WO2022101207A1 - Compositions comprenant des nanoplaquettes d'argent - Google Patents

Compositions comprenant des nanoplaquettes d'argent Download PDF

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Publication number
WO2022101207A1
WO2022101207A1 PCT/EP2021/081122 EP2021081122W WO2022101207A1 WO 2022101207 A1 WO2022101207 A1 WO 2022101207A1 EP 2021081122 W EP2021081122 W EP 2021081122W WO 2022101207 A1 WO2022101207 A1 WO 2022101207A1
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WIPO (PCT)
Prior art keywords
group
formula
silver
composition
nanoplatelets
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PCT/EP2021/081122
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English (en)
Inventor
Nikolay A Grigorenko
Andre OSWALD
Original Assignee
Basf Se
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Publication date
Application filed by Basf Se filed Critical Basf Se
Priority to CA3197947A priority Critical patent/CA3197947A1/fr
Priority to AU2021379955A priority patent/AU2021379955A1/en
Priority to EP21811267.0A priority patent/EP4244003A1/fr
Priority to CN202180058692.3A priority patent/CN116547090A/zh
Publication of WO2022101207A1 publication Critical patent/WO2022101207A1/fr

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F9/00—Making metallic powder or suspensions thereof
    • B22F9/16—Making metallic powder or suspensions thereof using chemical processes
    • B22F9/18—Making metallic powder or suspensions thereof using chemical processes with reduction of metal compounds
    • B22F9/24—Making metallic powder or suspensions thereof using chemical processes with reduction of metal compounds starting from liquid metal compounds, e.g. solutions
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
    • B22F1/05—Metallic powder characterised by the size or surface area of the particles
    • B22F1/054—Nanosized particles
    • B22F1/0545—Dispersions or suspensions of nanosized particles
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
    • B22F1/05—Metallic powder characterised by the size or surface area of the particles
    • B22F1/054—Nanosized particles
    • B22F1/0551—Flake form nanoparticles
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
    • B22F1/10—Metallic powder containing lubricating or binding agents; Metallic powder containing organic material
    • B22F1/103—Metallic powder containing lubricating or binding agents; Metallic powder containing organic material containing an organic binding agent comprising a mixture of, or obtained by reaction of, two or more components other than a solvent or a lubricating agent
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
    • B22F1/10—Metallic powder containing lubricating or binding agents; Metallic powder containing organic material
    • B22F1/107—Metallic powder containing lubricating or binding agents; Metallic powder containing organic material containing organic material comprising solvents, e.g. for slip casting
    • 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
    • B42D25/351—Translucent or partly translucent parts, e.g. windows
    • 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
    • B42D25/373—Metallic materials
    • 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
    • B42D25/378—Special inks
    • 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
    • C09D11/02—Printing inks
    • C09D11/10—Printing inks based on artificial resins
    • C09D11/101—Inks specially adapted for printing processes involving curing by wave energy or particle radiation, e.g. with UV-curing following the printing
    • 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
    • C09D11/50—Sympathetic, colour changing or similar inks
    • 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
    • C09D5/00—Coating compositions, e.g. paints, varnishes or lacquers, characterised by their physical nature or the effects produced; Filling pastes
    • C09D5/29—Coating compositions, e.g. paints, varnishes or lacquers, characterised by their physical nature or the effects produced; Filling pastes for multicolour effects
    • 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
    • C09D7/00—Features of coating compositions, not provided for in group C09D5/00; Processes for incorporating ingredients in coating compositions
    • C09D7/40—Additives
    • C09D7/60—Additives non-macromolecular
    • C09D7/61—Additives non-macromolecular inorganic
    • C09D7/62—Additives non-macromolecular inorganic modified by treatment with other compounds
    • 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
    • C09D7/00—Features of coating compositions, not provided for in group C09D5/00; Processes for incorporating ingredients in coating compositions
    • C09D7/40—Additives
    • C09D7/70—Additives characterised by shape, e.g. fibres, flakes or microspheres
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K9/00—Use of pretreated ingredients
    • C08K9/04—Ingredients treated with organic substances

Definitions

  • compositions comprising silver nanoplatelets
  • the present invention relates to compositions, comprising silver nanoplatelets capped by dithiocarbamate anions of formula (XX).
  • UV-Vis radiation curable inks, containing the silver nanoplatelets do not degrade and a coating, comprising the composition, shows a blue color in transmission and a metallic yellow color in reflection.
  • US2017246690 discloses a method for synthesizing metal nanoparticles, the method comprising: (a) preparing a metal precursor mixture comprising a metal precursor compound and a first aqueous liquid medium, (b) preparing a reducing agent mixture comprising a reducing agent and a second aqueous liquid medium, (c) optionally adding an acid or a base to the mixture prepared in step (a) or to the mixture prepared in step (b), wherein the metal precursor mixture and the reducing agent mixture are both free of stabilizing agent and free of seed particles, (d) combining the metal precursor mixture with the reducing agent mixture so as to allow the metal precursor compound to react with the reducing agent, thereby synthesizing the metal nanoparticles.
  • EP3156156 relates to a fine silver particle dispersion, which comprises fine silver particles, a short chain amine having 5 or less carbon atoms and a highly polar solvent, and a partition coefficient logP of the short chain amine is -1.0 to 1.4.
  • the method for producing the fine silver particles of EP3156156 comprises a first step for preparing a mixed liquid of a silver compound which is decomposed by reduction to produce a metal silver, and a short chain amine having a partition coefficient logP of -1.0 to 1.4, and a second step for reducing the silver compound in the mixed liquid to produce a fine silver particle where a short chain amine having 5 or less carbon atoms which is adhered to at least a part of the surface of the particle.
  • EP2559786 discloses a method comprising: a) providing a substrate; b) applying an aqueous catalyst solution to the substrate, the aqueous catalyst solution comprises nanoparticles of one or more metal chosen from silver, gold, platinum, palladium, iridium, copper, aluminum, cobalt, nickel and iron, and one or more stabilizing compounds chosen from gallic acid, gallic acid derivatives and salts thereof, the aqueous catalyst solution is free of tin; and c) electrolessly depositing metal onto the substrate using an electroless metal plating bath.
  • US9028724 discloses a method for preparing a dispersion of nanoparticles, comprising: dispersing nanoparticles having hydrophobic ligands on the surface in a hydrophobic solvent to form a first dispersion; mixing the first dispersion with a surface modification solution comprising (a) at least one wetting-dispersing agent selected from polydimethylsilane, alkylol ammonium salt of an acidic polyester and alkylol ammonium salt of a polyacrylic acid, (b) a surfactant, and (c) an aqueous-based solvent to form a first mixture solution; mixing the first mixture solution with a ligand removal agent to form a second mixture solution containing hydrophilic nanoparticles and separating the hydrophilic nanoparticles from the second mixture solution; and dispersing the hydrophilic nanoparticles in an aqueous-based solvent, wherein the nanoparticles comprise one of a metal and a metal oxide.
  • EP2667990B1 relates to a process comprising: forming an insoluble complex of a metal salt from a reaction mixture comprising a solvent, a first surfactant, a second surfactant, and a third surfactant, each surfactant being present in the insoluble complex of the metal salt, and reacting the insoluble complex of the metal salt with a reducing agent in the reaction mixture to form metal nanoparticles; wherein the first surfactant comprises a primary amine, the second surfactant comprises a secondary amine, and the third surfactant comprises a chelating agent comprising N,N'- dialkylethylenediamine.
  • EP1791702B9 relates to an ink for ink-jet printing or digital printing comprising a vehicle and metallic particles having a weight average particle size of from 40 nm to 1 micrometres, preferably from 50 nm to 500 nm, wherein the loading of metallic nanoparticles in the ink is comprised between 2 percent by weight and 75 percent by weight, preferably from 2 percent to 40 percent by weight, and the viscosity of the ink is comprised between 10 and 40 cP.
  • WO09/056401 relates to a method for the synthesis, isolation and re-dispersion in organic matrixes of nano-shaped transition metal particles, selected from the group consisting of Zn, Ag, Cu, Au, Ta, Ni, Pd, Pt, Co, Rh, Ir, Fe, Ru, and Ti, comprising a) adding to an aqueous solution of the transition metal salt an acrylate or methacrylate monomer or oligomer, or a polyacrylate or polymethacrylate and a reducing agent; b1) treating the colloidal solution with a peroxide; or b2) exposing the colloidal solution to UV- or visible light; c) adding a water-soluble amine; and d) isolating the nano-shaped transition metal particles or re-disperse the nano-shaped transition metal particles together with a dispersing agent in a liquid acrylate or methacrylate monomer.
  • WO2010108837 relates to a method of manufacturing shaped transition metal particles in the form of nanoplatelets, which metal is selected from the group consisting of Cu, Ag, Au, Zn, Cd, Ti, Cr, Mn, Fe, Co, Ni, Ru, Rh, Pd, Os, Ir and Pt, which method comprises the steps of first a) adding a reducing agent to an aqueous mixture comprising a transition metal salt and a polymeric dispersant, and subsequently b) treating the obtained colloidal dispersion with a peroxide, wherein the aqueous mixture in step a) comprises the transition metal salt in a concentration of higher than 2 mmol per liter.
  • WO11064162 relates to security, or decorative element, comprising a substrate, which may contain indicia or other visible features in or on its surface, and on at least part of the said substrate surface, a coating comprising platelet shaped transition metal particles having a longest dimension of edge length of from 15 nm to 1000 nm, preferably from 15 nm to 600 nm and particularly from 20 nm to 500 nm, and a thickness of from 2 nm to 100 nm, preferably from 2 to 40 nm and particularly from 4 to 30 nm and a method for forming for forming an optically variable image (an optically variable device) on a substrate comprising the steps of: forming an optically variable image (OVI) on a discrete portion of the substrate; and depositing a coating composition comprising platelet shaped transition metal particles having a longest dimension of edge length of from 15 nm to 1000 nm, preferably from 15 nm to 600 nm and particularly from 20 nm to 500 nm,
  • WO2013/186167 discloses a method for forming a surface relief microstructure, especially an optically variable image (an optically variable device, OVD) on a substrate comprising the steps of: A) applying a curable composition to at least a portion of the substrate wherein the curable composition comprises a1) at least one ethylenically unsaturated resin, a monomer or a mixture thereof; a2) at least one photoinitiator; and a3) a metal pigment which is in the form of platelet shaped transition metal particles having a longest dimension of edge length of from 5 nm to 1000 nm, preferably from 7 nm to 600 nm and particularly from 10 nm to 500 nm, and a thickness of from 1 nm to 100 nm, preferably from 2 to 40 nm and particularly from 3 to 30 nm; B) contacting at least a portion of the curable composition with a surface relief microstructure, especially optically variable image forming means; C) curing the composition by using at least
  • WO2014/041121 and WO2014/187750 relates to a security elements, comprising a coating comprising platelet shaped transition metal particles having a longest dimension of edge length of from 15 nm to 1000 nm, preferably from 15 nm to 600 nm and particularly from 20 nm to 500 nm, and a thickness of from 2 nm to 100 nm, preferably from 2 to 40 nm and particularly from 4 to 30 nm.
  • WO2020/083794 relates to compositions, comprising silver nanoplatelets, wherein the mean diameter of the silver nanoplatelets, present in the composition, is in the range of 20 to 70 nm with standard deviation being less than 50% and the mean thickness of the silver nanoplatelets, present in the composition, is in the range of 5 to 30 nm with standard deviation being less than 50%, wherein the mean aspect ratio of the silver nanoplatelets is higher than 1.5, a process for its production, printing inks containing the compositions and their use in security products.
  • the highest wavelength absorption maximum of the population of all silver nanoplatelets in the composition being within the range of 450 to 550 nm.
  • a coating, comprising the composition shows a red, or magenta color in transmission and a greenish-metallic color in reflection.
  • WO2020/224982 relates to compositions, comprising silver nanoplatelets, wherein the number mean diameter of the silver nanoplatelets, present in the composition, is in the range of 50 to 150 nm with standard deviation being less than 60% and the number mean thickness of the silver nanoplatelets, present in the composition, is in the range of 5 to 30 nm with standard deviation being less than 50%, wherein the mean aspect ratio of the silver nanoplatelets is higher than 2.0 and the highest wavelength absorption maximum of the population of all silver nanoplatelets in the composition being within the range of 560 to 800 nm.
  • a coating comprising the composition, shows a blue color in transmission and a metallic yellow color in reflection.
  • Dithiocarbamate capped silver, or gold nanoparticles are, for example described in Y. Liu et al., Chem. Commun.2008, 2140-2142; A. Wei et al., J. AM. CHEM. SOC.127 (2005) 7328- 7329; P. D. Beer et al., The Royal Society of Chemistry, Dalton Trans., 2007, 1459–1472, V. M. Rotello et al., Adv. Mater.2008, 20, 4185–4188 and Y. Huang et al., Analyst, 2013, 138, 2420–2426.
  • silver nanoplatelets capped by dithiocarbamate anions of formula (XX) have excellent stability of optical properties upon storage or heat exposure and high colloidal stability.
  • Silver nanoplatelets surface-modified in this way can be formulated in screen, rotogravure and flexography printing inks, which upon printing exhibit blue color in transmission and metallic yellow color in reflection and show excellent shelf stability.
  • the present application relates to compositions, comprising silver nanoplatelets, wherein the silver nanoplatelets are capped by dithiocarbamate anions of formula (XX), wherein R 41 is a C 2 -C 4 alkyl group, which is substituted by one, or two hydroxy groups, and R 42 is a C 1 -C 4 alkyl group, or a C 2 -C 4 alkyl group, which is substituted by one, or two hydroxy groups.
  • the number mean diameter of the silver nanoplatelets, present in the composition is preferably in the range of 50 to 150 nm. The standard deviation being preferably less than 60%.
  • the number mean thickness of the silver nanoplatelets, present in the composition is preferably in the range of 5 to 30 nm.
  • the standard deviation being preferably less than 50%.
  • the number mean diameter and the number mean thickness are determined by transmission electron microscopy (TEM).
  • the mean aspect ratio of the silver nanoplatelets is preferably higher than 2.0.
  • the highest wavelength absorption maximum of the population of all silver nanoplatelets in the composition being within the range of 560 to 800 nm.
  • any type of silver nanoparticles can be capped by dithiocarbamate anions of formula (XX). It is preferred that the silver nanoparticles are anisotropic (non-spherical). Most preferred are silver nanoplatelets.
  • the silver nanoplatelets may be in the form of disks, regular hexagons, triangles, especially equilateral triangles, and truncated triangles, especially truncated equilateral triangles, or mixtures thereof. They are preferably in the form of disks, truncated triangles, hexagons, or mixtures thereof.
  • the term "silver nanoplatelets” is a term used in the art and as such is understood by the skilled person.
  • silver nanoplatelets are preferably any silver nanoplatelets having a number mean diameter in the range of 50 to 150 nm and a number mean thickness in the range of 5 to 30 nm. The mean aspect ratio being higher than 2.0.
  • a "surface modified silver nanoplatelet (nanoparticle)” is a silver nanoplatelet (nanoparticle) having attached to its surface one or more (surface) stabilizing agents. Accordingly, the present invention relates to surface modified silver nanoplatelets capped by dithiocarbamate anions of formula (XX) and optionally bearing further surface stabilizing agent(s) and further stabilizing agents described below on their surface.
  • the number mean diameter of the silver nanoplatelets is in the range of 50 to 150 nm, preferably 60 to 140 nm, more preferably 70 to 120 nm. The standard deviation being preferably less than 60%, more preferred less than 50%.
  • the diameter of a silver nanoplatelet is the longest dimension of said silver nanoplatelet and corresponds to the maximum dimension of said silver nanoplatelet when oriented parallel to the plane of a transmission electron microscopy (TEM) image.
  • TEM transmission electron microscopy
  • number mean diameter of the silver nanoplatelets refers to the mean diameter determined by transmission electron microscopy (TEM) using Fiji image analysis software (or Image analysis software: ParticleSizer (Thorsten Wagner (2016) ij-particlesizer: ParticleSizer 1.0.9.
  • Zenodo 10.5281/zenodo.820296
  • ImageJ version 1.53f51 based on the measurement of at least 300, especially at least 500 randomly selected silver nanoplatelets oriented parallel to the plane of a transmission electron microscopy image (TEM), wherein the diameter of a silver nanoplatelet is the maximum dimension (maximum Feret diameter) of said silver nanoplatelet oriented parallel to the plane of a transmission electron microscopy (TEM) image.
  • TEM analysis was conducted on a dispersion containing silver nanoplatelets in isopropanol using an EM 910 instrument from ZEISS (INST.109) in bright field mode at an e-beam acceleration voltage of 100kV.
  • the number mean thickness of the silver nanoplatelets is in the range of 5 to 30 nm, preferably 7 to 25 nm, more preferably 8 to 25 nm. The standard deviation being preferably less than 50%, more preferred less than 30%.
  • the thickness of a silver nanoplatelet is the shortest dimension of said nanoplatelet and corresponds to the maximum thickness of said silver nanoplatelet.
  • the term “number mean thickness of silver nanoplatelets” refers to the mean thickness determined by transmission electron microscopy (TEM) based on the measurement of at least 50, especially of at least 300 randomly selected silver nanoplatelets oriented perpendicular to the plane of the TEM image, wherein the thickness of the silver nanoplatelet is the maximum thickness of said silver nanoplatelet.
  • TEM analysis was conducted on a dispersion containing silver nanoplatelets in isopropanol using an EM 910 instrument from ZEISS (INST.109) in bright field mode at an e-beam acceleration voltage of 100kV.
  • the thickness of at least 300 randomly selected silver nanoplatelets may be determined from the cross-sectional TEM images by fitting ellipses to the cross-sectioned particles by the software (ParticleSizer).
  • the minor axis (the shortest diameter) of the fitted ellipse is taken as particle thickness.
  • the diameter is the longer side of the nanoplatelet (width).
  • the thickness is the shorter side of the nanoplatelet (height).
  • the mean aspect ratio (defined as the ratio of number mean diameter to number mean thickness) being larger than 2.0, preferably larger than 2.2 and more preferably larger than 2.5.
  • the aspect ratio of the nanoplatelets is the ratio of its longest dimension, such as, for example, its diameter to its shortest dimension, such as, for example, its thickness.
  • the aspect ratio of a disk is the ratio of its diameter to its thickness.
  • the number mean diameter of the silver nanoplatelets is in the range of 70 to 120 nm with standard deviation being preferably less than 50% and the number mean thickness of the silver nanoplatelets is in the range of 8 to 25 nm with standard deviation being preferably less than 30%.
  • the mean aspect ratio of the silver nanoplatelets is higher than 2.5.
  • the highest wavelength absorption maximum of the population of all silver nanoplatelets in the composition being within the range of 560 to 800 nm, preferably 580 to 800 nm, most preferably 600 to 800 nm (measured in water at ca.5*10-5 M (mol/l) concentration of silver).
  • the absorption maximum has a full width at half maximum (FWHM) value in the range of 50 to 500 nm, preferably 70 to 450 nm, more preferably 80 to 450 nm.
  • the molar extinction coefficient of silver nanoplatelets measured at the highest wavelength absorption maximum of the population of all silver nanoplatelets in the composition, is higher than 4000 L/(cm*molAg), especially higher than 5000 L/(cm*molAg), very especially higher than 6000 L/(cm*molAg).
  • the silver nanoplatelets are capped by dithiocarbamate anions of formula (XX), wherein R 41 is a C 2 -C 4 alkyl group, which is substituted by one, or two hydroxy groups, and R 42 is a C 1 -C 4 alkyl group, or a C 2 -C 4 alkyl group, which is substituted by one, or two hydroxy groups.
  • R 42 is a C 1 -C 4 alkyl group and R 41 is a C 2 -C 4 alkyl group, which is substituted by two hydroxy groups.
  • R 41 is a C 2 -C 4 alkyl group, which is substituted by one hydroxy group and R 42 is a C 2 -C 4 alkyl group, which is substituted by one hydroxy group.
  • R 41 and R 42 are independently of each other selected from the group consisting of: –CH 2 CH 2 OH, –CH 2 CH(OH)CH 3 , – CH 2 CH 2 CH 2 OH, –CH(CH 3 )(CH 2 OH), –CH 2 CH(OH)CH 2 CH 3 , –CH 2 CH 2 CH(OH)CH 3 – CH 2 CH 2 CH 2 OH, –CH(CH 3 )CH(OH)CH 3 , –CH(CH 2 OH)CH 2 CH 3 , –CH(CH 3 )CH 2 CH 2 OH, – CH 2 CH(CH 2 OH)CH 3 , –CH 2 C(CH 3 )(OH)CH 3 , –CH 2 CH(CH 3 )CH 2 (OH), –CH 2 C(OH)(CH 3 ) 2 , – CH 2 C(CH 3 )(CH 2 OH), more preferably selected from the group consisting of: –CH 2 CH 2 OH,– CH 2 CH 2 CH 2
  • C 1 -C 4 alkyl may be linear and branched and is typically methyl, ethyl, n-propyl, isopropyl, n-butyl, sec.-butyl, isobutyl, or tert.-butyl.
  • C 2 -C 4 alkyl group, which is substituted by one, or two hydroxy groups, may be linear and branched and is typically ethyl, n-propyl, isopropyl, n-butyl, sec.-butyl, isobutyl, or tert.-butyl, wherein one, or two hydrogen atoms are replaced by hydroxy groups.
  • Examples are a - CH 2 CH(OH)CH 2 OH group, a –CH(CH 2 OH)2 group, a -CH 2 CH 2 OH group, a -CH 2 CH(OH)CH 3 group and a -CH 2 CH 2 CH 2 OH group.
  • R 41 and R 42 may be different, but are preferably the same and represent especially a - CH 2 CH 2 OH group, a -CH 2 CH(OH)CH 3 group, or a -CH 2 CH 2 CH 2 OH group; very especially a -CH 2 CH 2 OH group.
  • Examples of preferred dithiocarbamate anions of formula (XX) are and (E-3). The dithiocarbamate anion (E-1) is most preferred.
  • the dithiocarbamate capped silver nanoplatelets may be prepared i) by reacting CS 2 with an amine of formula R 41 R 42 NH in the presence of a composition of silver nanoplatelets; or ii) by reacting CS 2 with an amine of formula R 41 R 42 NH in the presence of a composition of silver nanoplatelets and subsequent treatment with a base; or iii) by reacting CS 2 with an amine of formula R 41 R 42 NH in the presence of a composition of silver nanoplatelets and a base; or iv) by reacting CS2 with an amine of formula R 41 R 42 NH in the presence of a base to obtain a compound of formula (XXI), which is then reacted with a composition of silver nanoplatelets; wherein R 41 and R 42 are defined above, or below, Cat k+ is a cation and k is 1, or 2.
  • the base is preferably selected from alkali or alkaline earth metal hydroxides, alkali or alkaline earth metal alkoxides, amines and quaternary ammonium hydroxides and mixtures thereof.
  • the base is preferably selected from alkali or alkaline earth metal hydroxides, alkali or alkaline earth metal alkoxides and mixtures thereof.
  • the obtained dispersions may comprise small amounts of xanthate salts.
  • the base is selected from alkali metal hydroxides, such as, for example, NaOH, KOH and CsOH, alkali metal alkoxides, such as, for example, NaOCH 2 CH 3 , KOCH 2 CH 3 and CsOCH 2 CH 3 , amines of formula R 43 R 44 R 45 N, especially (HOCH 2 CH 2 )2NH and (HOCH 2 CH 2 )3N, and mixtures thereof.
  • alkali metal hydroxides such as, for example, NaOH, KOH and CsOH
  • alkali metal alkoxides such as, for example, NaOCH 2 CH 3 , KOCH 2 CH 3 and CsOCH 2 CH 3
  • amines of formula R 43 R 44 R 45 N especially (HOCH 2 CH 2 )2NH and (HOCH 2 CH 2 )3N, and mixtures thereof.
  • R 41 and R 42 as in case of formula (XX) and Cat k+ is selected from H + , alkali metal cations, alkaline earth metal cations and R 43 R 44 R 45 NH + , such as, for example, (HOCH 2 CH 2 )2NH 2 + and (HOCH 2 CH 2 )3NH + , and mixtures thereof and is preferably selected from alkali metal cations, (HOCH 2 CH 2 )2NH 2 + , (HOCH 2 CH 2 )3NH + and mixtures thereof.
  • Cat k+ is more preferably selected from alkali metal cations and (HOCH 2 CH 2 )2NH 2 + and mixtures thereof, most preferred from Cs + , K + , Rb + , Na + and (HOCH 2 CH 2 )2NH 2 + and mixtures thereof.
  • R 43 is a C 2 -C 4 alkyl group, which is substituted by one, or two hydroxy groups
  • R 44 is a C1- C4alkyl group, or a C 2 -C 4 alkyl group, which is substituted by one, or two hydroxy groups
  • R 45 is H, a C 1 -C 4 alkyl group, or a C 2 -C 4 alkyl group, which is substituted by one, or two hydroxy groups.
  • R 43 is a C 2 -C 4 alkyl group, which is substituted by one hydroxy group
  • R 44 is a C 2 -C 4 alkyl group, which is substituted by one hydroxy group
  • R 45 is H, or or a C 2 -C 4 alkyl group, which is substituted by one hydroxy group.
  • R 43 and R 44 may be different, but are preferably the same and represent especially a - CH 2 CH 2 OH group, a -CH 2 CH(OH)CH 3 group, or a -CH 2 CH 2 CH 2 OH group; very especially a -CH 2 CH 2 OH group.
  • R 45 is preferably a hydrogen atom, a -CH 2 CH 2 OH group, a - CH 2 CH(OH)CH 3 group, or a -CH 2 CH 2 CH 2 OH group; more preferably a hydrogen atom, or a -CH 2 CH 2 OH group and most preferred a hydrogen atom.
  • the dithiocarbamate capped silver nanoplatelets are prepared i) by reacting CS2 with diethanolamine in the presence of a composition of silver nanoplatelets, ii) by reacting CS2 with diethanolamine in the presence of a composition of silver nanoplatelets and subsequent treatment with a base; or iii) by reacting CS2 with diethanolamine in the presence of a composition of silver nanoplatelets and a base; wherein the base is selected from alkali metal hydroxides, alkali metal alcoholates and amines of formula R 43 R 44 R 45 N and mixtures thereof, wherein R 43 is a C 2 -C 4 alkyl group, which is substituted by one hydroxy group, R 44 is a C 2 -C 4 alkyl group, which is substituted by one hydroxy group, and R 45 is H, or a C 2 -C 4 alkyl group, which is substituted by one hydroxy group, especially H; iv) by reacting CS2 with diethanolamine in
  • compositions comprising silver nanoplatelets, wherein the silver nanoplatelets are capped by a compound of formula (XXI), wherein R 41 is a C 2 -C 4 alkyl group, which is substituted by one, or two hydroxy groups, and R 42 is a C 1 -C 4 alkyl group, or a C 2 -C 4 alkyl group, which is substituted by one, or two hydroxy groups; Cat k+ is a cation and k is 1, or 2.
  • R 42 is a C 1 -C 4 alkyl group and R 41 is a C 2 -C 4 alkyl group, which is substituted by two hydroxy groups.
  • R 41 is a C 2 -C 4 alkyl group, which is substituted by one hydroxy group and R 42 is a C 2 -C 4 alkyl group, which is substituted by one hydroxy group.
  • R 41 and R 42 may be different, but are preferably the same and represent especially a - CH 2 CH 2 OH group, a -CH 2 CH(OH)CH 3 group, or a -CH 2 CH 2 CH 2 OH group; very especially a -CH 2 CH 2 OH group.
  • Cat k+ is selected from H + , alkali metal cations, alkaline earth metal cations and R 43 R 44 R 45 NH + , such as, for example, (HOCH 2 CH 2 )2NH 2 + and (HOCH 2 CH 2 )3NH + , and mixtures thereof and is preferably selected from alkali metal cations, (HOCH 2 CH 2 )2NH 2 + , (HOCH 2 CH 2 )3NH + and mixtures thereof.
  • Cat k+ is more preferably selected from alkali metal cations and (HOCH 2 CH 2 )2NH 2 + and mixtures thereof, most preferred from Cs + , K + , Rb + , Na + and (HOCH 2 CH 2 )2NH 2 + and mixtures thereof.
  • dithiocarbamate salts of general formula (XXI) include, but are not limited to, sodium bis(2-hydroxyethyl)dithiocarbamate, potassium bis(2-hydroxyethyl)dithiocarbamate, cesium bis(2-hydroxyethyl)dithiocarbamate, sodium bis(3-hydroxypropyl)dithiocarbamate, bis(3-hydroxypropyl)dithiocarbamate, cesium bis(3-hydroxypropyl)dithiocarbamate, sodium bis(4-hydroxybutyl)dithiocarbamate, bis(4-hydroxybutyl)dithiocarbamate, and cesium bis(4- hydroxybutyl)dithiocarbamate.
  • the surface stabilizing agent of general formula (XXI) may be present in an amount from about 0.4% to about 5%, preferably from about 0.5% to about 3.5% of the weight percent (wt-%) of the silver nanoplatelets.
  • Examples of compounds of formula (XXI) are listed below: (21a), which may be obtained by reacting CS 2 with diethanolamine in the presence of potassium C 1 -C 8 alcoholate, especially potassium ethanolate, or potassium hydroxide; (21b), which may be obtained by reacting CS2 with diethanolamine in the presence of cesium C1-C8alcoholate, especially cesium ethanolate, or cesium hydroxide; (21c), which may be obtained by reacting CS 2 with diethanolamine in the presence of sodium C 1 -C 8 alcoholate, especially sodium ethanolate, or sodium hydroxide; and (21d), which is obtained by reacting CS2 with diethanolamine.
  • reaction sequences iv) it is preferred that the compound of formula (XXI) is reacted with the silver nanoplatelets immediately after preparation.
  • the in-situ synthesis of the dithiocarbamate anions in the presence of the silver nanoplatelets, i.e. reaction sequences i), ii) and iii) are more preferred.
  • the composition may comprise one, or more surface stabilizing agent(s).
  • the silver nanoplatelets bear a surface stabilizing agent of formula (I) on their surface, wherein indicates the bond to the silver, R 1 is H, C 1 -C 18 alkyl, phenyl, C 1 -C 8 alkylphenyl, or CH 2 COOH; R 2 , R 3 , R 4 , R 5 , R 6 and R 7 are independently of each other H, C 1 -C 8 alkyl, or phenyl; Y is O, or NR 8 ; R 8 is H, or C 1 -C 8 alkyl; k1 is an integer in the range of from 1 to 500, k2 and k3 are independently of each other 0, or integers in the range of from 1 to 250; k4 is 0, or 1, k5 is an integer in the range of from 1 to 5.
  • R 1 is H, C 1 -C 18 alkyl, phenyl, C 1 -C 8 alkylphenyl, or CH 2 COOH;
  • the surface stabilizing agent of formula (I) has preferably a number average molecular weight of from 1000 to 20000, and more preferably from 1000 to 10000, most preferred from 1000 to 6000. All molecular weights specified in this text have the unit of [g/mol] and refer, unless indicated otherwise, to the number average molecular weight (Mn). If the compounds comprise, for example, ethylene oxide units (EO) and propylene oxide units (PO), the order of (EO) and (PO) may be fixed (block copolymers), or may not be fixed (random copolymers).
  • EO ethylene oxide units
  • PO propylene oxide units
  • R 1 is H, or C 1 -C 18 alkyl
  • R 2 , R 3 , R 4 , R 5 , R 6 and R 7 are independently of each other H, CH 3 , or C 2 H 5
  • k1 is 22 to 450
  • k2 and k3 are independently of each other 0, or integers in the range of from 1 to 250
  • k4 is 0, or 1
  • k5 is an integer in the range of from 1 to 5.
  • R 1 is H, or C 1 -C 4 alkyl
  • R 2 , R 3 , R 4 , R 5 , R 6 and R 7 are independently of each other H, or CH 3
  • k1 is 22 to 450
  • k2 and k3 are independently of each other 0, or integers in the range of from 1 to 100
  • k4 is 0
  • k5 is an integer in the range of from 1 to 4.
  • the most preferred surface stabilizing agent has the formula k1 (Ia), wherein R 1 is H, or a C1-C8alkyl group, and k1 is 22 to 450, especially 22 to 150.
  • R 1 is preferably H, or CH 3 .
  • the preferred surface stabilizing agents are derived from MPEG thiols (poly(ethylene glycol) methyl ether thiols) having an average Mn of 2000 to 6000, such as, for example, MPEG 2000 thiol (A-1, average Mn 2,000), MPEG 3000 thiol (A-2), MPEG 4000 thiol (A-3) MPEG 5000 thiol (A-4), MPEG 6000 thiol (A-5), PEG thiols (O-(2-mercaptoethyl)-poly(ethylene glycol)) having an average Mn of 2000 to 6000, such as, for example, PEG 2000 thiol (A-6, average Mn 2,000), PEG 3000 thiol (A-7), PEG 4000 thiol (A-8), PEG 5000 thiol (A-9), PEG 6000 thiol (A-10).
  • MPEG thiols poly(ethylene glycol) methyl ether thiols
  • the silver nanoplatelets bear a surface stabilizing agent which is a polymer, or copolymer described in WO200674969, which can be obtained by a process comprising the steps i1) polymerizing in a first step one or more ethylenically unsaturated monomers in the presence of at least one nitroxylether having the structural element , wherein X represents a group having at least one carbon atom and is such that the free radical X• derived from X is capable of initiating polymerization; or i2) polymerizing in a first step one or more ethylenically unsaturated monomers in the presence of at least one stable free nitroxyl radical and a free radical initiator; wherein at least one monomer used in the steps i1) or i2) is a C 1 -C 6 alkyl or hydroxy C 1 -C 6 alkyl ester of acrylic or methacrylic acid; and optionally ii) a second step, comprising the steps i1) polymerizing
  • the second step ii) is preferably a transesterification reaction.
  • the alcohol is preferably an ethoxylate of formula RA-[O-CH 2 -CH 2 -]n1-OH (A), wherein RA is saturated or unsaturated, linear or branched chain alkyl with 1–22 carbon atoms, or alkylaryl or dialkylaryl with up to 24 carbon atoms and n1 is 1 to 150.
  • step i1) or i2) is carried out twice and a block copolymer is obtained wherein in the first or second radical polymerization step the monomer or monomer mixture contains 50 to 100% by weight, based on total monomers, of a C 1 -C 6 alkyl ester of acrylic or methacrylic acid and in the second or first radical polymerization step respectively, the ethylenically unsaturated monomer or monomer mixture contains at least a monomer without primary or secondary ester bond.
  • the monomer or monomer mixture contains from 50 to 100% by weight based on total monomers of a C 1 -C 6 alkyl ester of acrylic or methacrylic acid (first monomer) and in the second polymerization step the ethylenically unsaturated monomer or monomer mixture comprises 4-vinyl-pyridine or pyridinium-ion, 2-vinyl-pyridine or pyridinium-ion, vinyl-imidazole or imidazolinium-ion, 3-dimethylaminoethylacrylamide, 3- dimethylaminoethylmethacrylamide, or corresponding ammonium ion, 3- dimethylaminopropylacrylamide, or corresponding ammonium ion, or 3- dimethylaminopropylmethacrylamide, or corresponding ammonium ion (second monomer).
  • the nitroxylether is preferably a compound of formula (O1).
  • the surface stabilization agent is preferably a copolymer which can be obtained by a process comprising the steps i1) polymerizing in a first step a first monomer, which is a C 1 -C 6 alkyl or hydroxy C 1 -C 6 alkyl ester of acrylic or methacrylic acid, and a second monomer which is selected from selected from 4-vinyl-pyridine or pyridinium-ion, 2-vinyl-pyridine or pyridinium-ion, 1-vinyl-imidazole or imidazolinium-ion, 3-dimethylaminoethylacrylamide, 3-dimethylaminoethylmethacrylamide 3- dimethylaminopropylacrylamide, and 3-dimethylaminopropylmethacrylamide; in the presence of at least one nitroxylether having the structural element ; and ii) a second step, comprising the modification
  • Copolymers represented by formula (III) are more preferred, where R 11 and R 12 are H or methyl, m, n and p are independently of each other integers from 1 to 200, o is an integer from 1 to 150, especially an integer from 1 to 149.
  • the order of monomers with indices m and n may be fixed (block copolymers) or not fixed (random copolymers).
  • Examples of preferred copolymers are the copolymers described in Example A3 (D-1), Example A6 (D-2) of WO200674969.
  • the composition may comprise further stabilizing agents.
  • Stabilizing agents may include, for example, phosphines; phosphine oxides; alkyl phosphonic acids; oligoamines, such as ethylenediamine, diethylene triamine, triethylene tetramine, spermidine, spermine; compounds of formula (IIa), (IIb), (IIc) and (IId) described below; surfactants; dendrimers, and salts and combinations thereof.
  • Surfactants include, for example, anionic surfactants, cationic surfactants, nonionic surfactants, amphoteric or zwitterionic surfactants.
  • Anionic surfactants include, for example, alkyl sulfates (eg., dodecylsulfate), alkylamide sulfates, fatty alcohol sulfates, secondary alkyl sulfates, paraffin sulfonates, alkyl ether sulfates, alkylpolyglycol ether sulfates, fatty alcohol ether sulfates, alkylbenzenesulfonates, alkylphenol ether sulfates, alkyl phosphates; alkyl or alkylaryl monoesters, diesters, and triesters of phosphoric acid; alkyl ether phosphates, alkoxylated fatty alcohol esters of phosphoric acid, alkylpolyglycol ether phosphates (for example, polyoxyethylene octadecenyl ether phosphates marketed as LUBRHOPHOS(R) LB-400 by Rhodia), phosphonic
  • Cationic surfactants include, for example, aliphatic, cycloaliphatic or aromatic primary, secondary and tertiary ammonium salts or alkanolammonium salts; quaternary ammonium salts, such as tetraoctylammonium halides and cetyltrimethylammonium halides (eg., cetyltrimethylammonium bromide (CTAB)); pyridinium salts, oxazolium salts, thiazolium salts, salts of amine oxides, sulfonium salts, quinolinium salts, isoquinolinium salts, tropylium salts.
  • CTLAB cetyltrimethylammonium bromide
  • cationic surfactants suitable for use according to the present disclosure include cationic ethoxylated fatty amines.
  • cationic ethoxylated fatty amines include, but are not limited to, ethoxylated oleyl amine (marketed as RHODAMEEN® PN-430 by Solvay), hydrogenated tallow amine ethoxylate, and tallow amine ethoxylate.
  • Nonionic surfactants include, for example, alcohol alkoxylates (for example, ethoxylated propoxylated C8-C10 alcohols marketed as ANTAROX® BL-225 and ethoxylated propoxylated C10-C16 alcohols marketed as ANTAROX(R) RA-40 by Rhodia), fatty alcohol polyglycol ethers, fatty acid alkoxylates, fatty acid polyglycol esters, glyceride monoalkoxylates, alkanolamides, fatty acid alkylolamides, alkoxylated alkanol-amides, fatty acid alkylolamido alkoxylates, imidazolines, ethylene oxide-propylene oxide block copolymers (for example, EO/PO block copolymer marketed as ANTAROX® L-64 by Rhodia), alkylphenol alkoxylates (for example, ethoxylated nonylphenol marketed as IGEPAL® CO
  • nonionic surfactants include addition products of ethylene oxide, propylene oxide, styrene oxide, and/or butylene oxide onto compounds having an acidic hydrogen atom, such as, for example, fatty alcohols, alkylphenols or alcohols.
  • Examples are addition products of ethylene oxide and/or propylene oxide onto linear or branched fatty alcohols having from 1 to 35 carbon atoms, onto fatty acids having from 6 to 30 carbon atoms and onto alkylphenols having from 4 to 35 carbon atoms in the alkyl group; (C6-C30)-fatty acid monoesters and diesters of addition products of ethylene oxide and/or propylene oxide onto glycerol; glycerol monoesters and diesters and sorbitan monoesters, diesters and triesters of saturated and unsaturated fatty acids having from 6 to 22 carbon atoms and their ethylene oxide and/or propylene oxide addition products, and the corresponding polyglycerol-based compounds; and alkyl monoglycosides and oligoglycosides having from 8 to 22 carbon atoms in the alkyl radical and their ethoxylated or propoxylated analogues.
  • Amphoteric or zwitterionic surfactants include, but are not limited to, aliphatic quaternary ammonium, phosphonium, and sulfonium compounds, wherein the aliphatic radicals can be straight chain or branched, and wherein the aliphatic substituents contains about 6 to about 30 carbon atoms and at least one aliphatic substituent contains an anionic functional group, such as carboxy, sulfonate, sulfate, phosphate, phosphonate, and salts and mixtures thereof.
  • zwitterionic surfactants include, but are not limited to, alkyl betaines, alkyl amidopropyl betaines, alkyl sulphobetaines, alkyl glycinates, alkyl carboxyglycinates; alkyl amphopropionates, such as cocoamphopropionate and caprylamphodipropionate (marketed as MIRANOL® JBS by Rhodia); alkyl amidopropyl hydroxysultaines, acyl taurates, and acyl glutamates, wherein the alkyl and acyl groups have from 6 to 18 carbon atoms, and salts and mixtures thereof.
  • the stabilizing agent may be a compound of formula R 20 —X (IIa), wherein R 20 is a linear or branched C 1 -C 25 alkyl group, or C 1 -C 25 alkenyl group, which may be substituted by one, or more groups selected from -OH, -SH, -NH 2 , or —COOR 19 , wherein R 19 is a hydrogen atom, or a C 1 -C 25 alkyl group, and X is -OH, -SH, -NH 2 , or —COOR 19’ , wherein R 19’ is a hydrogen atom, a C 1 -C 25 alkyl group, or a C2-C25alkenyl group, which may be substituted by one, or more groups selected from -OH, -SH, -NH 2 , or —COOR 19’’ , wherein R 19’’ is a hydrogen atom, or a C 1 -C 25 alkyl group.
  • Examples of compounds of formula (IIa) are 1-methylamine, 1-dodecylamine, 1- hexadecylamine, citric acid, oleic acid, D-cysteine, 1-dodecanethiol, 9-mercapto-1-nonanol, 1-thioglycerol, 11-amino-1-undecanethiol, cysteamine, 3-mercaptopropanoic acid, 8- mercaptooctanoic acid and 1,2-ethanedithiol.
  • the stabilizing agent may be a compound of formula (IIb), wherein R 21a is a hydrogen atom, a halogen atom, a C 1 -C 8 alkoxy group, or a C 1 -C 8 alkyl group, R 21b is a hydrogen atom, or a group of formula -CHR 24 -N(R 22 )(R 23 ), R 22 and R 23 are independently of each other a C 1 -C 8 alkyl, a hydroxyC 1 -C 8 alkyl group, or a group of formula -[(CH 2 CH 2 )-O] n1 -CH 2 CH 2 -OH, wherein n1 is 1 to 5, R 24 is H or C 1 -C 8 alkyl.
  • the stabilizing agent is a “polyhydric phenol”, which is a compound, containing an optionally substituted benzene ring and at least 2 hydroxy groups attached to it.
  • polyhydric phenol comprises polyphenols, such as, for example, tannic acid and polycyclic aromatic hydrocarbons which consist of fused benzene rings, wherein at least one benzene ring has at least 2 hydroxy groups attached to it, such as, for example, 1,2-dihydroxynaphthalene.
  • the “polyhydric phenol” may be substituted.
  • Polyhydric phenols are preferred, which have two hydroxy groups in ortho-position.
  • the polyhydric phenol is a compound of formula (IIca’), wherein R 26 is a hydrogen atom, a C 1 -C 18 alkyl group, or a C 1 -C 18 alkoxy group, especially a C1-C8alkoxy group, such as, for example, (methyl gallate, C-1), (ethyl gallate, C-2), (propyl gallate, C-3),
  • An unsubstituted or substituted amino group is, for example, a group of formula -NR 27 R 28 , wherein R 27 and R 28 are independently of each other a hydrogen atom, a C 1 -C 18 alkyl group, a phenyl group, preferably a hydrogen atom, or a C 1 -C 18 alkyl group.
  • the stabilizing agent is selected from compounds of formula (IIb), (IIc), or mixtures thereof.
  • the silver nanoplatelets comprise one, or more surface stabilizing agents of formula (I) and one, or more surface stabilizing agents of formula (III).
  • the silver nanoplatelets may comprise one, or more stabilizing agents of formula (IIb).
  • a process for producing the composition according to the present invention, comprising the silver nanoplatelets comprises: (a) preparing a solution (a) comprising a silver precursor, a compound of formula (I’), wherein R 1 is H, C 1 -C 18 alkyl, phenyl, C 1 -C 8 alkylphenyl, or CH 2 COOH; R 2 , R 3 , R 4 , R 5 , R 6 and R 7 are independently of each other H, C1-C8alkyl, or phenyl; Y is O, or NR 8 ; R 8 is H, or C1-C8alkyl; k1 is an integer in the range of from 1 to 500, k2 and k3 are independently of each other 0, or integers in the range of from 1 to 250; k4 is 0, or 1, k5 is an integer in the range of from 1 to 5; and a polymer, or copolymer which can be obtained by a process comprising the steps i1) polymerizing in a first step
  • the silver precursor is preferably a silver(I) compound, selected from the group consisting of AgNO3; AgClO4; Ag2SO4; AgCl, AgF, AgOH; Ag2O; AgBF4; AgIO3; AgPF6; R 200 CO2Ag, R 200 SO3Ag, wherein R 200 is unsubstituted or substituted C 1 -C 18 alkyl, unsubstituted or substituted C5-C8cycloalkyl, unsubstituted or substituted C7-C18aralkyl, unsubstituted or substituted C6-C18aryl or unsubstituted or substituted C2-C18heteroaryl; Ag salts of dicarboxylic, tricarboxylic, polycarboxylic acids, polysulfonic acids, P-containing acids and mixtures thereof.
  • a silver(I) compound selected from the group consisting of AgNO3; AgClO4; Ag2SO4; AgCl, AgF, Ag
  • the silver precursor is selected from the group consisting of silver nitrate, silver acetate, silver perchlorate, silver methanesulfonate, silver benzenesulfonate, silver toluenesulfonate silver trifluoromethanesulfonate, silver sulfate, silver fluoride and mixtures thereof.
  • Silver nitrate is most preferred.
  • the reducing agent is selected from the group consisting of alkali, or alkaline earth metal borohydrides, such as sodium borohydride, alkali, or alkaline earth metal acyloxyborohydrides, such as sodium triacetoxyborohydride, alkali, or alkaline earth metal alkoxy- or aryloxyborohydrides, such as sodium trimethoxyborohydride, aryloxyboranes, such as catecholborane, and amine-borane complexes, such as diethylaniline borane, tert- butylamine borane, morpholine borane, dimethylamine borane, triethylamine borane, pyridine borane, ammonia borane and mixtures thereof.
  • alkali, or alkaline earth metal borohydrides such as sodium borohydride, alkali, or alkaline earth metal acyloxyborohydrides, such as sodium triacetoxyborohydride, alkali, or alkaline earth
  • the one or more complexing agents are selected from the group of chlor-containing compounds, which are capable to liberate chloride ions under reaction conditions, such as metal chlorides, alkyl or aryl ammonium chlorides, phosphonium chlorides; primary or secondary amines and corresponding ammonium salts, such as methyl amine or dimethylamine; ammonia and corresponding ammonium salts; and aminocarboxylic acids and their salts, such as ethylenediaminetetraacetic acid.
  • chlor-containing compounds which are capable to liberate chloride ions under reaction conditions, such as metal chlorides, alkyl or aryl ammonium chlorides, phosphonium chlorides; primary or secondary amines and corresponding ammonium salts, such as methyl amine or dimethylamine; ammonia and corresponding ammonium salts; and aminocarboxylic acids and their salts, such as ethylenediaminetetraacetic acid.
  • Nonlimiting examples of complexing agents include ammonia, methylamine, dimethylamine, ethylamine, ethylenediamine, diethylenetriamine, ethylene-diamine-tetraacetic acid (EDTA); ethylenediamine N,N′-disuccinic acid (EDDS); methyl glycine diacetic acid (MGDA); diethylene triamine penta acetic acid (DTPA); propylene diamine tetracetic acid (PDT A); glutamic acid N,N-diacetic acid (N,N-dicarboxymethyl glutamic acid tetrasodium salt (GLDA); nitrilotriacetic acid (NTA), and any salts thereof; N-hydroxyethylethylenediaminetri- acetic acid (HEDTA), triethylenetetraaminehexaacetic acid (TTHA), N- hydroxyethyliminodiacetic acid (HEIDA), dihydroxyethylglycine (DHEG), ethylenediaminete
  • the defoamer is a compound or composition, capable to suppress foam formation in the reaction mixture, such as, for example, commercially available TEGO® Foamex 1488, 1495, 3062, 7447, 800, 8030, 805, 8050, 810, 815N, 822, 825, 830, 835, 840, 842, 843, 845, 855, 860, 883, K 3, K 7, K 8, N, Antifoam SE-15 from Sigma, Struktol SB-2080 and the like.
  • the amount of the defoamer is in the range of from 0.00001 % to 5% by weight based on total weight of reaction mixture prior to hydrogen peroxide addition, preferably from 0.0001 % to 3% and more preferably from 0.001 % to 2 % by weight.
  • the defoamer can be added to any of the solutions (a) and (b).
  • the reaction of silver nanoplatelets formation is carried out at a total silver concentration of >1% w/w after combining the first solution with the second solution.
  • the reaction of silver nanoplatelets formation is carried out by gradually adding the silver precursor solution into reducing agent solution, whereas the temperature of both solutions is in the range of -3 to 40°C and the gradual addition is completed within 15 minutes to 24 h time.
  • the silver nanoplatelets can be isolated by known methods such as decantation, filtration, (ultra)centrifugation, reversible or irreversible agglomeration, phase transfer with organic solvent and combinations thereof.
  • the silver nanoplatelets may be obtained after isolation as a wet paste or dispersion in water.
  • the silver nanoplatelets content in the final preparation of said particles may be up to about 99% by weight, based on the total weight of the preparation, preferably between 5 to 99% by weight, more preferably 5 to 90% by weight.
  • a preferred aspect of the present invention relates to a method which comprises further a step e), wherein the dithiocarbamate capped silver nanoplatelets are prepared i) by reacting CS2 with an amine of formula R 41 R 42 NH in the presence of a composition of silver nanoplatelets; or ii) by reacting CS2 with an amine of formula R 41 R 42 NH in the presence of a composition of silver nanoplatelets and subsequent treatment with a base; or iii) by reacting CS2 with an amine of formula R 41 R 42 NH in the presence of a composition of silver nanoplatelets and a base; or iv) by reacting CS2 with an amine of formula R 41 R 42 NH in the presence of a base to obtain a compound of formula (XXI), which is then reacted with a composition of silver nanoplatelets; wherein R 41 and R 42 are defined above, or below, Cat k+ is a cation and k is 1, or 2.
  • the base is preferably selected from alkali or alkaline earth metal hydroxides, alkali or alkaline earth metal alkoxides, amines and quaternary ammonium hydroxides and mixtures thereof.
  • the base is preferably selected from alkali or alkaline earth metal hydroxides, alkali or alkaline earth metal alkoxides and mixtures thereof.
  • bases are NaOH, KOH and CsOH, NaOCH 2 CH 3 , KOCH 2 CH 3 , CsOCH 2 CH 3 , and mixtures thereof.
  • the base is selected from alkali metal hydroxides, such as, for example, NaOH, KOH and CsOH, alkali metal alkoxides, such as, for example, NaOCH 2 CH 3 , KOCH 2 CH 3 and CsOCH 2 CH 3 , amines of formula R 43 R 44 R 45 N, especially (HOCH 2 CH 2 )2NH and (HOCH 2 CH 2 )3N, and mixtures thereof.
  • alkali metal hydroxides such as, for example, NaOH, KOH and CsOH
  • alkali metal alkoxides such as, for example, NaOCH 2 CH 3 , KOCH 2 CH 3 and CsOCH 2 CH 3
  • amines of formula R 43 R 44 R 45 N especially (HOCH 2 CH 2 )2NH and (HOCH 2 CH 2 )3N, and mixtures thereof.
  • R 41 and R 42 as in case of formula (XX) and Cat k+ is selected from alkali metal cations, alkaline earth metal cations and R 43 R 44 R 45 NH + , such as, for example, (HOCH 2 CH 2 )2NH 2 + and (HOCH 2 CH 2 )3NH + , and mixtures thereof and is preferably selected from alkali metal cations, alkaline earth metal cations and mixtures thereof.
  • Cat k+ is more preferably selected from alkali metal cations, most preferred from Cs + , Rb + , K + and Na + and mixtures thereof.
  • Examples of compounds of formula (XXI) are compound (21b), (21b) and (21c). Compounds (21a) and (21b) are more stable and are preferred. In reaction sequences iv) it is preferred that the compound of formula (XXI) is reacted with the silver nanoplatelets immediately after preparation The in-situ synthesis of the dithiocarbamate anions in the presence of the silver nanoplatelets, i.e. reaction sequences i), ii) and iii) are more preferred.
  • reaction sequence i) carbon disulfide or its solution in a solvent and an amine of formula R 41 R 42 NH or its solution in a solvent are successively added to an Ag nanoplatelets dispersion under inert gas atmosphere at 0-30°C.
  • the reaction mixture is stirred for 5 minutes to 24 h at 0-30°C.
  • reaction sequence ii) carbon disulfide or its solution in a solvent and an amine of formula R 41 R 42 NH or its solution in a solvent are successively added to an Ag nanoplatelets dispersion under inert gas atmosphere at 0-30°C.
  • reaction mixture is stirred for 5 minutes to 24 h at 0-30°C and then a solution of a base, such as, for example, cesium hydroxide, potassium ethoxide or diethanolamine, in a solvent is added and the reaction mixture is stirred for 5 min to 24 h at 0-30°.
  • a base such as, for example, cesium hydroxide, potassium ethoxide or diethanolamine
  • reaction sequence iii) carbon disulfide or its solution in a solvent and a mixture of amine of formula R 41 R 42 NH and a base, such as, for example, cesium hydroxide, potassium ethoxide or diethanolamine, or their solution in a solvent, are successively added to an Ag nanoplatelets dispersion under inert gas atmosphere at 0-30°C and the reaction mixture is stirred for 5 min to 24 h at 0-30°.
  • the amine of formula R 41 R 42 NH and the base may also be added separately in parallel.
  • suitable solvents are water, ethanol, isopropanol, ethyl-3-ethoxypropionate and 1-methoxy-2-propanol, or mixtures thereof.
  • a preferred aspect of the present invention relates to a method which comprises further a step f), wherein the dispersion of the silver nanoplatelets is concentrated and/or water is replaced at least partially with an organic solvent.
  • suitable organic solvents are ethanol, isopropanol, ethyl acetate, ethyl-3-ethoxypropionate and 1-methoxy-2-propanol, or mixtures thereof, optionally with water.
  • the present application is also directed to compositions, comprising silver nanoplatelets, which are obtained by above-described process.
  • the compositions of the present invention may be used in coatings, or printing inks, which are described for example, in WO2020/224982.
  • the 1 st European patent application of SICPA HOLDING SA describes UV-VIS radiation curable security inks, wherein said inks comprise: a) from about 7.5 wt-% to about 20 wt-% of silver nanoplatelets having a mean diameter in the range of 50 to 150 nm with a standard deviation of less than 60%, a mean thickness in the range of 5 to 30 nm with a standard deviation of less than 50%, and a mean aspect ratio higher than 2.0, wherein the mean diameter is determined by transmission electron microscopy and the mean thickness is determined by transmission electron microscopy, and wherein the silver nanoplatelets bear a surface stabilizing agent of general formula (XXI), wherein the residue R 41 is a C 2 -C 4 alkyl group substituted with a hydroxy group; the residue R 42 is selected from a C1-C4 alkyl group, and a C 2 -C 4 alkyl group substituted with a hydroxy group; and Cat k+ is a cation selected from the group consist
  • the combination of the ditiocarbamate capped silver nanoplatelets of the present invention and the specific ink vehicle described in the European patent application of SICPA HOLDING SA allows expedient migration of the silver nanoplatelets contained in an ink layer obtained by printing the security ink from the mass of the ink layer at the interface between the ink layer and air and at the interface between the ink layer and the substrate and alignment at said interfaces to form thin reflective layers, thereby producing independently of the thickness of the printed ink layer the metallic yellow color in reflection and the blue color in transmission.
  • the expedient development of the metallic yellow color in reflection and of the blue color in transmission cannot be achieved with the inks descried in the prior art.
  • the cationically curable binder or hybrid curable binder contained by the UV- Vis radiation curable security ink provides the dichroic security feature obtained from said ink with a high mechanical resistance.
  • the UV-Vis radiation curable ink described therein has outstanding shelf stability.
  • a UV-Vis radiation cationically curable security ink may comprise: a) from about 7.5 wt-% to about 20 wt-% of silver nanoplatelets having a mean diameter in the range of 50 to 150 nm with a standard deviation of less than 60%, a mean thickness in the range of 5 to 30 nm with a standard deviation of less than 50%, and a mean aspect ratio higher than 2.0, wherein the mean diameter is determined by transmission electron microscopy and the mean thickness is determined by transmission electron microscopy, and wherein the silver nanoplatelets bear a surface stabilizing agent of general formula (I) (XXI), wherein the residue R 41 is a C 2 -C 4 alkyl group substituted with a hydroxy group; the residue R 42 is selected from a C1-C4 alkyl group, and a C 2 -C 4 alkyl group substituted with a hydroxy group; and Cat k+ is a cation selected from the group consisting of Na + , K + , Rb + and C
  • a UV-Vis radiation hybrid curable security ink may comprise: a) from about 7.5 wt-% to about 20 wt-% of silver nanoplatelets having a mean diameter in the range of 50 to 150 nm with a standard deviation of less than 60%, a mean thickness in the range of 5 to 30 nm with a standard deviation of less than 50%, and a mean aspect ratio higher than 2.0, wherein the mean diameter is determined by transmission electron microscopy and the mean thickness is determined by transmission electron microscopy, and wherein the silver nanoplatelets bear a surface stabilizing agent of general formula (XXI), wherein the residue R 41 is a C 2 -C 4 alkyl group substituted with a hydroxy group; the residue R 42 is selected from a C1-C4 alkyl group, and a C 2 -C 4 alkyl group substituted with a hydroxy group; and Cat k+ is a cation selected from the group consisting of Na + , K + , Rb + and Cs + ; b
  • the 2 nd European patent application of SICPA HOLDING SA describes UV-VIS radiation curable security inks, wherein Cat + in formula (XXI) is an ammonium cation of general formula R C R D NH 2 + , wherein the residue R C is a C 2 -C 4 alkyl group substituted with a hydroxy group, and the residue R D is selected from a C 1 -C 4 alkyl group, or a C 2 -C 4 alkyl group substituted with a hydroxy group.
  • Further details of the security inks are described in the two European patent applications of SICPA HOLDING SA. The following examples are intended to illustrate various aspects and features of the present invention.
  • UV-Vis spectra of dispersions were recorded on Varian Cary 50 UV-Visible spectrophotometer at such concentration of dispersions as to achieve the optical density of 0.3 to 1.5 at 1 cm optical path.
  • TEM analysis was conducted on dispersions containing silver nanoplatelets in isopropanol using an EM 910 instrument from ZEISS, INST.109, in bright field mode at an e-beam acceleration voltage of 100kV. At least 2 representative images with scale in different magnification (5.000x, 10.000X and 20.000X) were recorded in order to characterize the dominant particle morphology for each sample.
  • the “number mean diameter of the silver nanoplatelets” refers to the mean diameter determined by transmission electron microscopy (TEM) using Fiji image analysis software (or Image analysis software: ParticleSizer (Thorsten Wagner (2016) ij-particlesizer: ParticleSizer 1.0.9.
  • Zenodo 10.5281/zenodo.820296
  • ImageJ version 1.53f51 based on the measurement of at least 300, especially at least 500 randomly selected silver nanoplatelets oriented parallel to the plane of a transmission electron microscopy image (TEM), wherein the diameter of a silver nanoplatelet is the maximum dimension of said silver nanoplatelet (maximal Feret diameter) oriented parallel to the plane of a transmission electron microscopy (TEM) image (recorded at magnification 20.000X).
  • TEM transmission electron microscopy
  • the "number mean thickness of silver nanoplatelets” refers to the mean thickness determined by transmission electron microscopy (TEM) based on the measurement of at least 50, especially of at least 300 randomly selected silver nanoplatelets oriented perpendicular to the plane of the TEM image (recorded at magnification 25.000X), wherein the thickness of the silver nanoplatelet is the maximum thickness of said silver nanoplatelet.
  • TEM analysis was conducted on dispersions containing silver nanoplatelets in isopropanol using an EM 910 instrument from ZEISS, INST.109, in bright field mode at an e-beam acceleration voltage of 100kV. In detail, a part of the dispersion is transferred to a smooth foil.
  • the sample After drying the sample is embedded in Araldit®, which is cross-linked below 60°C. Ultrathin cross-sections of the embedded sample are prepared perpendicular to the foil surface.
  • the thickness of at least 300 randomly selected silver nanoplatelets may be determined from the cross-sectional TEM images (recorded at magnification 25.000X) by fitting ellipses to the cross-sectioned particles by the software (ParticleSizer). The minor axis (the shortest diameter) of the fitted ellipse is taken as particle thickness.
  • Synthesis Example 1 (see Example 1 of WO2020/224982) a) In a 1 L double-wall glass reactor, equipped with anchor-stirrer, 365 g of de-ionized water was cooled to +2°C.13.62 g of sodium borohydride was added, and the mixture was cooled to -1°C with stirring at 250 rounds per minute (RPM, Solution A).
  • reaction mixture was warmed up to +5°C within 15 minutes, and a solution of 862 mg of KCl in 10 g of deionized water was added in one portion, followed by addition of 9.6 g of ethylenediaminetetraacetic acid (EDTA) in 4 equal portions with 10 minutes time intervals. After addition of the last EDTA portion, the reaction mixture was stirred for 15 minutes at +5°C, then warmed up to 35°C over 30 minutes and stirred for 1 h at this temperature. Upon this time, hydrogen evolution is completed. 3.0 mL of 30% w/w solution of ammonia in water was added, followed by addition of 5.76 g of solid NaOH, and the mixture was stirred for 15 min at 35°C.
  • EDTA ethylenediaminetetraacetic acid
  • the dispersion was diluted to 400 g weight with de- ionized water and ultrafiltered to the end volume of ca.50 mL using a polyethersulfone (PES) membrane with 300 kDa cut-off value. The procedure was repeated in total 4 times to provide 60 g of Ag nanoplatelets dispersion in water. After ultrafiltration was completed, 0.17 g of compound (B-3) was added to the dispersion. Ag content 28.9% w/w; yield ca.89% based on total silver amount; Solids content (at 250°C) 33.5% w/w; Purity 86% w/w of silver based on solids content at 250°C.
  • PES polyethersulfone
  • Example 6 Preparation of Dispersion D6. In-situ synthesis of diethanolaminedithiocarbamate diethanolammonium salt.
  • the weight of the resulting dispersion was adjusted to 32.1 g by addition of 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate (corresponds to the calculated total solids content of 41.2% w/w).
  • 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate corresponds to the calculated total solids content of 41.2% w/w.
  • composition of the UV-Vis radiation curable screen printing inks E1 – E8
  • Ingredient Commercial name Amount [wt-%] E5 E6 E7 E8 7.4 6 36.8 36.8 20 31.1 16.2 16.2 7 16.8 16.8 4.5 9.1 2.5 5.9 5 11.5 11.5 11.5 3.1 3 25 25 31.3 31.3 n ic Cationic Cationic Hybrid Cationic 6 10.1 10.2 12.9 12.9 7 0 0 18.4 0 C1.
  • Preparation of security inks (E1 – E8) and dichroic security features thereof C1a.
  • Preparation of the security inks E1 – E8 Ingredients provided in Table 1b were independently mixed and dispersed at room temperature using a Dispermat CV-3 for 10 minutes at 2000 rpm so as to yield 50g of the inks E1 – E8. C1b.
  • Preparation of security features The UV-Vis radiation curable screen printing hybrid security inks E1 – E8 were independently applied on pieces of transparent polymer substrate (PET Hostaphan® RN, thickness 50 ⁇ m, supplied by Pütz GmbH + Co. Folien KG) using a 160 thread/cm screen (405 mesh). The printed pattern had a size of 5 cm x 5 cm.
  • the L*a*b* values of the printed security features were determined at 0° to the normal with an illumination angle of 22.5° on the side of the transparent polymer substrate that was printed.
  • the C* values (chroma, corresponding to a measure of the color intensity or color saturation) were calculated from a* and b* values according to the CIELAB (1976) color space, wherein: The C* values (reflection 22.5/0°) are displayed in Table 1c below.
  • Transmission measurements were carried out using a Datacolor 650 spectrophotometer (parameters: integration sphere, diffuse illumination (pulse xenon D65) and 8° viewing, analyzer SP2000 with dual 256 diode array for wavelength range of 360-700nm, transmission sampling aperture size of 22mm).
  • the C* values are displayed in Table 1c below.
  • a visual assessment was carried out observing each security feature with the naked eye in reflection with a diffuse source (such as the light coming through a window without direct sun, the observer facing the wall opposite to the window). The following colors have been observed: - Dark brown to brown colors with matte appearance and no metallic effect; - Gold color (i.e. metallic yellow color) with glossy appearance and metallic effect. The metallic effect appears for a chroma value C* in reflection 22.5/0° higher than about 20.
  • a visual assessment was also carried out observing each security feature with the naked eye in transmission.
  • the sample of ink E7 stored in the oven was cooled at room temperature for 6 hours, and subsequently applied on a piece of transparent polymer substrate (PET Hostaphan® RN, thickness 50 ⁇ m, supplied by Pütz GmbH + Co. Folien KG) using a 160 thread/cm screen (405 mesh).
  • the printed pattern had a size of 5 cm x 5 cm. 10 seconds after the printing step, the piece of printed substrate was cured at room temperature by two times exposure at a speed of 100 m/min to UV-Vis light under a dryer from IST Metz GmbH (two lamps: iron-doped mercury lamp 200 W/cm 2 + mercury lamp 200 W/cm 2 ), to generate a security feature.
  • the optical properties of the security feature obtained each month were independently assessed in reflection, and visually using the tests described at item C1c.
  • Table 1d summarizes the color in reflection and transmission and the C* values (reflection 22.5/0°) exhibited by the security features.
  • Table 1d Color properties of security features a) the security feature was manufactured with the freshly prepared ink E7 according to the present invention. As attested by the optical properties of security features shown in Table 1d, the ink E7 remains stable over an extended period of time at high temperature, which is an indication of outstanding shelf stability at room temperature.

Abstract

La présente invention concerne des compositions comprenant des nanoplaquettes d'argent coiffées par des anions dithiocarbamates de formule (XX), formule (XX). Des encres durcissables par rayonnement UV-Vis, contenant les nanoplaquettes d'argent, ne se dégradent pas et un revêtement, comprenant la composition, présente une couleur bleue en transmission et une couleur jaune métallique en réflexion.
PCT/EP2021/081122 2020-11-10 2021-11-09 Compositions comprenant des nanoplaquettes d'argent WO2022101207A1 (fr)

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CA3197947A CA3197947A1 (fr) 2020-11-10 2021-11-09 Compositions comprenant des nanoplaquettes d'argent
AU2021379955A AU2021379955A1 (en) 2020-11-10 2021-11-09 Compositions, comprising silver nanoplatelets
EP21811267.0A EP4244003A1 (fr) 2020-11-10 2021-11-09 Compositions comprenant des nanoplaquettes d'argent
CN202180058692.3A CN116547090A (zh) 2020-11-10 2021-11-09 包含银纳米片的组合物

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