Optically effective surface relief microstructures and method of making them

• US 10,350,843 B2
• Filed: 12/17/2013
• Issued: 07/16/2019
• Est. Priority Date: 05/12/2006
• Status: Active Grant

• Current Assignee: Rolic AG
• Original Assignee: Rolic AG
• Inventors: Stalder, Martin
• Primary Examiner(s): Wieczorek, Michael P
• Assistant Examiner(s): Miller, Michael G
• Application Number:
  US14/108,453
• Publication Number:
  US 20140106091A1
• Time in Patent Office: 2,037 Days
• Field of Search: 427160-169
• CPC Class Codes: B29D 11/00865 Applying coatings; tinting; colouring printing, marking or copying processes B41M; identification in general G09F3/00; producing decorative effects in general B44C; positioning or marking of lenses B24B13/0055
• CPC Class Codes: B42D 25/29 Securities; Bank notes
• CPC Class Codes: B42D 25/324 Reliefs
• CPC Class Codes: B42D 25/328 Diffraction gratings; Holograms
• CPC Class Codes: B42D 25/445 using chemical means, e.g. etching
• CPC Class Codes: G02B 5/0221 the surface having an irregular structure G02B5/0226 takes precedence
• CPC Class Codes: G02B 5/0257 creating an anisotropic diffusion characteristic, i.e. distributing output differently in two perpendicular axes
• CPC Class Codes: G02B 5/0263 with positional variation of the diffusing properties, e.g. gradient or patterned diffuser
• CPC Class Codes: G02B 5/0268 characterized by the fabrication or manufacturing method
• CPC Class Codes: G02B 5/0284 used in reflection

Abstract

The present invention relates to an element comprising a surface area with a specific, optically effective surface relief microstructure (12). The surface relief microstructure has a surface modulation of top regions (13) and bottom regions (14), wherein in a first lateral direction of the surface area there is in average at least one transition from a top to a bottom region or vice versa within every 20 micrometer, and in a second lateral direction of the mask, which is perpendicular to the first direction, there is in average at least one transition from a first to a second zone or vice versa within every 200 micrometer. In the microstructure, (i) in the first direction the lateral arrangement of the transitions is non-periodic, and (ii) the top regions substantially lie in the same top relief plateau (15) and the bottom regions substantially lie in the same bottom relief plateau (16).

Claims

1. Method for making an element having at least one surface area with a surface relief micro-structure, which method comprises:

creating a mask with a microstructure of first and second zones of different transparency, by including the steps;

depositing on a layer of a mask material a film with a topologically structured corrugated surface structure;

reducing the thickness of the film until the material of the film in lower zones of the corrugated surface is cleared away and parts of the underlying mask material are set free; and

removing the parts of the mask that are set free,

wherein at least in a first lateral direction of the mask there is, in average, at least one transition from a first to a second zone or vice versa within every 20 micro-meters, and wherein in the first lateral direction the lateral arrangement of the transitions is non-periodic;

generating with the help of the mask a relief microstructure in the surface of a resin or resist to produce top regions corresponding to the first zones of the mask and bottom regions corresponding to the second zones of the mask, wherein the top regions substantially lie in a top relief plateau and the bottom regions substantially lie in a bottom relief plateau, such that the relief modulation depth is substantially equal over the whole surface area.

2. Method according to claim 1, wherein the topologically structured corrugated surface structure is made by making a mixture of at least two materials of which at least one is crosslinkable and at least one other is non-crosslinkable, applying the mixture to the layer of the mask material, cross-linking at least a substantial portion of the crosslinkable material, and removing at least a substantial portion of the non-crosslinkable material.

3. Method according to claim 2, wherein the crosslinkable material is maintained in an oriented state during cross-linking.

4. Method according to claim 1, wherein in a second lateral direction of the mask, which is perpendicular to the first direction, there is in average at least one transition from a first to a second zone or vice versa within every 200 micro-meters.

5. Method according to claim 1, wherein the element is a security element.

6. Method according to claim 1, further comprising a step of coating the relief microstructure with a reflecting material after the relief microstructure is generated.

7. Method according to claim 6, wherein the reflecting material is aluminum, gold, chromium, or copper.