Optical device having an illusive optical effect and method of fabrication
A method is provided for manufacturing an image on a substrate, wherein the image includes an indicia and a frame. The method includes covering at least a portion the substrate with a carrier comprising magnetically alignable flakes, aligning the magnetically alignable flakes with a magnetic field of a magnetic assembly comprising a metal plate with an opening, and solidifying the carrier. The frame is formed at an edge of the opening and the indicia is visible within the frame. The magnetic assembly includes two magnets disposed so that the North pole of one magnet and the South pole of another magnet are proximate to the metal plate at opposite sides of the opening.
1. A method of manufacturing an image comprising an indicia and a frame, the method comprising:
forming the indicia on a first surface of a substrate;
covering at least a portion of the first surface of the substrate with a carrier having magnetically alignable flakes dispersed therein;
generating a magnetic field with a magnetic assembly comprising a metal plate surrounding an opening through the metal plate and at least two oppositely oriented magnets;
aligning the magnetically alignable flakes with the magnetic field to form a frame of the magnetically alignable flakes at the edge of the opening, and
solidifying the carrier;
wherein the indicia is visible within the frame.
2. The method as defined in claim 1 , wherein the at least two oppositely oriented magnets are proximate to the metal plate at opposite sides of the opening.
3. The method as defined in claim 1 , wherein the metal plate has a thickness in the range of from 0.004″ to 0.1″.
4. The method as defined in claim 1 , wherein the metal plate comprises a material having a permeability in the range of from 0.01 to 0.3 H/m.
5. The method as defined in claim 1 , wherein the opening has a shape of a circle, a square, or a hexagon.
6. The method as defined in claim 1 , wherein the indicia comprises a symbol or logo.
7. The method as defined in claim 1 , wherein the substrate is a banknote substrate.
8. The method as defined in claim 1 , wherein a concentration of the magnetically alignable flakes in the carrier is in the range of from 4 wt % to 40 wt %.
9. The method as defined in claim 1 , wherein the magnetically alignable flakes are color shifting flakes.
10. The method as defined in claim 1 , wherein the indicia is printed in ink that does not include magnetically alignable flakes.
11. The method as defined in claim 1 , wherein the indicia is formed during the step of covering at least the portion the substrate with the carrier, and wherein the indicia is not covered by the carrier.
12. The method as defined in claim 1 , wherein the indicia is printed on the substrate prior to covering at least the portion the substrate with the carrier.
13. The method as defined in claim 1 , wherein the indicia is printed on the substrate after covering at least the portion the substrate with the carrier.
14. The method as defined in claim 1 , wherein the magnetic assembly is installed in a cylinder so that the metal plate is at a surface of the cylinder.
15. The method as defined in claim 1 , wherein the magnetic field bends at an edge of the opening in the metal plate.