COMPOSITIONS, COMPRISING PLATELET-SHAPED TRANSITION METAL PARTICLES

Abstract

The present invention relates to compositions, comprising platelet-shaped transition metal particles, wherein the number mean diameter of the platelet-shaped transition metal particles, present in the composition, is in the range of 15 nm to 1000 nm and the number mean thickness of the platelet-shaped transition metal particles, present in the composition, is in the range of 2 to 40 nm, the transition metal is selected from silver, copper, gold and palladium and the platelet-shaped transition metal particles bear a surface modifying agent of formula A-(CHR.sup.9).sub.r—R.sup.10 (V), wherein if r is 1, A is a C.sub.1-C.sub.25alkyl group substituted with one, or more fluorine atoms; a C.sub.2-C.sub.25alkenyl substituted with one, or more fluorine atoms; a C.sub.2-C.sub.25alkynyl group substituted with one, or more fluorine atoms; a C.sub.3-C.sub.20cycloalkyl group substituted with one, or more fluorine atoms; or a C.sub.6-C.sub.24aryl group substituted with one, or more fluorine atoms, CF.sub.3 or —O—CF.sub.3 groups; if r is 0, A is a C.sub.6-C.sub.24aryl group substituted with one, or more fluorine atoms, CF.sub.3 or —O—CF.sub.3 groups; or a C.sub.7-C.sub.24aralkyl group substituted with one, or more fluorine atoms, CF.sub.3 or —O—CF.sub.3 groups;

R.sup.9 is H, or a C.sub.1-C.sub.4alkyl group; and R.sup.10 is a thiol group, or an amino group.

Surface modification with fluorinated thiols/amines allows to tune the surface properties of silver nanoplatelets in such a way, as to, on the one hand, make them dispersible and colloidally stable in the finished printing ink system, and on the other hand, allow them to migrate to the substrate and print surfaces upon drying of the solvent in the printed layer.

Claims

1.-14. (canceled)

15. A composition, comprising platelet-shaped transition metal particles, wherein the number mean diameter of the platelet-shaped transition metal particles, present in the composition, is in the range of from 15 nm to 1000 nm and the number mean thickness of the platelet-shaped transition metal particles, present in the composition, is in the range of from 2 to 40 nm, the transition metal is selected from silver, copper, gold and palladium, wherein if r is 1, A is a C.sub.1-C.sub.25alkyl group substituted with one, or more fluorine atoms; a C.sub.2-C.sub.25alkenyl substituted with one, or more fluorine atoms; a C.sub.2-C.sub.25alkynyl group substituted with one, or more fluorine atoms; a C.sub.3-C.sub.20cycloalkyl group substituted with one, or more fluorine atoms; or a C.sub.6-C.sub.24aryl group substituted with one, or more fluorine atoms, CF.sub.3 groups, or —O—CF.sub.3 groups; or a C.sub.7-C.sub.24aralkyl group substituted with one, or more fluorine atoms, CF.sub.3 groups, or —O—CF.sub.3 groups; if r is 0, A is a C.sub.6-C.sub.24 aryl group substituted with one, or more fluorine atoms, CF.sub.3 or —O—CF.sub.3 groups; R.sup.9 is H, or a C.sub.1-C.sub.4alkyl group; and R.sup.10 is a thiol group, or an amino group.

16. The composition according to claim 15, wherein the surface modifying agent of formula (V) is a surface modifying agent of formula A-CHR.sup.9—R.sup.10 (Va), wherein A is a C.sub.1-C.sub.8alkyl group substituted with one, or more fluorine atoms, especially a group F—(CF.sub.2).sub.s1—(CH.sub.2).sub.s2—CH.sub.2—SH, wherein s1 is 0, or an integer of 1 to 7, s2 is 0, or an integer of 1 to 7, and the sum of s1 and s2 is equal, or smaller than 7; or a surface modifying agent of formula A-R.sup.10 (Vb), wherein A is a phenyl group substituted with one, or more fluorine atoms, CF.sub.3 groups, or —O—CF.sub.3 groups, and R.sup.10 is a thiol group, or an amino group, especially a thiol group.

17. The composition according to claim 15, wherein the surface modifying agent is selected from 1H,1H,2H,2H-perfluoro-1-octanethiol, 1H,1H-perfluorooctylthiol, 1H,1H,2H,2H-perfluoro-1-hexanethiol, 3,3,4,4,4-pentafluoro-1-butanethiol, 4,4,4-trifluoro-1-butanethiol, 2,2,3,3,3-pentafluoropropane-1-thiol, 3,3,3-trifluoro-1-propanethiol and 2,2,2-trifluoroethanethiol and mixtures thereof, especially 2,2,2-trifluoroethanethiol, 3,3,3-trifluoro-1-propanethiol and 4,4,4-trifluoro-1-butanethiol and mixtures thereof.

18. The composition according to claim 15, wherein the transition metal particles are in the form of nanoplatelets and have a number mean diameter of from 20 to 600 nm and a number mean thickness of from 2 nm to 40 nm.

19. The composition according to claim 15, wherein the composition, comprises 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, especially 600 to 800; or the composition comprises silver nanoplatelets, wherein the number 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 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 1.5 and the highest wavelength absorption maximum of the population of all silver nanoplatelets in the composition being within the range of 450 to 550 nm.

20. The composition according to claim 15, wherein the silver nanoplatelets bear a surface stabilizing agent of formula ##STR00062## on their surface, wherein R.sup.1 is H, C.sub.1-C.sub.18alkyl, phenyl, C.sub.1-C.sub.8alkylphenyl, or CH.sub.2COOH; R.sup.2, R.sup.3, R.sup.4, R.sup.5, R.sup.6 and R.sup.7 are independently of each other H, C.sub.1-C.sub.8alkyl, or phenyl; Y is O, or NR.sup.8; R.sup.8 is H, or C.sub.1-C.sub.8alkyl; 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/or a surface stabilizing agent which is a polymer, or copolymer, which is 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 ##STR00063## 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 ##STR00064## and a free radical initiator; wherein at least one monomer used in the steps i1) or i2) is a C.sub.1-C.sub.6alkyl or hydroxyC.sub.1-C.sub.6alkyl ester of acrylic or methacrylic acid; and optionally ii) a second step, comprising the modification of the polymer or copolymer prepared under i1) or i2) by a transesterification reaction, an amidation, hydrolysis or anhydride modification or a combination thereof.

21. The composition according to claim 15, which comprises one, or more stabilizing agents selected from the group consisting of compounds of formula ##STR00065## wherein R.sup.21a is a hydrogen atom, a halogen atom, a C.sub.1-C.sub.8alkoxy group, or a C.sub.1-C.sub.8alkyl group, R.sup.21b is a hydrogen atom, or a group of formula —CR.sup.24—N(R.sup.22)(R.sup.23), R.sup.22 and R.sup.23 are independently of each other a C.sub.1-C.sub.8alkyl, a hydroxyC.sub.1-C.sub.8alkyl group, or a group of formula —[(CH.sub.2CH.sub.2)—O].sub.n1—CH.sub.2CH.sub.2—OH, wherein n1 is 1 to 5, R.sup.24 is H or C.sub.1-C.sub.8alkyl, and compounds of formula ##STR00066## wherein R.sup.5 can be the same, or different in each occurrence and is a hydrogen atom, a halogen atom, a C.sub.1-C.sub.18alkyl group, a C.sub.1-C.sub.18alkoxy group, or a group —C(═O)—R.sup.26 R.sup.26 is a hydrogen atom, a hydroxy group, a C.sub.1-C.sub.18alkyl group, unsubstituted or substituted amino group, unsubstituted or substituted phenyl group, or a C.sub.1-C.sub.18alkoxy group, and n3 is a number of 1 to 4, m3 is a number of 2 to 4, and the sum of m3 and n3 is 6.

22. A coating, or printing ink composition, comprising the composition according to claim 15.

23. The coating, or printing ink composition according to claim 22, which comprises (i) the composition, (ii) a binder, and (iii) optionally a solvent.

24. A security, or decorative element, comprising a substrate, optionally containing indicia or other visible features in or on its surface, and on at least part of the said substrate surface, a coating, comprising the composition according to claim 15.

25. The security, or decorative element according to claim 24, wherein the coating, comprising the composition, shows a turquoise, or blue color in transmission and a yellowish metallic color in reflection; or wherein the coating, comprising the composition, shows a red, or magenta color in transmission and a greenish metallic color in reflection.

26. The security, or decorative element according to claim 24, wherein the security element comprises a substrate, a coating on at least a portion of the substrate comprising at least one liquid crystal compound, the coating being applied on the reverse side of the substrate if the substrate is transparent or translucent or on the surface side if the substrate is transparent, translucent, reflective or opaque and a further coating on at least a portion of the coating containing the liquid crystal compound or direct on the substrate if the coating containing the liquid crystal compound is placed on the reverse side of the substrate, the further coating comprising the composition; or the security element consists of a mutlilayer structure capable of interference, wherein the multilayer structure capable of interference has a reflection layer, a dielectric layer, and a partially transparent layer, wherein the dielectric layer is arranged between the reflection layer and the partially transparent layer, wherein the reflection layer is formed by a colored layer, comprising the composition; or the security element comprises a transparent carrier substrate, a layer containing a diffractive optical element (DOE) and a semi-transparent functional layer, comprising the composition; or the security, or decorative element is a blister for tablets, comprising a transparent carrier substrate that includes a semi-transparent functional layer, comprising the composition; or the security, or decorative element is a packaging comprising a plastic film shaped part and a cover film, wherein said plastic film shaped part defines the front side of the packaging and the cover film defines the rear side of the packaging, and the cover film is based on a carrier substrate provided with a semi-transparent functional layer, comprising the composition.

27. A product, comprising the security or decorative element according to claim 24.

28. A method comprising including the security or decorative element according to claim 24 and preventing counterfeit or reproduction, on a document of value, right, identity, a security label or a branded good.

Description

EXAMPLES

[0480] 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.

[0481] TEM analysis of dispersions and coatings was performed on EM 910 instrument from ZEISS in bright field mode at an e-beam acceleration voltage of 100 kV. At least 2 representative images with scale in different magnification were recorded in order to characterize the dominant particle morphology for each sample.

[0482] The diameter of the particles was determined from TEM images as maximum dimension of nanoplatelets, oriented parallel to the plane of the image, using Fiji image analysis software, based on the measurement of at least 300 randomly selected particles.

[0483] The thickness of the particles was measured manually as the maximum thickness of nanoplatelets, oriented perpendicular to the plane of the image, from a TEM image, based on the measurement of at least 50 randomly selected particles.

Example 1

[0484] 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).

[0485] In a 0.5 L double-wall glass reactor, equipped with anchor-stirrer, 132 g of deionized water and 4.8 g of MPEG-5000-thiol were combined, and the mixture was stirred for 10 minutes at room temperature. 72 g of the product of Example A3 of WO2006074969 was added, and the resulting mixture was stirred for another 10 minutes at room temperature for homogenization. The solution of 30.6 g of silver nitrate in 30 g of de-ionized water was added in one portion and the mixture was stirred for 10 minutes, resulting in an orange-brown viscous solution. To this solution 96 g of deionized water was added, followed by addition of 3 g of Struktol SB2080 defoamer, pre-dispersed in 36 g of de-ionized water. The resulting mixture was cooled to 0° C. with stirring at 250 RPM (Solution B).

[0486] After that, Solution B was dosed with a peristaltic pump at a constant rate over 2 h into Solution A under the liquid surface via a cooled (0° C.) dosing tube, resulting in spherical silver nanoparticles dispersion. During pumping, the Solution A was stirred at 250 RPM.

[0487] After dosing was complete, the 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.

[0488] 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.

[0489] 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. Then 180 mL of 50% w/w hydrogen peroxide solution in water were dosed with a peristaltic pump at a constant rate over 4 h into the reaction mixture under the liquid surface with stirring at 250 RPM, while maintaining the temperature at 35° C. This has led to a deep blue colored dispersion of silver nanoplatelets, which was cooled to room temperature. 1.23 g of compound of formula

##STR00061##

was added, and the mixture was stirred for 1 h at room temperature.

[0490] b) Isolation and purification of Ag nanoplatelets

[0491] b1) Decantation

[0492] 9.6 g of sodium dodecylsulfate was added to the reaction mixture and then ca. 25 g of anhydrous sodium sulfate powder was added in portions with stirring until the transmission color of the dispersion changed from blue to pink. Then the mixture was kept without stirring at room temperature for 24 h, allowing the coagulated nanoplatelets to sediment at the bottom of the reactor.

[0493] 890 g of supernatant was pumped out from the reactor with a peristaltic pump, and 890 g of deionized water was added to the reactor. The mixture in reactor was stirred for 1 h at room temperature, allowing the coagulated particles to re-disperse.

[0494] b2) Decantation

[0495] Ca. 64 g of anhydrous sodium sulfate powder was added in portions with stirring until the transmission color of the dispersion changed from blue to yellowish-pink. Then the mixture was kept without stirring at room temperature for 12 h, allowing the coagulated nanoplatelets to sediment at the bottom of the reactor. 990 g of supernatant was pumped out from the reactor with a peristaltic pump, and 90 g of deionized water was added to the reactor. The resulting mixture was stirred for 30 minutes at room temperature, allowing the coagulated particles to re-disperse.

[0496] b3) Ultrafiltration in water

[0497] The resulting dispersion of Ag nanoplatelets was subjected to ultrafiltration using a Millipore Amicon 8400 stirred ultrafiltration cell. 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.

[0498] 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.

[0499] b4) Ultrafiltration in isopropanol

[0500] The dispersion was further ultrafiltered in isopropanol. 60 g of Ag nanoplatelets dispersion, obtained after ultrafiltration in water, was placed in a Millipore Amicon 8400 stirred ultrafiltration cell and diluted to 300 g weight with isopropanol. The dispersion was ultrafiltered to the volume of ca. 50 mL using a polyethersulfone (PES) membrane with 500 kDa cut-off value. The procedure was repeated in total 4 times to provide 72 g of Ag nanoplatelets dispersion in isopropanol.

[0501] Ag content 24.1% w/w; Solids content (at 250° C.) 25.7% w/w; Purity 93.5% w/w of silver based on solids content at 250° C.

[0502] The UV-Vis-NIR spectrum was recorded in water at Ag concentration of 9.8*10.sup.−5 M.

[0503] λ.sub.max=700 nm; extinction coefficient at maximum ε=10200 L/(cm*mol Ag), FWHM=340 nm.

[0504] Reference is made to FIG. 1. UV-Vis-NIR spectrum of Ag nanoplatelets from Example 1 b4). Number mean particle diameter 93±40 nm, number mean particle thickness 16±2.5 nm.

[0505] b5) Treatment of Ag nanoplatelets with 2,2,2-trifluoroethanethiol and solvent switch.

[0506] 95.3 g of the dispersion of Ag nanoplatelets in isopropanol, obtained in step b4) of Example 1, was placed in a 0.5 L round-bottom flask, equipped with a magnetic stirring bar, under N.sub.2 atmosphere, and 0.98 g of 2,2,2-trifluoroethanethiol was added in one portion with stirring. The mixture was stirred for 96 hours at room temperature. 100 g isopropanol and 37 g of ethyl 3-ethoxypropionate were added and isopropanol, along with the traces of unreacted 2,2,2-trifluoroethane thiol, was distilled off on rotary evaporator at 45° C. bath temperature. Pressure was slowly reduced to 20 mbar and distillation was continued until no more solvent was separating. Then 100 g of isopropanol was added and distillation was repeated under the same conditions, until no more solvent was separating. In the obtained dispersion, the solids content was adjusted to 40% w/w by addition of ethyl 3-ethoxypropionate.