Tamper-proof medium for thermal printing

Patent metadata

Field	Value
Publication number	US-11524514-B2
Application number	US-201816622342-A
Country	US
Kind code	B2
Filing date	Jun 12, 2018
Priority date	Jun 22, 2017
Publication date	Dec 13, 2022
Grant date	Dec 13, 2022

Abstract

The present invention relates to method of manufacturing a tamper-proof medium for thermal printing, wherein a liquid treatment composition comprising at least one acid is deposited on a substrate which comprises a thermochromic coating layer comprising at least one halochromic leuco dye.

First claim

The invention claimed is:

1. A method of manufacturing a tamper-proof medium for thermal printing, the method comprising the following steps:
a) providing a substrate, wherein the substrate comprises on at least one side a thermochromic coating layer comprising at least one halochromic leuco dye,
b) providing a liquid treatment composition comprising at least one acid, and
c) applying the liquid treatment composition onto at least one region of the thermochromic coating layer in form of a preselected pattern,
wherein the thermochromic coating layer further comprises a salifiable alkaline or alkaline earth compound and the salifiable alkaline or alkaline earth compound is at least partially converted into a corresponding acid salt when the liquid treatment composition is applied.

2. The method of claim 1 , wherein the substrate is selected from the group consisting of paper, cardboard, containerboard, plastic, cellophane, textile, wood, metal, glass, mica plate, and nitrocellulose.

3. The method of claim 1 , wherein the at least one halochromic leuco dye is colourless.

4. The method of claim 1 , wherein the at least one halochromic leuco dye is selected from the group consisting of arylmethane phthalide dyes, quinone dyes, triarylmethane dyes, triphenylmethane dyes, fluoran dyes, phenothiazine dyes, rhodamine lactam dyes, spiropyran dyes, and mixtures thereof.

5. The method of claim 1 , wherein the thermochromic coating layer comprises the at least one halochromic leuco dye in an amount from 1 to 60 wt.-%, based on the total weight of the thermochromic coating layer.

6. The method of claim 1 , wherein the thermochromic coating layer further comprises a colour developing agent.

7. The method of claim 1 , wherein the at least one acid is selected from the group consisting of hydrochloric acid, sulphuric acid, sulphurous acid, phosphoric acid, citric acid, oxalic acid, acetic acid, formic acid, sulphamic acid, tartaric acid, phytic acid, boric acid, succinic acid, suberic acid, benzoic acid, adipic acid, pimelic acid, azelaic acid, sebaic acid, isocitric acid, aconitic acid, propane-1,2,3-tricarboxylic acid, trimesic acid, glycolic acid, lactic acid, mandelic acid, acidic organosulfur compounds, acidic organophosphorus compounds, HSO 4 − , H 2 PO 4 − or HPO 4 2− , being at least partially neutralized by a corresponding cation selected from Li + , Na + , K + , Mg 2+ or Ca 2+ , and mixtures thereof.

8. The method of claim 1 , wherein the liquid treatment composition further comprises a dye, a solvent-soluble dye, a pigment, a fluorescent dye, a phosphorescent dye, an ultraviolet absorbing dye, a near infrared absorbing dye, a thermochromic dye, a halochromic dye, metal ions, transition metal ions, lanthanides, actinides, magnetic particles, quantum dots, or a mixture thereof.

9. The method of claim 1 , wherein the liquid treatment composition comprises the at least one acid in an amount from 0.1 to 100 wt.-%, based on the total weight of the liquid treatment composition.

10. The method of claim 1 , wherein the preselected pattern is a continuous layer, a pattern, a pattern of repetitive elements, a repetitive combination(s) of elements, a guilloche, a one-dimensional bar code, a two-dimensional bar code, a three-dimensional bar code, a QR-code, a dot matrix code, a security mark, a number, a letter, an alphanumeric symbol, a logo, an image, a shape, a signature, a design, or a combination thereof.

11. The method of claim 1 , wherein the liquid treatment composition is applied by spray coating, inkjet printing, offset printing, flexographic printing, screen printing, plotting, contact stamping, rotogravure printing, spin coating, slot coating, curtain coating, slide bed coating, film press, metered film press, blade coating, brush coating, stamping and/or a pencil.

12. A tamper-proof medium for thermal printing obtainable by a method according to claim 1 .

13. The tamper-proof medium of claim 12 , wherein the tamper-proof medium is a branded product, a security document, a non-secure document, a decorative product, a packaging, a container, a compact disc (CD), a digital video disc (DVD), a blue ray disc, a sticker, a label, a seal, a tag, a poster, a passport, a driving licence, a bank card, a credit card, a bond, a ticket, a postage stamp, tax stamp, a banknote, a certificate, a brand authentication tag, a business card, a greeting card, a voucher, a tax banderol, a point-of-sale receipt, a plot, a fax, a continuous recording sheet or reel, or a wall paper.

14. The tamper-proof medium for thermal printing according to claim 12 , wherein the tamper-proof medium for thermal printing is suitable for use in security applications, in overt security elements, in covert security elements, in brand protection, in deviation prevention, in microlettering, in micro imaging, in decorative applications, in artistic applications, in visual applications, in packaging applications, in printing applications, in monitoring applications, or in track and trace applications.

15. The method of claim 1 , wherein the substrate is selected from the group consisting of paper, cardboard, containerboard, and plastic.

16. The method of claim 1 , wherein the thermochromic coating layer comprises the at least one halochromic leuco dye in an amount from 20 to 40 wt.-%, based on the total weight of the thermochromic coating layer.

17. The method of claim 1 , wherein the thermochromic coating layer further comprises a colour developing agent in an amount from 1 to 80 wt.-%, based on the total weight of the thermochromic coating layer.

18. The method of claim 1 , wherein the thermochromic coating layer further comprises a colour developing agent in an amount from 40 to 60 wt.-%, based on the total weight of the thermochromic coating layer.

19. The method of claim 1 , wherein the at least one acid is phosphoric acid.

20. The method of claim 1 , wherein the liquid treatment composition comprises the at least one acid in an amount from 10 to 50 wt.-%, based on the total weight of the liquid treatment composition.

21. The method of claim 1 , wherein the thermochromic coating layer further comprises fillers, binders, or sensitizers.

22. The method of claim 1 , wherein the salifiable alkaline or alkaline earth compound comprises calcium carbonate and the at least one acid is sulphuric acid or phosphoric acid.

23. The method of claim 1 , wherein the thermochromic coating layer comprises calcium carbonate.

24. The method of claim 1 , wherein the thermochromic coating layer comprises calcium carbonate and the at least one acid is selected from the group consisting of citric acid, oxalic acid, tartaric acid, and phosphoric acid.

Assignees

• Omya Int Ag

Inventors

• Bollstrom Roger
• Botty Gilbert
• Hunziker Philipp

Classifications

• B41M3/142 Primary

  using chemical colour-formers or chemical reactions, e.g. leuco-dye/acid, photochromes · CPC title

• B41M5/323

  Organic colour formers, e.g. leuco dyes · CPC title

• B41M2205/04

  Direct thermal recording [DTR] · CPC title

• B41M5/3335

  Compounds containing phenolic or carboxylic acid groups or metal salts thereof · CPC title

• B41M1/30

  on organic plastics, horn or similar materials {(recording sheets having a coating to improve ink, dye or pigment receptivity B41M5/50; marking or recording on plastic by irradiation with electromagnetic beams, e.g. laser, B41M5/267)} · CPC title