METHOD OF PRODUCING MICRO-IMAGE ELEMENTS ON A SUBSTRATE

• US 20200130397A1
• Filed: 12/27/2019
• Published: 04/30/2020
• Est. Priority Date: 06/30/2017
• Status: Active Grant

• Current Assignee: CCL Secure Pty Ltd.
• Original Assignee: CCL Secure Pty Ltd.
• Inventors: Jolic, Karlo Ivan, Power, Gary Fairless
• Granted Patent: US 11,167,580 B2
• Time in Patent Office: Days
• CPC Class Codes: B41M 3/142 using chemical colour-formers or chemical reactions, e.g. leuco-dye/acid, photochromes
• CPC Class Codes: B42D 25/324 Reliefs
• CPC Class Codes: B42D 25/425 by deformation, e.g. embossing

Abstract

Embodiments relate to producing micro-image elements on a substrate for a security document, the method comprising: producing a plurality of microstructure units comprising three-dimensionally structured formations in a clear or pale relief layer on the substrate; and applying a coloured ink fluid to the relief layer, wherein the coloured ink fluid accumulates preferentially in regions of high surface curvature on each microstructure unit to provide contrasting areas of different ink density.

Claims

1. A method of producing micro-image elements on a substrate for a security document, the method comprising:

producing a plurality of microstructure units comprising three-dimensionally structured formations in a clear or pale relief layer on the substrate; and

applying a coloured ink fluid to the relief layer,

wherein the coloured ink fluid accumulates preferentially in regions of high surface curvature on each microstructure unit to provide contrasting areas of different ink density.

2. The method of claim 1, wherein a repeating array of substantially identical microstructure units is produced in the relief layer, and wherein the coloured ink fluid accumulates in a substantially uniform distribution on each substantially identical microstructure unit.

3. The method of claim 1, wherein the plurality of microstructure units is produced by embossing the three-dimensionally structured formations into the relief layer.

4. The method of claim 1, wherein the plurality of microstructure units is produced by:

filling a plurality of recesses in a surface of a printing tool with a clear or pale lacquer; and

transferring the lacquer from the recesses to the substrate by contacting the surface of the printing tool with the substrate.

5. The method of claim 1, wherein the microstructure units comprise at least one formation side wall that intersects with a surrounding surface region, wherein the coloured ink fluid accumulates preferentially in a region of high surface curvature at the intersection of the side wall and the surrounding surface region.

6. The method of claim 1, wherein the microstructure units comprise at least one recess recessed into surrounding regions of the relief layer, the recess having side walls and a recess base surface between the side walls.

7. The method of claim 6, wherein the coloured ink fluid accumulates preferentially in regions of high surface curvature within the recess by flowing from the surrounding regions into the recess.

8. The method of claim 6, wherein the coloured ink fluid accumulates preferentially within the recess and covers the recess base surface.

9. The method of claim 8, wherein the coloured ink fluid does not fill the recess.

10. The method of claim 6, wherein the coloured ink fluid accumulates preferentially within the recess in regions of high surface curvature at an intersection of the side walls and the recess base surface, wherein the contrasting areas of different ink density comprise areas of high ink density adjacent to the side walls and a contrasting area of low ink density on the recess base surface intermediate the side walls.

11. The method of claim 1, wherein the microstructure units comprise at least one protrusion protruding from surrounding regions of the relief layer, the protrusion having side walls.

12. The method of claim 11, wherein the coloured ink fluid accumulates preferentially in regions of high surface curvature at the intersection of the side walls and the surrounding regions of the relief layer.

13. The method of claim 1, wherein micro-image elements comprising ink accumulated in the regions of high surface curvature produce a visible optical effect when viewed through an array of focusing elements disposed on the substrate.

14. The method of claim 1, further comprising applying a contrast coating over the relief layer after applying the coloured ink fluid, wherein the contrast coating has a different colour to the coloured ink fluid such that micro-image elements comprising ink accumulated in the regions of high surface curvature are contrasted against the contrast coating when viewed in reflected light through the substrate.

15. Micro-image elements on a substrate for a security document, produced according to the method of claim 1.

16. A micro-optic device on a substrate for a security document, comprising:

a plurality of microstructure units comprising three-dimensionally structured formations in a clear or pale relief layer on the substrate; and

a coloured ink on the relief layer,

wherein the coloured ink is accumulated preferentially in regions of high surface curvature on each microstructure unit, thereby providing contrasting areas of different ink density.

17. The micro-optic device of claim 16, wherein the relief layer comprises a repeating array of substantially identical microstructure units, and wherein the coloured ink is accumulated in a substantially uniform distribution on each substantially identical microstructure unit.

18. The micro-optic device of claim 16, further comprising an array of focusing elements disposed on the substrate, wherein micro-image elements comprising the coloured ink accumulated in the regions of high surface curvature produce a visible optical effect when viewed through the array of focusing elements.