Method for producing a marking

Abstract

The present invention relates to a method for producing a marking in a coating on a substrate or on the surface of a molding, where the marking represents a negative marking within a luminescent surrounding field and is generated using a laser beam, to a marking produced with the aid of the method, and to the use thereof, in particular for the labeling of products.

Claims

1. A method for producing a marking on a surface of a moulding or a coating located on a substrate, each of which comprises luminescent particles, comprising bringing said surface or coating into contact with a laser beam, wherein the particles on area units of the surface or coating which are contacted by the laser beam are changed in such a way that their luminescence capability is destroyed, wherein the luminescent particles are included in a non-luminescent, inorganic matrix, which is in the form of pigments in the moulding or coating, and wherein the inorganic matrix comprises dielectric metal oxides and/or metal oxide hydrates.

2. The method according to claim 1, wherein the dielectric metal oxides are Al.sub.2O.sub.3, SiO.sub.2, silicon dioxide hydrate, aluminium oxide hydrate or mixtures of two or more thereof.

3. The method according to claim 1, wherein the inorganic matrix is in the form of a flake-form pigment.

4. The method according to claim 1, wherein the pigment comprises one or more luminescent particles having a primary particle size of 500 nm.

5. The method according to claim 4, wherein the pigment comprises luminescent particles which have a particle size of 1 m.

6. The method according to claim 1, wherein the luminescent particles are stimulated to luminescence in the UV wavelength region and emit visible light.

7. The method according to claim 1, wherein the luminescent particles consist of inorganic materials.

8. The method according to claim 6, wherein the luminescent particles consist of doped or undoped metal oxides, doped metal sulfides, metal selenides, metal oxysulfides of the lanthanides or fluorescent mixed oxides, or of mixtures of two or more thereof.

9. The method according to claim 1, wherein the moulding consists of polymeric material.

10. The method according to claim 1, wherein the substrate consists of a polymeric material, a cellulose-containing material, glass, ceramic or metal.

11. The method according to claim 1, wherein the coating comprises a binder.

12. The method according to claim 1, wherein the coating is applied to the substrate in the form of a printing ink and solidified.

13. A marking on the surface of a moulding or of a coating located on a substrate which has a non-luminescent structure within a luminescent area unit, produced by the method according to claim 1.

14. The marking according to claim 13, wherein the luminescent area unit is stimulated to luminescence under the action of electromagnetic radiation in the UV wavelength region and emits light in the visible wavelength region.

15. The marking according to claim 13, wherein the non-luminescent structure is an alphanumeric symbol or a sequence of alphanumeric symbols, a logo, a symbol, a pattern, a graphical element, a picture, a line structure, a bar code or a data matrix code.

16. A labelling of a product comprising a marking on the surface of a moulding or of a coating located on a substrate according to claim 13.

17. The labelling of a product according to claim 16, wherein the products are consumer goods, industrial goods, electronic articles, clothing, packaging materials or security products.

18. A method for producing a marking on a surface of a moulding or a coating located on a substrate, each of which comprises luminescent particles, comprising bringing said surface or coating into contact with a laser beam, wherein the particles on area units of the surface or coating which are contacted by the laser beam are changed in such a way that their luminescence capability is destroyed, wherein the luminescent particles are included in a non-luminescent, inorganic matrix, which is in the form of pigments in the moulding or coating, and wherein at least one of the following is satisfied: the inorganic matrix is in the form of a flake-form pigment, or the luminescent particles consist of inorganic materials, or the luminescent particles are stimulated to luminescence in the UV wavelength region and emit visible light, and said luminescent particles consist of doped or undoped metal oxides, doped metal sulfides, metal selenides, metal oxysulfides of the lanthanides or fluorescent mixed oxides, or of mixtures of two or more thereof, or the coating is applied to the substrate in the form of a printing ink and solidified.

19. A marking on the surface of a moulding or of a coating located on a substrate which has a non-luminescent structure within a luminescent area unit, produced by the method according to claim 18.

20. A labelling of a product comprising a marking on the surface of a moulding or of a coating located on a substrate according to claim 19.

Description

EXAMPLE 1

(1) a)

(2) Pigments which have an SiO.sub.2 matrix in which luminescent particles comprising ZnS:Cu are included are prepared by the process described in WO 2009/071167, Example 1. In contrast to Example 1 from WO 2009/071167, however, ZnS:Cu particles whose primary particle size is less than 400 nm (Lumilux Green CD 179 FSI from Honeywell) are used. The UV-luminescent pigments obtained have a particle size in the range 2-60 m and green UV luminescence (fluorescence).

(3) b)

(4) The procedure as under a) is followed with the difference that ZnS:Mn particles (Lumilux Orange CD 181 FSI from Honeywell) having a primary particle size of less than 400 nm are incorporated into the SiO.sub.2 matrix. An orange-red-luminescent pigment having a particle size in the range 2-60 m is obtained.

(5) A gravure-printing ink is prepared from 90% by weight of an NC (nitro-cellulose) varnish (NC varnish 2001, Siegwerk) and 10% by weight of the green-fluorescent pigments from Example 1)a and applied to an optically transparent and laser-transparent plastic film (polyester or OPP (oriented polypropylene) film) in the gravure-printing process.

(6) The printed plastic films are laser-marked using lasers of the wavelengths 1064 nm or 355 nm. Both alphanumeric symbols and data matrix codes are written in. In each case, edge-sharp labels without fluorescence capability are obtained, irrespective of whether the laser structuring is carried out from the coated or uncoated side of the plastic film. Apart from a dark, sharp marking on green-fluorescent film under excitation by UV light, the marked area has absolutely no changes or damage under normal conditions (daylight).

(7) The following conditions are preferred:

(8) IR laser (neodymium-yttrium vanadate solid-state laser, 12 W)

(9) Wavelength: 1064 nm

(10) Laser mode: pulsed (Q switch)

(11) Power: 80-95%

(12) Pulse frequency: 10-30 kHz

(13) Speed: 300-600 mm/s

(14) UV laser (frequency-tripled neodymium-yttrium vanadate solid-state laser)

(15) Wavelength: 355 nm

(16) Laser mode: pulsed (Q switch)

(17) Power: 80-95%

(18) Pulse frequency: 10-30 kHz

(19) Speed: 1000-3000 mm/s

(20) Depending on the plastic material used and the layer thickness of the coating, the laser marking can also be carried out up to 7 mm on both sides of the laser focus in order reliably to prevent laser ablation of the coating.

EXAMPLE 2

(21) A screen-printing ink is prepared from 10% by weight of the green-fluorescent pigment according to Example 1)a and 90% by weight of a screen-printing varnish (FGLM from Prll).

(22) In the same way, a screen-printing ink is prepared from 10% by weight of the orange-red-fluorescent pigment according to Example 1)b and 85% by weight of a screen-printing varnish (Noripet 093 from Prll) and 5% by weight of thinner (Noripet 090 from Prll).

(23) Both screen-printing inks are in each case applied to metallic mobile telephone shells in the screen-printing process and, after solidification of the print layer, subsequently provided with a marking by laser.

(24) The following laser conditions have proven particularly preferred:

(25) UV laser (frequency-tripled neodymium-yttrium vanadate solid-state laser)

(26) Wavelength: 355 nm

(27) Laser mode: pulsed (Q switch)

(28) Power: 80-95%

(29) Pulse frequency: 10-30 kHz

(30) Speed: 1000-3000 mm/s

(31) Here too, the laser marking can be carried out slightly away from the laser focus in order reliably to avoid laser ablation of the coating.

(32) Edge-sharp, permanent markings are obtained which are invisible under normal light conditions (daylight) and represent non-fluorescent markings which are readily visible under UV light within green- or orange-red-fluorescent surroundings.

(33) The marked area regions have absolutely no visible changes under daylight.