Security ink and security article, such as a banknote, with a tri-luminescent effect

Abstract

A security ink contains at least a first fluorescent and phosphorescent pigment and a second fluorescent pigment, wherein the security ink if excited with a first wavelength emits radiation with a first emission spectrum, if excited with a second wavelength emits radiation with a second emission spectrum being different from the first emission spectrum, and after the excitation has been terminated emits radiation with a third emission spectrum being different from the first emission spectrum and being different from the second emission spectrum.

Claims

1-15. (canceled)

16. A security ink containing at least a first fluorescent and phosphorescent pigment and a second fluorescent pigment, wherein the security ink if excited with a first wavelength emits radiation with a first emission spectrum, if excited with a second wavelength emits radiation with a second emission spectrum being different from the first emission spectrum, and after the excitation has been terminated emits radiation with a third emission spectrum being different from the first emission spectrum and being different from the second emission spectrum.

17. The security ink in accordance with claim 16, wherein the first pigment has a first fluorescence excitation spectrum with at least one peak and a first phosphorescence excitation spectrum with at least one peak and the second pigment has a second fluorescence excitation spectrum with at least one peak, wherein the highest crest of all peaks of the first fluorescence excitation spectrum is at a different wavelength than the highest crest of all peaks of the second fluorescence excitation spectrum.

18. The security ink in accordance with claim 16, wherein one of the first fluorescence excitation spectrum and of the second fluorescence excitation spectrum has a high excitation at one or two of the wavelengths 254 nm, 312 nm and 365 nm and a low excitation at the remaining of these wavelengths, whereas the other of the first fluorescence excitation spectrum and of the second fluorescence excitation spectrum has a high excitation at at least one of the remaining of these wavelengths and a low excitation at the one or two of the wavelengths, at which the other excitation spectrum has a high excitation, wherein high excitation means that the emission obtained by excitation of the respective pigment at one or two of the wavelengths 254 nm, 312 nm and 365 nm is at least 15% higher than the emission obtained by excitation (which is therefore called the low excitation) of the same pigment at the remaining of these wavelengths.

19. The security ink in accordance with claim 16, wherein the first fluorescence emission spectrum, the second fluorescence emission spectrum and the first phosphorescence emission spectrum each have at least one peak having a crest in the visible light range so that the security ink if excited with a first wavelength emits radiation with a first color, if excited with a second wavelength emits radiation with a second color being different from the first color, and after the excitation has been terminated emits radiation with a third color being different from the first color and being different from the second color.

20. The security ink in accordance with claim 16, wherein the first pigment is selected from the group consisting of: AEAl.sub.2O.sub.4:Eu.sup.2+ (Dy.sup.3+, Ho.sup.3+, Nd.sup.3+), Zn(S,O):(Cu, Ag), AE.sub.4Al.sub.14O.sub.25:Eu.sup.2+:Dy.sup.3+, AE.sub.2MgSi.sub.2O.sub.7:Eu.sup.2+ (Dy.sup.3+, Ho.sup.3+, Nd.sup.3+) and AE.sub.2SiO.sub.4:Eu.sup.2+ (Dy.sup.3+, Ho.sup.3+, Nd.sup.3+), wherein AE is an alkaline earth metal ion selected from the group consisting of Ca, Ba and Sr.

21. The security ink in accordance with claim 20, wherein the first pigment is selected from the group consisting of: AEAl.sub.2O.sub.4:Eu.sup.2+ (Dy.sup.3+, Ho.sup.3+, Nd.sup.3+), Zn(S,O):Cu, Ag and AE.sub.4Al.sub.14O.sub.25:Eu.sup.2+, Dy.sup.3+.

22. The security ink in accordance with claim 16, wherein the second pigment is selected from the group consisting of: Ln.sub.2O.sub.3:Do, Ln.sub.2O.sub.2S:Do, LnBO.sub.3:Do, LnPO.sub.4:Do, LnVO.sub.4:Do, Ln.sub.3Al.sub.5O.sub.12:Do, Ln.sub.3Ga.sub.5O.sub.12:Do, Ln.sub.2SiO.sub.5:Do, Ln.sub.2Si.sub.2O.sub.7:Do, LnVO.sub.4:Do in each of which Ln being selected from Sc, Y, La, Gd and Lu and Do being selected from Pr, Sm, Eu, Tb, Tm and Cr, Ln.sub.2Me.sub.3O.sub.12:Do with Ln and Do being defined as above and with Me being selected from Mo and W, M.sub.2LnMe.sub.2O.sub.8:Do with Ln, Me and Do being defined as above and with M being selected from Li, Na, K, Rb and Cs, Y.sub.2O.sub.2S:Do with Do being defined as above, AE.sub.2SiO.sub.4:Eu, Mg.sub.2SiO.sub.4:Eu, ZnS:DP with DP being selected from Cu, Ag and Au, LnMgAl.sub.11O.sub.19:Eu with in being selected from La and Gd and LnMgAl.sub.11O.sub.19:Eu, Mn with Ln being selected from La and Gd.

23. The security ink in accordance with claim 22, wherein the second pigment is selected from the group consisting of Ln.sub.2O.sub.2S:Do, ZnS:DP, LnMgAl.sub.11O.sub.19:Eu, LnMgAl.sub.11O.sub.19:Eu, Mn, LnVO.sub.4:Do and Y.sub.2O.sub.2S:Do.

24. The security ink in accordance with claim 16, wherein the security ink is formulated as printing ink being selected from the group consisting of offset inks, intaglio inks, die embossing inks, flexographic inks and screen inks.

25. The security ink in accordance with claim 16, wherein security ink comprises: i) 5 to 50% by weight in sum of the first pigment, the second pigment and optional further pigment(s), ii) 10 to 40% by weight of one or more binders and iii) 20 to 60% by weight of one or more solvents, wherein the solvent is selected from the group of vegetable oils, mineral oils, wood oils and arbitrary combinations of two or more of the aforementioned solvents.

26. A security article, which comprises: i) a substrate, and ii) a security ink in accordance with any of the preceding claims, which is applied onto at least a part of at least one surface of the substrate or onto the uppermost layer of one or more layers of printing ink being arranged on the substrate.

27. The security article in accordance with claim 26, wherein the security ink is applied on a part of one surface of the substrate or on the uppermost layer of one or more layers of printing ink being arranged on the substrate in the form of a line, of a dot, of a raster or of a pattern.

28. The security article in accordance with claim 26, wherein between the substrate and the security ink one or more layers of printing ink are arranged, wherein at least one of the one or more layers of printing ink contains at least one pigment having an emission spectrum being identical or so similar to emission spectrum of one of the first pigment and second pigment contained in the security ink that the one of the first pigment and second pigment is hidden, when it is excited.

29. The security article in accordance with claim 26, wherein between the substrate and the security ink one or more layers of printing ink may be arranged, wherein at least one of the one or more layers of printing ink may contain at least one pigment with a bifluorescence effect, wherein this pigment emits at the first excitation wavelength radiation in the visible light range observable by a human being as a first color and emits at the second excitation wavelength radiation in the visible light range observable by a human being as a second color, wherein the first and second color are different to each other.

30. A method for evaluating the genuineness of a security document comprising a security article in accordance with claim 26 comprising the steps of: i) irradiating the security article with a first wavelength, wherein the first wavelength is able to excite the first pigment of the security ink, and determining, whether a fluorescence radiation is emitted from the security ink, and, if so, characterizing the fluorescence radiation, ii) terminating the irradiation with the first wavelength, iii) irradiating the security article with a second wavelength, wherein the second wavelength is able to excite the second pigment of the security ink, and determining, whether a fluorescence radiation is emitted from the security ink, and, if so, characterizing the fluorescence radiation, and iv) terminating the irradiation with the second wavelength, and v) determining, whether a phosphorescence radiation is emitted from the security ink, when the security article is neither irradiated with the first wavelength nor with the second wavelength, and, if so, characterizing the phosphorescence radiation.

Description

EXAMPLES

Example 1

Emission Measurements on Pigments and Ink Examples

[0151] Paper prints were prepared by various printing methods using corresponding security inks all containing a pigment mixture LP-H99V-04-00 from Leuchtstoffwerk Breitungen GmbH as used in the below examples 2 to 5, which is a pigment mixture containing a first inorganic pigment that shows a first fluorescence and a first phosphorescence spectrum selected from the group of first pigments mentioned above and a second inorganic pigment that shows a second fluorescence spectrum selected from the group of second pigments mentioned above.

[0152] The emission color at different excitation wavelengths was determined by taking emission spectra at excitation wavelengths of 312 nm and 365 nm, respectively, by a fluorescence spectrometer (FLS920 from Edinburgh Instruments). The parameter for the recordal of the emission spectra of the printing samples were: [0153] FLS920 with Front-Face-sample holder, mode: emission scan, [0154] excitation: Xe-lamp (double monochromator, grid 300 nm blazed); Aexc=312 and 365 nm, Iris 99 [0155] Excitation band width: 2 nm [0156] Filter: Excitation: UG11, Emission: GG420 [0157] Emission band width: 1 nm [0158] Emmission area: 400 to 900/1 nm [0159] Dwell-Time: 0.05 s [0160] Repeats: 1 [0161] Reference Correction: on [0162] Emission Correction: on

[0163] As shown in the below table 1, all paper prints showed the described effect of changing the emission color at two different excitation wavelengths. The emission colors are expressed by the x,y-coordinates of the CIE 1931 chromaticity diagram and verbally by name of the corresponding color range.

TABLE-US-00002 TABLE 1 Color change effect observed on paper prints occasionated by fluorescence at different excitation wavelengths and phosphorescence, expressed by coordinates of emission color in the CIE 1931 chromaticity diagram and its verbal description Fluorescence Fluorescence Phosphorescence Conc. of Excitation 312 nm Excitation 365 nm excitation stopped Print pigment CIE-x CIE-x CIE-x name mixture CIE-y Name CIE-y Name CIE-y Name Intaglio printing inks TRL 20 20 0.539 Reddish 0.353 Yellow 0.237 Yellowish 0.381 orange 0.426 green 0.563 green TRL 21 25 0.544 Reddish 0.362 Yellow 0.239 Yellowish 0.383 orange 0.437 green 0.564 green TRL 22 30 0.549 Reddish 0.367 Yellow 0.231 Yellowish 0.384 orange 0.444 green 0.568 green Offset printing inks TRL157 45 0.531 Reddish 0.337 whitish 0.237 Yellowish 0.367 orange 0.391 0.545 green TRL156 50 0.534 Reddish 0.346 whitish 0.237 Yellowish 0.372 orange 0.402 0.553 green TRL170 55 0.546 Reddish 0.350 whitish 0.237 Yellowish 0.368 orange 0.396 0.548 green Water-based screen printing inks TRL44 20 0.560 orange 0.395 Yellow 0.227 Yellowish 0.391 0.483 green 0.558 green Water-based screen printing inks with pearlescent pigments (Colorstream T10-04) TRL45 20 0.557 orange 0.395 Yellow 0.233 Yellowish 0.395 0.489 green 0.562 green Water-based screen printing inks with pearlescent pigments (Colorstream T10-03) TRL46 20 0.552 orange 0.392 Yellow 0.228 Yellowish 0.397 0.492 green 0.558 green Cationic screen printing inks TRL47 20 0.479 yellowish 0.355 Yellow 0.232 Yellowish 0.357 pink 0.427 green 0.557 green

Example 2

Offset Security Ink and Security Article Formed Therewith

[0164] A printing ink with the following composition has been prepared.

TABLE-US-00003 Content [% by Material Trade Name weight] Supplier Mixture of first LP-H99V-04-00 40 Leuchtstoffwerk and second Breitungen GmbH pigment Color pigment Ti-Pure TS-4657 5 The Chemours Company TT, LLC Filler Bentone ® 38 2 Elementis plc Alkyd resin Setalin V 454 E 8.5 Lawter, Inc. Vegetable oil Alberdingk 27.5 Alberdingk Boley linseed oil GmbH, refined Phenolic R 4189 13 Respol Resinas, modified S.A. rosin resin Wax Ceralene 1X 2 euroceras Sp. z o.o Hydrochinon sta- Mono-tert-butyl- 0.4 Eastman Chemical bilizer hydrochinon Company (MTBHQ) Oxidatively Borchers Dry 1.6 OMG Borchers GmbH drying agent 0246

Manufacturing Process

[0165] First, a varnish was prepared. Phenolic modified rosin resin and vegetable oil were heated until a homogeneous mixture was formed. After that, the varnish was mixed with the other ingredients listed in the table, except for the oxidatively drying agent. The resulting paste was ground by a laboratory three-roll mill. Finally, the oxidatively drying agent was added by mixing.

Test Methods

Proof Printing

[0166] The ink was applied by using a Prüfbau Printability Testing Instrument MZ II. Around 1.0 g/m.sup.2 of ink are applied on vellum paper free of whitening compounds (Papierfabrik Louisenthal GmbH; 90 g/m.sup.2 grammage).

Viscosity

[0167] The measurement was made using a Haake RheoStress 6000, supplied by Thermo Scientific with a cone-plate measuring geometry 20 mm/1°.

Measurement of Pigment Particle Size

[0168] The particle size was investigated using an optical microscope (ZEISS 47 30 11-9901). A small amount of the ink sample is applied on a glass plate as a very thin film. Colorless particles are investigated with polarized light to enhance the visible contrast between particles and medium. The assessment was made according to the measuring scale in the eyepiece.

Emission Measurements

[0169] The assessment of the emission maximum was measured with a spectrofluorophotometer RF-6000 from Shimadzu. The offset ink was applied as described above to obtain a grammage around 1.0 g/m.sup.2, the measurement range was 200-900 nm, the edge filters UV-340 (incident beam; excitation side) and Vis L-42 (outgoing beam; emission side) were used. The emission maxima stated were measured at the stated excitation wavelengths.

Test Results

[0170]

TABLE-US-00004 Tests Offset ink Viscosity @20° C. [Pa*s], @ 40 s.sup.−1 95 Pigment particle size, microscope [μm] 1-5 Emission maximum [nm], @ λ.sub.ex = 365 nm 575-650; 675-720

Example 3

UV-Curing Water-Based Screen Ink and Security Article Formed Therewith

[0171] A printing ink with the following composition has been prepared.

TABLE-US-00005 Content [% by Material Compound weight] Supplier Mixture of first and LP-H99V-04-00 20 Leuchtstoffwerk second pigment Breitungen GmbH Pearlescent pigment Colorstream 8 Merck KGaA T10-03 Urethane acrylate Lux 481 65.9 Alberdingk Boley dispersion GmbH Wetting additive Tego Dispers 655 0.3 Evonik Industries AG Substrate wetting Byk 333 1 BYK-Chemie GmbH additive Defoamer Agitan ® 150 0.3 Munzing Chemie GmbH Photoinitiator Omnirad 500 4.5 IGM Resins B.V.

Manufacturing Process

[0172] The urethane acrylate dispersion, wetting additive and defoamer were stirred (3000 rpm/min) with a dissolver (Erichsen 492-II) for 15 minutes. Then the mixture of first and second pigment and the pearlescent pigment were added in small portions and the mixture dissolvered (1000 rpm/min) until it was homogeneous. Finally, substrate wetting additive and photoinitiator were added and the mixture was dissolvered (1000 rpm/min) for another 20 minutes.

Test Methods for Screen Inks

Proof Printing

[0173] The ink formulation was applied by using a 12 μm K-bar with an Erichsen K Control Coater on vellum paper free of whitening compounds (Papierfabrik Louisenthal GmbH; 90 g/m.sup.2 grammage).

Emission Measurements

[0174] These measurements are performed as described above for example 2.

Viscosity

[0175] The measurement was made using a Haake RheoStress 6000, supplied by Thermo Scientific with a cone-plate measuring geometry 35 mm/1°.

Test Results

[0176]

TABLE-US-00006 Tests Screen ink, water-based Viscosity @20° C. [Pa*s], @ 4 s.sup.−1 4 Emission maximum [nm], @ λ.sub.ex = 365 nm 575-650; 675-720

Example 4

Cationically Radiation-Curing Screen Ink and Security Article Formed Therewith

[0177] A printing ink with the following composition has been prepared.

TABLE-US-00007 Content [% by Material Trade Name weight] Supplier Mixture of first and LP-H99V-04-00 20 Leuchtstoffwerk second pigment Breitungen GmbH Pearlescent pigment Colorstream T10-03 8 Merck KGaA Cycloaliphatic Cyracure UVR-6110 73.6 Dow Chemical epoxide resin Company Fumed silica Aerosil 200 2 Evonik Industries AG Defoamer Tego Airex 900 0.6 Evonik Industries AG Photosensitizer SpeedCure CPTX 0.3 Lambson Ltd Photoinitiator Omnicat 250 3.5 IGM Resins B.V.

Manufacturing Process

[0178] The Cycloaliphatic epoxide resin, fumed silica, defoamer and photosensitizer were dissolvered (3000 rpm/min) for 30 minutes and left to stand overnight. Then the mixture of first and second pigment and the pearlescent pigment were added in small portions and the resulting mixture dissolvered (1000 rpm/min) until it was homogeneous. Finally, the photoinitiator was added and the mixture again dissolverted (1000 rpm/min) for 30 minutes.

Test Methods for Screen Inks

Proof Printing

[0179] The ink formulation was applied by using a 12 μm K-bar with an Erichsen K Control Coater on vellum paper free of whitening compounds (Papierfabrik Louisenthal GmbH; 90 g/m.sup.2 grammage).

Emission Measurements

[0180] These measurements are performed as described above for example 2.

Viscosity

[0181] The measurement was made using a Haake RheoStress 6000, supplied by Thermo Scientific with a cone-plate measuring geometry 35 mm/1°.

Test Results

[0182]

TABLE-US-00008 Screen ink, Cationically Tests curing Viscosity @20° C. [Pa*s], @ 4 s.sup.−1 3 Emission maximum [nm], @ λ.sub.ex = 365 nm 575-650; 675-720

Example 5

Intaglio Ink and Security Article Formed Therewith

[0183] A printing ink with the following compositions has been prepared.

TABLE-US-00009 Ink Content [% by Material Trade Name weight] Supplier Mixture of LP-H99V-04-00  20% Leuchtstoffwerk first and Breitungen second GmbH pigment Color Ti-Pure TS-4657 2.5% The Chemours Pigment Company TT, LLC Filler Aerosil 200, 36.7%  Evonik Resource Omya EXH1 SP, Efficiency GmbH, Precarb 200, Omya AG, Claytone 40, Bassermann minerals Blanc Fixe N GmbH & Co. KG, BYK- Chemie GmbH, Solvay GmbH Alkyd resin Trionol ™ 9000 E 12.1%  Lawter, Inc. Vegetable Alberdingk linseed 10.2%  Alberdingk Boley oil oil refined, GmbH, Soybean oil refined Mercur Handel GmbH Phenolic Sylvaprint MP 6364 .sup. 6% Arizona Chemical modified Ltd. rosin resin Wax Licowax ® PE 190, 7.5% Clariant Plastics & Ceraflour 927 Coatings Ltd., BYK- Chemie GmbH Drier Borchers Dry 0246 0.7% OMG Borchers GmbH Diluent Shellsol D70, 4.3% Shell Global Solutions Alberdingk linseed International B.V., oil refined Alberdingk Boley GmbH

Manufacturing Process

[0184] First, a varnish was prepared. Phenolic modified rosin resins and vegetable oils were heated until a homogeneous mixture was formed. After that, the varnish was mixed with the other ingredients listed in the table, except for the oxidatively drying agents. The resulting paste was grounded by a lab three-roll mill. Finally, the oxidatively drying agents were added by mixing and the viscosity of the ink was adjusted by adding a diluent.

Test Methods

Proof Printing

[0185] The inks were applied by using a Prüfbau Printability Testing Instrument MZ II. Around 8.0 g/m.sup.2 of ink was applied on vellum paper free of whitening compounds (Papierfabrik Louisenthal GmbH; 90 g/m.sup.2 grammage). Further proof prints were produced on a Currency I-311-P Intaglio Proof Press from Komori Corporation and an Ormag-press Masterproof from De La Rue Giori.

Emission Measurement

[0186] These measurements are performed as described above for example 2.

Viscosity

[0187] The measurement was made using a Haake RheoStress 6000, supplied by Thermo Scientific with a cone-plate measuring geometry 20 mm/1°.

Measurement of Particle Size

[0188] A grindometer device was used to determine the particles size of the pigments in the inks. The inks were poured into the deep end of the groove and scraped towards the shallow end with a flat metal scraper. At the point where the depth of the groove equals the largest particles in the ink formulation, irregularities (for example pinholes in an ink sample) will become visible. The depth of the groove was marked off on a graduated scale next to it, so that the size of the largest particles in the ink formulations could be easily determined.

Test Results

[0189]

TABLE-US-00010 Tests Intaglio ink Viscosity @ 40° C. [Pa*s], 1000 s.sup.−1 15 Pigment particle size [μm] 6 Emission maximum [nm], @ λ.sub.ex = 365 nm 575-650; 675-720