PROCESS FOR MAKING ETCHED PATTERNS

Abstract

The present invention relates to a process for making an etched pattern comprising a step of depositing onto a printable metal surface droplets of an ink composition provided by a printing method, wherein the ink composition comprises a first ink vehicle being water, a second ink vehicle being an organic compound and an etchant being an acid or abase according to the Brnsted definition, characterized in that the ink composition has a pH in the range of from (0) to (4) or from (9) to (14). The invention further relates to substrates having a metal surface with an etched pattern, to the use of such substrates in various applications, to articles comprising the inventive substrate and to the use of the inventive process for the production of metal products.

Claims

1. A process for making an etched pattern, the process comprising the following steps: (a) providing a substrate having a printable metal surface; (b) providing an ink composition comprising (i) a first ink vehicle being water; (ii) a second ink vehicle being an organic compound; and (iii) an etchant being an acid or a base according to the Brnsted definition; (c) depositing onto the printable metal surface of the substrate provided in step (a) droplets of the ink composition provided in step (b) by a printing method; and (d) allowing the deposited ink composition to react with the printable metal surface to obtain a metal surface comprising an etched pattern; wherein the ink composition has a pH in the range of from 0 to 4 or from 9 to 14, wherein in step (c) the ink composition is deposited onto the printable metal surface in the form of a pattern, and wherein in step (d) the metal is reacted only partially so that the substrate comprises unreacted metal in vertical direction to the printable metal surface directly below the etched pattern.

2. The process of claim 1, wherein the metal is selected from Al, Ag, Cr, Cu, Fe, Ni, Sn, Ti, V, Zn and alloys of these metals.

3. The process of claim 1, wherein the organic compound is selected from organic solvents, alcohols, glycols, esters, ethers, polymeric ethers, monohydric alcohols, glycols, ethanol and mixtures thereof.

4. The process of claim 1, wherein the ink composition has a pH in the range of: (i) from 0.01 to 2.5; or (ii) from 10 to 14.

5. The process of claim 1, wherein the acid is selected from H.sub.3PO.sub.4, H.sub.2SO.sub.4, HCl and mixtures thereof.

6. The process of claim 1, wherein the base is selected from MOH, MNH.sub.2, NH.sub.3 and mixtures thereof and M is a metal selected from Li, Na, K and mixtures thereof.

7. The process of claim 1, wherein: (i) the acid has a pK.sub.a of 3.5 or less; and/or (ii) the base has a pK.sub.b of 5 or less.

8. The process of claim 1, wherein the second ink vehicle is present at a concentration of from 1 to 65 wt %, based on the total weight of the ink composition.

9. The process of claim 1, wherein the etchant is present at a concentration of from 0.1 to 85 wt % based on the total weight of the ink composition.

10. The process of claim 1, wherein: (i) the droplets of the ink composition deposited in step (c) have a drop size in the range of from 0.1 to 50 pl; and/or (ii) the droplets of the ink composition deposited in step (c) are deposited at a drop spacing in the range of from 1 to 1000 m.

11. The process of claim 1, wherein the substrate is a non-layered solid metal substrate, a metal foil or a metal plate.

12. The process of claim 1, wherein the pattern is a bar code, a two-dimensional bar code, a QR code, a security mark, a label, a number, a letter, an alphanumeric symbol, a logo, an image, a braille marking or any combination thereof.

13. The process of claim 1, wherein the printing method is selected from inkjet printing, electronic syringe dispensing, offset printing, flexographic printing, screen printing, plotting, contact stamping, rotogravure printing, and pad printing.

14. The process of claim 1, wherein the ink composition further comprises a pigment, a colorant, a fluorescent dye, a phosphorescent dye, an ultraviolet absorbing dye, a near infrared absorbing dye, a thermochromic dye, a halochromic dye, metal salts, magnetic particles or a mixture thereof.

15. The process of claim 1, wherein in step (d) the ink composition is allowed to react with the printable metal surface: (i) for at least 0.01 seconds; and/or (ii) for 60 seconds or less.

16. The process of claim 1, wherein the process further comprises a step (e) of heating the substrate and/or the surrounding atmosphere before and/or during and/or after step (c) and/or before and/or during and/or after step (d).

17. A substrate having a metal surface comprising an etched pattern obtainable by a process of claim 1.

18. The substrate according to claim 17, wherein etched pattern differs from the metal surface in surface roughness, gloss, light absorption, electromagnetic radiation reflection, fluorescence, phosphorescence, magnetic property, electric conductivity, thermal conductivity, whiteness and/or brightness.

19. The substrate of claim 17, wherein the substrate is suitable for use in tactile applications, in braille applications, in printing applications, in analytical applications, in diagnostic applications, in bioassays, in chemical applications, in electrical applications, in security devices, in overt or covert security elements, in brand protection, in micro lettering, in micro imaging, in decorative, artistic, or visual applications, or in packaging applications.

20. An article comprising a substrate of claim 17.

21. The article of claim 17, wherein the article is a print medium, a packaging, a data storage, a security document, a non-secure document, a decorative substrate, a drug, a tobacco product, a bottle, a garment, a container, a sporting good, a toy, a game, a mobile phone, a compact disc, a digital video disc, a blue ray disk, a machine, a tool, a vehicle part such as a car part, a sticker, a label, a tag, a poster, a passport, a driving licence, a bank card, a credit card, a bond, a ticket, a postage stamp, a tax stamp, a banknote, a certificate, a brand authentication tag, a business card, a greeting card, a braille document, a tactile document, or a wall paper.

22. The process of claim 1, wherein the etched pattern is on metal foils, metal bottles, metal cans, metal containers, metal packaging materials, metal device covers, metal mobile phone covers, metal toys, metal tools, metal decorative articles, metal art, metal vehicle parts, metal construction parts, metal labels or metal stickers.

Description

EXAMPLES

[0196] The scope and interest of the invention may be better understood on basis of the following examples which are intended to illustrate embodiments of the present invention.

(A) ANALYTICAL METHODS

[0197] All parameters defined throughout the present document and those mentioned in the following examples are based on the following measuring methods:

[0198] pH Values

[0199] Any pH value is measured at 25 C. using a Mettler-Toledo Seven Easy pH meter and a Mettler-Toledo InLab Expert Pro pH electrode. A three point calibration (according to the segment method) of the instrument is first made using commercially available buffer solutions having pH values of 4, 7 and 10 at 25 C. (from Aldrich). The reported pH values are the endpoint values detected by the instrument (signal differs by less than 0.1 mV from the average over the last 6 seconds).

[0200] pK.sub.a and pK.sub.b Values

[0201] Any pK.sub.a or pK.sub.b value specified herein refers to the values listed in textbooks, preferably Harris, D. C. Quantitative Chemical Analysis: 3.sup.rd Edition, 1991, W.H. Freeman & Co. (USA), ISBN 0-7167-2170-8. The skilled person will know that pK.sub.a and pK.sub.b values can be converted into each other.

[0202] Scanning Electron Microscope Micrographs (SEM)

[0203] The prepared samples were examined by a Sigma VP field emission scanning electron microscope (Carl Zeiss AG, Germany) and a variable pressure secondary electron detector (VPSE) and/or secondary electron detector (SE) with a chamber pressure of about 50 Pa.

[0204] Optical Microscope Pictures

[0205] The prepared samples were examined by a Leica MZ16A stereomicroscope (Leica Microsystems Ltd., Switzerland).

(B) EXAMPLES

[0206] The following examples are not to be construed to limit the scope of the claims in any manner whatsoever.

[0207] Materials and Methods

[0208] Ink Compositions [0209] L1: 50 wt % phosphoric acid, 24 wt % ethanol and 26 wt % water (wt % are based on the total weight of the ink composition) [0210] L2: 2 wt % sodium hydroxide, 21 wt % ethanol, 77 wt % water (wt % are based on the total weight of the ink composition)

[0211] Printing Method

[0212] Preselected patterns, e.g. in form of a logo, were created on metal substrates by applying either ink composition L1 or L2. The ink compositions were deposited onto the substrate by inkjet printing using a Dimatix Materials Printer (DMP) of Fujifilm Dimatix Inc., USA, with a cartridge-based inkjet print head having a drop volume of either 1 pL or 10 pL. The print direction was from left to right, one row (line) at a time. The ink compositions were applied onto the substrates with a drop volume of 10 pL and by using various drop spacings (30, 40, 50, 60, 80, 120 m).

[0213] Printing Trials

Example 1Acidic Print on Aluminium

[0214] A preselected pattern (Mozaiq) in form of a logo was applied onto the matt side of a kitchen aluminium foil substrate by printing ink composition L1 at a drop volume of 10 pL and a drop spacing of 80 m.

[0215] FIG. 1 and FIG. 2: Digital camera images of the printed Mozaiq logo were taken at a normal (FIG. 1) and at a grazing angle (FIG. 2), respectively. From the top, the printed area looks brighter/whiter than the matt side of the kitchen aluminium foil substrate while, at a grazing angle, it looks darker than the surrounding substrate. In both cases, the logo can be clearly distinguished from the remaining non-printed area.

[0216] FIG. 3 shows an optical microscope image of the Mozaiq logo with separated reaction areas of the individual ink droplets.

[0217] FIG. 4 shows a SEM micrograph of the Mozaiq logo. The visible cracks are formed when cutting the aluminium foil by scissors, which indicates that a layer of aluminium phosphate is formed as a result of the reaction (approx. 0.5 m thickness).

Example 2Alkaline Print on Aluminium

[0218] A preselected pattern in form of an array of squares was created on the glossy side of a kitchen aluminium foil substrate by printing ink composition L2 at a drop volume of 10 pL and a drop spacing of 30 m.

[0219] FIG. 5 shows a digital camera image of an array of squares taken at a normal viewing angle.

[0220] FIG. 6 shows a SEM micrograph of an individual drop formed as a result of a reaction between ink composition L2 and aluminium substrate.

Example 3Acidic Print on Copper

[0221] A preselected pattern in form of a square was created on a copper thin plate substrate. For this purpose, ink composition L1 was applied onto the substrate at a drop volume of 10 pL and a drop spacing of 50 m.

[0222] FIG. 7 shows a top view digital camera image of a square printed with ink composition L1 on a copper plate.

Example 4Alkaline Print on Copper

[0223] A preselected pattern in form of a square was created on a copper thin plate substrate. For this purpose, ink composition L2 was applied onto the substrate at a drop volume of 10 pL and a drop spacing of 30 m.

[0224] FIG. 8 shows a top view digital camera image of a square printed with ink composition L2 on a copper plate.

[0225] Further SEM Micrographs

[0226] SEM micrographs were taken to show that the metal is reacted only partially and that the substrate comprises unreacted metal in vertical direction to the printable metal surface directly below the etched pattern.

[0227] FIG. 9 is a SEM micrograph of the glossy side of kitchen aluminium foil printed with ink composition L2 as described in Example 2.

[0228] FIG. 10 is a SEM micrograph of a copper substrate printed with ink composition L1 as described in Example 3.