# US 12,215,242 B2 · UV-VIS radiation curable security inks for producing dichroic security features

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- Number: US 12,215,242 B2
- Document ID: US12215242B2
- Status: Granted
- Kind: B2
- Application number: 18/252,452
- Filed: 2021-11-09
- Published: 2024-01-18
- Granted: 2025-02-04
- Earliest claimed: 2020-11-10
- Assignees: Sicpa Holding SA
- Applicants: Sicpa Holding SA
- Inventors: Hervé Pittet; Marlyse Demartin Maeder; Patrick Veya; Nikolay Grigorenko; Andre Oswald
- Web page: https://patentgrep.com/patent/US12215242B2

## CPC

- C09D 11/50: Sympathetic, colour changing or similar inks
- B41M 3/14: Security printing {(securities B42D25/29)}
- B42D 25/378: Special inks
- C09D 11/03: characterised by features other than the chemical nature of the binder
- C09D 11/033: characterised by the solvent
- C09D 11/037: characterised by the pigment
- C09D 11/101: Inks specially adapted for printing processes involving curing by wave energy or particle radiation, e.g. with UV-curing following the printing
- C09D 11/102: containing macromolecular compounds obtained by reactions other than those only involving unsaturated carbon-to-carbon bonds
- C09D 11/106: containing macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds
- C08K 7/00: Use of ingredients characterised by shape
- C08K 9/04: Ingredients treated with organic substances {(treated with macromolecular compounds C08K9/08)}
- C08K 2003/0806: {Silver}
- C08K 2201/003: Additives being defined by their diameter
- C08K 2201/011: Nanostructured additives
- 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 (cosmetics A61K; processes for applying liquids or other fluent materials to surfaces, in general, B05D; staining wood B27K5/02; glazes or vitreous enamels C03C; natural resins, French polish, drying-oils, driers, turpentine, per se, C09F; polishing compositions other than French polish, ski waxes C09G; adhesives or use of materials as adhesives C09J; materials for sealing or packing joints or covers C09K3/10; materials for stopping leaks C09K3/12; processes for the electrolytic or electrophoretic production of coatings C25D)
- B41M: PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING, (correction of typographical errors B41J; processes for applying transfer pictures or the like B44C1/16; fluid media for correction of typographical errors by coating C09D10/00; printing textiles D06P)
- 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
- C08K: Use of inorganic or non-macromolecular organic substances as compounding ingredients (paints, inks, varnishes, dyes, polishes, adhesives C09)

## Abstract

The present invention provides a UV-Vis radiation curable security ink for producing a security feature for securing value documents, wherein said security feature exhibits a blue color upon viewing in transmitted light and a metallic yellow color upon viewing in incident light. The UV-Vis radiation curable security ink comprises a cationically curable or a hybrid curable ink vehicle, and silver nanoplatelets bearing a surface stabilizing agent of general formula (I) wherein the residue RA is a C2-C4alkyl group substituted with a hydroxy group; the residue RB is selected from a C1-C4alkyl group, and a C2-C4alkyl group substituted with a hydroxy group; and Cat+ is an ammonium cation of general formula +NH2RCRD, wherein the residue RC is a C2-C4alkyl group substituted with a hydroxy group; and the residue RD is selected from a C1-C4alkyl group, and a C2-C4alkyl group substituted with a hydroxy group.

## Claims

### Claim 1

A UV-Vis radiation curable security ink for producing a security feature exhibiting a blue color upon viewing in transmitted light and a metallic yellow color upon viewing in incident light, wherein said ink comprises:
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)
wherein
the residue RA is a C2-C4alkyl group substituted with a hydroxy group;
the residue RB is selected from a C1-C4 alkyl group, and a C2-C4alkyl group substituted with a hydroxy group; and
Cat+ is an ammonium cation of general formula +NH2RCRD,
wherein the residue RC is a C2-C4alkyl group substituted with a hydroxy group; and
the residue RD is selected from a C1-C4alkyl group, and a C2-C4alkyl group substituted with a hydroxy group;
b) from about 45 wt-% to about 80 wt-% of either a cycloaliphatic epoxide, or a mixture of a cycloaliphatic epoxide and one or more UV-Vis radiation curable compounds;
c) one or more cationic photoinitiators;
d) a perfluoropolyether surfactant functionalized with one or more functional groups selected from the group consisting of: hydroxyl, acrylate, methacrylate, and trialkoxysilyl;
e) from about 3 wt-% to about 12 wt-% of a polyvinyl chloride copolymer containing at least 60 wt-% of vinyl chloride; and optionally
f) up to about 25 wt-% of an organic solvent;
the weight percents being based on the total weight of the UV-Vis radiation curable security ink.

### Claim 2 (depends on 1)

The UV-Vis radiation curable security ink according to claim 1, wherein the security ink is selected from a screen-printing security ink, a rotogravure security ink, and a flexography security ink.

### Claim 3 (depends on 1)

The UV-Vis radiation curable security ink according to claim 1, wherein the mean diameter of the silver nanoplatelets is in the range of 70 to 120 nm with the standard deviation being less than 50%, the mean thickness of the silver nanoplatelets is in the range of 8 to 25 nm with the standard deviation being less than 30%, and the mean aspect ratio of the silver nanoplatelets is higher than 2.5.

### Claim 4 (depends on 1)

The UV-Vis radiation curable security ink according to claim 1, wherein the surface stabilizing agent of general formula (I) is present in an amount from about 0.5% to about 5% of the weight percent (wt-%) of the silver nanoplatelets of a).

### Claim 5 (depends on 1)

The UV-Vis radiation curable security ink according to claim 1, wherein the residues RA and RB are independently of each other a C2-C4alkyl group substituted with a hydroxy group.

### Claim 6 (depends on 1)

The UV-Vis radiation curable security ink according to claim 1, wherein the silver nanoplatelets bear a further surface stabilizing agent of general formula (II)
wherein
indicates the bond to the silver;
R1 is H, C1-C18alkyl, phenyl, C1-C8alkylphenyl, or CH2COOH;
R2, R3, R4, R5, R6 and R7 are independently of each other H, C1-C8alkyl, or phenyl;
Y is O, or NR8;
R8 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; and
k5 is an integer in the range of from 1 to 5.

### Claim 7 (depends on 1)

The UV-Vis radiation curable security ink according to claim 1, wherein the silver nanoplatelets bear a further surface stabilizing agent of general formula (III)
wherein
R17a, R17b and R17c are independently of each other H, or methyl;
R18a and R18b are H, or methyl;
R19a is saturated or unsaturated, linear or branched chain alkyl with 1-22 carbon atoms;
R19b is Rc—[O—CH2—CH2—]c—O—;
R19c is
—C(═O)—NH—(CH2)yN+HR15R16An−;
wherein
An− is an anion of a monovalent organic, or inorganic acid;
y is an integer from 2 to 10;
R15 is saturated or unsaturated, linear or branched chain alkyl with 1-22 carbon atoms,
R16 is saturated or unsaturated, linear or branched chain alkyl with 1-22 carbon atoms,
Rc 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 c is 1 to 150, and
y1, y2 and y3 are independently of each other integers from 1 to 200.

### Claim 8 (depends on 1)

The UV-Vis radiation curable security ink according to claim 1, wherein the silver nanoplatelets bear a further surface stabilizing agent of general formula (IV)
wherein
R9 is a hydrogen atom, or a group of formula —CHR11—N(R12)(R13);
R10 is a hydrogen atom, a halogen atom, a C1-C8alkoxy group, or a C1-C8alkyl group;
R11 is H, or C1-C8alkyl; and
R12 and R13 are independently of each other a C1-C8alkyl, a C1-C8alkyl group substituted by a hydroxy group, or a group of formula —[(CH2CH2)—O]n1—CH2CH2—OH, wherein n1 is 1 to 5.

### Claim 9 (depends on 1)

The UV-Vis radiation curable security ink according to claim 1, wherein the one or more UV-Vis radiation curable compounds comprise one or more cationically curable monomers selected from the group consisting of: vinyl ethers, propenyl ethers, cyclic ethers other than a cycloaliphatic epoxide, lactones, cyclic thioethers, vinyl thioethers, propenyl thioethers, hydroxyl-containing compounds, and mixtures thereof.

### Claim 10 (depends on 1)

The UV-Vis radiation curable security ink according to claim 1, wherein the one or more UV-Vis radiation curable compounds comprise one or more radically curable monomers and/or oligomers, and the UV-Vis radiation curable ink further comprises g) one or more free radical photoinitiators.

### Claim 11 (depends on 1)

The UV-Vis radiation curable security ink according to claim 1, wherein the UV-Vis radiation curable security ink comprises an amount of perfluoropolyether surfactant from about 0.025 wt-% to about 5 wt-%, wherein the weight percents are based on the total weight of the UV-Vis radiation curable security ink.

### Claim 12 (depends on 1)

The UV-Vis radiation curable security ink according to claim 1, wherein the UV-Vis radiation curable security ink is solvent-free.

### Claim 13 (depends on 1)

A process for producing a security feature for securing a value document, wherein said security feature exhibits a blue color upon viewing in transmitted light and a metallic yellow color upon viewing in incident light, said process comprising the following steps:
A) printing the UV-Vis radiation curable security ink according to claim 1 on a transparent or partially transparent region of a substrate of a value document to provide an ink layer; and
B) UV-Vis curing the ink layer obtained at step A) to form the security feature.

### Claim 14 (depends on 13)

The process according to claim 13, wherein the value document is selected from the group consisting of banknotes, deeds, tickets, checks, vouchers, fiscal stamps, agreements, identity documents such as passports, identity cards, visas, driving licenses, bank cards, credit cards, transactions cards, access documents, and cards, entrance tickets, public transportation tickets, academic diploma, and academic titles.

### Claim 15 (depends on 13)

The process according to claim 13, wherein the printing is performed by screen printing, rotogravure, or flexography.