compound B of Example 2 in the dry composition.
• Fig. 1 is a plot of the wavelength of the maximum normal reflection as a function of the concentration of the chiral dopant compound B of Example 1 in the dry composition
• Fig. 2 which is a plot of the wavelength of the maximum normal reflection as a function of the concentration of the chiral dopant compound B of Example 2 in the dry composition.
• the wavelength of the maximum normal reflection of the cured composition is around 550nm, which affords a green color of the corresponding layer.
• the wavelength of the maximum normal reflection of the cured composition is also around 550 nm, which also affords a green color of the corresponding layer.
• increasing (or decreasing) the concentration of chiral dopant compound B in the composition results in a decrease (or increase) of the wavelength of the maximum normal reflection.
• the reflection band of the cured liquid crystal composition is shifted towards higher wavelengths and in this example the maximum normal reflection of the composition is around 620 nm as measured with the LabSpec Pro device made by Analytical Spectral Devices Inc. of Boulder, Colorado. Both the unmodified color shift (550 nm) and the modified colour shift (620 nm) show an increased reflection intensity providing a better color contrast compared to the substrate disclosed in US 2012/0141697 Al .
• the black paper substrate is obtainable by flexography printing of a layer of a UV curable conventional black ink such as, for example the UV black ink "process black” (available from SIEGWERK) on a white paper (90gr, available from GASCOGNE LAMINATES).
• a UV curable conventional black ink such as, for example the UV black ink "process black” (available from SIEGWERK)
• a white paper 90gr, available from GASCOGNE LAMINATES.
• the functionalization is carried out by flexography printing of the UV curable varnish composition set forth above and subsequent curing thereof.
• the following compounds may, for example, be employed in the above Examples 1 and 2 as chiral dopant compound B of formula (I):
• nematic compound A in the above Examples the following compounds may, for example, be employed: benzoic acid, 4-[[[4-[(l -oxo-2-propen-l -yl)oxy]butoxy]carbonyl]oxy]-l ,1 '-(2 -methyl- 1 ,4- phenylene) ester;
• 2-methoxybenzene-l 4-diyl bis ⁇ 4-[4-(acryloyloxy)butoxy]-3,5-dimethoxybenzoate ⁇ ; 2-methoxybenzene-l ,4-diyl bis ⁇ 4-[4-(acryloyloxy)butoxy]-3-methoxybenzoate ⁇ ;

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• 2014
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